Perennials, annuals, and bulbs
During the fall months of September, October and November, after soil temperature drops below 60°F, the bulbs of spring – tulips, daffodils, hyacinths, scilla, dwarf irises, anemone, and crocus should be planted. Add bone meal or bulb fertilizer into the planting hole as you prepare the soil.
Winter pansies, flowering kale, flowering cabbage, and fall mums may be planted now, to give a little color to the garden when the summer flowers have faded away.
Scatter the seeds of perennials in a row or in open beds this month so that the young seedlings will be ready to be transplanted into their permanent spot next spring.
As the weather cools, perennials which have overgrown their space or become crowded should be dug and divided, or moved to a new area of the garden. New or replacement perennials can also be planted this month.
Tender bulbs should be dug up and stored in a cool, dark area after first frost.
Shrubs and trees
Fall is a good time to select and plant trees and shrubs. Fall planting encourages good root development, allowing the plants to get established before spring. If weather is dry, provide water until the ground freezes.
Stop fertilizing your trees and flowering shrubs to allow this years growth to harden off before winter.
After you have finished harvesting your summer vegetables, plant a cover crop of clover or soybeans for the purpose of plowing under next spring. These nitrogen producing plants will provide good organic matter and food for your garden crops next year, as well as helping to control weeds over the winter.
Lawn
When the fall rains arrive, fertilize your lawn with a slow-release 3-1-2 ratio fertilizer.
September is one of the best months of the entire year for seeding or sodding new lawns.
If the lawn needs thatching, it can be done during the early fall.
Overseed old lawns with fresh seed to help fill in the bare spots and crowd out weeds and mosses.
House Plants
Pot up some spring flowering bulbs for indoor color during the winter. Store the pots in a cool, dark place, until new growth emerges from the soil, and then move them to a bright window.
Begin conditioning your Poinsettias and Christmas cactus to get them ready for the upcoming holiday season. Both of these plants are short day plants. Although they will eventually bloom, if you want the plants in bloom in time for the holidays they must be kept at about 65 to 70 degrees, and subjected to at least six weeks of 14 hours of total darkness per day (mid to late September). This may be accomplished by placing the potted plant in a closet or unlighted room, or by covering the plant with black cloth, black plastic over a frame or a cardboard box. The plant must then be returned to the light each day and given a minimum of 4 hours of direct sun, or 10 hours of bright light. The application of a 0-10-10 fertilizer this month and again next should help encourage the development of flower buds, then feed your plant every 2 weeks with a high nitrogen fertilizer once color has begun to show.
Christmas cactus needs the same general care, with the exception that they require cooler temperatures of about 50 to 60 degrees.
Continue to watch for insect or disease damage and take the necessary steps to control the problem.
Zone 5
• Plant winter-hardy pansies and fall annuals (calendula, dianthus, ornamental cabbage and kale)
• Plant tag teams of perennials and spring-blooming bulbs that will complement each other or bloom in sequence next season
• Water trees and shrubs when rainfall is scarce to “winterize” them
• Dethatch and aerate the lawn
• Deadhead chrysanthemum plants to keep flower buds forming through the fall
• Clean out rose beds; apply fungicide; leave hips for winter color and bird food
• Prune summer-bearing raspberries
• Mow back strawberry plants; remove weeds and re-mulch
• Move tender houseplants, etc. indoors after rinsing and repotting, and set up a grow light to supplement natural light
Next month will be time enough for some bulb planting; though it is better for the daffodils to go into the ground as soon as the bulbs are delivered.
Roses also may be ordered in September for delivery and planting during the month.
The hardier house plants which still remain in the garden must come into the house before danger of frost, Lift the pots, prune, and keep on the porch for a few days before taking inside, so that the shock of removal may be less violent.
If any plants are growing in these and borders which you desire to take in for winter use, the earlier they are potted the better. They may need severe pruning, and the pruned portions may be used for cuttings to make new plants. Root these in flats of moist sand and transplant later into pots of mixed loam, sand, and peat.
Late-blooming flowers such as chrysanthemums, dahlias, and asters need plenty of water, fertilization, and perhaps spraying during September to insure fine bloom later on.
Rose bushes may be thankful for September spraying and watering if rainfall is scanty, as some of the finest blooms come during the cool, late autumn weeks.
Peonies can be transplanted best early in September. Purchase plants now. Do not divide or replant old-established peonies unless they show signs of flowering less vigorously in their original positions.
Iris, gaillardia, hardy asters, phlox, and bleeding heart, can be transplanted successfully in September.
Pansies, English daisies, and myosotis (forget-me-nots), which were planted in August, are ready in late September for a light winter protection. Evergreen boughs laid across the bed are most effective for this purpose, though good substitutes are excelsior or salt hay held down lightly by a few pruned tree branches.
