What to do in the garden in September & October

by cathym on September 11, 2020

Hips on Rosa rugosa

Continue to deadhead some perennials and annuals to keep them blooming, others to avoid self-sowing. You may want to leave seedheads for the birds on plants like echinacea. 

Stop deadheading most roses. This will allow them to start transitioning to winter. Rosehips are an added bonus with some kinds of roses.

Keep container plants watered and fertilized.

Evergreens, including conifers, should be planted by mid-September to allow them plenty of time to root. The newly planted broadleaf evergreens will need winter protection from sun and wind. Continue to water all newly planted woody plants. Ten to fifteen gallons of water is needed weekly when rainfall is less than one inch. 

Protect tree trunks from buck rub as soon as possible.

Plan to protect woody plants from browsing by deer, rabbits and rodents. The bark and the buds on the branches are all susceptible.

Bearded irises should have been divided and/or planted last month but if you do so in September, place a stone or brick on top of the rhizome to prevent winter heaving (this tip courtesy of the Southern Tier Iris Society).

Keep water gardens full. Continue to prevent mosquito development. Use mosquito dunks if necessary—these contain a type of natural Bt that kills mosquito larvae.

September is the best time to renovate or install a lawn. Cooler weather and hopefully more moisture allow better germination and growth of the grass seedlings. Mowing the lawn as high as possible results in a healthier lawn with deeper roots more tolerant of drought and denser turf that will prevent germination of some weed seeds. 

Now is a good time to move spring-blooming bulbs if you can locate them. Many will already have roots so don’t let them dry out.

Photograph your garden and make notes of needed changes. I put notes on next year’s calendar so I don’t forget what I wanted to do next April or May.

Now is a good time to plant hardy perennials and woody plants. Keep them watered to encourage rooting.

Narcissus is best planted in September after the soil has cooled a little. Delicate bulbs such as fritillaria and trout lilies should be planted as soon as you get them. Winter aconite tubers and Anemone blanda tubers should be soaked in lukewarm water for several hours before planting. This is very effective for A. blanda, less so for winter aconites, which are best propagated by seed.

Nursery stock goes on sale and may be a good money saver if it has been well cared for. Score the rootball of pot-bound plants with vertical cuts to ensure root growth into the surrounding soil. If rain is insufficient, water weekly. Continue watering until the ground freezes.

Check viburnums for viburnum leaf beetle (VLB) adults, especially if the shrubs were defoliated by the larvae. Consider a pesticide treatment to save the shrubs. Do NOT cut back branches just because the leaves have been eaten or damaged. Scratch the bark with your fingernail, if it’s green underneath, the branch is alive. Snip off and destroy the twigs that contain the VLB eggs. Although the egg-laying sites are most obvious in the fall, one actually has until April to trim the affected twigs.  

It is too late to fertilize woody plants, as doing so may encourage tender late growth that may not harden off in time for winter.

It is also too late to prune woody plants, except for dead or diseased wood. Be especially mindful not to prune spring-blooming shrubs that have already formed next spring’s flower buds, such as forsythia.

Bring in poinsettias and Christmas cacti to get them adapted to indoor conditions. Start exposing them to long nights (short days) for flower buds to set. After checking for insects, bring in houseplants before nights cool off too much outside and heating systems start operating. 

Consider having windowsill herbs for winter use. You may pot up small ones or take cuttings—basil, sage, rosemary (especially susceptible to drying out in my experience) are some of the possibilities. Chives are a hardy perennial; pot them up and bring them inside in late fall.

If you live in a cold site, you may want to dig tender bulbs such as dahlias, tuberous begonias, and cannas before the frost hits. This winter I am planning to keep canna ‘Stuttgart’ growing on a windowsill. Cannas do not need a rest period.  Gladioli seem to be marginally hardy even in my cold site. One has persisted and bloomed for three years outdoors now, and others survived last winter, but may not bloom this year. I may leave them all in the ground and see what happens!

You should already have harvested garlic.

Keep up with weeding! If you can’t remove all the weeds right away, at least don’t let them go to seed.

Renew the mulch in your veggie garden or consider planting hardy cover crops to improve the soil.

Pick fall raspberries every day, especially if the weather is wet or humid. If raspberries or other soft fruits look moist or misshapen, check for the maggots of the spotted wing drosophila fruit fly. Destroy all the bad fruit. If a lot of fruit has been set, you can then use row cover to keep the fruit flies out, but this will also prevent further pollination. Also look out for the brown marmorated stink bug. 

