From The Professor's Greenhouse: Biennials (Part 2)

Season-relevant tips on planting, growing, and maintaining thriving gardens and landscapes from

Professor Kevin Jones, Botanist & Biology Professor at Charleston Southern University.

Life is like a garden; perfect moments can be had but not preserved, except in memory - Leonard Nimoy

Ornamental biennials

These include some of my favorite flowers, including the silver-fuzzy mullein (I just want to pet them), foxgloves, honesty, the stately hollyhocks, sweet William (a plant that always reminds me of helping my grandmother with her flowers 60 years ago), and those oh-so-delightful forget-me-nots. In August through September, these can be directly sown into a prepared bed or started in a flat to be transplanted into the flower border later.

Old dogs and new tricks.

I love dates. Especially Medjool dates. I have spit out enough seeds from these to grow several hundred acres of new date palms. I was told, and I tried it this year. Collect the seeds, soak them overnight, wrap them in a damp paper towel, and place them in a plastic bag. After a few weeks (for me, it was three weeks), they will sprout a root and can be potted in a good potting mix. I am told these dates will survive and produce in our zone 8b climate. I have yet to test that last point, but I will let you know.

Harvesting Herbs

August is a good time to begin harvesting herbs for drying. Many herbs, both perennial and annual, can be harvested now and dried or used in herb-infused vinegar, oil, or butter. Annual herbs such as basil, chervil, cilantro, and dill and the perennials such as chives, oregano, rosemary, sage, and thyme, as well as others, can all be harvested this month. When harvesting herbs, I take the approach of pruning them and try not to remove more than one-third of the plant. In addition, I try to leave the remaining plant in a pleasing shape for its future growth.

To dry herbs, spread them on cheesecloth in a warm, dark, well-ventilated area. A little added air movement from a small fan blowing over but not on them will speed up the process. They can also be bundled to hang to dry. This last method can become ornamental in itself.

Herb-infused vinegar is excellent for seasoning many dishes, is visually appealing in clear glass bottles, and makes an outstanding gift: add a ribbon and card, and you have a gift from your garden, that you harvested, and then made – how much more personal can you get?

I like the visual appeal of seeing the herbs in the vinegar I am using, so usually leave them in the bottle.

This is one of only hundreds of ways to make herb-infused vinegar:

You will need herbs, a good white wine or red wine vinegar, and a glass jar or bottle.

Wash and gently dry the herbs (the choice of herbs to use is yours, basil, rosemary, thyme, oregano, and others. Add garlic if you like.)

Gently crush the herbs to release the oils but not to destroy the shape of the herb.
Place the herbs, and a clove or more of garlic if you like, into the jar.
Cover with a plastic lid or cork stopper.
Label
Store in a dark location, such as a pantry, or cabinet, for two or more weeks to infuse the flavors into the vinegar.

Ornamental August chores (Veggie Chores are in Part I)

Consider the last feeding of perennials. Feeding later than late August or early September can cause growth too late in the season to harden off before the fall chill, leading to more winter damage than is necessary or desirable.
For the same reason, avoid pruning shrubs and trees this late in the season. Pruning stimulates dormant buds to start growing, and these may not have time to harden off before the chills of fall.
Some shrubs, such as oakleaf hydrangea, Azaelia, loropetalum, weigela, and forsythia, have already set the buds that will bloom in the spring. Pruning now will remove them, reducing their display in the spring. Pruning azaleas now will result in green shrubs with a spot of color here and there instead of the radiant display of this shrub that defines the Low Country in March and April.
Continue deadheading flowers to extend the flower display. The more you cut, the more flowers you will get unless you want the plant to produce seeds for self-seeding or collecting and planting next year. But, some plants, biennials such as foxglove and sweet William, for example, that self-seed. Deadheading these will prevent the next generation, so care must be taken to ensure new plants from self-seeding.
Cutting flowers for arrangements accomplishes the same thing as deadheading – with the added delight of a beautiful display indoors or to give as a gift.
For those annuals such as petunias and impatiens that have become leggy, they can be rejuvenated by cutting them back by up to one-third. They will respond quickly with a new flush of flowers.
Weeds are plants too. They are likely setting seeds now, also. Every weed allowed to set seeds this year is a family of little weeds next year. Get rid of them before they set or scatter seeds to save bother next year.
But. Weeds. I once heard the definition: ‘Weeds are plants growing where they are not wanted.’ Crabgrass and Florida betony are no one’s friend, but English plantain can make a lovely display in a semi-shaded location, and spotted spurge (Euphorbia maculata) makes an interesting ground cover that is easy enough to remove if it gets too enthusiastic
Keep an eye on those containers and hanging baskets. The hot weather, breeze, and low relative humidity can make watering daily necessary. Avoiding stress on these plants by maintaining moisture levels will prolong a beautiful show of flowers and lush foliage.
Another consideration of container plants is that, with frequent watering, the nutrients in the potting mix are washed away more quickly. Continue feeding containers into fall with the weakly-weekly fertilizer routine.
Take cuttings of favorite annuals and perennials that might be iffy in our winters to root, keep, and plant in the spring. Some, such as geraniums, make excellent houseplants that can be set out in the spring.
Consider ordering fall-planted bulbs. They should be set out in late October and into November here.