Continue to remove weeds to prevent perennial ones from having a head start in the spring and to prevent annual ones from shedding seeds into the soil. If you don’t have time to weed, at least cut off and discard the seed heads.
Water trees and shrubs. This is as important as watering your perennials and extremely important for anything planted this season.
Mulch newly planted perennials, trees and shrubs to prevent heaving in the winter. Make sure the mulch is not touching plant and shrub stems or tree trunks.
Add compost to your beds..
Prevent mouse and rabbit damage to thin-barked trees and shrubs by installing 18 to 24 inch high hardware cloth. Remove any grass around the base of trees short to discourage nesting by these critters.
Move, divide, and/or share your perennials so you will have one less thing to do next spring.
Remove and discard all diseased plant material. Do not place in your compost pile as some fungal spores can winter over and re-infect plants next season.
Disinfect your pruner after working on diseased plants before moving to a new plant. A quick wipe with rubbing alcohol or a dip in a 10% bleach solution works well.
Remove and destroy iris foliage to eliminate the eggs of the iris borer.
Mound soil around your roses when the temperature drops. Bring in fresh soil to avoid disturbing roots.
You can leave the seed heads of plants such as astilbe, black-eyed-Susan, and coneflower intact to provide food for the birds and winter interest.
Don’t cut back grasses and plants such as red osier dogwood. These can also provide winter interest.
Divide any perennials that have become overgrown, have diminished bloom or formed a “doughnut” shape with a bare spot in the center of the clump. It’s best to transplant early in the fall while there is still enough time for their roots to settle in for the winter.
Begin planting spring bulbs. You will get the best results if you plant mid-September to mid-October. This allows the bulbs to set strong roots. But if you miss that planting window don’t be afraid to plant them later, as long as the ground isn’t frozen solid.
Fertilize bulbs when you plant them using compost or 5-10-10. Cover the planting area with 2-3 inches of compost.
With some bulbs it’s difficult to tell the top from the bottom. The skin is loose at the top and attached at the bottom. If you can’t tell, plant them sideways!
To deter moles, voles and squirrels, put a layer of pea gravel or small gauge chicken wire between the bulbs and soil surface.
Plant bulbs 2 to 3 times as deep as their height, a little deeper for naturalizing varieties.
Over-seed bare spots in the lawn. Filling in bare spots helps prevent weeds in those areas next year.
September is the best time to fertilize your lawn and seed a new one. A top-dressing of good compost is an ideal and natural fertilizer.
Remember choose high quality seed appropriate for your site and to water regularly to keep the soil moist.
In early September check your lawn for grubs by lifting up about a square foot of sod. If there are more than 10-12 grubs per square foot you may want to treat the lawn. First identify what type of grub you have so you know the proper treatment. Complete your grub control program by the middle of September. Contact your Cooperative Extension for help in identification and treatment options.
Keep mowing the lawn as needed though late fall. Make the last cutting one inch lower than usual to prevent matting and to discourage snow mold.
If the leaves aren’t too thick on your lawn leave them there when you mow; it feeds your lawn naturally.
Vegetables & Herbs:
Any time after the first frost through late October is a good time to plant garlic.
Pick off tomato blossoms that won’t have time to develop so the nutrients go into the tomatoes already growing on the vine.
Plant cover crops such as peas or clover as you harvest your vegetables. This will reduce the need for weeding and will add nitrogen to the soil. Another option is to sow a cover crop such as rye or winter wheat in the vegetable garden. Turn it over in the spring.
Wait until the seeds of your sunflowers are firm and done growing. Cut off the sunflower head leaving about one foot of stem. Hang in an airy dry place until ripening is complete.
Dig mature onions on a dry day. Store in well ventilated mesh bags (or even panty hose).
Plant radish, kale, spinach, and lettuce seeds in early September as your last crops.
Pull up your hot pepper plants and hang them until the peppers are dry. (Or thread the peppers on a string to dry.)
Allow nuts to fully mature on the trees. Remove the outer green hull of butternuts and walnuts.
Try potting up some of your garden herbs and bring them in the house for fresh herbs during the winter.
If you had any vegetables with fungal problems make sure that area is cleaned of all plant debris. Avoid planting the same variety in the same spot next year.
Dig and store summer blooming bulbs, caladium and elephant’s ears before frost and tuberous begonias, cannas, dahlias after the foliage is blackened by frost.
Bring in tender perennials such as scented geraniums and rosemary and any annuals you want to overwinter BEFORE you have to turn on the furnace. This cuts down on the shock of moving inside.
Make cuttings of plants treated as annuals such as scented geraniums, strobilanthus, impatiens, and coleus.
Collect seeds from open pollinated plants such as kiss-me-over-the-garden-gate, Big Max Pumpkin, and Brandywine tomatoes. Be sure to keep them dry and chilled at 35-45 degrees Fahrenheit.
Join a seed exchange such as Seed Savers. Contribute extra seeds to organizations such as the American Horticulture Society and the Herb Society of America.
Add color to the autumn garden by planting mums, kale, flowering cabbage, and pansies.
Plant trees and shrubs now. They will have time to develop roots before winter sets in.
Fallen leaves are one of the most wasted natural resources the home gardener has. They can be used as a mulch to improve soil texture and to add nutrients. (Get some from your neighbors as well!)
Small leaves like linden or birch trees can be spread on gardens directly. Larger leaves can be shredded or run over with your lawn mower before spreading. Avoid using black walnut or butternut, as they can be toxic to many plants. Excess leaves can be composted for use next spring. They decompose faster if shredded first
Begin bringing in houseplants that lived outdoors all summer. Wash off with a good spray of soapy water. Check for diseases and insects before bringing inside.
Take pictures of your gardens. Make notes for next year’s gardens now. What worked, what didn’t, what to add, remove, or move.
Begin to get Poinsettias ready for December flowering. They need fourteen hours of total uninterrupted darkness and ten hours of bright light.
Lay out thick layers of cardboard or newspaper over areas that will become new beds in the spring. These will kill grasses and/or weeds as they break down making spring efforts easier.
—Carol Ann Harlos & Lyn Chimera, Erie County Master Gardeners