Colorado Gardening Calendar for August 2022

By Terry Deem-Reilly, CSU Extension-Denver Master Gardener since 2003

The dog days are upon us, but with any luck, our gardens are still perking along without much assistance from us humans. With heat and drought still afflicting the plants, however, there’s still some garden mindfulness to practice before winding things down for the year.

WATERING

Nonxeric plants still require an inch to an inch-and-a-half of water each week in the August heat; without substantial rainfall, we’re stuck with manual or machine irrigation to keep gardens going for the time being. If our monsoon does kick in, inserting a water gauge in the garden to measure weekly precipitation totals will help limit irrigation to the proper amount for the season.

Keep an eye on sprinkler-system performance. Sprinklers should be sending water to plants and turf, not onto sidewalks, and amounts should be sufficient to dampen soil to a depth of four to six inches.

Check mulch to make sure that it’s still covering plant roots; it can be dislodged over time by humans, critters, and/or irrigation. Consider acquiring an extra bag or two (or more!) for use in the fall.

Discouraged by plants drooping in the heat? Don’t grab the hose and soak them immediately; if the soil around them is moist and mulching is sufficient, they have adequate moisture and should recover in cooler nighttime temperatures. And recent research on plants’ coping mechanisms when under stress will have a nice calming effect on the mind.

FERTILIZATION

Feed tomatoes, squash, and other flowering vegetables with low-nitrogen fertilizers as prescribed by their labels to promote continued fruiting. Don’t despair if production slows; fruit usually won’t set when temperatures exceed 80 degrees.

Feed roses for the last time in mid-August to prevent the growth of tender shoots that can be blasted by early frosts. Late-flowering perennials will appreciate feeding with slow-release organics through early fall. (Fall dieback of herbaceous perennials is part of their life cycle, so frost damage on new growth won’t be a concern.)

WEEDING, HARVESTING, AND DEADHEADING

Keep after the weeds! They’ll continue to grow and set seed for next year if they’re not removed.

Continue to harvest ripe produce and clear a patch for a fall crop of cool-season plants like lettuce, radishes, and spinach – these can be seeded in mid- to late August. CMG GardenNotes #720 contains cultivation pointers for hardy and semi-hardy vegetables in Colorado. (Buy row covers and other protection from early frosts this month so you won’t get caught by the inevitable surprise September freeze.) Avoid the end-of-season rush by removing and composting healthy plants that have ceased fruiting.

Keep deadheading roses but gradually stop removing blooms to promote dormancy. If your roses make hips, this practice will also allow hip formation before frost.

PESTS AND DISEASES

Japanese beetles may have mainly disappeared by now, but August and September are prime months for applying grub-killers to turf. Get a start on control for next year by using products like grubGONE! and GrubEx.

Late-summer pests will annoy until cold temperatures kill them off or force them into hibernation, so check out this science-based advice from The Burlington Record for Front Range gardeners. July and August heat boosts development of powdery mildew and other plant and turf diseases; consult these Extension fact sheets for the lowdown on symptoms, causes, and remedies for the most common plant and turf disorders.

PRUNING

Taking out dead, diseased, and dying branches and canes is always in order – but take a look at this general guide on when to prune before wielding those Felcos. The general rule is to prune spring bloomers right after flowering, and summer and fall bloomers in spring.

Roses are happy with pruning in late April or early May. Many gardeners earmark this task for Mother’s day weekend, which is usually past the average last frost of the season. Find more on pruning roses here.

Hold off on pruning most trees until late winter, with four exceptions: maples, birches, walnuts, and elms – these “sappy” trees appreciate having their grooming in August.

PLANTING

Can gardeners plant trees, shrubs, and perennials in late summer? Absolutely, provided they do three things: select larger plants with good root systems, install them during the cooler parts of the day, and provide mulch and sufficient irrigation to establish them before the ground freezes (usually in mid-October at the Denver elevation). Nurseries will shortly begin their sales, so visit a few to see what you fancy.

Whatever you choose to do this month, County Extension offices are eager to help with your problems; give yours a call anytime!

Planning a Dry Shade Garden: Making Lemonade with Dusty Strawberries

Lori Williams, CSU Extension – Denver Master Gardener Since 2016

This is a dry shade garden story of happy accidents, fortunate timing due to 100+ degree temps, and purely unexpected research wrapped in a beautiful day at Denver Botanic Gardens Chatfield Farms.

After more seasons than I’d like to admit there is part of my yard that has silently been waiting for attention for many years. It’s fully dry shade, anchored with a lovely oak tree that has reliably made this space look pretty good despite lacking design and plantings, and receiving water only for the tree’s sake. Lackluster turf is more grayish than green and sparse to say the least. Hello Sad Spot, it’s finally time for your makeover.

