Colorado Gardening Calendar for April 2024

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

Last week’s snow covering forsythia starting to bloom. Photo: Molly Gaines

Signs of spring are everywhere in Denver. Daffodils, crocus and other spring flowers in full bloom one day; covered in ice and snow the next. Oh, to be a gardener at 5,280 feet!

While it’s too early to spend a lot of time planting, it’s a perfect time to prepare your soil, garden beds, tools, pots and lawn for the 2024 growing season. Below are a few gardening activities to consider before Mother’s Day, May 12 (around the safe zone from hard frosts) for planting most plants, flowers and vegetables.

Crocus are always a welcome first sign of springtime. Photo: Molly Gaines

As you plan your garden, it’s worth noting that some of the Denver metro is in a new gardening zone. Last November, the USDA announced updates to its “Plant Hardiness Zone Map,” updating this go-to tool for gardeners for the first time since 2012. The new map, which can be found here, places parts of Denver in Zone 6a rather than 5b. Zone numbers reflect the average extreme minimum temperatures and help determine what plants will thrive in each zone.  Higher numbers equal incrementally warmer low temperatures. For background about how to use this map as a planting guide, visit this helpful article from the National Gardening Association’s learning library.    

New USDA Plant Hariness Zone Map now places parts of Denver in Zone 6A. Credit: USDA

Vegetable Garden

• Clear remaining debris. Pull emerging weeds.
• When the soil is dry, add a fresh 2-3-inch layer of compost to your beds. This supports soil health and plant vigor. Gently work compost into the top layer of your existing soil with your hands, a trowel or a cultivator. Let rest a few weeks before planting.
• Plant frost-tolerant spring plantings, such as peas, spinach, arugula, radishes, Swiss chard, etc.
• Start indoor seeds for warm-weather vegetables such as tomatoes, peppers, squash, melons, etc.
• Reference this Vegetable Planting Guide to plan what you will plant when.

Trees & Shrubs

• The snowpack is solid Colorado-wide this year, well above 100 percent. This includes Denver. That said, if this month is dry, be sure to water your trees and shrubs.
• Early this month, prune deciduous trees, conifers and summer-blooming shrubs.
• Later in April into mid-May, prune rose bushes. For details on exactly how, why and when to do this, visit here.  This is weather dependent so watch for low temperatures and delay if a cold snap is predicted.
• Remove broken branches from trees and clear dead leaves and decayed fruit from the base.
• If you’re looking to plant a new tree, consider the Park People’s annual fruit and yard tree sale that begins April 20. Trees range from $50 to $80, and sales support the Denver Digs program. More details can be found here.  

Lawn Care

• Prep your mower, sharpening the blade as necessary and conducting other maintenance. Lawn mower blades should be sharpened at least once per season.
• If you use a pre-emergent weed product, apply in early April. For more details about how to use, visit here.
• Fertilize as desired, reading labels for proper application. Keep in mind that fall is the most important time for lawn fertilization. Applying only in the spring can mean excessive top growth and shallow root systems.

Perennial Beds

• Cut back perennial plants if this wasn’t done last fall, leaving 3 inches of the plant above the soil.
• Similar to your vegetable garden, the soil in these beds will also benefit greatly from compost, with the exception of native plants which generally prefer unamended soil.
• Pull emerging weeds now. Stay on top of them from the start.
• Divide overgrown perennials such as chives, sedum, grasses, phlox, daisies, hosta, etc. This will lead to healthier plants and better growth.

Other April Gardening Thoughts

• Assess garden supplies. Purchase or plan to borrow anything needed. Sterilize and sharpen garden tools.
• Empty any pots or containers still holding last year’s dead plantings. Clean and disinfect them to prevent disease in new plantings.

These pots need to be cleared of last year’s plantings, disinfected and filled with new soil for plantings. Photo: Molly Gaines

• Denver Water recommends waiting to turn on your irrigation until after the last freeze, typically in early May. Hand water until then.
• Sow wildflower and pollinator seed mixes.
• Prepare for frost, hail and other bad weather. Have sheets of plastic, old bedsheets and five-gallon buckets in easy reach for late-season snow or spring and summer hail. Remember the hailstorm that hit Denver late June last season?

