September Garden Tips

Weekly Garden tips for Massachusetts Gardens

It’s vegetable planting time again.  If you put lettuce, arugula, spinach and even pea seeds (but only those that mature in 40 days or less) in the bare areas of your garden now, you can have a fresh crop before the weather turns too cold.  And you can stretch the season even further by using floating row covers—lightweight cloth—over the plants on cool nights.

Tomatoes have taken over center stage now, and perhaps your kitchen counter.  But they cannot tolerate cool temperatures so remove the topmost growth on plants to encourage ripening what is already on the vine, instead of producing more fruit that will not have time to ripen.  Fried green tomatoes are a wonderful side dish if you have some that don’t get ripe before frost is forecast.

The biggest problem with winter squash and pumpkins is that they all ripen at almost the same time.  For better results storing your squash crop, allow them to thoroughly ripen before harvesting.  While we probably won’t see a frost until October, keep an eye on the weather: if there’s a frost warning, cover your ripening squash with newspapers or blankets.  If there’s a freeze warning, harvest your crop.  Squash that had been hit by a freeze has to be processed immediately.  And remember to keep your harvested squash in a cool but not cold place.

As each vegetable finishes producing, remove the plants from the garden in order to prevent diseases or pests from wintering over in the old foliage.  Sowing winter rye will provide roots to stop erosion of uncovered soil, and when turned over in the spring, it will add nutrients and biomass to the garden.

September is great month to divide and plant many perennials that have completed their bloom cycle.  Everything from peonies to hostas to bleeding hearts can benefit.  When you plant your divisions, make certain to put them into ground at the proper depth — exactly as deep as they were growing before.  And enrich the soil with compost or well-aged manure to give the roots a great start. Don’t allow the new plantings to dry out, and don’t mulch the area until cooler temperatures arrive.

You can plant certain spring seeds now!  Some flowers (such as bachelor buttons) do better if they are planted in the fall (the way Mother Nature would) and allowed to winter over.  In the spring you will have a serious jump on the season.  Putting seeds in the ground this fall means stronger, earlier flowers next summer.

September is the month to plant all narcissus (daffodils) as well as smaller bulbs such as grape hyacinth.  Don’t plant tulips until the end of the month.  And remember, while deer and rabbits love tulips, they generally ignore daffodils and hyacinths.

September is the best month to establish a new lawn, feed your existing lawn, or deal with bare spots or thin grass in established lawns. Grass seeds face virtually no competition if planted in the fall because grass is a cool season plant (and most annual weeds are not).  Existing lawns should be mowed short and raked thoroughly before reseeding.  Water new or reseeded lawns as required to prevent the seed from drying out before it develops mature roots.  Do not mow or rake again until the new grass has established strong enough roots not to be pulled out. Feed lawns but do not put down weed killer now—the weeds are annuals and already dying as days get cooler.

Be On the Look Out!  Japanese Knotweed was brought to this country as a decorative plant, but it also a terrible thug.  It spreads by seed but also by underground rhizomes.  If you cut it down, the stems must be bagged and sent to the dump.  It can re-root itself if just dumped.  After you’ve cut it down (and properly disposed of the canes), make a note to go back in a month to six weeks.  You’ll find it will be thriving again.  It takes at least four cuttings to kill the underground rhizomes.   Why bother?  Because it is bad for the environment.  Knotweed crowds out native plants, which makes it bad for the native birds and animals that live off those native plants — and may even drive them into your garden looking for something to eat!

Be On the Look Out!  Black swallowwort is one terrible invader.  And it’s about to send it’s seeds out into the world.  Distantly related to milkweed, it can be mistaken for the only plant that is a nursery to Monarch butterfly larva.  The female Monarch butterfly thinks she’s laying her eggs on the perfect host, is instead laying them on a plant that will kill the caterpillars soon after they hatch.  Please look around your home, the areas where you walk, your town parks (some was growing in a bed at my local Library!) and pull it out.  Too much to pull—then take clippers and a bag and cut off the seed heads, bag them, tie it securely and send them to your local dump.  Never compost any part of the plant.

Top your tomatoes
Most varieties of tomatoes are ‘indeterminate’, meaning the vines that will keep growing until killed by frost.  By cutting off the top of your tomato plants down to where fruit has already set, you encourage the plant to put its energy into ripening the fruit already on the vine rather than generating new leaves and flowers.

Row covers are back in fashion
The row covers you used in May and June to keep out bean beetles and other bad bugs can be pulled out again, this time to provide a few degrees of nighttime protection against cold.  Check your town’s swap area for a hard plastic or glass covers (old doors or windows work well) to give you a simple cold frame that can keep your garden growing until covered with snow.   You can add 60 days or more to your growing season.

What to compost, what to bag and discard
As you remove spent plants from your vegetable garden, look at each one with a critical eye.  Send any plant that is either diseased or infested with bugs to the dump.  Compost the clean plant material to create ‘Black Gold’ for next year’s garden.

Clean up your yard
Take advantage of cooler mornings and evenings to do the weeding we avoided in August.  If it seems like weeds were the only thing that managed to grow during the drought, it isn’t an illusion.  Weeds such as crabgrass thrive in dry soils.  Reward that hardiness with a good tug and a trip to the dump.  Every weed that goes to seed means many more to deal with next year.

Think twice before you rake
While cleaning your yard remember the leaves that fall are food for the plants.  Use a mulching mower to chop up the ones on the lawn.  They will finish disintegrating over the winter.  Under bushes and around perennial beds, fallen leaves serve as a winter mulch and a home for many beneficial insects like butterfly caterpillar so please don’t chop them and leave them be.

Freshen your containers
It has been a tough summer for plants in containers.  The unrelenting heat and the regular dousing with chlorinated tap water (in place of the non-existent rain) is not conducive to a long happy life for your annuals.  It’s too early to use cut evergreens, so consider putting in some transitional plantings such as the multi-colored kale, perennial grasses and heuchera.  Avoid using mums.  They aren’t a good choice if you like to keep the season going until Thanksgiving because the flowers will die long before that.