Colorado Gardening Calendar for June 2023

By Linda McDonnell, CSU Extension – Denver County Master Gardener since 2013

June is my favorite month in the garden – from the explosion of colorful blooming perennials and the promise of the summer harvest to the comfortable temperatures – it just doesn’t get any better. We’re also coming off a month of record-setting moisture, which makes the landscape greener and lusher than usual.

Early June columbines, coral bells & tulip foliage. Photo: Linda McDonnell

Our May gardening calendar covered the season-long essentials of weeding, mulching, and watering. Refer to it for those tips. On this post, let’s look at ways to keep plants healthy, troubleshoot potential issues, and enjoy the garden.

Trees and Shrubs

• Check apple, crabapple, mountain ash, and pear trees for fireblight, a bacterial disease that emerges in spring, especially when there’s been wet, warm weather. Look for curled, bent shoots with brown or black leaves, and limbs shaped like a shepherd’s hook. Learn how to properly treat fireblight here.

Fireblight on an apple tree. Photo:  I, Paethon via Wikimedia Commons

• Suckers are shoots that spring up from the base of the tree trunk or root system. Aspen, sumac, chokecherry, and plum trees are prone to suckering. Suckers can indicate the tree is stressed. Hand prune suckers where they attach to the trunk or root system. CSU reports Sucker Stopper RTU™ may help with control.

• Prune spring flowering shrubs now to control their size/shape, remove dead wood, increase air circulation, and improve flowering next year. Find tips here.

Vegetables and Herbs

• CSU’s Grow & Give program is a way to share your harvest with the community. Consider signing up to donate excess produce on the Grow & Give website. You’ll also find excellent growing tips and insect/disease help on the site.

• If you’re growing in containers, remember that they dry out quickly. Check daily as temperatures rise. Mulch will help retain moisture.

• For the best flavor, remove flower buds from culinary herbs.

It’s hard to pluck lovely chive blooms! Photo: Pitsch from Pixabay

Perennials and Spring Flowering Bulbs

• When flowers fade, snip tulip and daffodil flower stems at the base. Leave the foliage until it yellows and goes limp. As it dies back it’ll provide valuable nutrients to the bulb which will help with next year’s flower production. Apply bulb food now too. If you already pulled the foliage, you could still add fertilizer.

• Deadheading, or removing flowers that have finished blooming is a matter of personal preference. Deadheaders cite encouraging re-flowering, creating a tidier landscape, and reducing unwanted reseeding as motivators. Others prefer a more natural appearance that provides food and shelter for birds and other animals, reseeds freely, and features interesting seed heads. Many gardeners deadhead some, but not all plants.

• If you deadhead perennials, consider the plant’s growth habit when pruning. For example, cut the flower stem about ¼” above the next set of leaves or an emerging bud on upright clumping perennials such as echinacea. Shear mounding plants – such as catmint, golden storksbill, and cranesbill geranium – down to about three inches. This is quick and easy. They’ll look scruffy but rebound quickly.

• Ornamental grasses and most climbing roses bloom once a season so deadhead for aesthetics or to remove diseased foliage.

Shear golden storksbill to get more flowers & contain size. Photo: Linda McDonnell

• To keep mid to late season blooming perennials from flopping, reduce their height by 25-30% in early to mid-June before flower buds emerge. This Chelsea Chop promotes side branching, creates shorter, stockier plants, and delays flowering by a week or two. Good candidates include soft stemmed, clumping plants such as New England aster, chrysanthemum, and false dragonhead.

Manage Unwelcomed Visitors

• Creeping bellflower (Campanula rapunculoides) is prolific in Denver. Treat it as a weed. Unlike other campanula species, it’s a fast growing, sharp elbowed invasive that will choke out any plant in its way. It has heart-shaped leaves at its base, which become narrower as they move up the stalk, and green to reddish stems. Mature plants have stubborn, deep, white fibrous roots. Left unchecked it can reach three feet tall and produce nodding light blue bell-shaped flowers on one side of the stem. Control by digging out the roots and removing new growth as it pops up. If you’re plagued with this thuggish plant, this handout from Wisconsin Extension is a must read.