Sad peas in a bed covered with hail. June 29, 2023. Photo: Molly Gaines

Springtime in Denver is special. I love watching new life slowly unveil itself. It’s a time full of promise, new beginnings and high anticipation of the color, flavor and textures around the corner. The more prepared you are in April, the more enjoyable your summer gardening season will be.

As always, if you have questions about plants, planting and any other gardening and yard related topics, visit the CSU Extension Yard and Garden website for tips.

How to Build a Three-Bin Composting System

By Rikki Hanson
CSU Extension-Denver Master Gardener since 2014 and a Denver Urban Gardens (DUG) Master Composter since 2013

Composting is an amazing process that produces one of the best soil amendments gardeners can use. One of my favorite composting systems uses three bins for creating brown gold in your own backyard. This composting system is efficient and gives the option of having two bins to work with at all times. It can also be built to fit any space, making it easy to maintain.

To Build a Three-bin Composting System, you’ll need:

• Gloves
• Untreated barriers for the three bins, such as bricks, cinder blocks, nontoxic landscape timber, chicken wire, 2×4 construction lumber, wooden pallets, etc.
• Pitchfork or shovel
• Tarp or plastic cover
• Sifter

Step 1: Finding a Location for Compost Bins

In our semi-arid climate it’s important to locate the three-bin system on a level site, in a semi-shady location that’s protected from drying winds. With our hot summers and intense sunlight, compost in a south or southwest-facing location could potentially heat up too much, killing the living decomposers.

Step 2: Building the Bins

Set up the bins to fit your space, such as 3x3x3-feet or 5x5x5-feet using bricks, blocks, lumber or your choice of building material to create three separate bins.

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  An example of a 3-bin compost system with materials added to the middle and right bin, leaving the bin on the far left open for turning. Photo by Rikki Hanson

CSU Extension explains the three-bin system in the Fact Sheet on Composting Yard Waste as an efficient wood structure that allows plant material to be aerated by turning it from one bin to the next as it decomposes.

Once the three-bin structure is in place, use a pitch fork or shovel to expose about an inch or so of earth in each bin area. Exposing the bottom of the bin attracts microorganisms living in the soil.

Step 3: Adding Materials to Bins

Add organic matter to two bins and leave one bin empty at all times to promote faster compost production and allow turning the material from one bin to another.

Spread 4-6-inches of mixed, chopped up carbon material, the tough brown, woody materials like leaves, cornstalks, straw, shredded newsprint, paper, brown paper bags, small amounts of sawdust, vacuum contents, wood chips, clumpy grass and discarded stems from annuals pulled at the end of the season.

Add 2-to-4-inches of mixed, chopped-up nitrogen material, the green layer that includes vegetable scraps, coffee grounds, grass clippings, alfalfa, eggshells, oats, beans, bread, fruit scraps and rinds, hair, garden waste, cotton rags and strings, pond algae and non-synthetic dryer lint.

NOTE: Don’t add meat, dairy products, fat, bones or lime. Eggshells are fine, but not eggs.

If you have a large quantity of grass clippings, let them dry for a day or two before adding them to the pile. Untreated grass clippings can be added to food scraps, alfalfa hay, weeds, or hair to vary texture.

Add a thin layer of soil from the garden on top of the green layer to introduce decomposing microorganisms to your system.

Composting Tips:

• Mix and moisten the layered sandwich of brown and green material plus soil until it feels like wrung-out sponge.
• The layering should continue until the piles are about 3-4-feet tall in two of the bins.
• Cover with a tarp or opened black trash bag and secure with rocks or bricks to help trap heat and activate the microorganisms and decomposers.

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  A tarp covers the middle bin in this 3-bin system. The bin to the left has materials composting in it. The bin on the right is empty for turning compost into it. Photo by Rikki Hanson

Step 4: Maintaining the Bins

When the bin system is set up, maintaining them is a breeze. Keep a compost bucket in your kitchen for the valuable food scraps and empty them into a bin when you turn your pile every 2-3 weeks.

You have two bins to work with, so if you want to dispose of your scraps sooner, go for it! Or you can store the food scraps in the freezer until you’re ready to turn.

For every new nitrogen/green material you add, you also want to add double the amount of carbon/brown material every time you turn the piles.

Ask friends and neighbors for their leaves to help you while diverting their organic materials from the landfill.

Step 5: Collecting the Compost

After you’ve turned the materials in your bins for a few weeks, you’ll see the raw materials have turned into a rich brown compost. Congratulations! You now have the most sought-after soil amendment money can buy.