With these hot temps I’ve retreated inside and have been pouring over xeric plant guides, watched the uber helpful presentation ‘Dry Shade Planning and Planting by Amy Lentz of Boulder County Extension, and investigated various garden designs and plant suggestions offered by the fine folks at Plant Select, Denver Water, and our very own CSU Extension.

The added bonus was finding myself immersed in a treasure trove of design and plant specimens at Denver Botanical Gardens Chatfield Farms a few weeks ago. Dry shade garden inspiration abounds!

A clear pattern of attack is laid out for not only dry shade but any new garden spot:

  • plan ahead
  • improve the soil
  • limit turf
  • efficient irrigation
  • select plants
  • mulch
  • maintain

Plan ahead…hmmm…plan ahead….me? Oh but it’s a heat wave and due to travel plans and work obligations I’m doing research for a garden spot that I won’t be able to implement or plant until early fall. That sounds like I’m planning ahead!

Step one? Check! I even have time to have my soil tested.  And I’ll have time to actually amend the soil. This is going great! Look at me, planning ahead. It’s a new and different approach but I think I like it.

Next, I literally trip over one of the oak’s roots while collecting dusty soil samples and find myself looking at something that wasn’t half scorched turf but rather a mixture of barren and fruiting strawberries with yellow and pink blossoms. They were as dusty as the grass, but they’ve voluntarily planted themselves in this neglected space. Brazen little things! Congratulations, guys – you’ve just won the ‘Right Plant, Right Place’ award. Based on your gumption I decided on the spot that strawberries are the ground cover of choice.

I’ve spent time on cool mornings removing the patchy grass with my hori hori, providing more space for the strawberry tendrils to reach out and set roots. It’s delightful to see them take hold.

Thankfully, we have a sprinkler system, but the heads are all wrong (have been forever) for this area and I’ve been hose watering this dry shade zone instead for years. Once I fully determine the plants’ placement and they are well established, soaker hoses will replace the sprinkler heads to water the new guys more effectively. I’ll stick to the garden hose with my ancient frog eyed sprinkler during the establishment phase.

One of my best-ever gifts from Mom was Denver Water’s series of xeriscape books.  They developed the whole xeric gardening concept to begin with, so Colorado-proud of them. Highly recommended reading!

Mulch selection is still a bit up in the air, but I am a diehard fan and believer. I feel like mulch is kind of the reward topper-offer at the end of newly planted garden spaces. It really makes things pop and look fully finished while stealthily helping manage weeds and providing moisture retention in the garden. Win Win Win!

As mentioned earlier, I happily found myself at Denver Botanic Gardens Chatfield Farm recently. I was expecting a lovely visit of course, involving a great stroll while surrounded by beauty. Perfect! Embarrassingly, I think I’ve only been to the arboretum for holiday lights during the winter.

This visit turned into Christmas in July as I opened my eyes and mind and phone camera – a dry shade plant selection opportunity extraordinaire! Lenten rose? Bergenia cordifolia? Siberian Bugloss? Now I only need to ‘weed’ through approximately 47 plants to select the 3-5 for my make over garden. But as I’m planning ahead, ahem, I have time.

Additional sources:

Kinds of Shade

Zero Water Gardening

Dry Shade Solutions

A Gardening Project for the Hell Strip

By Gail Leidigh, CSU Extension-Denver Master Gardener since 2021

One of my goals this summer was to fix up a small 9’ x 6’ section of the hell strip area that I have ignored for several years while the weeds thrived. Between weeds, trash, and being a favorite spot for the neighborhood doggies, it was quite an eyesore. So, I finally decided to tackle this project and do something that would be sustainable, pleasant to look at, and attract pollinators.

Over the winter I worked on a plan, and first, needed to do some research! Since I live in a historic district, I consulted the guidelines published by the Denver Landmark Preservation Commission, which recommends that homeowners “Maintain grass and/or low-water ground cover in an existing or new tree lawn (the landscaped area between the street and the sidewalk).” Since the tree lawn (isn’t that term so much more charming than hell strip?) was long gone, and I did not wish to irrigate the area, I wanted to go with low-water plantings.

For inspiration, I did lots of reading from various sources, including an earlier post on this blog, Reimagining a Denver Hell Strip, which detailed the process Denver Master Gardeners Elizabeth and Daniel Neufeld used to transform their space. If they happen to read this, I’d love to know how it looks now!

5280 magazine also has a helpful article from 2015 with locally specific suggestions on planting in the hell strip.

I also borrowed the library book Hellstrip Gardening: Create a Paradise Between the Sidewalk and Curb by Evelyn J. Hadden (2014) for some very interesting gardening ideas from around the United States.

