Seedlings in Pots

HORTICULTURAL HINTS

AUGUST HORTICULTURAL HINTS

Last chance to stop swallowwort. 15 years ago, black swallowwort was almost unknown in New England. Now, it is endemic. Who should we care? Because of butterflies and, specifically, Monarch butterflies. Swallowort is a distant relative of milkweed - the primary food source and sole egg-laying venue for Monarchs. When a Monarch deposits its eggs on swallowwort, it is a death sentence for those eggs.

Swallowwort thrives in 'border' sites such as the edge of woods, untended vegetative areas. Swallowwort plants have already produced their green seed pods. Once they ripen, each of those pods will disperse hundreds of seeds that will scatter to create new stands.

If you have swallowwort on your property, pull it out of the ground or, at the very least, pull off the seed pods. Once it is off your property, look for it on your neighbors' property and where you walk. Encourage your town’s DPW to clear it from public right-of-ways. Here are two photos to help you identify this noxious plant.

Swallowwort in early August.jpeg
Keep up with your weeding in August.jpeg

In the garden.  Keep weeding!  The weed seeds you prevent now are the weeds you won’t have to pull next year. And, to keep your garden clean, take off any leaves infected with mildew or other diseases and place them in the trash (never the composter) along with the weeds you pulled.  It is better to sacrifice one plant with persistent problems than to allow it to spread throughout your garden.

With August comes insects.  Always treat insects with the least toxic methods available.  Most insects you see do little or no damage to plants and can be left alone.  Those seriously damaging plants can sometimes be removed with a hard spray from a hose which sends them to the ground where they become other bugs’ dinner.  Others can be hand-picked; no one ever said gardening was easy!

Thesse red aphids on Heliopsis can be cleared by hand.jpeg
You can get an extra bloom out of your annuals by deadheading spent flowers in August.jpeg

Remove spent flowers from perennials and annuals.  Your goal is more flowers, not seeds.  Keep the flowers coming by encouraging the plant to use its energy to set more buds.  Keep your garden looking at its best by cutting back any plant that has finished flowering, leaving enough foliage to add energy to the roots but allowing space for the late bloomers to shine. 

In the vegetable garden.  Keep picking!  If you let cucumbers or squash, beans or any other vegetable over-ripen - producing seeds - the plant will think its work is done and stop producing flowers and setting fruit. Replant peas, beets, green beans and lettuce and you’ll have a new crop in September.  In late August, remove flowers from tomato plants.  There’s not enough time for them to set fruit and ripen before frost. And. removing new flowers tells the plant to devote its energy to growing and ripening the fruit already in the vine.

Keep picking from your garden.jpeg
Deadhead and prune annuals in containers in August 1.jpeg

Container gardens need extra attention now.  Keep deadheading annuals and don’t be afraid to cut back spreading plants such as petunias and verbena to get them back in scale with their container and promote new flowers.  Stop adding fertilizer to any container with perennials or small shrubs which you plan to winter over.  The perennials you wish to keep should be transplanted into the garden before the end of the month so they can establish roots to carry them through the winter and next spring.

Plan next spring’s garden.  August is the month to order spring bulbs.  You will have the best selection from any grower if you order now. Tulips, daffodils and other spring beauties don’t want to go into the ground until the soil temperature has dropped to 55 degrees and you are turning on your car heater in the morning.  Look at photos you took this spring and judge where more bulbs are needed.  When you plant, remember bulbs look best in groups, single bulbs spread out along a border or walkway have very little visual impact.  If you sometimes have visits from deer and rabbits, daffodils and hyacinths are deer resistant, tulips are deer (and rabbit) candy.

Shop catalogs now for the best selection of spring 2022 bulbs.jpeg
August is when garden centers lower prices, but inspect pot-bound plants carefully.jpeg

Look for sales.  If woody plants are on sale, shrubs like winterberry holly (Ilex verticillata) and red twig dogwood (Cornus stolonifera) add structure and color while trees such as paperbark maples show off beautiful bark in the winter landscape.  Many garden centers have begun discounting plants, but there is still time for new trees and shrubs to settle in before the ground freezes.