Now’s the time to use chicken wire, ¼-inch mesh, old fireplace screen or a laundry basket to sift the compost. The compost can be as fine or as chucky as you want depending on where you want to use it and how much of it you want to use or give away.

Need Answers to Your Composting Questions?

CSU Extension-Denver Master Gardeners can answer your composting questions or direct you to other local resources: email denvermg@colostate.edu or call 720-913-5278.

Take a Virtual Container Garden Tour

CSU-Denver Master Gardeners have had extra time to spend in their gardens this summer, but few opportunities to show them off – until now.

Please join our virtual tour to see seven stunning container gardens overflowing with beauty and creativity. The tour features containers of different shapes, sizes, materials, and of course, fabulous plants. These talented gardeners also share their secrets to success.

We hope you enjoy the tour!

Steve Aegerter, CMG since 1999
Steve’s hanging basket includes Calibrachoa in three colors, sweet potato vine and orange nasturtiums (peeking out on right side). He grew nearly everything from seeds, except the potato vine. His planting recipe includes about 3-4 sections of a deep six-pack of Calibrachoa, probably 3-4 nasturtium seeds and 2 sweet potato vines from cuttings.
The basket is low maintenance as flowers are self-cleaning. Steve used 4-month slow-release fertilizer at planting, plus peat moss and vermiculite in a potting soil medium. He waters the hanging basket “every other day which wouldn’t be necessary if I didn’t use sweet potato vine,” he says.

Steff Grogan, CMG since 2018
Steff says she loves to mix perennials and annuals together in her containers, “at least until the perennials outgrow the pot!” One of her favorite plantings this summer included a large container meant for a mostly-shady spot. The container includes 6 varieties of Coleus, 1 Lime Margarita sweet potato vine and 1 purple sweet potato vine.
Steff’s foliage container get 3-4 hours of morning sun and she waters it every other day, depending on heat and precipitation.

Jan Davis, CMG since 2012
Jan sent in a view of one of her large container gardens brimming with a variety of flowering plants. Her secret to such a spectacular display is to use 2-3 plants of the same type in each pot for a bigger splash. She says the show stoppers are the fragrant pink Oriental Trumpet lilies. The lilies are planted in large plastic pots so Jan can remove them from the grouping after blooming is finished. She overwinters them in the garage, after they have gone dormant. “I love this container garden because it is right outside my kitchen window and next to our outdoor eating area,” Jan says. “It gets enjoyed all the time!”

Ashley Cosme, CMG Apprentice
“I love the simple color line of this pot,” says Ashley. “Sometimes going with a straightforward white and green color brings out the beauty in the textures. I have left the perennial lysimachia and the heuchera in the pot for a few years which is very budget friendly as well.”
Ashley’s recipe for planting includes one 6-inch Kimberly fern, two 4.5-inch tropical white sunpatien, three 4.5-inch euphorbia, one #1 citronelle heuchera, two 4.5-inch Niagara Falls coleus, one 4.5-inch ipomea and one #1 lysimachia. This pot gets morning sun with afternoon shade and requires a bit of extra water as the sunpatien and the fern are thirsty plants.

Lois Margolin, CMG since 2010
Lois’s raised bed garden was built by her son-in-law and includes three large containers, each 2-feet by 4, 5, and 8 feet lengths. She says the raised beds are large enough to grow enough vegetables for two people. “The raised beds work great because I don’t have to bend or get down on my knees to garden.” In the longest of the three containers she’s planted 2 rows of carrots along the front side, carrots, scallions and carrots on the back side. Other plants include bell peppers, marigolds, Early Girl tomato, Japanese eggplant and 2 cucumber plants along the edge so they trail over the side of the container.
Lois places plants close together and uses potting soil, compost and slow release fertilizer at planting time, plus a liquid fertilizer once a month during the growing season.

Anne Beletic, CMG since 2016
Anne’s container garden is composed of 7 troughs that are planted with 11 6-inch Pincushion plants, 5 2.5-inch Dusty Miller plants, Forget-Me-Not, Borage, Cornflowers (from seeds); trailing plants are Sweet Potato vines, variegated Vinca (both 2.5 ” pots).
Anne says she likes this planting because the Pincushions have been flowering for weeks, the flowers attract bees and the Borage star shaped flowers are “exquisite.” The only downside is the borage has become too big and thirsty, she says.
Anne used a good quality potting soil with slow release fertilizer at planting, waters daily and cuts back the Pincushions to the next bud. She plans to keep the Pincushions in a flower bed “as these were the only plants I spent real money on, and they should be a viable perennial in Denver.” Anne notes, “the Pincushions were the bulk of the planting until seeds grew, and so merited buying a little larger.”