Once the weather began warming enough to work outside, I started clearing the area of debris and had a small elm tree that had grown itself from seed dug out. I did not know what to expect as far as soil conditions and anticipated that I’d need to remove and replace loads of dirt. But to my pleasant surprise the soil was quite loose, loamy, and I would be able to plant without amendments!

Naturally, as the weather continued to warm, the weeds were growing like crazy, and I spent many, many, hours digging them out and getting their roots as best I could. I will need to stay on top of these weeds throughout the season this year, and hopefully the healthy new plants will eventually crowd them out.

In choosing plants I looked at information on recommended native plants on the CSU Extension website, and using the wonderful “Find a Plant” feature on the Plant Select website.

Plant choices were narrowed down based on my must-have criteria: safe for kids and pets, low-height (24” or less), low water needs, poor soil (non-composted) tolerant, and overall tough plants that could deal with being in a busy high traffic area.

I ended up selecting Kannah Creek Sulphur Buckwheat (Eriogonum umbellatum) and Wild blue flax (Linium lewisii). The area is 54 square feet, and I drew up some plans to help with arranging things.

In typical Colorado fashion, as soon as I finished planting everything in mid-May, after I thought the danger of frost had passed, we got one of our wild late spring snowstorms extra late this year.

Thankfully, the snow in our area remained mostly wet slush which prevented most of the heavy build up on plants and trees that causes problems. Unfortunately, other areas were not so lucky: while driving through Washington Park after the storm, I saw significant damage to older trees throughout that neighborhood.

I put a small fence around the area to keep out wandering feet and covered the garden bed with pea gravel (the suggested mulch for these two plants). I have been watering about every 2-3 days by hand, which is more frequent than I would suggest for clay or rich soils, but this small space has exceptionally well-drained soil and I want to make sure to get the plants established during this rather warm and dry spring and summer. All of the plants have shown good growth in the last two months, and for now they appear to be happy in this place!

Colorado Gardening Calendar for July

By Terry Deem-Reilly, CSU Extension-Denver Master Gardener since 2003

Spring sprang (along with a surprise 19 hours of snow in late May), and now midsummer heat has descended. The major gardening tasks are in the rearview mirror, but that doesn’t mean that there aren’t some things left to do, irrespective of the summer temperatures!

Our keywords for July are observation, assessment, and maintenance. Focus on these tasks for continued garden success.

WATERING

Typically the monsoon kicks in around mid-July, so smart irrigation will be a priority this month.

Check the mulch around perennials, trees, and shrubs to make sure that it’s in place over root balls (not against the stems) and that it remains at the recommended depth of two inches. Replenish mulch if needed. Infrequent, deep watering of these plants will produce the best results. Non-xeric plants, especially roses, require an inch of water weekly during hot periods; soak the areas around the bases of new xeric plants twice a week to promote root growth. 

Check the soil of annuals, fruits, and veggies to a depth of one inch, and water if the topsoil is dry. Mulching will reduce the frequency of irrigation, discourage weed germination, and prevent soil compaction as you move around the plants. Container plants generally require daily watering.

DON’T wash off pollen by spraying the foliage of tomatoes, squash, and other fruiting plants that require fertilization.

Try the “footprint” test to determine when turf should be irrigated: if grass remains flat after being walked on, it’s time to water; otherwise, wait a day or two. Watch the spray patterns of your sprinkler heads to make sure that water is landing evenly on the turf and not on sidewalks. (Uneven irrigation is a likely cause of brown spots in the lawn.)

If plants are given proper irrigation and mulching but droop in the daytime, don’t rush to turn on the hose – many plants wilt under high heat and revive overnight. Nevada Extension has contributed some good hints for coping with stressed-out plants.

FERTILIZATION

Fertilization schedules and amounts vary widely between types of plants, so this topic is therefore highly complex! Right now, plants like tomatoes and summer-blooming perennials will require regular feedings to promote flowering, but shrubs and trees can take a break until fall or even next spring. Research fertilization requirements of plants when in doubt, and check labels for rates and times of application.

See the Extension fact sheet Fertilizing the Vegetable Garden  for information on food crops. 

WEEDING, HARVESTING, AND DEADHEADING

Get the weeds as soon as you see them; the bigger they are, the more difficult they are to remove and the more likely to set seed as they mature. If using products like Roundup (glyphosate), apply in the early mornings or on days when the temperatures reach no higher than 80 degrees. Foliage won’t absorb these products in extreme heat. 

Harvesting of many vegetables and fruits can begin this month per this table from PickYourOwn.org; for others, we’re still in the observation and maintenance modes. Pick fruit and vegetables in our cool mornings.

Deadhead both summer-blooming plants (to promote budding) and plants that have finished flowering (to keep them tidy). Remove spent blooms on lilacs early this month to allow the plants enough time to set buds for next spring.

