In New England, the moderating air temperatures and increased rainfall make the autumn months a good time to plant trees and shrubs. Unlike in spring, the soil in late summer and early fall is warm, encouraging good root growth. Even as the soil temperature cools and the top growth of trees and shrubs slows or stops, the roots of most woody plants will continue to put out new growth far into fall. Keeping the new plants watered until the ground freezes or the weather is really cold is key.
- Divide and transplant poor-blooming old peonies or set out new ones this month. They need sun, good drainage and only two to three inches of soil over the crowns.
- Don’t deadhead perennials, biennials and annuals if you want to collect seed (non-hybrids only) or plan to let some self-sow.
- Dig and divide daylilies as they complete their bloom cycle.
- Rest Amaryllis bulbs by putting them in a dry, dark place where they will have no water at all for a couple of months.
- If houseplants need repotting, do it before they come inside later this month. Only increase the size of the pot by an inch for small pots or several inches for large ones. Most plants don’t like to swim in their containers.
- If slugs are eating your cabbage leaves, spread garden lime or agricultural-grade diatomaceous earth beneath the plants.
- Harvest the carrots you need and leave the rest in the ground over winter. At the first spring thaw you will have a delicious treat.
- As your garden winds down, build vegetable-garden soil by sowing cover crops. In the spring, you will turn this “green manure” under to improve soil fertility. Leave some areas for fall crops like garlic.
- Once the nights are consistently below 50 degrees F, harvest remaining mature green tomatoes (those that have turned light green to white), even if the vines haven’t yet been hit by frost. They will ripen better indoors.
- Harvest pumpkins and winter squash before the first heavy frost. Otherwise they can suffer chilling injury that will keep them from storing well.
- Pick winter squashes when color is fully developed, the rind is hard enough that you can’t dent it with a fingernail, and the stem turns hard and begins to shrivel.
- Wait until the ferny top growth of asparagus plants has yellowed and dried before cutting it back. Burn or discard the fronds if asparagus beetles were a problem.
- Kale, Brussels sprouts, and collards all taste sweetest if you harvest after light frost. If an early cold snap into the teens is predicted, cover plants, as it may injure them.
- Leaves of collards and kale are ready to pick as soon as they reach usable size. Sprouts are ready when they’re an inch in diameter. Pick off and compost yellowing lower leaves.
- Keep deadheading, but stop feeding your roses, so they prepare for winter dormancy, not new growth.
- If it’s been dry, be sure to water young trees and shrubs now through hard frost, so they enter dormancy in a well-hydrated state. Evergreens are particularly vulnerable to desiccation and winter burn if not well watered before the cold and winds set in.
- Watch for dead, damaged, diseased wood in trees and shrubs and prune them out as discovered. No hard pruning now since you don’t want to risk encouraging new growth.
- Conifers such as pine and spruce do best when they go in the ground from mid-August through September, so the roots can become established before winter. Maples, ashes, lindens, elms, and most deciduous shrubs can also be planted now. Keep newly planted trees watered regularly throughout the fall.
- Drought-stressed birches are particularly susceptible to potentially fatal infestation by the bronze birch borer. Avoid the most susceptible species, such as European white birch, and plant trees where the roots will stay cool and moist. Use mulch, not turf, in the tree’s root zone, and keep trees well watered during dry spells.
- Pears don’t develop good eating quality if completely ripened on the tree. Pick when they are slightly immature. If you gently lift the pears from their normal vertical hanging position on the tree to horizontal, the fruits should separate without twisting or pulling.
- Don’t bag or rake grass clippings. Let them lie on the lawn to return nitrogen to the soil.
- Now is a good time to seed a new lawn or patch up bare areas in existing lawns. New grass will grow until late fall, when the ground freezes, but frost will eliminate any annual weeds that have sprouted.
- Core aeration is the best way to revive a lawn that’s developed a thick layer of thatch or to improve areas where the soil has become compacted.
- Apply a winterizing fertilizer later in the month with a low nitrogen formula to strengthen the lawn before winter without encouraging new growth.
- For a better lawn next year, remove the weeds in early fall since they’re storing food energy for winter. Hand-pull individual weeds or use least-toxic herbicides.
- For hard-to-mow areas, spots too shady for lawn grass, or hard-to-water places, plant suitable groundcovers. Consider planting them over spring bulbs to camouflage the fading foliage after the bulbs have bloomed.