Jill Fielder, CMG since 2012
Jill says she played with new types of fancy coleus, both for color and because many of these can now be successfully grown in either sun or shade. She has two of these containers on either side of her front porch. “They get different amounts of sunlight, are bright with color that doesn’t rely on big flowers or wide leaves susceptible to hail and these are (mostly) plants that aren’t all that attractive to Japanese Beetles,” she says.
Jill’s recipe includes 1 Coleus Fireworks (purple & lime), 2 Fuchsia Gartenmeister, 2 Asparagus fern, 2 Impatiens Walleriana Peach Butterfly, 1 Coleus Maharaja (red), and 2 Dragon Wing Red begonias.
This container gets dappled morning light, is on a daily drip system and was planted up with slow release fertilizer early in the season.

A Special Thank You to the seven generous CMGs who shared their gardens and tips with us. We hope this virtual container garden tour inspires you to plant something a little different in your garden next year!

By Jodi Torpey
Master Gardener since 2005
Photos provided by each CMG

Vegetable Growing Tips for Beginning Gardeners

New to vegetable gardening? We’re here to help!

A group of experienced CSU-Denver Master Gardeners answered the call to help new vegetable gardeners plant and grow their first gardens. These tips cover most of the basics for the best chance of success growing fruits, vegetables and herbs this season.

Their advice covers how to get your garden started, what to plant, when to plant, where to plant, how to care for your garden and a primer on growing tomatoes.

John Ashworth

John H. Ashworth, Master Gardener since 2014, shares his thoughts on various veggies that do well in Colorado vegetable gardens:

Radishes are the ideal crop to start with, especially if you get your kids involved. Radishes emerge very quickly, even in cold soil, and are ready for eating in 30 days or less.

Carrots can do well here, but can struggle if you have heavy clay soil in your garden. Before you plant in clay soil, mix in a healthy dose of play sand and mix in well. This will allow the carrot roots to grow down without extensive use of a garden fork for cultivating. Plant the shorter, stubbier carrot varieties, Nantes and half Danvers, if you have heavy soil.

Basil seeds can be started indoors under lights or in a sunny window, but  DO NOT plant them outside too soon!  Wait until early to mid-June. Basil grows well in containers — I plant ten basil plants in a large pot and get enough to make pesto all summer long. Be aware that Japanese beetles love basil, so pick the beetles off the plants early each morning.

Tomatoes are heavy feeders and like rich soil. Add compost and fertilizer (either well-rotted steer manure or a balanced chemical fertilizer) to the planting hole. Fertilize every few weeks. Because our climate is dry and lacks humidity, some tomato varieties, like large beefsteak tomatoes, tend to split open prematurely. Instead, try Sungold cherry tomatoes, Early Boy or Early Girl varieties, or any of the heirloom varieties such as Brandywine,  or the Eastern European varieties such as Black Krim or Polish paste tomatoes.

John’s final piece of advice: Above all, have fun!

Mary Carnegie, Master Gardener since 2002, is also the Garden Leader for the Denver Urban Gardens (DUG) Park Hill School garden. Her top three tips for new gardeners are concise and to the point:

1. Be willing to get your hands dirty; stick your finger in the soil to see if plants need water.

2. Know the “safe” planting dates; don’t plant too early. (CSU Extension’s Vegetable Planting Guide can help with planting dates.)

3. Learn as much as you can about watering and mulching. (CSU Extension’s Watering Guide and Mulches for Home Grounds are two good resources.)

Rikki Hanson

Rikki Hanson, Master Gardener since 2014, says something that stuck with her as a beginning gardener is that “Colorado gardeners do it for the challenge. Lucky for me, I like a challenge.” To meet that challenge, she advises to start small.

1. Start with a few veggies that you enjoy eating. Have a mix of things that grow quickly and slowly, that way you can enjoy the fruits of your labor sooner while you wait for the big-ticket items. Radishes and lettuces are great fast-rewards foods.