PESTS AND DISEASES

Keep an eye out for foliar damage, stunted growth, holes in produce, and distorted fruit and blossoms; these indicate the presence of pests and disease. Pests tend to be species-specific, while diseases like powdery mildew afflict plants across a wide spectrum of genera and species. CSU Extension’s site features a great page listing their resources regarding insects (including beneficials); the “Yard & Garden” page includes fact sheets devoted to garden diseases. There’s also a searchable Online Resources for Gardening and Landscape page that directs users to all gardening pages, including blogs with updated information.

When using pesticides, make sure that their application won’t harm beneficial insects. Carefully follow all label directions for usage.

Japanese beetles will begin infesting our favorite plants this month. Many systemic insecticides are harmful to our pollinators; the safest and most reliable methods for control continue to be handpicking/drowning and applying products containing bacillus thuringiensis var. galleriae (Btg) to plants. (Btg will not kill the beetles immediately but will reduce their numbers over time; it’s also included in products like grubGONE! that can be applied to turf containing the grubs in late summer.) The ever-popular and useful Extension fact sheet “Japanese Beetles” offers numerous suggestions for dealing with these pests.

As always, County Extension offices are eager to help when problems emerge; give them a call anytime!

Growing Raspberries in Colorado

By: Molly Gaines, CSU Extension-Denver Master Gardener since 2019

Picking and eating homegrown raspberries are a quintessential summer pleasure. Before moving to Colorado in 2017, we lived in Minneapolis, where I had a prolific raspberry patch. Picking a mix of red and black raspberries in late June through early July, at the height of ripeness and flavor, was always a joy for our family. Yet it was a labor of love, as we didn’t have good walkways weaving through the patch. For about two weeks each summer, we’d happily head to the large patch each morning, donning our heaviest long-sleeve shirts to avoid pricks from the thorny canes. The heaping bowls of fresh raspberries were always worth our efforts.

I find the flavor of homegrown raspberries to be rivaled only by homegrown peaches, another Colorado favorite. They are a perennial, like other fruits, so once they are planted, they will come back for many years if properly tended. 

Following are a few ideas on planting and caring for your own successful raspberry patch.

Selecting Varieties

While I had great luck in Minnesota — a considerably harsher climate than Denver — with summer raspberries, fall-bearing raspberries seem best-suited for the Front Range, according to tests conducted by Colorado State University. For a better guarantee of success, consider growing a variety of raspberry types. (For more information on varieties, see the CSU Extension Raspberries for the Home Garden fact sheet.)

Finding the Right Spot 

With good growing conditions, a raspberry patch may last 10 to 15 years. Raspberries need full sun but avoid planting them in areas with a lot of reflected heat, such as alleys, where already hot temperatures may be even hotter. In open windy areas, wind protection is important. Dry winds, common here in Denver, can dehydrate and kill exposed canes. 

Soil Conditions

Raspberries require good soil with slight acidity and adequate drainage. They also require one to three inches of water a week. As the berries get close to harvest, more water is required. Apply enough water to maintain a moderate moisture level in the root zone. During flowering and fruiting, more water is required. 

Merrill Kingsbury, CSU Denver’s Colorado Master Gardener program assistant, has grown raspberries for years and often gets asked about her tips for success. She recommends not overhead watering, as it leads to disease. As with most other fruits and vegetables, drip irrigation is preferred so the water goes straight to the roots, rather than soaking the foliage. Another benefit of drip irrigation is that it leads to less water waste, as water goes straight to the plants’ roots, versus being lost in the air. 

Planting

New plants should be planted in the spring. They prefer well-drained, sandy loam soil and perform poorly in compacted clay soil, or soil with poor drainage. If your soil has a lot of clay, consider planting in a raised bed. Add compost and other amendments frequently to improve the soil’s organic content. As a long-term crop, your raspberries will perform better as a result of your efforts.

Due to soil borne diseases, do not plant raspberries where raspberries, strawberries, tomatoes, peppers, eggplant, potatoes, or vine crops (cucumbers, squash, and melons) have been grown in the past four years. To reduce virus potential, do not plant raspberries next to blackberries. Be sure to purchase certified virus-free nursery stock.

Other Notes on Care

Trellising is advisable for all bramble crops in Colorado. Without some type of support, canes will flop and sprawl in such a way as to make weed control and harvesting much more difficult.

For summer-bearing varieties, remove the spent canes by cutting them off at the ground after they bear fruit. Dispose of these canes, as they often harbor insects and disease. In the spring, remove the dead, weak and small canes. Remove winter-killed tips of the canes that remain.

While a raspberry patch requires continual work and attention, your efforts to grow them successfully — like most wonderful things in life and the garden — will be well worth it. 

