Low-Water Vegetable Gardening in Colorado

By Felicia Brower, CSU Extension – Denver Master Gardener since 2020

Water and vegetables go hand-in-hand. The more water you give to your growing vegetables, the bigger and better tasting the harvests tend to be. As water restrictions become common and conserving water becomes more important than ever, it’s going to be crucial for gardeners in Colorado to figure out how to resourcefully use water if they want to keep growing fresh vegetables.

There are a few key ways to cut back on water in the garden. Simple things like choosing vegetables that can survive (and even thrive) using less water, maximizing the water that you do use, and preventing water loss are all ways to keep your garden looking great without relying on excess water.

Chives are always the first thing to pop up in spring without any supplemental water. Photo by Felicia Brower

When it comes to choosing what to grow in your garden, it’s important to remember that different vegetables require different amounts of water. Vine crops need less water (and actually tend to be overwatered in the home garden), while beans and sweet corn typically need more water than other types of vegetables. Many perennial herbs don’t require a lot (if any) supplemental watering to do well. My parsley, chives, sage, thyme, and lemon balm are the first things to show up every year in my garden without any extra water to help them grow.

Not only do vegetables have different water needs, but some also need more water during certain parts of their life cycles. For example, peas need more water during their pod filling period while tomatoes need more water during flowering and fruiting. 

It’s also important to choose regionally-adapted vegetables. Vegetables that are selectively bred to excel in areas where drought is common are more likely to have fewer issues when they’re watered less in the home landscape. Search online for Colorado seed companies and choose vegetable varieties that are drought tolerant. While beans can often be huge water users in the garden, varieties like Zuni Gold, Paiute Gold tepary, and Sonoran White tepary are drought-tolerant and grow well without needing huge amounts of water. In fact, during some of my drier years, they stayed greener and kept producing while their neighbors wilted and struggled. 

Zuni Gold beans, a southwest Pueblo variety, are highly adaptable and drought tolerant, making them a favorite in my home garden.
Photo by Felicia Brower.

One of the best ways to conserve water is to maximize water efficiency. If possible, install in-ground drip irrigation or use cost-effective soaker hoses so that your water reaches the roots of the plants instead of being wasted on foliage or in spots without anything growing. Water at soil level near the roots in the morning, avoiding the heat of the day, to reduce the amount of water lost to evaporation and to avoid issues like powdery mildew on the leaves of your plants. 

Here are a few additional ways to grow a low-water vegetable garden: 

• Different soil types have different water needs, so water according to your specific soil type. Loamy soil needs deep, infrequent watering instead of regular, light daily watering while sandy soils need more frequent, less deep watering because they lose water faster than clay soils. 
• If you use overhead watering, don’t water your plants on very windy days. The wind will blow your water away and prevent it from reaching the roots. 
• Before you do any watering, test your soil’s moisture level. The surface of the soil might be dry but the roots might not be.
• Your garden layout can also impact how much and often you have to water your garden. Narrow rows need more water, so grow your veggies in beds, grids, or wide rows. 
• As with any plants in your home landscape, plant vegetables with similar water needs together. If you have a mix of drought tolerant plants and high-water plants, make sure they’re kept separate so you don’t overwater or underwater, both of which cause stress and can impact the quality of your harvest.
• Use mulch (green or otherwise) to keep moisture in the soil. You won’t have to water as much if you grow intensely (close together) or use another organic mulch to slow down evaporation. 
• Grow during Colorado’s shoulder seasons to take advantage of moisture from snow and spring rains and cooler temperatures, so there’s less water loss due to heat.
• Before you plant anything, take time to amend and prep your soil. Healthy soil retains water and is full of nutrients that prevent you from overwatering to try and make your plants stronger. 

As water conservation becomes more important in the west, it’s crucial to find ways to use less, especially for things like growing food. Follow CSU’s Colorado Vegetable Guide and the “Water Conservation in the Vegetable Garden” GardenNotes chapter for advice on best low-water vegetable gardening practices. 

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!