2. Make a plan for watering: early in the morning or after 6 pm. This is especially important when you have seeds and seedlings. We have a very dry climate that lends itself nicely to mulch.

3. Find the joy in your own plot of Earth. Vegetable gardening is something to be enjoyed and to help you destress!

Jill Fielder

Jill Fielder, Master Gardener since 2012, is happy to share her trio of tips:

Tip 1:  Many vegetable plants need sunlight to grow sturdy and strong. Planting  sun-worshiping  vegetables like tomatoes, peppers, cucumbers and eggplants in less than full sun (about 6-8 hours of sun) sets one up for heartbreak. Tomato plants aren’t going to be vigorous and productive in 3 or 4 hours of sun no matter how much you will it. If you don’t have adequate sun in your space, choose plants that will thrive in partial sun (3-5 hours) such as lettuces, chard, spinach, scallions, kale, beets, Asian greens and radishes. In Colorado basil, thyme, chives, mint, oregano and parsley grow beautifully with just morning sun.

Tip 2:  Find a place for bunching onions or scallions (also called Welch onions, spring onions and green onions). These onions are super easy, speedy and fun. They can be grown from seed or slender starts from the nursery. Choose the customary white variety or scoop up the pretty deep red ones if you can find them. Plant in mid spring and you can eat the greens during the summer (snipped into eggs, stir fries and salads) and harvest the whole onion plants in the fall. Left in the garden, they’ll usually overwinter.

Tip 3:  Start seeds for ruffled, loose leaf lettuces outdoors early, even if there will likely still be frosts and maybe snow. Lettuce seedlings are remarkably tough. Depending on the lettuce variety, leaves can be ready in 40-55 days. Don’t let your precious garden space go unused in the spring!

Elizabeth Gundlach Neufeld

Elizabeth Gundlach Neufeld, long-time gardener and Master Gardener since 2017, reveals her 8 tips for tomato growing. These are the key points she wishes she would’ve known years ago when it comes to planting tomato seedlings:

1. Choose seedlings that are strong and relatively straight.

2. Harden off all seedlings for a good week after purchasing. “Hardening Off” means leaving them outside, in a sheltered location, with little exposure to the elements. Be sure to water the seedlings to keep moist before planting.

3. When ready, plant tomatoes in a trench. Cut off all the leaves and small branches EXCEPT for the top 2 inches. Plant the rest sideways in the trench. Those fuzzy little hairs on the stem will become roots! Planting the tomatoes more-or-less horizontally will produce greater numbers of roots and lead to a stronger plant.

4. Here’s the hard part. For the subsequent 3 weeks, remove ALL the flowers. Doing this allows the plant to spend its energy producing a strong root system. I sometimes compare this to humans in the following way: Although, say, young teenagers may be physically possible to bear children, they are not ready to. Similarly, the tomato plant needs to mature in the ground before producing tomatoes.

5. Pinch off all ‘suckers’ in indeterminate varieties. Suckers appear in the crotches of the tomato branches and can harm the overall plant by weakening the main stem.

6. Stake or cage the plants! Because you’ve trench-planted and picked the blossoms, the main stock will be thick and able to support many more tomatoes.

7. Water tomatoes ONLY at the bottom at soil level, trying not to wet any leaves. Keep only moderately moist. They will likely not need watering every day.

8. Enjoy the harvest!

A big thank you to John, Mary, Rikki, Jill and Elizabeth for generously sharing their hard-won secrets to vegetable-growing success.

Of course, Master Gardeners are available to answer specific questions through the Denver Master Gardener Helpline at 720-913-5278 or email denvermg @ colostate.edu. Also, please take a minute to review the list of Free CSU Extension Spring Gardening webinars and our new Grow & Give program.

By Jodi Torpey, Master Gardener since 2005
Photos provided by each gardener

Meet the Garden Squad—Gardening Help at the Denver Botanic Gardens

Meet the Garden Squad is a way to get better acquainted with some of our CSU Extension Master Gardener volunteers.

Meet the Gardening Help Volunteers

The CSU Extension Master Gardeners usually pick up the gardening helpline at the Denver Botanic Gardens or answer questions when people walk-in the door. Even though buildings at DBG are closed for now, gardeners can still get their gardening questions answered by Gardening Help from Colorado Master Gardeners at Denver Botanic Gardens, only remotely.