For more information on growing raspberries in Colorado, visit the following links: 

Designing a Garden Using Xeriscape and Colorado Native Plants

By Terry Deem-Reilly, CSU Extension-Denver Master Gardener since 2003

Sustainability has become a byword in many areas of life, so why not apply the concept to our gardening by using the plants best suited to the challenging Colorado climate, as they love sun and low irrigation and flourish in soils with very little organic material and no fertilization? 

Planting xeric and Colorado native species in our gardens isn’t only a smart choice during drought conditions, but will save time in the garden, improve the looks of our properties and our neighborhoods, and support necessary pollinators and other wildlife in our ever-expanding urban areas.

Basic Garden Design

Before selecting and buying plants, consider basic design principles (as slightly modified for a xeriscape/native garden):

  • How big is the garden going to be, where will it be placed, and what other uses will be made of the site and the surrounding area? 
  • Is the ground level, sloped, or a combination of the two? (Water will run down a slope to collect at its foot, which will affect the placement of plants: more xeric plants belong at the top, less xeric at the bottom.)
  • Consider the soil type (clay, sand, or loam), sun exposure (full sun, part shade, or full shade), wind exposure, and accessibility of water. (Xeric and native plants require regular watering in their first year.) Organic amendments are not indicated for this type of garden, but drainage can be improved by tilling in pea gravel.
  • How much time are you willing to spend to establish and maintain the plantings? (Native and xeric plants are easy-care after their first season, but tasks like weeding and pest and disease control are forever.)
  • David Salman of High Country Gardens recently posted a great article incorporating basic design pointers with suggestions for the xeric garden: 9 Tips for Professional-Looking Garden Design
  • If you’re converting a yard from turf to xeric/native plantings, consult the Extension fact sheet Xeriscaping: Retrofit Your Yard for ideas on how to proceed and suggestions for xeric substitutes for popular plants.

Think About the Contents of this Specific Garden

  • What varieties of plants do you like, and what does well in your area? Take a look at neighbors’ yards, demonstration gardens, and local-nursery offerings to find your preferences. 
  • Look at the ‘Native Plants’ section of this list of CSU Extension fact sheets to read and download information on Colorado’s native trees, shrubs, perennials, and grasses.
  • Links to the native plant guides for five regions in Colorado published by the Colorado Native Plant Society are available on this page.
  • For xeric plant suggestions, consult the page listing xeric demonstration garden plants on the Adams County Extension website. Most nurseries here have caught on to xeriscape principles and have added many xeric plants to their stock, so spend some time prowling their aisles.
  • Will you plant for a lush look, which may entail buying many plants and a great deal of work, or space plants widely and use groundcovers or mulch to fill in between them? (This might be a good strategy for the first-year garden.)
  • What are the space requirements for the selected plants? Remember that perennials, trees, and shrubs will take more than one season to attain their mature sizes. Take the mature sizes listed for xeric and Colorado native plants VERY seriously; these plants like our short growing season and will grow to the sizes shown much more readily than plants that originated in less rugged climates and longer growing seasons than ours.
  • What are the cultivation requirements for the plants? Group plants that have similar water, soil, and sun requirements together – many Colorado natives have adapted over the centuries to our clay soils and might falter in the sharply-draining soil loved by xeric varieties. Check the tag for water needs or research the plant to be sure.
  • Be prepared to mulch; what is used is a personal choice, but DO NOT use landscape fabric. Groundcovers are a good living mulch if you like them.
  • Consider how the garden will look throughout the year. Plant tall grasses and evergreen shrubs and groundcovers and leave stems and seedheads on perennials for winter interest (and to feed and shelter wildlife in colder months). Look for plants that fruit and/or display colorful fall foliage.

That’s the skinny (or most of it) on xeric and Colorado plants. Remember to take your time with selection and establishment, and to contact your local Extension office with any questions. 

Colorado Gardening Calendar for June

By Valerie Podmore, CSU Extension-Denver Master Gardener since 2020

So, who had the fifth earliest 90-degree day and the eleventh latest spring snowstorm in May on their garden bingo cards last month? Well, it’s June and who knows what else Mother Nature will throw at us! 

Thank you to those who attended the CMG Plant Sale during the great snowstorm of May 2022. Likely, you’ve either have planted your new purchases or will be doing so soon! 

JUNE is one of the best months for being happy that we can go outside into our gardens and watch (or MAKE) them grow. Mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable Garden

  • If you’ve planted your cool season-veggies (peas, lettuce, kale, and spinach) last month, this is the time to harvest to prevent these going to seed.
  • Warm-season plants like tomatoes, peppers, and eggplant will thank you for continuing to transplant them this month to keep your harvest going.
  • Water evenly, close to the soil rather than overhead to prevent fungus and other plant diseases from forming.
  • Don’t forget to continue to perform the most fun activity ever…WEEDING! You don’t want your lovely veggies having to compete with these evil garden monsters.
  • Apply organic mulch to keep the moisture up and the weeds down. Untreated grass clippings (i.e., chemical-free) are a good option.
  • Make sure to join the Grow and Give program which supplies fruits and veggies to folks in our local communities who might have a need for our extra bounties.