Keep harvesting veggies and herbs and continue to water if it is dry.

If you garden in a cold site, start watching for frost after October 1 be prepared.  (The average first frost in zones 5 and 6 is in mid-October.) 

Now is a good time to do a soil test and make pH amendments as needed but wait until spring to apply fertilizer.

Continue to water newly planted woodies. You can continue to plant hardy perennials and woody plants such as tall phlox, hostas and lilacs. The shallow-rooted perennials such as Heuchera should have been planted earlier.

This is the best time to move peonies. Normally, they don’t need to be moved or divided unless they are growing in too much shade. It may take a couple of years for them to recover after dividing or moving. Do not plant them too deeply; doing so may cause them not to bloom.

Continue to plant spring-blooming bulbs. Tulips can be planted last. Many spring-blooming bulbs are deer-resistant, such as alliums, winter aconite, snowdrops, snowflake, Siberian squill, glory-of-the-snow, puschkinia, fritillaria, and Anemone blanda. Grape hyacinths send up fall foliage but even when it’s browsed it doesn’t seem to affect their vigor.

Cut off all the peony foliage down to the ground to remove botrytis spores.

Some perennials can be cut back now for the winter, if the foliage has senesced already.  Leave stalks of natives in place in case beneficial insects use them for overwintering.  Also, do not trim back the stalks of certain plants that overwinter better with the protection of the old stalks. This group includes mums, lavender, culinary sage, Kniphofia and butterfly bush.

Late in the month, look for spring bulbs on sale. Consider forcing some: daffodils, crocuses, hyacinths, and smaller bulbs like Siberian squill all force well. Tulips can be forced, too, but they require a longer rooting period and stronger light in the foliage-growing stage or they will be leggy and floppy.

Listen to the fall forecasts and be prepared to protect tender plants from an early frost with old sheets, towels, etc., as we frequently get a couple weeks of nice weather afterwards. Otherwise, when frost is predicted, do a quick harvest to get produce indoors.

Mid to late October is the best time to plant garlic. Be sure to rotate garlic; pick a new spot with lots of sun and good drainage. I mulch it with a couple inches of woodchips to give it plenty of time to root but preferably not to sprout.

Remove all the brown asparagus ferns to reduce the number of overwintering asparagus beetles.

Continue weeding, watering and mulching as needed.

— Pat Curran and the Tompkins County Master Gardeners


What to do in the garden in July & August

by cathym on June 30, 2020

It is the heart of summer gardening season. The Northeast sees its hottest weather in July but, August can bring hot, humid weather as well and can be unpredictable, with extended periods of rain and even cooler temperatures as garden stands begin to show pumpkins and fall mums. Below we provide you with some gardening tasks to help keep your gardens flourishing through the late summer.

Step back and look at your garden to see what is in bloom and where you lack floral color. It is the perfect time to take pictures and notes as to where you can improve next year.

Make sure tall plants and climbers are well supported in case of bad weather. Also, pruning wisteria at this time will encourage new growth and help keep it in balance with the trellis.

Water at dusk to reduce evaporation; mulch garden beds to retain moisture around plants and help keep roots cool. Always practice effective watering by watering the soil around the base of the plants rather than the foliage. Control water and sprinkler use so as not to waste water by losing it to pavement, driveway, or any other unintended area.

Newly planted trees and shrubs (deciduous and evergreen) need extra watering in dry periods. Make sure they get a good, regular deep drink that will go down to their roots. Keep an eye on them for signs of wilting, a sign they are lacking water.

Do not mow too low in summer. Mow as high as possible—that will result in a healthier lawn with deeper roots that are more tolerant of the drought and stress of summer. Slightly higher turfgrass also helps shade out the weeds. 

Regularly deadhead annual and perennials as well as roses to encourage new blooms. Cut back faded perennials to keep gardens neat. Some spring blooming perennials, such as lupine, can be sheared back hard to encourage a second flush of blooms later in the summer. Now is the time to cut back any remaining spring bulb foliage as well.

Keep containers fresh.