The interest in gardening has soared ever since people have had to hunker down at home and find ways to keep busy. First-time gardeners will likely have questions on how to get started, what to plant now, what can grow in containers, and much more.

Even gardeners with some experience have questions, too. All gardening questions can be emailed to gardeninghelp@botanicgardens.org and a CMG, working remotely, will reply by email.

Gardening Help volunteers include: Back row, left to right: Jan Fahs, Jan Davis, Ken Zwenger, Mark Zammuto, Gordon Carruth, Fran Hogan
Middle row: Lynne Conroy, Harriet Palmer Willis, Kathleen Schroeder, Leona Berger, Cindy Hanna, Mary Adams, Nancy Downs
Kneeling: Dee Becker, Charlotte Aycrigg, Jan Moran
Not pictured: Mary Carnegie, Linda Hanna, Maggie Haskett, April Montgomery, Ann Moore, Kathy Roth, Amy White

Gardening Help is a project of the CSU Extension-Denver Master Gardeners at the DBG. Volunteers provide reliable and research-based information to thousands of home gardeners each year.

Volunteers commit to at least one year in the role, with a minimum of six shifts spread across the year. The commitment starts early in the year with an orientation and training from Nancy Downs, project coordinator.

Many volunteers are GH regulars and they return to the project every year. In addition to being an active CMG, they have to satisfy DBG volunteer requirements, too. That means they’re a member of the DBG and enrolled there as a volunteer.

Some of the key characteristics of GH volunteers are good research, plant identification and diagnostic skills. Because the project is located at DBG, volunteers need to keep on top of what’s blooming at the DBG by season, so they can answer common questions that might pop up.

Photo provided by Nancy Downs

Text by Jodi Torpey
Master Gardener volunteer since 2005

Never Put a $10 Plant in a 10¢ Hole and Other Gardening Tips From Denver Master Gardeners

Passionate gardeners love to talk about gardening, so with that in mind, we recently asked Denver Master Gardeners for their best gardening advice. Responses included tried-and-true practices, creative suggestions and good reminders for all of us as the gardening season kicks into full gear.

As the title of this post implies, we believe that great plants come from appropriate soil preparation. Amending with compost is often imperative as soil in our region tends to lack organic matter. But proceed with caution, as some plants, such as natives, prefer a leaner, less fertile soil. Too rich soil will cause these plants to underperform and often just flop over. It pays to do a little homework before planting, read seed package directions and have your soil tested.

One of our gardeners shared her recipe for amending soil: Add 1/2 a handful of both Alaskan fish pellets and triple super phosphate to half a bucket (such as a kitty litter pail) full of compost. Mix this into the planting hole for strong root development and beautiful blossoms.

A tip borrowed from the Rock Garden Society is to plant bare root. By gently shaking off most or all of the soil that the plant is purchased in, the plant will adjust to the garden soil without the soil interface (or boundary) that can occur between two soil types. Bare root planting promotes healthy root development.

Mulch, mulch, mulch is the mantra of many of our survey respondents as it keeps weeds out and moisture in. Add it like crazy each time you dig in the veggie, perennial and annual gardens and don’t forget container plants too. Small to medium-sized bark chips are popular, practical and pleasing to the eye. Natural mulch options are very effective, including not quite finished compost from the compost bin which will add carbon, feed living organisms, prevent water runoff and prevent compaction. Local arborists are often willing to drop off wood chips which would otherwise fill up the landfill. In the fall, mow over your leaves and spread them throughout the yard, they’ll breakdown by spring and add organic matter to your soil. Consider purchasing a chipper to grind up branches and other garden waste.

Suggestions for responsible use of water include watering when the plant needs it instead of on a set schedule. Soaker hoses, often made from recycled material, are effective for watering plants at the soil line. Plants (even xeric ones)  need moisture to maintain healthy roots and overall strength, but often less than we think. For example, the Water Smart Garden at the Denver Botanic Gardens is watered about seven times during the season.

Weeding can feel like a no-win battle, but attacking weeds after a soaking rain makes the task easier. Pull weeds and unwanted volunteer shrub and tree seedlings when they are small, before they take hold in the ground or develop seed. Add stepping stones to the garden to avoid stomping on plants and compacting soil when working in the garden.