Trees and Shrubs

  • If there has been no precipitation in a month, make sure to water your tree(s). Trust me even with the recent snow, we are still very dry.
  • If you are thinking of doing more xeriscaping, take a look at this information sheet on trees, remembering that less water for the landscape means less for trees and shrubs as well if we don’t set up the landscape in a water-wise way.

Lawn Care

  • As mentioned in last month’s calendar blog, Japanese beetle control at the grub stage by using products like GrubGONE! that contain bacillus thuringiensis var. galleriae (Btg) must be applied to turf in May and early June to take effect. Check with a local nursery regarding availability of these products or order them online. Consult this Extension fact sheet regarding Japanese beetles for advice on dealing with this pest throughout the summer.
  • This information sheet gives great information on watering during a drought, which we are experiencing even with late moisture we received.
  • This might be a good time to start looking at more xeric plants as mentioned above in the tree/shrub section. Colorado and the west are getting dryer and we could look at different ways to reduce our water use including cutting back on traditional, high water needs lawns. Watch for our upcoming blog post on this topic, too.

Perennial/Annual Flower Beds 

  • Our perennials require good watering during the month, low-level, slow watering to prevent fungus and other plant diseases caused by over-head watering. This applies to annuals as well, whether in containers or beds, to prevent them from drying out.
  • Dead heading (the practice of removing spent blooms) will keep new flowers blooming throughout the month.
  • If you have iris plants that have been in place for 3-4 years, consider dividing them after they finish blooming to keep them growing strong…kind of like us cutting our hair!
  • This article contains a trove of information on creating and maintaining a perennial flower bed.
  • Low-water flowering plants information (for both perennials and annuals) can be found here. An awesome read!

In closing, as June is Colorado Pollinator Month, take a look at this post on how we can attract these very important animals to our gardens.  Also visit the CSU Extension Yard and Garden website for more gardening tips.

Native and Diverse, Our Solitary Bees

By Lori Williams, CSU Extension – Denver Master Gardener since 2016

There are approximately 4,000 species of bees found in North America: 90% are native to the USA, Mexico, and Canada, and the remaining 10% are European honeybees transported here by pilgrims and other world travelers. In Colorado there are over 900 native bee species.

CSU’s Fort Collins campus is a Bee Certified Campus so it’s bee-friendly and also bee-autiful! CSU also offers an exceptional community science project, Native Bee Watch that encourages Coloradoans to engage in research and education to support pollinator conservation. The website is a trove of information and ideas for encouraging and learning about native bees.

Research Says:  Solitary Native Bees Are Giants of Pollination!

Due to their ‘technique’ when visiting plants, native bees basically pollinate everything along their daily route be it an alfalfa crop, an orchard, our backyard flowers, or the neighbor’s veggie plot. 

Here’s more about these ‘super-spreaders’:

  • Solitaries have a habit of ‘belly flopping’ into the plants they visit. Pollen then sticks all over them. As they move on, they generously deposit this pollen on plants in their path. 
  • Natives supplement the organized and human-assisted honeybees, which are often transported thousands of miles to aid farmers in crop pollination. Native bees very effectively pollinate plants within the travel radius of their nest.
  • Graceful, maybe even messy in their daily routines, solitary bee activity contributes significantly to food production, blooming blossoms, and microclimate success. 

Native Solitary Bees Compared to European Honeybees

Solitary bees look, behave, and live somewhat differently than non-native honeybees. Here are some notable comparisons:

  • Solitary bees are typically smaller (1/4” to 3/4” in length) than their European compadres. They can be black, dark blue, or metallic green.
  • Natives live solo in nests they create using natural materials (mason bees use mud, leaf cutters line their nest with leaves and beyond). Many species nest underground. Non-native honeybees are communal dwellers and live in hives often provided by humans.
  • No job goes undone for solitary bees – they do every job needed to live and reproduce.
  • Every native female is a queen. She collects pollen to store in her nest for each egg she produces in an approximately 6″ long nest, housing 6-10 eggs. Every male is born to mate as he emerges and then dies so on this point, honeybee males/drones are pretty similar.
  • Honeybees work as a community to collect pollen and make generous amounts of honey for the queen, her eggs, and harvesting. Native bees don’t create honey, nourish themselves as they go, and leave the exact amount of pollen for their eggs to eat before they emerge from the nest. 
  • Honeybees have aggressive guard bees at hive entrances. Native bees don’t have time for this as they are busy eating, nest building, and collecting pollen for their eggs. They typically say ‘oh hello, excuse me, I’m off’ to anyone looking around their haciendas. Most don’t even have barbed stingers.
  • Diverse native bee populations are not susceptible to mono-species diseases, pests, or Colony Collapse Disorder.