Though we cannot always count on the seed, gathered from our own garden flowers, it is worthwhile to gather specimen blooms for planting in spring. Dry the seeds thoroughly in the sun before placing them in small manila coin envelopes. Mark plainly with name, date, etc. These envelopes can be filed like index cards.
After the seeds are harvested, dead flower stalks may be collected and discarded. This will help to prevent the spread of disease, which may have attacked the plants.
Gladiolus bulbs should be harvested, tops cut off close to bulb, and dried in flats a short time until surface moisture has disappeared. Store in a cool, dry cellar in the same flats in which they were dried.
Tuberous-rooted begonias must also come up with a clump of earth attached to the tuber before danger of hard frost. If the foliage is still alive, it is cut to prevent rotting and the tubers are stored in a cool cellar.
Evergreens demand our attention. This is a good month for pruning and cleaning. Dead wood can be easily discovered during this dormant period. Bagworms may be removed, and sulfur applied if red spider is still present.
Most hardy deciduous shrubs, which bloom in spring and early summer, can be transplanted during this month.
Watering must not be neglected especially for newly set trees and shrubs. The roots are not yet thoroughly established in their unaccustomed positions, and need more than a normal amount of moisture.
Week One
This is a good time to shop. End-of-year sales at nurseries will be in full swing. Look for smaller materials; nurseries can easily hold over larger trees and shrubs.
Week Two
Most perennials will welcome division now, but some definitely will not. These include phlox, Shasta daisies, and Siberian and Japanese iris. Don’t even try.
The Japanese anemone is the queen of the fall garden. Other dependable September bloomers are Heliopsis and Bluebeard (Caryopteris x clandonsis), a low-growing blue-flowering shrub better treated as a perennial.
If rainfall is adequate, little watering will be needed from now on. The exception is new plantings and, of course, roof gardens, which will need watering right up to hard frost.
Bring in pots of amaryllis that have been summering outdoors.
Week Three
Trim long stems of perennial vines and tie up or train as you like.
Cut back iris foliage to three inches.
Pot up wax begonias that have been blooming outdoors and cut back all stems to two inches before bringing indoors.
Don’t let phlox go to seed or they will self-sow, reverting to their original magenta and the new seedlings will crowd out your carefully cultivated variety.
Week Four
Last call to bring house plants indoors.
Pull out vegetable plants when all the crops have been gathered, and plant a winter cover crop. Winter rye or small grains are good in our region.
Fertilize lawns and sow seeds in thin or worn areas.
This is the best time to plant daffodils, although almost everyone waits at least until October, and often drag their feet into November.
You can still plant perennials, but they will have to be protected against the winter’s alternate freezing and thawing.
Start cutting back perennials. You can compost all but the leaves and stems of the peonies.
How and when to divide hosta
If you’ve got Hosta that are growing so tightly that the center of the plants has died out, it’s time to divide them.
Division is a simple plant propagation technique that is exactly as it sounds. You dig the plant up and divide
the root ball into multiple pieces. This technique only works with plants that have multiple crowns emerging from the ground. Most perennials fall into this category, flowering shrubs and trees do not.
If you have Hosta that you would like to divide, you can do so now, about 30 days before they go dormant. That
way the soil is still warm enough for the new divisions to establish some new roots before winter.
Or you can wait until spring. Just wait for the plant to start growing. As the new growth just starts to emerge
divide them then, not after the new growth opens up with leaves. Once they produce leaves it’s best to wait
until fall.
To divide them simply dig up the root ball and with your spade cut the root ball into multiple pieces. Replant the pieces. It’s as simple as that.
Tender perennials
Prepare clean pots and fill with fresh soil, then transplant tender perennials like lemon verbena, geranium, and bay laurel so they can be over wintered in the house or on a sun porch. If weather isn’t freezing they can go outside on milder days.
Odds and ends
Mark your perennials with permanent tags, or create a map showing their locations so you’ll know where and what they are when they die back at the end of the season. This will help you to avoid digging up something you intended to keep when you plant bulbs and plants this fall and next spring.
One last effort at weeding will help to improve the appearance of your garden throughout the winter.
The birds will soon begin their winter migrations. Give them a helping hand by providing them with some food for their long journey. No one likes to travel on an empty stomach, and you may even persuade a few of them to stick around for the winter, if they know they have a reliable food source!
Continue to watch for insect, slug and snail, or disease damage throughout the garden, and take the necessary steps to control the problem.
Plant phlox now for blooms next summer. Plant just before freezing and cover with straw. In spring, remove straw to encourage plantlets. Transplant to a border as soon as they are large enough to handle.
Nasturtiums may make good house plants. Try digging up a couple clumps and placing them in low bowls. Keep them moist and in a sunny window. (This may work better for folks who keep the temperatures low. Nasturtiums might not be happy in our well insulated, heated winter homes.)
Vinca will winter over if protected. Take up the vine, cut back, then place in a buried pot in the garden and cover with straw. In the spring, bring the pot into the house and treat it to water and warmth. Place in a sunny window to facilitate growth.