A clever tip to eliminate stubborn weeds, such as the nasty bindweed shown here, is to take a large piece of heavy cardboard, make a cut from the edge to the center. Keep the cardboard as level as possible, slip the vine in the center and spray the vine with the herbicide of your choice or horticultural vinegar, which is sold in garden centers. The cardboard will protect surrounding plants from overspray. Aggressive weeds may require multiple treatments during the season.

One of our members recommends a tomato planting technique passed on through generations of farmers. She adds blackened banana peel to the soil and feeds them with skim milk upon planting and again one month after that. This less conventional practice yields her sweet, abundant fruit. While CSU can’t vouch for the scientific efficacy of this, the banana could be adding potassium and the addition of calcium may reduce the chances of blossom end rot.

Growing tomatoes in containers is recommended for those with limited space. Select varieties which produce smaller fruit such as Patio, Cherry or Sungold. Use a large container (18+ inches in diameter), a sturdy support and a tray with casters. This allows plants to be moved from the path of hail or to optimal conditions. Container plants of all kinds benefit from weekly feeding of 1/2 strength fertilizer.

To keep pests at bay, try a thorough weekly spray of water during the growing season, including the walls of the house and fence. It’s a kinder way to shoo pests away.

If your vines need a sturdier trellis consider building one out of remesh, which can be found at hardware stores. It makes a durable, cost-effective support and can easily be cut with bolt cutters. It also can be attached to supports to create a dog run or create plant cages.

In the flower garden, invest in perennials for texture and dimension and add annuals for bold color. “Enjoy the randomness of some plants that choose their own spots to thrive” suggests one gardener. What a positive way to think of the seedlings that sprout up at this time of the year. Remember, too, that perennials may not come into their glory until the second growing season.

Gardening is a four season hobby. Winter watering of trees and shrubs will help keep them healthy and  veggie gardeners can get a jump on the season by using a cold frame or floating row cover to get an early start on lettuce, spinach and other cool season crops. Fall is a fantastic time to fertilize, aerate and over-seed the lawn. It is also an ideal season to divide perennials so that they settle in and are ready to take off in the spring.  Share your divisions with your neighbors, too, or trade for plants you’ve admired (envied?) in their yards. If you need more gardening space, solarizing or sheet composting is an excellent technique to ready a new garden bed and can be started throughout the year.

And lastly, a veteran gardener advises us to “Remember each little garden flower or planting arrangement is a moment in time. It will change. Don’t worry about it or take it too seriously.”

 

Written by Linda McDonnell with thanks to the many Denver Master Gardeners who shared their advice.

All photos courtesy of http://www.pixabay.com, a source of royalty free images.

CSU Webinar Helps Solve Garden Mystery

Every summer is different in the garden, but this year I found something I hadn’t seen before with two container tomato plants. The new leaves on these  plants was stunted and twisted into odd shapes.

Like many gardeners, I’ve seen plenty of tomato problems in my garden over the years. Early blight, late blight, blossom end rot and insect damage have cropped up from time to time, but these twisted leaves had me stumped.

I looked for images of similar problems online and checked my Tomato MD app, but I couldn’t find anything else that looked like that deformed growth.

In a great gardening coincidence while I was finishing my Colorado Master Gardener continuing education requirements, I clicked on a Small Acreage Management (SAM) webinar, and the mystery was solved.

These SAM webinars are posted on YouTube, so any gardener can watch them for free. The one that helped me diagnose my tomato plant problem is called “Herbicide Carryover and Fall Garden Care” led by Darrin Parmenter of CSU Extension in La Plata County, dated Sept. 4, 2013.

Herbicide carryover can happen when gardeners use herbicide-treated hay, straw or grass clippings as mulch or compost in their gardens. Herbicide carryover can also occur if gardeners apply manure from livestock that ate treated pasture or crops. Tomatoes and members of the tomato family are especially susceptible to herbicide carryover.

I’ve used well-aged horse manure in my garden for years and there’s never been a problem until this season. It turns out that herbicide carryover from horse manure is the top pathway because herbicides can pass through horses so quickly.

As soon as I understood the problem, I started a remediation program to improve soil microbial activity in the two containers with the affected tomato plants. I’ve cultivated the soil to increase oxygen, added a different kind of organic matter to increase beneficial soil organisms and used a home-made organic mulch. I’m also keeping the soil evenly moist and using a liquid fertilizer once a week.

According to Darrin in the webinar, the tomato plants may recover if there’s enough vegetative growth. I’m certainly going to be more thoughtful with how I amend my garden soil in the future.