Gardening in Colorado’s Warmer, Drier Climate

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

As we begin 2022, Denver just had its first big snow of the season. It finally comes amid an extreme drought, blamed largely on climate change, and the day after the massive Marshall fire on Dec. 30, the most destructive fire in Colorado history.

As our climate warms, drought worsens and moisture and weather patterns become more unpredictable, it is greatly impacting how gardeners in Denver and beyond approach what they grow and how they garden.

Lucky for us, as people who are passionate about plants and soil, we can help create climate resiliency through our home and community gardening efforts. It’s one reason I’m so drawn to gardening. During these wildly unpredictable times, it feels like something I can do to have a positive short- and long-term impact on my neighborhood and community.

Stacks of books could be written on this topic, but I’d like to offer a few ideas on how we as gardeners can work with our changing climate to grow successfully and in ways that help create higher-quality living environments in the face of more extreme weather.

1) Build up the soil.

Whether you’re planting directly in the ground or in containers, focus on building healthy soil. The healthier the soil, the stronger plants will grow and, if you’re growing food, the more nutrient-dense that food will be. Healthy soil, packed with microorganisms and earthworms, is also vital to sequestering carbon.

Plants grown in healthy soil are more pest and disease resistant and overall have better outcomes. For information on how to build healthy soil in your gardens, see this PlantTalk Colorado article, “Maintaining Healthy Soils”.

Building healthy soil with compost and other amendments creates nutrient-density and plant resilience. Photo by Molly Gaines

2) Plant trees — and be sure to water them adequately.

A New York Times headline on this topic last summer caught my eye, “What Technology Could Reduce Heat Deaths? Trees” (July 3, 2021, by Catrin Einhorn). Scientists have found that trees can lower air temperature in city neighborhoods 10 degrees, reduce electricity demand for air conditioning, save money and emissions and help avoid massive power failures during heat waves, according to the article.

For more on proper tree planting, particularly in urban environments, see a post I wrote last fall, “Fall Tree Planting Considerations and Tips.”

In Denver, particularly during extended periods with no to little moisture, year-round watering is critical. Most homeowners don’t water their trees enough, which leads to poor tree health, wind damage and premature death. The general rule of thumb is 10 gallons of water for each diameter inch of the tree’s trunk.

For additional winter watering information, see our recent post “Winter Watering.”

Healthy urban trees in their fall glory. Photo by Molly Gaines

3) Use native, drought resistant perennials for landscaping.

Plants that are native to Colorado are already naturally adapted to our growing conditions. They will require less water and fertilizer and be more resistant to pests and disease.

As water becomes scarcer, minimizing water usage for landscaping will become more critical. Landscaping our yards and gardens with native plants can lessen our overall usage of water.

4) Grow a vegetable garden.

Planting a garden and growing some of your own food for friends and neighbors is a wonderful way to lessen your impact on the environment. It helps cut down on carbon emissions, reducing the amount of food that travels on trucks for miles to the grocery store.

When food is grown with minimal chemical inputs, it also reduces toxins in our environment and increases the number of pollinators around our homes and communities, providing them safe habit and more balance in our ecosystem.

A bounty of vegetables grown in a modestly sized home garden. Photo by Molly Gaines

As gardeners, particularly in Colorado, we are used to planning, tending, working with nature and being flexible in the midst of adverse weather. Our warming climate and more extreme weather events will make these skills more imperative than ever before.

Keeping these ideas top-of-mind will help us all grow successfully, while also experiencing the joy and respite our gardens bring during these challenging times.

Winter Watering

By Uli Klein, CSU Extension – Denver Master Gardener since 2019                                                

After the fall clean-up is complete and our sprinkler systems are winterized, it’s easy to think the gardening season is over and it’s time to bask in the late autumn sunshine. Because the visible parts of plants go dormant in late fall, it is very easy to overlook the importance of off-season moisture. But to ensure the health and longevity of the landscape, it’s wise to keep an eye on the amount of moisture received during the next several months. In Denver, relying solely on fall and winter precipitation alone can be insufficient for trees, shrubs, turf, and perennials.