Check your containers. Cutting back growth in hanging baskets (i.e., petunias) can encourage new flowers and foliage to revive the display; fertilize well after doing this. Make sure you are fertilizing your containers regularly throughout the hot months. When it comes to container plants, remember the soil dries out faster, so pay special attention to make sure these plants are receiving sufficient water. Terracotta pots will particularly dry out quicker, so dampen the pots to reduce evaporation and help keep the plants roots cool.

Consider dividing bearded iris now. If your plants did not bloom well, chances are they need to be divided. July through August is the best time to do this. Using a digging fork, carefully dig around the plant, being careful not to pierce the rhizome. Once lifted, shake off loose soil or rinse it off with a hose so that you can better inspect the rhizomes for any damage. Separate the individual rhizomes. Cut the foliage to about six inches. Cut sections of the rhizome so that you have pieces about three inches long with healthy roots growing from the cut, using a sharp knife to make clean cuts. Replant, being careful not to bury the rhizome with more than an inch of soil; these plants will not bloom well if planted too deeply.

Avoid transplanting roses when the temperatures are above eighty degrees. If you do transplant them in summer, prune heavily. Water the roses slow and deep. Add mulch to help suppress weeds. 

Harvest vegetables and fruits regularly; July is a good month to harvest beets, peas, carrots, chard, lettuce, and some tomatoes. Routinely inspect your vegetable garden and prune any yellow foliage. Remove garden debris to cut down on insect or disease issues. Continue to remove suckers from tomato plants and check that they are adequately supported with stakes or cages. Water crops daily in hot weather to ensure they are consistently moist. Uneven watering may cause blossom end rot on tomatoes. Blueberries are especially sensitive to drought conditions. Feed crops with a general-purpose fertilizer. Weed regularly, since weeds can compete with your crops for nutrients and water.

In late July, consider a fall crop of snow peas, spinach, or lettuce. Other cool season crops do well in mid to late summer to give you a nice fall harvest.

Observe your garden daily. If you see a harmful pest consider integrated pest management practices: cultural, biological, and mechanical controls. Use chemical controls as the last resort. Handpick Japanese beetles using a pail of soapy water. Just hand pick or shake plants and the pests will just fall into the bucket and drown. Look at the undersides of plant and crop foliage where insects such as aphids can hide. Keep an eye out for the scarlet-colored lily leaf beetles on your ornamental lilies. Check for sticky brown larvae on the undersides of lily foliage. 

Protect bramble crops such as blackberries or raspberries from birds by installing netting around the plants.

Shrubs may require some pruning to give much needed shaping and to allow good air circulation at this time. 

Look at your containers; if they are looking a bit shabby, consider a container rehab! You can use houseplants, individual plants from the garden bed, plants from other containers, or plants on sale to give your container a fresh look. Carefully pull out those that are past their peak and replace them with fresh plants. Be sure to fertilize after replanting.

After the month of August, cease fertilizing your roses—this will help to prepare them for fall and winter months ahead.

Think about which bulbs you might like to add to your garden for next spring. Now is the time to order them. In late August, you can plant fall-blooming bulbs such as colchicums or autumn crocus as soon as they are available.

Make notes on your garden’s pros and cons. Take more photos of your garden. Do you want to make any changes or additions? Garden centers will be having sales and it could be a good time to add plants. It is a great time to plan for next year.

In a Zone 5 garden, August is the latest to consider growing edible crops for the fall such as lettuce, spinach, or broccoli. You may have to consider protecting them from the hot sun by using row covers or milk crates.

Keep mowing your lawn high. Late August into September is the perfect time to renovate a tired lawn or start a new one.

Harvest beans, cucumbers, zucchini, eggplant, peppers, tomatoes, etc. so that plants continue to produce. Peppers can stay on the plant longer to allow them to color. Consider what to do with your herbs; it is a good time to freeze or preserve them in other ways for use over the winter months.

Take cuttings of your favorite annuals such as coleus, impatiens, or geraniums. You can grow them indoors later to save for next year. Many plants, such as coleus, will easily root in a glass of water.

Consider adding a perennial fruit or fruit tree to your garden. The upcoming fall is the perfect time to plant and stock may be available on sale and could be a good money saver.

Feel free to reach out to your local Cornell Cooperative Extension office’s Master Gardener volunteers for answers to any questions you might have.

