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If you leave the dead tops of perennials until spring instead of cutting them back in late fall or winter, it can be impossible to cut back the dead tops and clean out perennial beds without damaging the new spring growth.

Courtesy Meredith Seaver, USU Extension

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Thick layers of leaves aren't healthy for lawns. Fall leaves should be mowed frequently with a mulching mower or removed and composted.

Courtesy Meredith Seaver, USU Extension

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Tomatoes that are full-sized and mature but still green can be harvested before a frost event and brought indoors to ripen off the vine.

Courtesy Meredith Seaver, USU Extension

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Evergreen trees and shrubs need a deep soak in late November to avoid leaf or needle damage, like the desiccation on the tips of these fir needles, during our dry winter weather.

Courtesy Meredith Seaver, USU Extension

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Autumn is here, and many are starting their annual fall yard cleanup. Here is a list of things to do plus some to avoid.

Trees and shrubs

Many like to prune trees and shrubs in the fall. This is not the time of year to do this because pruning delays dormancy in woody plants. They want to try to regrow their missing branches. It is always fine, though, to prune out dead and diseased limbs or limbs that pose some sort of hazard. If you are very tempted to perform unnecessary pruning, turn your loppers over to a responsible party until at least mid-January. Additionally, do not fertilize trees and shrubs in the fall. Like pruning, fertilization also delays dormancy. Mid-March to early April is the best time to fertilize, but only if trees and shrubs need it (most ornamental trees and shrubs don’t).

Conifers and other evergreen plants

Do not allow pines, spruce, fir and broadleaf evergreens such as boxwood to go into winter with dry soil. Because they keep their needles or leaves through the winter, they continuously lose water at a slow rate through the winter. If the soil is dry, needles and leaves dry out due to the water not being replaced and turn brown by spring. Drought stress also makes them more susceptible to pests and diseases. A deep soak in late November plus a 3-inch layer of bark mulch over their root zones helps avoid this problem.

Lawns

In late October or early November, mow the lawn to a height of 1 ½ to 2 inches. This keeps the lawn from matting down under a blanket of snow and helps prevent a lawn disease called snow mold. Snow mold thrives at temperatures just above freezing and in low oxygen environments. The most important lawn fertilization of the year is the late fall fertilization in late October or early November. You do not need to purchase a special “winterizer” fertilizer, though, if you still have what you used during the summer. The lawn cannot read the bag of fertilizer and won’t know whether you used “winterizer” or not. A standard bag of 20-0-0 or whatever you have is fine.

Hard-to-kill weeds

Some of the hardest-to-kill weeds are perennials such as field bindweed (erroneously called morning glory) and white top. Like other perennial plants, they are drawing nutrients from the leaves down into the roots. If these weeds are sprayed with a weed killer, the likelihood of them being killed is much greater because the active ingredient from the weed killer will be stored in the roots and have all winter to do its job. For grass, use a lawn-safe herbicide. For other areas, use glyphosate or another systemic herbicide registered for use where you are going to spray. Unfortunately, it is not effective to use organic herbicides for this purpose because they are not systemic and will not be absorbed into the roots.

Annuals and perennials

Allow annuals to be killed by frost before removing them. Many will last until November. Perennials can be cut to within a few inches of the ground once their tops are killed by hard frost. Compost or send spent annuals and perennials to green waste, if available.

Vegetable gardens

Remove or turn under warm season crops like tomatoes and peppers once they are killed back by hard frost. If green tomato fruit is picked before frost, it can be stored indoors at 55 degrees for several weeks. Bring a few tomatoes at a time into a warmer room. The fruit will turn red and ripen in five to seven days.

Ten timely tips for October from Master Gardeners

1. Watch the 10-day forecast. Be prepared to protect or harvest warm season vegetables before the first frost.

2. Wait until morning dew has dried before collecting flowers for pressing, hanging, freeze drying or preserving them in silica gel.

3. Clear away weeds, clutter and debris to reduce pest issues next season. Turn under or compost dead vegetable plants, spent annuals and trimmed perennials.

4. Clean garden tools, disconnect hoses from spigots and bring tools, hoses, fertilizers, yard art/décor and other supplies into a protected, dry storage area.

5. Dig up tender bulbs, tuberous roots and corms such as dahlias, calla lilies, begonias and canna lilies for indoor winter storage in a cool, dark, dry place. Check monthly.

6. Plant tulips, daffodils, crocuses and other spring blooming plants/flowers.

7. Fall is also a good time for planting trees and shrubs.

8. Keep lawns clear of leaves by collecting and composting the leaves or by frequently mowing with a mulching mower.

9. Winterize mowers and rototillers. Also, winterize your sprinkler system.

10. Evaluate your garden season. Make notes of what worked, what didn’t and what to do differently next year. Write it down!