Consumer Horticulture Agent
Milwaukee County University of Wisconsin-Extension
October is a month of preparation for winter. It’s a race against time since the weather can turn wintery at any time. The killing frost hits the southeastern part of the state last, usually sometime around the third week of this month. Earlier light frosts will still do in tender impatiens, begonias, basil, tomatoes and peppers unless they are blanketed for the night.
Wait to dig and store dahlias, cannas, tuberous begonias, caladiums and gladiolas until they have died back. Harvest winter squashes and gourds before a frost if you wish to store them for later use.
Drain the hoses and empty the bird baths before a hard frost. Potted perennials can be buried in an empty part of the vegetable garden or surrounded with a thick layer of straw to get them through the winter.
Remove and destroy any plant debris that might have been infected with powdery mildew, tomato leaf spot diseases, scab or any other disease. When the frost kills everything else, chop it up and add it to the compost pile.
Look for information on the Wisconsin Horticulture website at http://hort.extension.wisc.edu. Use the search box or the drop down menus. You can send in a question to ask the experts in your county. Milwaukee County residents can get assistance with plant questions and problems by e-mailing to firstname.lastname@example.org. Searching on the internet is most reliable when you add the suffix “site:.edu” to your search.
All lawn fertilization should be completed by now. This is the new recommendation that resulted from recent research by UW-Extension specialists. September 1st or Labor Day weekend should be the last fertilizer application of the year. Research shows that after that, the percentage of nitrogen taken up by the grass decreases dramatically and is, therefore, a waste.
The new recommendations for lawn fertilization also include applications around Memorial Day and Independence Day on July 4th. When you include Labor Day, these three applications and the clippings you leave on your lawn are all the nitrogen needed for the year. Another new finding is that every application should be of a fertilizer product high in slowly soluble nitrogen such as urea or organic products.
Lawn fertilizer research also led to the recommendation that established lawns that have been regularly fertilized for up to 15 years, need only half the fertilizer. Either apply half the amount at all three applications or only fertilize at Memorial Day and Labor Day.
Broadleaf weeds in lawns and gardens are most effectively controlled by spot treating with a broadleaf weed killer after the first light frost or when the night temperatures have dipped into the 30’s for three nights in a row. This will kill dandelions, creeping Charlie, clover, etc.
For perennial grassy weeds like quackgrass you will have to use a non-selective, total vegetation killer such as Roundup. In lawn areas, this will also kill the surrounding grass and leave dead spots in the lawn. Try to keep these as small as possible so that the vigorously growing grass in the spring can quickly fill them in.
Dethatching or core aerating your lawn may be done in spring and fall while the grass is growing vigorously so that it has time to recover. Dethatching can help invigorate lawns that show ½ inch of thatch or more. Lawns with thick thatch layers on compacted soils will need core aerating. Cores should be 2 to 2 ½ inches deep and spaced every 4 to 6 inches to provide maximum benefit. Vertical impact coring machines may be needed to penetrate. Remove debris produced by dethatching but DO NOT REMOVE the plugs deposited on the surface by core aerating.
Collect soil samples now for testing to prepare for next year’s fertilization of the lawn, the vegetable garden, the shrub border and flower beds. Submit separate samples for distinct areas used to grow different types of plants and where growing conditions are different for the same plants. A shady lawn area on a slope should be a different sample than a sunny lawn area.
Dig and divide spring and summer flowering perennials now. Late summer and fall flowering ones can be done in the spring. Cut foliage back, fertilize and water well. Wait until the ground has frozen to add new mulch for winter protection during their first winter.
Amaryllis should be allowed to thoroughly dry down and then rest for three months in a cool location.
Poinsettias carried over from last year need complete darkness from 5:00 p.m. until 8:00 a.m. every night for their colorful bracts to develop. Daytime conditions should be bright, warm, and kept moist.
With the cooler temperatures now, Thanksgiving and Christmas cacti will set flower buds if allowed to dry out thoroughly between waterings for about one month. They do not require dark nights like poinsettias.
Cyclamen also need cooler temperatures. Gradually increase water to stimulate buds.
Collect and dry colorful fall flowering weeds, grasses, seedpods and other plant remnants. Check into microwave drying because it allows some of the more tender flowers to be dried intact without losing their color.