By Jodi Torpey
A Colorado Master Gardener

Take a Soil Test to Start the Gardening Season

When it comes to growing a garden, if a little fertilizer is good, a lot is better. Right?

Not really. Fertilizer applications should match the needs of the soil and plants. Too much fertilizer, especially applied to smaller areas, can create more problems. One proven way to avoid overfertilizing is to invest in a simple soil test. It’s a tool that gives the most accurate method to tell the fertility of a garden, lawn, field or pasture.

“It’s important to get a soil test to know how your garden will grow over the season,” says Tegan Deeney, a lab tech with CSU’s Soil, Water and Plant Testing Lab in Fort Collins.

“I tested my soil when my pumpkin plants started dying when they were only two inches tall. My soil test showed there wasn’t enough nitrogen nitrate in the soil, and there was a simple fix.” She says a lot of pumpkins grew that year after she amended the soil with the recommended nutrients.

“The earlier you test, the better. You won’t run into the issues of trying to amend the soil around plants,” she adds.

Instead of guessing what your soil needs, a routine garden and landscape soil test will give you the specifics. For the $35 fee per sample, you’ll get results on soil pH, EC (Electrical Conductivity measures the available nutrients in the soil), organic matter, nitrate, phosphorous, potassium, zinc, iron, copper, manganese, boron, lime, and texture estimates.

In 2015 CSU’s Soil Testing Lab evaluated 2700 soil samples from horticulture alone. That total doesn’t include research soils or soil samples from farmers.

A soil test uses samples collected from the yard, garden or field. Soil sample collection kits are available from CSU Extension offices or some garden centers. CSU’s Soil Lab website has soil collection forms, instructions and a list of participating garden centers. For more information contact the lab at 970-491-5061.

A typical sample uses only two cups of soil that’s a combination of 5 to 15 samples (depending on the size of the area). Here are the basic steps for collecting a sample:

1. Use a clean, rust-free trowel or spade.
2. Collect samples at a depth of 6 inches; dig straight down, not at an angle.
3. Take at least 5 samples of soil from the area and combine in a clean plastic container.
4. Remove about two cups of soil and allow to air dry.
5. Place the sample in a CSU soil container or a sandwich-size plastic bag.
6. Seal and label with name, address and location of the sample.
7. Send the sample to the testing lab.

The turnaround time for results is about two weeks. Results will be mailed to you or include an email address for a faster reply. The lab results will tell you which nutrients your garden needs or if there’s an overabundance of nutrients.

With all the time, money and effort it requires for successful planting and growing, it makes sense to invest in a simple soil test. Consider it a gardening investment, almost like buying a plant insurance policy.

By Jodi Torpey
Denver Master Gardener

Decoding Fertilizer Labels

On a recent visit to a garden center, a customer was overhead asking  about the prominent numbers on the front of the fertilizer package. What  does  13-25-12 mean?

The numbers correspond to the percentages of three different compounds: Nitrogen, Phosphorous and Potash (or Potassium). Each can contribute to plant health. Nitrogen, along with other nutrients, helps plant foliage grow strong. It is used in large amounts by plants. Ever notice your lawn has a growth spurt after fertilizing? That’s likely Nitrogen at work. High Nitrogen fertilizers  make for quick growth but weaker plants, which can more easily succumb to pests and diseases

Phosphorous helps plants develop strong roots and abundant flowers and is very beneficial to sandy soils, which are common in Colorado. Phosphorous does not leach out of our soil, so continual additions are not needed in the landscape.

Potash aides in overall plant health. Front Range soils have ample potash, so it is not advised to add more in our soils. It won’t help either your garden or your wallet.

So which is best?   There is no one-size-fits-all answer, but in general:

• Lush, flowering garden pots benefit from weekly feeding of water-soluble fertilizer high in phosphorous.
•  Houseplants can benefit from fertilizers with equal numbers of each nutrient.
•  In the garden, it is best to get your soil tested. Information can be found at: http://www.soiltestinglab.colostate.edu/. This will greatly help you add the correct nutrients for your soil and growing needs.

A word of caution: More is not better. Always follow the application instructions and give the plant time to absorb the nourishment.

Lots more information on fertilizers and soil amendments can be found at:  http://www.ext.colostate.edu/mg/gardennotes/234.pdf