By Terry Deem-Reilly, CSU Extension-Denver Master Gardener since 2003
Congratulations! You’ve decided to plunge into gardening, which will improve your diet, health, property values, and mental equilibrium. Before wielding that spade and acquiring your plants, however, you’ll want to consider some facts about Colorado gardening that will ensure a productive and stress-free (well, mostly stress-free) first year.
Firstly, Colorado is an unusual place to grow a garden. It’s at once one of the easiest and one of the most challenging locations to cultivate plants. Knowing a few facts about our growing conditions and planning to how to cope with them are the first steps in a happy garden experience. Here are the basics about our growing conditions:
- The average elevation of locations in Colorado is 6800 feet above sea level.
- High elevation equals intense sun and low humidity.
- Colorado experiences drastic temperature swings, sometimes within the same day.
- Soil is characterized by high pH and clay texture, so tilth (ability of the soil to support plant life) is poor, namely:
- A high concentration of calcium carbonate in our soil raises pH (ratio of acidity to alkalinity) above the neutral level of 6.0-7.0; and
- Clay soil contains small pore spaces, making drainage slow and limiting root growth and oxygen content.
- Untimely, damaging snows occur in the spring and fall (remember the snow just before Memorial Day last year?).
- Our growing season begins about May 15th and ends around October 15th – that’s only five months between the last frost of winter and the first frost of fall. This makes vegetable gardening particularly daunting.
For a more detailed discussion of Colorado gardening challenges, consult the Extension Fact Sheet Colorado Gardening: Challenge to Newcomers (natives will like it, too!).
Secondly, employing these strategies will minimize the difficulties and maximize the results in your first Colorado garden:
- Test the soil. The CSU Soil, Water, and Plant Testing Laboratory has (yay!) reopened. Click on the link for information on preparing and submitting samples and get yours in early – the lab gets a lot of business. Results include recommendations for soil management and fertilization.
- Amend your soil as needed. The correct amendments will add organic matter, improve aeration and water infiltration, and encourage the growth of useful organisms like bacteria, fungi, and earthworms. Use caution with manure-based composts that may be high in salt, wood chips that consume nitrogen while decomposing, and biosolids that contain pathogens and chemicals. For more details on selecting and using soil amendments, consult the Extension Fact Sheet Choosing a Soil Amendment. Bear in mind that minerals like iron and nitrogen are inaccessible to plants in our soil and must be added in formulations that the roots can absorb.
- Apply the principle “right plant, right place” by selecting plants appropriate for our region and siting them in the proper soil and sun/wind exposures. Consider the plants’ requirements when shopping – check plant tags and catalog descriptions before making your purchases. And remember to group plants with similar needs in the same area of the garden; avoid placing roses that need regular irrigation and fertilization among native grasses that will perform nicely without either.
- The advice given by clerks at Home Improvement Megastore notwithstanding, we CANNOT change the pH of our soil. If you’re really dying to have a holly, blueberry, or other acid-loving plant in your garden, consider growing a dwarf variety in a large container with a soil composed of planter’s mix and peat moss. (Container plants require protection or a move into the garage in winter temperatures.)
- Mulch, mulch, mulch nonxeric plants to a depth of about two inches – this includes vegetables!
- Water appropriately. Newly planted trees, shrubs, and perennials, including xeric varieties, require correct watering in their first summer and winter watering in dry periods. Vegetables need water at least once a day in hot weather, often twice a day if they’re grown in containers. Consult this PlantTalk Colorado™ script for some irrigation tips for trees and shrubs.
- Use season extenders like hot caps, row covers, and cold frames to lengthen our short growing season at both ends.
- Learn which vegetables are cool season (greens, chard) and warm season (tomatoes, peppers) and when to plant both.
- When caught in a quandary, always, ALWAYS rely on research-based information to answer your questions; these resources are your source for science-based solutions to garden problems:
Ask Extension (Colorado)
Colorado State University Extension (posts and fact sheets)
Gardening Help at Denver Botanic Gardens
firstname.lastname@example.org or 720-865-3575