— Rosanne Loparco, John Slifka, and Ron Broughton, Master Gardener volunteers at Cornell Cooperative Extension, Oneida County



We gardeners have been waiting for spring. However, during May, PATIENCE is the rule. A common problem is planting too soon. If the soil is too cold or wet seeds may rot and roots may stop growing. 

Soil temperature should be above 50 F. If soil feels cold in your hand, it’s too cold for plants! Try making a ball with a handful of soil. Does it crumble? Great. Does it form a ball? It’s too wet.

Purchase compact, healthy plants with unopened buds that are appropriate for your gardens. Read plant tags and note the final height and width. Are they appropriate for your space? Mix compost, or other organic materials into the soil before planting. Mulch lightly around the new plants.

Planting holes should be a deep as the root mass and twice as wide. Be sure to spread or “spider” the roots to encourage root growth into the soil instead of circling, self-strangling roots which can lead to disaster.

Leave bulb foliage intact until it yellows and wilts, but remove spent flowers to prevent seed formation. The foliage is required to give bulbs the food necessary to form next year’s blooms. Spring bulbs can be moved or divided as soon as the foliage dies. Do the same for bearded irises so the energy goes into the rhizomes. Divide Virginia bluebells, bloodroot, trilliums, and other spring ephemerals when the leaves turn yellow and before they disappear from sight. 

Weeding never ends. Mulching helps. Plant warm-season annuals by mid-June, before it gets too hot for them to establish good roots. These include cosmos, marigolds, begonias, torenias, petunias, ageratum, and cleome.

Check for signs of insects (chewed leaves, puncture wounds, sticky substances, trails in leaves) or disease (yellow leaves, stunted growth, signs of fungi). Be sure to look on both sides of the leaves before buying any plant. Don’t forget to check for healthy roots. Slug control can start as soon as you can get into the garden. Take a look on top and under the leaves of tomato, potato, pepper, and eggplants for hornworm eggs (only one-tenth of an inch in diameter). Yellow trails in columbine leaves are caused by leaf miners, the larva of a genus of fly. This is more of an aesthetic problem … you don’t have to do anything OR you can remove the affected leaves.

Buy yourself at least one new plant! Consider some native plant species to help pollinators and to feed young birds. Keep newly planted trees, shrubs, vegetables, perennials, and flowers well-watered (about one inch per week.)

Try deer repellants or consider deer resistant plants. Check the Cornell website for a great deer resistant plant list. 

Cut back spring-flowering perennials such as pulmonaria and perennial geraniums after they bloom to encourage reblooming and/or growth of new foliage. Deadhead perennials and annuals to prevent seed formation and to encourage new growth and more flowers.

At the end of June, cut back perennials such as phlox, beebalm, sedum, aster, and goldenrod by one-third to one-half to control height or delay flowering. This is known as the Chelsea Chop.

Place supports over taller flowering plants so the plants can grow up through them without damage to foliage and flowers later in the season.

Spring-blooming shrubs like weigela, forsythias, and spirea can be pruned back after blooming. Cut about one-third of the oldest stems to the ground for renovation.

If growing azaleas and/or rhododendrons in higher pH soil be sure to add acidifying agents. However, don’t disturb the roots.

Mow lawn at least three inches high. This encourages deeper, healthier root growth. Leave grass clippings on the lawn to return nutrients to the soil.

The first application of lawn fertilizer, if needed, can be put down around Memorial Day. If fertilizer was applied in the fall a spring application is not necessary. A quarter to a half inch top dressing of compost adds nutrients, feeds soil microbes, and improves the water-holding capacity of the soil. 

For optimal pre-emergent crabgrass control, do not apply until soil is close to 60 degrees. Crabgrass doesn’t germinate until the soil temperature 2 inches deep is between 60 & 64 degrees. Applying when the ground is too cold is a waste of money and chemicals.

Check the Cornell recommended vegetable list for suggested and disease resistant varieties.

Plant your brassicas now: broccoli, cauliflower, Brussels sprouts and summer cabbage. Reseed bush beans every few weeks to increase production.

Plant your tomatoes, eggplant, squash, pumpkins, cucumbers, and peppers when the ground is warm to promote root growth. Usually this time comes closer to the end of May.

After direct-sowing seeds, be sure to thin the seedlings to prevent crowding and competition for light, water, and fertilizer. If plants were grown from seed be sure to harden them off before planting them in the garden.

—Carol Ann Harlos and Lyn Chimera, Master Gardeners, Erie County