Creating Solitary Bee Habitats 

It’s easy and beautiful as they love flowering ‘stuff’ and need four basic ‘things’ to create nests, lay and protect eggs, and store pollen and nectar: food, water, shelter, and a solitary space for their nest. You’ll find this CSU Fact Sheet and video provide lots of details on creating habitats.

Here are some key tips:

  • Design gardens with plants that bloom in waves to provide food and nesting materials spring through fall. A mix of bloom sizes, colors, shapes, and timing will keep them happy. 
  • Native bees are four times more attracted to native plants than non-natives.
  • ‘Bird’ baths are for all pollinators: bees, butterflies, birds, and more. Creating a ‘beach’ or place to land in your water source offers pollinators a resting place while they hydrate.
  • Insecticides and pesticides with any bee, bird, beneficial bug, or other pollinator are not a good mix.  Please evaluate carefully when considering the necessity of using these products and always follow directions to a T, for your safety too.
  • Stacked ‘log hives’ offer great habitat, so do cracks in tree bark and undisturbed ground, leaf mulch also creates nesting opportunities. Wooden homemade bee ‘hotels’ that are south facing are welcome refuge for happy homemaking solitary bees, too.

Be sure to keep your eyes peeled for these fascinating bees and consider their needs when working in the garden!

Growing Vegetables and Herbs in Containers

By Lois Margolin, CSU Extension-Denver Master Gardener since 2011

Benefits of Growing in Containers

There are many reasons for growing vegetables and herbs in containers:

  • Place strategically in full sun areas.
  • Ease of use – no need to bend down.
  • Bring inside or easily cover in bad weather.
  • Limited outdoor space or no yard? Containers are perfect on patios, balconies, window boxes, or in small yards.
  • Planning to move this summer? Take your garden with you.
  • Add architectural, artistic, and textural interest to outdoor spaces.
  • Taller containers can keep rabbits out of crops.

Containers and Potting Soil

My favorite container is a plastic wheelbarrow. It holds enough soil to grow a delicious salad bowl of lettuces, spinach, kale, peas, scallions, and nasturtiums – even a tomato plant. It’s easily moved throughout the day to sunny or shady areas depending on what you’re growing. It’s also high enough that you don’t need to bend when planting, tending, and harvesting.

For vegetables, choose containers large enough for the plants at maturity. The wheelbarrow holds a lot, but smaller containers can hold a single tomato or pepper plant. For more information on container sizes refer to CMG Garden Notes #724.

All pots must have drainage holes to avoid root rot. Plastic containers are best for water retention. Ceramic pots need to be “high fired” to be frost-proof and not crack in winter. Wooden containers should be made from rot-proof lumber. Do not use creosote treated railroad ties for edible plants as they can be poisonous.

Strawberry pots are perfect containers for herbs. See my blog post on planting in a strawberry pot for tips on how to successfully grow in this container.

Large containers can be very heavy. If you plan to move the container around, place it on a sturdy container dolly. For taller containers, the bottom 1/3 can be filled with capped, crushed water bottles or packing “peanuts.”  (Test the peanuts by placing some in a glass of water to make sure they don’t dissolve.)  Place a layer of landscape cloth over this filler to keep out the soil. Then fill the remaining 2/3rds of the container with potting soil.

Do not use soil from the ground (native soil) as it’s too high in clay content and may have disease organisms, insects, or weed seeds.

Purchase good quality potting soil which is high in organic matter and contains perlite or vermiculite. Some brands contain water-holding polymers or gels. Or make your own potting soil by mixing 1/3 peat moss, 1/3 vermiculite or perlite, and 1/3 organic matter (compost).

For more information, see CSU’s Fact Sheets on growing salad greens and growing in containers.

Sun, Water, and Fertilization

When considering container placement remember sun requirements:

  • Fruiting vegetables – 8 hours of full sun
  • Root vegetables – 6 hours of full sun
  • Leafy vegetables and most herbs – 4 or more hours of sun

Group plants that require similar amounts of water and sunshine. In the heat of summer, you might have to water twice a day as containers require more water than in-ground plants. Check for moisture by inserting your finger into the soil about an inch. If it’s dry, it needs water.

Vegetables like consistent moisture. Ideally, water in the early morning so that plants can absorb the moisture and avoid wilting during the heat of the day.

Container vegetables also need more fertilizer than in-ground plants. I fertilize weekly with half-strength water-soluble fertilizer. You can also apply a time-release fertilizer when planting. Always follow the directions on the label.

Time to Plant!