If you haven’t already done so, buy and plant those spring flowering bulbs. Technically, bulbs can be planted all the way up until the soil is frozen but getting an early start will allow good root development yet this fall.
Hyacinths and crocus purchased now and held at 38 to 45 degrees for 6 to 8 weeks can be forced into bloom in time for the December holiday season. Tulips, daffodils, and larger bulbs will require 12 weeks of cooling before bringing out into warmer temperatures to sprout and grow.
Garlic is a bulb, too, that can be planted in the fall to emerge and grow next season. Plant individual cloves now each of which will produce an entire garlic bulbs next summer. Select the largest cloves to produce the largest bulbs. Plant them 3 inches deep and at least 6 inches apart. Water and fertilize after planting. Mulch them for winter protection after the ground freezes. [Watch garlic planting video]
Warm season vegetables like tomato, pepper, eggplant, beans, and all of the vine crops will be injured by even a light frost so be prepared to provide protection for them if early frost is predicted. Be especially cautious with plants in low lying or exposed areas on cloudless nights with temperatures expected to be in the mid-thirties. Cover plants just before sundown but be sure to remove the covering when temperatures begin to rise again in the morning. Squashes, pumpkins, gourds, tomatoes, peppers and eggplants that have been touched by frost, will not store well so use them right away.
Frost will actually improve the flavor of the cabbage family vegetables such as Brussels sprouts, cauliflower, broccoli, kale, cabbage, collards, turnips, parsnips, radishes and Chinese cabbage. Don’t pull these and pile them on the compost heap until winter leaves you no choice.
Cut and dry or freeze remaining herbs. Place a few sprigs in white vinegar for holiday giving. After cleaning the dried leaves off the stems, save the twigs for burning in a fireplace or to add to the charcoal grill when cooking meat. Chop cilantro and place in ice cube trays with water. Cubes can be added to taco meat and salsa and cheese dishes all winter long. Mix fresh diced basil with olive oil for longer refrigerator storage or to freeze.
Dig and pot up a few chive and parsley plants for growing on a sunny window indoors.
Dig frost sensitive, shade loving annuals like impatiens, begonias, and fuschias to bring indoors for winter blooms. You may also want to take cuttings to root and transplant later into containers. By January you could have flowering plants to brighten your home again.
Annual flowers that can really take the cold include pansies, lobelia, snapdragons, petunias, dusty miller and allysum so do not give up on them too soon.
Geraniums can be saved for next year by taking 2 to 4″ cuttings to root and grow indoors. Or dig and pot the entire plant. Once rooted, cut them back to form bushier growth. Some people dig their geraniums, clean all soil off the roots, and hang them upside down in the basement. Most modern basements are too hot and dry for this to be successful unless soaked monthly in a basin of water or misted regularly.
The third week of October is also the prime time to fertilize established trees and shrubs. Fertilization is probably only necessary for prized specimens and plants known to be under stress of some type.
Unless you will be providing supplemental lighting to your houseplants, fertilize now for the last time until next March.
Remove, chop, and compost asparagus tops after they have yellowed and died for the season. Wait until the ground has frozen to mulch.
Continue mowing the lawn as long as it is growing. Mow to chop up fallen leaves as long as there are leaves to mow. Watch the forecast for snow and try to mow one final time before it comes. If leaves are still thick on the lawn, rake and remove so they are not left under the snow all winter.
Many root crops in the vegetable garden can be left in the ground and mulched to insulate them from freezing temperatures this winter. Do not apply winter mulches until the ground has cooled thoroughly usually around Thanksgiving.
Cannas, dahlias, gladiolus, tuberous begonias, and caladiums should be dug after the foliage has died down. Always discard any damaged tubers. Label colors and varieties carefully. All have very specific requirements for curing and storage.
After chrysanthemum flowers have turned brown from hard frost, mound up soil over the bottom of the plant. After the ground has frozen, add an additional couple of inches of mulch. Do not cut stems back, however, until spring clean-up.
Mark or make a note of crabgrass infested lawn areas after they have been killed by the first hard frost. Crabgrass preventer can then be selectively applied to these spots at the end of next April.
Delay pruning of woody plants until trees and shrubs are fully dormant or until the end of the dormant season in March or early April. Fall pruning leaves wounds that will heal slowly increasing the potential for disease or damage.