You’ll regret letting creeping bellflower get this big! Photo: Linda McDonnell

• Aphids are back. These soft bodied, green, tan, or orange sesame seed shaped insects are relatively harmless to shade trees and ornamental plants. They suck on tender young foliage and mark foliage with a sticky honeydew secretion. Lady beetles, green lacewings and parasitic wasps feast on aphids. A strong stream of water may be enough to dislodge aphids without compromising biodiversity. Insecticidal soaps can also be effective.

• Aphids on food crops can be more problematic. See this University of Utah article for advice.

• Rabbits are cute but can be destructive to plants and turf. Find tips for creating barriers and using safe repellants here.  

• Japanese beetles will emerge from the ground in late June or early July. Get ready to pick and drown or stomp them. Review CSU’s report for details and watch for our July JB post for helpful tips.

Lawn Care

• Water only when needed and in compliance with Denver Water Department’s rules. CSU’s lawncare handout can help you use water responsibly while maintaining a healthy lawn.

I hope you enjoy this beautiful time of the year. Remember to visit the CSU Extension Yard and Garden website https://extension.colostate.edu/topic-areas/yard-garden) for more Colorado gardening tips and solutions.

Harvesting and Storing Vegetables for Peak Flavor and Freshness

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

Summer’s Bounty. Photo by Molly Gaines

If you’re a vegetable gardener, you’ve likely begun to harvest some of the goodness resulting from your spring and summer efforts. My garden favorite, ‘Sun Gold’ cherry tomatoes, are just ripening. They taste like pure sunshine (those of you who’ve grown or eaten know what I’m talking about!) and I eat them like candy, straight from the vine. Because of this, it’s rare for more than a handful to make it into my kitchen.

Yet everything else in my garden — the herbs, cucumbers, green beans, summer squash and hot peppers — require some prepping, peeling, chopping, or cooking. They all need proper picking and storage until I’m ready to use them.

How and when to harvest, and how best to store your bounty, can be confusing. It’s a combination of art and science. I hope the following information helps guide you through one of the best parts of a vegetable gardener’s season: harvest time.

A handful of sweet and fruity ‘Sun Gold’ tomatoes. Photo by Molly Gaines

Knowing What’s Ready

In order to assess what’s ready for harvest, I do an early morning garden walk. It’s become one of my favorite parts of my summer days. It’s when I harvest vegetables from my garden, as it is best to pick in the morning when it’s cooler. There’s more time to gather your harvest and bring it into the kitchen before it wilts. Additionally, veggies regain moisture they’ve lost during the day, leading to overall better produce. See more about the benefits of morning harvesting here.

When you planted last spring, you may have noted when your produce should be ready. Every seed packet has a number of days until harvest, as do the tags in starter plants. However, “days to harvest” is an estimate, as it will vary depending upon your growing conditions. Soil fertility, sunshine, heat, water, etc. all impact maturity. In my own garden, our red onions should be ready to dig, but they aren’t even close because they’re partially shaded by large Zinnias above. For specific estimates on days to harvest for each vegetable, visit this helpful link from the University of Minnesota Extension. While Colorado’s climate is quite different from Minnesota, we have a similar growing season.

While it may seem counterintuitive, the more you pick, the more a plant will produce. Don’t let those zucchinis and cucumbers get too big; they won’t taste great or could be inedible. Pick produce frequently and when they are smaller, versus letting vegetables that are ripe enough continue to hang out on the vine. To keep my garden producing at an optimal level when I’m out of town, I like to hire neighbor kids to harvest or invite a friend who loves fresh vegetables to stop by and fill a bucket.

This one was hidden and missed. Try to find and pick those zucchinis early! Photo by Molly Gaines

How to Harvest and Store

Harvest your produce gently and with care. Snapping off the end of your green beans or cucumbers will invite quicker decay in the fridge. It can also damage the plant, inviting disease and pests. If you’re not able to easily twist or pull a pepper or tomato or any other veggie from the vine, it’s time to use scissors or pruners. I always keep scissors close to my garden for easy use.