Lettuces, spinach, kale, beans, zucchini, cucumbers, beets, parsley, cilantro, dill, radishes, and carrots do well in Colorado when planted from seeds. Longer maturation plants such as tomatoes, all peppers, most other herbs, and eggplants should be started early indoors or purchased in starter sizes. Check labels for the number of days till maturity. The metro Denver area has a short growing season – late May through early to mid-September (the average dates of the last frost in spring and the first frost in fall.) Higher elevations have an even shorter season.

Choose dwarf plants as they do better in containers than full-sized varieties. Cherry tomatoes do exceptionally well in containers. Try plants like Megabite tomatoes, Big Dwarf tomatoes, Potomatoes with clusters of yellow cherry tomatoes that grow on an 18-inch plant, Cute Stuff red peppers, Raven zucchini, and Hensel eggplants are all good options.

For vegetable containers that are decorative and colorful as well as productive, consider planting small flowers with the veggies. Marigolds add nice color as do nasturtiums that hang over the sides.

Edible flowers add drama and flavor to salads, main courses, and desserts. Not sure which flowers are edible? This CSU Fact Sheet has an extensive list.

Container gardening is fun, easy, and very rewarding. Remember to harvest as soon as the vegetables are ripe. Many plants will continue to produce during the summer and into early fall. ENJOY!

Colorado Gardening Calendar for May and 2022 Denver Master Gardener Plant Sale

By Terry Deem-Reilly, CSU Extension-Denver Master Gardener since 2003

May is the month when gardening really goes into high gear! Here are the areas and tasks to tackle this month:

VEGETABLES AND HERBS

  • Veggies and herbs can be planted this month; be prepared to cover them if nighttime temperatures go below 40 degrees. It’s advisable to plant tomatoes when overnight temperatures are consistently above 50 degrees.
  • Start weeding now, in all areas of the garden. Get ‘em while they’re young!
  • Find hints for combatting vegetable pests in this list of CSU fact sheets.

LAWNS

  • Make sure that hoses and sprinklers are in good condition; apply an inch of water to the lawn each week, except during rainy periods. Denver Water has some excellent suggestions regarding lawn irrigation and general care from May 1st through September 30th, when watering restrictions are in effect.
  • Consider irrigating the lawn at night or in the early morning hours when evaporation is minimal. This can be a real turf AND water-saving measure in the hotter months, and it won’t promote diseases.
  • Set mower blade height at two inches – higher grass keeps the soil moist and promotes good root growth.
  • A thick thatch layer interferes with efficient watering and fertilization, so check for thatch and arrange for power-raking if the thatch is at least one-half inch thick.
  • Products like GrubGONE! that contain bacillus thuringiensis var. galleriae (Btg) as a control against Japanese beetle grubs must be applied to turf in May and early June to take effect. Check with a local nursery regarding availability of these products or order them online. Consult this Extension fact sheet regarding Japanese beetles for advice on dealing with this pest throughout the summer.
  • How lawns are watered, mowed, cultivated, and fertilized in their early growth will determine their appearance and health throughout the summer and fall (and perhaps for the next year as well). This fact sheet on lawn care outlines the best practices for tackling these tasks from now until fall.

TREES AND SHRUBS

  • Take a look at the garden to spot any “holes” that can be filled with a good-looking shrub, rose, or small tree – right now is when nurseries have the best selection. Be sure to call the Utility Locator Service at 811 before digging any large holes.
  • Begin watering existing trees and shrubs deeply once a week and check to ensure that plants are well-mulched. Here’s helpful information on selecting the correct mulch for your plants.
  • Start checking for pests; they will become more active as the weather warms and our spring rainfall commences (we hope). Consult this list of CSU fact sheets for information on specific insects and controls. When selecting pest controls, consider their effects on beneficial insects!
  • Now’s the time to apply copper spray to susceptible trees such as apples, pears, quince and crabapples, to prevent fire blight.
  • Finish spring fertilization and pruning of roses; make sure to apply two inches of mulch at the base of each plant and water newly planted roses twice a week for the first two or three weeks to promote root growth. Once established, roses will appreciate getting at least an inch of water weekly as temperatures rise.

ANNUALS AND PERENNIALS

  • Perennials can be hardened off and planted now; wait until at least the last average frost date in mid-May to fill annual beds and containers. Keep frost covers handy if we have one or two chilly nights before Memorial Day.
  • Summer bulbs can be planted now, so check them out at your local nurseries. It’s also a great time to divide summer and fall blooming perennials, find excellent info here.
  • Treat pollinators by seeding bare spots with their favorite annual plants, including borage, dill, zinnia, and/or cosmos. Plant as recommended by the seed packets and water. Seeds will germinate in a week or two; sprinkle the seedlings gently every few days and wait for the bees and butterflies to arrive! More pollinators mean more tomatoes, squash, fruit, etc., etc.

May certainly is a busy month in the garden! What’s on your to-do list?