According to the graph above, the average amount of annual precipitation in Denver is ~14 inches and varies significantly from year to year. For example, we received 26 inches of precipitation in 2015, but only 9.5 inches in 2020. November through February are often the driest.

How does lack of moisture affect trees and plants?

Under continued dry conditions, the delicate hairs on feeder roots can eventually be permanently damaged and unable to absorb water or transport nutrients. Most root hairs are in the top 12 – 15 inches of the soil and often extend beyond the dripline. These roots provide moisture to the upper parts of the tree. If these structures cannot supply enough water, leaves will wilt at first; and if drought conditions continue or worsen, twigs or entire branches may die. This loss of branches is a tree’s attempt to resize the canopy in relationship to how much water the roots provide and is called dieback. I’ve often spotted dieback on trees in Denver parks. This University of Kentucky article further explains how dry seasons affect woody plants.

Evergreen affected by drought conditions. Photo by Uli Klein

In the spring of 2020 many Denver trees, especially pines and arborvitae, died from a combination of pronounced temperature swings, unseasonably cold temperatures, and a mid-winter drought. Signs of stress are not typically visible until spring, when evergreen needles yellow or drop, or in severe cases, plants are lost.

Tree with minor dieback. Photo Uli Klein

Tree with major dieback. Photo by Uli Klein

Newly planted trees and shrubs are particularly vulnerable to extreme conditions and need extra TLC during the cold seasons. To fully establish, trees generally need one growing season for each inch of trunk caliper. During that time, they are particularly sensitive to lack of moisture, temperature swings, and strong, drying winds.

Herbaceous perennials can also suffer from lack of moisture, although the damage is less eye-catching than that exhibited by shrubs and trees. While it is easier and less costly to replace a perennial than a large tree or conifer, replacement plants will likely be smaller, take time to establish, and are unnecessary expenses.

Our lawns will also benefit from watering during prolonged dry periods of 4–6-weeks. Find tips for winter care at Lawn Care – 7.202 – Extension (colostate.edu).

When deciding how much to water, take local factors into account: A good layer of mulch reduces evaporation and helps plants to retain more moisture, while those in more wind-prone sites and/or facing south-west require extra moisture. BTW: 10” of average snow, 4 to 5” of wet snow, or 15” of powdery snow are equivalent to 1” of rain.

Let’s recap the facts

• In Colorado, the winter months (November through March) are often the driest.
• Precipitation varies from year to year – monitor local weather conditions.
• Make newly planted trees, shrubs, and perennials a priority since they need more moisture than established ones.
• Don’t forget that your lawn needs extra water.
• Healthy trees and plants are an asset that are under-appreciated until they need to be replaced.

Tips for winter watering

• Water only when it’s above 40°F, ideally around midday so the water is absorbed before nightly temperatures dip.
• Apply a gentle stream of water, either from a watering can or a hose with a watering wand, so the water soaks in and doesn’t pool.
• In dry conditions, all plants (trees, shrubs, perennials, turf) benefit from extra water from October through March. Pay particular attention to recently planted specimens or those in windy locations or south-west exposures.
• A good layer of mulch reduces watering needs.

How much water is needed?

Trees

• Approximately 10 gallons of water per each diameter of the tree trunk per month (i.e., a 2” tree needs ~20 gallons/month) distributed at several locations within its dripline.

Shrubs

• Newly planted:  approximately 5 gallons every 2 weeks.
• Established <3ft: approximately 5 gallons per month.
• Established >6ft: approximately 18 gallons per month.

Final thoughts

Preparing this blog has really motivated me to do the right thing for my plants this winter season. I hope that it will convince you, the reader, that winter watering is worth the effort and preserves precious plants. Therefore, fellow gardeners, keep your watering can at the ready!

Additional references

https://www.canr.msu.edu/news/how_do_trees_survive_in_the_winter

https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/

https://planttalk.colostate.edu/topics/trees-shrubs-vines/1751-fall-winter-watering-drought/