Speaking of proper storage, it’s disappointing to open the fridge and finding hard-fought basil browned, or last week’s fresh cucumber now mushy. We Colorado gardeners work very hard for our veggies, so it’s worth storing them properly until use. Visit here for a terrific guide to harvesting and then storing garden favorites, from when to pick to proper storage directions, including ideal temperatures.

What to Do with Excess Harvest

If you find yourself with more fresh produce than you can handle, there are a number of Denver-based organizations that will accept your extra vegetables. Here is a recent article listing some of those organizations. For more information about how to best contribute your produce locally, visit the Grow and Give website, for general donation information.

These harvest and storage tips should find you enjoying your summer bounty as long as possible, enjoying peak flavor and maximum freshness — and savoring every last bite.

Other Helpful Resources on Harvesting

https://planttalk.colostate.edu/topics/vegetables/1842-harvest-vegetables/

https://web.extension.illinois.edu/tog/harvest.cfm

https://growgive.extension.colostate.edu/wp-content/uploads/sites/63/2021/01/Colorado-Vegetable-Guide-2.1.pdf

Colorado Gardening Calendar for April and Grow & Give 2022

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

April is one of my favorite months in Colorado, a time when signs of life are everywhere –– trees are budding, the crocus and daffodils are in bloom. Mostly empty garden beds beckon, promising beauty and bounty for the next six months. And, while the garden to-do list is long, I feel inspired to tackle each task and eager to be back in my garden.

Having a monthly “to-do” gardening list helps break down the many gardening tasks into less overwhelming chunks, reminding me what to do when. April is a great time to get your gardening ducks in a row, peruse your favorite gardening centers, prep your gardening soil for planting, and begin putting a shovel and seeds in the soil. 

A Gardener’s Yard and Garden Checklist for April

If you haven’t done it yet, it’s time to finish cleaning up of last year’s garden, removing any annual plant remnants, cutting back perennials and pulling early emerging weeds. Clear any mulch, such as dried leaves laid last fall over vegetable beds or around perennials. Add compost if you didn’t do it last fall. When the soil is mostly dry and workable, add 1-2″ of compost into your soil at a 3-5″ depth.

Also consider testing your soil. It’s not too late! I wrote a blog post last January about getting your soil tested. Testing is the best way to fully understand what your soil needs to growth healthy plants.

Here are some additional April gardening “to-dos” in Denver: 

Vegetable Garden

• Plant cool weather seedlings such as broccoli, cabbage and cauliflower. Want to grow asparagus or rhubarb? Now’s the time to get those perennials into the ground. 
• Direct sow early season veggies and greens, such as arugula, peas (I soak in warm water in advance for quicker germination), spinach and radishes. Water well if rain is sparse. 
• Plan for snow and hail. How will you try to protect your early plantings? It’s always good to have some old bed sheets or plastic near your garden in case a late winter storm or spring hail passes through. 

Arugula pops up early in the garden. Photo by Molly Gaines

Peas can take a late-season snow. Photo by Molly Gaines

Trees and Shrubs

• Look closely at your trees for any winter damage that may need an arborist’s attention. Inspect shrubs and other perennials for signs of life. Take note of plants that should be showing initial green or growth but are instead brown and brittle. This way, you can inspect again in a few weeks and determine if they need replaced. 
• Start planting both shrubs and trees if the ground is thawed. Water thoroughly.

Lawn Care 

• Check your irrigation to be sure your system is working. Your lawn needs 1″ of water weekly. 
• In early April in Denver, or by the time forsythia is blooming, apply pre-emergent herbicides to prevent summer crabgrass.

Perennial Flower Beds 

• Remove any dead foliage still lingering from last season and pull early-season weeds.
• Divide perennials that have grown too large for your space or haven’t been divided in a few years. It’s good for the plant and your budget! You can store in pots and water until you’re ready to plant elsewhere in your yard or give them away to neighbors. 
• Sow some wildflower seeds for flowers pollinators will love later. Water well. 
• New growth for roses can typically be seen as April progresses. Prune canes that are damaged or dead and then all others (except climbing roses) to 12” to 24” above ground. 

