×

Master Gardener: Autumn, the not so dormant season

Have you made a list of your fall garden chores?  Fall is a busy time for gardeners. Here is a short-list of projects to prepare the garden for winter. Focus on lawn repair, planting, leaves, a general garden clean-up, pest control, pruning, mulching, and garden tool clean-up.

Lawn repair: What you do in the fall prepares that lawn for a gorgeous spring. Fall is the best time for serious work on the lawn. Plan to get your grass seed and fertilizer down by early September to mid-October. Prepare the site by getting rid of weeds and loosening the soil by raking or with a core aerator. Keep new seedlings moist by sprinkling one to three times a day. Give established lawns one inch of water a week during the growing season (fall and spring). Mow correctly–about 3 inches high–with a sharp mower blade.

Insects abundant in the fall: Fall is the time many insects lay eggs to prey on your garden next spring, but don’t be too quick to spray insecticides. Be sure you know what the insect is; is it beneficial or harmful? Not all pesticides are effective on all insects or an insect may be susceptible to the pesticide only at certain times of year or stage of development. Never apply pesticides randomly, “just in case.”

Here are a few insects that you should try to take care of:

Late August is the time to think about doing battle with Japanese beetles. In July, the adult beetles burrow into the ground to lay their eggs. The white grub larvae hatch, feed on grass roots, overwinter deep in the soil, and emerge in late spring the following year. The University of MN recommends ausing either a biological treatment like Milky Spore or a chemical insecticide at this time of year. They caution gardeners to first verify an infestation (five or more grubs per square foot of soil) and to apply a pesticide only when grubs are actively feeding near the soil surface.

Webworms: make their nests in trees in the fall. Pull the nests down and let the birds enjoy eating the worms. Look for bagworms: By September, the female has laid her eggs and the larvae have spun the protective bag where they will overwinter, emerge as caterpillars in summer, and devour the plant foliage. The best defense in the fall is to remove the bags by hand. Insecticides won’t penetrate the bagworm nests in the fall.

Other insects like scale, lacebugs, and spider mites. These insects lay their eggs in fall and overwinter on branch stems. The most effective time to treat with insecticidal soap or horticultural oils is when the crawlers emerge in the spring. Watch for scale on susceptible plants. Spider mites, which prefer spruce, fir, and junipers, thrive in drought conditions. Their damage is often not apparent until the heat of summer.  

Fall is a good time to plant: Trees and shrubs. Fall is the right time to add new plants to the garden. Get them in the ground by mid-October. Their roots will grow all winter and jumpstart the plants before spring. Just be sure to keep new plants watered until the ground freezes. 

Bulbs: Choose from an amazing variety of colorful, showy bulbs (daffodils, tulips, crocus, and more). Get your spring-blooming bulbs planted in October or November.

Perennials: Are your perennials crowded? Are their centers dying out? Now’s the time to divide them (or plant new ones). Divide by digging up whole clumps, then cut or separate them with a spade or knife. Ornamental grasses are an exception. Plant or divide them in late spring. 

Annuals: Plant pansies, snapdragons, and ornamental cabbage in September for some fall color in your flower garden. 

Cool season veggies: Plant a fall vegetable crop mid to late August. Include lettuce, spinach, kale, collards, broccoli, and onions. Keep your tomatoes producing until frost by maintaining your watering schedule.

Plant correctly: You may buy plants in containers that are root bound, especially at the end of the growing season. Be sure to loosen their roots before planting. Slice a small amount off the bottom of the root ball and loosen the side roots by rolling the root ball around in your hands. Cut into the center of the root ball from the bottom and gently pull the roots apart. When you put the plant in the ground, spread the roots outwards in the planting hole. Remove burlap, straps, and wire baskets before planting trees and shrubs not container-grown.

Planting container-grown trees and shrubs. Do not plant too deeply. The top of the root ball should be at or just above the surface line of the ground. The planting hole should be twice as wide as the root ball, but doesn’t need to be deeper. Break up the dirt you’ve removed from the planting hole into fine particles and reuse it. Mix in some compost or a soil amendment. Water to settle the soil and mulch.

Prepare spring flower and vegetable beds: Fall is a great time to prepare spring planting beds. Work some organic matter into a raised, tilled bed and let it rest over the winter. The organic matter will continue to decay and enrich the soil. Next spring, you’ll be rewarded with a garden ready to plant.

Shredded leaves as garden mulch: Leaves, we have lots of them! Shred them with a lawn mower or shredding machine, put them in the compost pile, and later work the decaying leaves into your soil to enrich it. In late fall, pull dead leaves out of shrubs in order to keep interior branches aerated and healthy. A thin layer of shredded leaves also makes great mulch. Use leaves to cover dormant perennial beds and vegetable gardens over the winter–then remove wet, compacted leaves in the spring from emerging plants.

Pruning: There is no need to rush to prune shrubs in the fall when the weather cools, but do remove dead or diseased branches from both trees and shrubs. Pruning technique and timing vary by tree and shrub type.

The best time to prune trees and most broadleaf shrubs is when they are dormant in the winter. Try not to remove more than one-third of shrubs in any one year. Prune summer-flowering shrubs. Note: Most conifers will not regenerate new growth if their branches are cut back into old, brown wood; but if your conifer is misshapen from the previous season’s growth, trim away excess growth. Conifers, however, are best pruned as new “candle” growth appears in June and July, cutting only about one-third of the emerging candle before the needles unfurl.

Prune spring-flowering shrubs after they flower–usually no later than early July. If you prune these shrubs in fall or winter, you cut off all the lovely spring buds. Hydrangeas demand their own unique pruning schedule, so identify your variety and take time to research before you cut. Cut back ornamental grasses to the ground just before new foliage shoots emerge.

General garden clean-up: Remove dead or diseased plant materials–especially spent annuals–before winter. Leaving the plants on the ground to decay only invites insects and disease to your garden. If the plant material is disease free, chop it up and toss into your compost pile. You can leave some plants, such as asters, coreopsis, rudbeckia, and Echinacea, until spring. The seed heads provide winter interest in the garden, as well as food for the birds to enjoy. Now is the time to dig bulbs that won’t reliably overwinter in our climate. These include dahlias, caladiums, cannas, and gladioli. Bring in houseplants, but be sure to check them first and wash off any insects you find. Hydrate young trees, shrubs, and new plantings well before winter.

Mulch: Adding a couple inches of mulch to new plantings will help insulate against cold and lack of moisture. Existing landscapes do not necessarily need a yearly application of fresh mulch. If you do need to add mulch, wait until all the leaves are off your trees and you’ve thoroughly cleaned up the flowerbeds. Add only 2 to 3 inches. Keep it pulled slightly away from the trunks of trees and shrubs to discourage voles, and never pile mulch up around a plant like a volcano. Mulch adds organic matter to the soil, controls weeds, and conserves moisture.

Clean and sharpen garden tools before winter: Before you put your tools away, thoroughly clean them, sharpen the edges, and apply oil to hinges so your tools will be ready to use in spring. Disconnect and drain your hoses before below-freezing temperatures.

——

Resource: University of MN, University of Nebraska, Beth Leonard, Extension Master Gardener

Newsletter

Today's breaking news and more in your inbox

I'm interested in (please check all that apply)
Are you a paying subscriber to the newspaper?
   

COMMENTS

[vivafbcomment]

Starting at $4.38/week.

Subscribe Today