As the second and third weeks of April demonstrated, Colorado weather is changeable, and we can have spring-like weather in winter, followed by winter-like weather in spring. With a generally dry climate, and desiccating winds occurring year-round one of the best ways to lessen the impact on plants is with mulch.
You don't have to be a specialist to improve your plants' situations with mulch. Mulch is any material that provides protection and may also improve the soil. Mulching reduces soil moisture loss, improves water and air penetration into the soil, and keeps soil temperature above freezing until later in the fall (especially important for fall transplants). It can reduce frost heave, and delay spring growth, which protects bulbs such as crocus from premature emergence. When used for this purpose mulch should be applied after the ground has frozen. When used to protect fall transplants it should be applied soon after transplanting. If mulch is being used to keep weeds down, for general insulation against heat and to retain moisture, or for appearance it can be applied anytime. Because of cost and work involved choose mulch that will break down slowly. For safety, don't use anything that could be a fire hazard.
There are two categories of mulch: organic and inorganic/inert. Organic ones include wood and bark chips, straw, grass clippings, seed hulls, leaves, pine needles, sawdust, cocoa-bean hulls, crushed corncobs, peat etc. Inorganic/inert mulches include gravel, stone, clay aggregates, plastic and weed barrier fabrics. The choice depends upon the purpose of the mulch. Sometimes a combination of organic and inorganic mulch is used. The inorganic/inert mulches may be the best choice for appearance and weed control. Clay aggregates are available in gray/brown colors, are lighter than gravel, but can be expensive. Gravel and stone are also available in colors and are inexpensive, but will not prevent the growth of some weedy grasses. Rock mulch often radiates heat, however, and can increase plant stress. Black plastic should not be used around trees and shrubs. Weed barrier fabrics allow air and water penetration to the soil, reduce weeds, and are long lasting if covered with mulch.
Organic mulches are advantageous because they can improve the soil -- a plus in Colorado because of high clay content in many areas -- and improve aeration and water-holding capacity. Earthworms and other soil organisms will help incorporate the organic component into the soil. Cocoa-bean hulls and shredded bark are relatively expensive, however along with wood chips and shavings they are long lasting. Leaves, grass clippings, crushed corncobs, and shredded bark become matted or compacted. Cocoa-bean hulls, peat, and fine sawdust may crust on the surface. Pine needles are the best for winter protection of fall transplanted items. Unless you want to see your mulch taken by our high winds, consider the weight and location of the mulch.
As organic mulch decomposes, some of the soil nitrogen in contact with the mulch is used by the breakdown organisms, which may cause temporary nitrogen deficiency. Yellowing -- primarily of the lower leaves -- is a sign that this could be occurring. Nitrogen should be added in the following ratio: two pounds of a complete fertilizer, or one-fourth pound of ammonium nitrate, for every 100 square feet of mulched area. Never use weed-and-feed type fertilizer in mulched areas.
For further information on mulch, see Fact Sheet #7.214 - Mulches for Home Grounds, #7.228 - Xeriscaping: Creative Landscaping and #7.225 - Landscaping for Energy Conservation. You can also call Planttalk Colorado toll free at 1-888-666-3063 and select #1905 - Mulches.
Q: What are some good grass choices for naturalized wildflower gardens?
A: Blue grama and side-oats grama are good. They are clump-forming natives that grow well in our conditions and will not choke out the wild flowers.
Q: We would like to plant flowers under our crab apple tree but there's not much soil. Will it damage the tree if we add soil to make a flowered?
A: Soil added around a tree base acts as a blanket and prevents much needed oxygen from reaching the roots. Adding as little as 4" of soil can be harmful. In addition most tree roots grow in the top 18 inches of soil. Tilling the soil around the tree for planting flowers can be damaging to small roots that absorb water and nutrients for the tree.
Q: My lawn is greening up slowly. What should I do for it?
A: Some lawns take longer than others to perk-up in the spring. However, core aerating will encourage healthy roots and reduce compaction. Apply a slow release nitrogen fertilizer if you didn't fertilize last fall and mow the grass to a height of 2 to 3 inches. This will also encourage deeper roots.
Q: I am considering purchasing zoysia grass for my lawn in Fort Collins. Is this a good choice?
A: Zoysia grass is not recommended for home lawns in this area. It is subject to winter kill, is slow to establish (2 - 3 years), and stays brown 2 to 3 months longer than blue grass. It is subject to rust and fairy ring disease and does not grow well in shady areas.
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