Daffodils are a quintessential April flower in Denver. Photo by Molly Gaines

Annual Flower Beds

• Start planting early-season annuals that can tolerate light frost. Consider pansies earlier in the month and flowers, such as snapdragons and sweet alyssum, later in April. 

(For additional April gardening tips and ideas, check out the CSU Extension garden calendar for April 2017.)

Grow + Give Program

If you’re a Denver vegetable gardener, start thinking now about joining CSU’s Grow + Give, a modern victory garden project. The goal of the Grow and Give program is to help address food insecurity in Colorado.

If you commit to the program now, you can plan to plant a little extra to donate to your neighborhood food pantry, neighbors in need, or other organizations that accept excess produce. Visit growgive.extension.colostate.edu for details. Watch for the 2022 season sign up; it should be posted soon. 

Colorado Gardening Calendar for August

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

• 

  Pond Lilies.  Photo by Valerie Podmore

August is one of the best months for enjoying the fruits of your gardening labors and planning for quickly approaching fall. The word of the month is WATER! Mark your calendar to get these gardening to-do’s done in your yard and garden.

A Gardener’s Yard and Garden Checklist for August

Vegetable Garden

• Harvest your crops often to encourage continued production and prevent insects.  Cucumbers, summer squash, tomatoes and beans are some which should be ready to pick now.  Make sure to use clean scissors or shears to cut them from their stalks – don’t pull them away.
• Start to direct sow fall season veggies such as lettuce, radishes, beets, and Swiss chard.  Follow the instructions on the seed packets.
• After harvesting, as areas become empty, sow cover crops such as annual rye grass to build garden soil.
• If you find you have more than you can use, in addition to making gifts to neighbors and friends, consider donating surplus crops to the Grow and Give program, as a way of helping those in need.
• If you are having issues with any of your crops, the Grow and Give website gives excellent troubleshooting advice on their “What’s Wrong With My Plant?” page.

Trees and Shrubs

• Make sure to give trees and shrubs consistent, deep watering around the drip line, not just at the base, to help them stay healthy or become established if new.  Giving adequate moisture to soil will prevent plant injury later in Fall and Winter.  Watering early in the day (before 10am) allows soil to absorb moisture.  Find out more about watering on CSU Extension’s Fall and Winter Watering and Watering fact sheets.
• This is a good time to start thinking about planting shrubs as the soil is still warm and they will get a good head start before the colder weather comes in.  Just remember to water them generously in order to help them establish.
• It is best not to fertilize or prune after mid-August except to remove any broken or damaged branches as woody plants begin to move into their dormant period.  This prevents new growth that won’t have time to harden off before the cold weather hits.

Lawn Care

• The middle of August is a good time to start renovation and repair of lawns. Build up low areas with garden soil and overseed areas that are thin or bare.
• Make sure you keep up the good watering practices you’ve been following. Continue to monitor your sprinklers. Give your lawn enough water as mentioned in last month’s blog entry for July tasks. 
• Like clockwork, our friends the Japanese Beetles are back, and we are all thinking of how to stop them!  Now is when the adult Japanese Beetles are laying their eggs which will grow into larvae and feed on the roots of grass.  Keeping grass healthy will encourage a strong root system and help prevent damage to your lawn.  There are also several methods to fight these invaders, including biological controls such as parasitic nematodes, and insecticides.  Just make sure to read the labels carefully and apply as instructed.  This factsheet has everything you need to know: Japanese Beetle – 5.601 – Extension (colostate.edu)
• Finally, for excellent, in-depth information on lawn care see the Lawn Care fact sheet on the extension website.

Perennial Flower Beds

• Continue dead heading of spent flower blooms, and remove dead or diseased foliage.
• Don’t stop that weeding!  As much work as it is, it will help prevent more weeds and you’ll thank yourself later.
• Fertilize roses around the middle of the month.  Any later can cause growth which can damage the plant if there’s an early frost.
• Divide Spring blooming perennials such as Basket of Gold (Aurinia saxatilis) Daylily (Hemerocallis species), Hardy Geranium (Geranium species), Hosta (Hosta species), Coral Bells (Heuchera species), Coreopsis (Coreopsis species), Garden Phlox (Phlox paniculata) and Speedwell (Veronica species).

Annual Flower Beds

• Tidy up flower containers by getting rid of spent flowers and dead patches.
• This is a good time to find annuals on sale, if you want to swap out the old for something new.

August is a great time to keep working on your garden, enjoy the beauty and plan for any changes or additions so you can use the winter months to prepare for next Spring!

You can find a plethora of gardening tips on the CSU Extension Yard and Garden website.

Grow & Give Colorado

By Laurie Daniels, CSU-Extension Denver Master Gardener since 2014

Have you ever secretly left a pile of zucchini on your neighbor’s porch after dark? Does just the thought of canning one more jar of applesauce make you sweat?  Do you eat tomatoes at breakfast, lunch and dinner at a certain point in the summer?

If any of this sounds familiar, the CSU Grow & Give project is for you!

The Grow & Give project was created by Colorado State University Extension to make it easy for any gardener to get fresh produce, grown in their garden, distributed to people in need. By participating in Grow & Give, you will learn how to easily donate your extra produce to organizations that will welcome it.

What Produce Works Best?

^{Photo credit: Laurie Daniels}

Let’s first talk about what is the best produce for donating. It’s best if the produce is easy to use by home cooks. It’s also important that your donation is easy to keep fresh and doesn’t need a lot of extra packaging to keep it safe during distribution. Some of the produce that Grow & Give recommends for donation include:

• Melons
• Tree fruit
• Summer & Winter Squash (they’ll love that extra zucchini!)
• Cucumbers
• Roma or slicing tomatoes (no cherry or large heirloom tomatoes—too fragile)
• Corn
• Green beans
• Carrots
• Eggplant
• Bulb onions
• Peppers (sweet, mild, medium)

Your local organization may accept other items such as berries, kale, beets, etc. but check with them first.

How Do I Participate?

1. The first step is registering your garden with the Grow & Give project. You can sign up by completing a short survey. Now, you are ready to garden!

• Check out the many resources on the website including a free to download, 85-page full color Colorado Vegetable Guide (available in English and Spanish). The Guide covers topics including garden layout, soil preparation, watering, fertilizing, managing insects/pests in your garden and detailed descriptions for growing vegetables from asparagus to winter squash.

• Next, find a nearby organization for your planned donation. You will find an interactive map on the website that lists organizations all over Colorado. When I registered, I was able to find three organizations near my home. It is important to find an organization early on, since many only accept donations on certain days/times of the week and ask that you contact them in advance of dropping off your produce. Be prepared!  NOTE: If you know a neighbor, perhaps a senior living on a fixed income, who would appreciate receiving some of your extra produce, Grow & Give also has an option for donating directly to a neighbor-in-need.

• Now, enjoy working in your garden. If you find bindweed in your garden beds or discover aphids on your broccoli, go back to the Grow & Give website (https://growandgivecolorado.org) and look for the tab on “Insects, Diseases and Weeds” to find short videos and fact sheets about how to handle these issues and many others.

• When you begin harvesting produce from your garden and find yourself with an  excess of zucchini or a bounty of beans, check back on the Grow & Give website for tips on safely handling your produce for donation. The tips cover everything from:
  • washing or not washing your produce (be sure to let the organization you donate to know if the produce has not yet been washed)
  • using clean containers (do not reuse grocery bags)
  • washing your hands thoroughly before you harvest
  • leaving your produce whole—do not chop or cut as it shortens its shelf life
  • time your harvest so your donation can be made immediately

^{Photo credit: Laurie Daniels}

• Just a few more steps will enhance your donation. You can find printable Grow & Give labels on the website to designate your donation as part of the project. And, weigh your donation so you (and the project) have a record of what you gave.  Grow & Give also has links to tasty recipes that can be made with the produce you donate—what a nice gift for the recipient of your fruit or vegetables!

• Finally, head back to the website and tell Grow & Give about your donation—photographs and stories are welcome through social media as well—and enjoy the good feelings that flow from helping your neighbors.

“Grow Food, Share the Harvest” is the slogan of the Grow & Give project. I hope you will consider joining us in our efforts “to address food insecurity in our state, one garden at a time.”