The growing season isn’t over yet, but as fall approaches, your garden may be looking woebegone, especially if the twin scourges of heat and drought have battered your plants. Chances are, many annuals and perennials look exhausted with few flowers, lots of spent blooms and leaves that are tattered and scorched. The odd specimen may appear diseased or even dead.
What to do? Time for a garden facelift: give thirsty plants a drink and your beds a thorough weeding, cut back what doesn’t look good, deadhead (remove spent flowers) and fill gaps with new plants or pop a container into bare spots. Here’s the drill:
True annuals flower, produce seeds and die, so deadheading prolongs bloom. This, along with regular watering and feeding with a balanced fertilizer (such as 15-15-15), keeps cosmos, geraniums, marigolds and zinnias flowering longer. Some annuals, including impatiens and some petunia varieties, don’t need deadheading and will bloom until frost, but if they look leggy with fewer flowers, cut them back to half their height and they’ll rebound.
Shear back early perennials by half their height. Some, such as lady’s mantle (Alchemilla spp.), have fresh leaves under old ones. Cutting back spent flower stems also promotes lush new foliage in rock cress (Arabis and Aubrieta spp.), many-coloured spurge (Euphorbia polychroma), creeping phlox, catmint and cranesbill.
For later perennials, American horticulturist Tracy DiSabato-Aust suggests deadheading “when the seedpods outnumber the flowers or when the [flower] spike is about 70 per cent finished with blooming.” This encourages repeat flowering with some plants, but the second flush won’t be as prolific. Repeat bloomers include campanula, delphinium, foxglove and echinacea.
Sick or dead-looking plants
Be sure your plants are truly dead before you throw them out. To cope with excess heat and drought, established perennials may jettison their foliage; the leaves may be dried out, but the roots are alive and ready for next season’s growth. The same applies to many plants eaten by pests, such as hostas. To test if your plant is alive, give it a gentle tug; if the roots hold fast, it should be fine. As for diseased specimens—for example, older varieties of phlox that develop powdery mildew on leaves—cut them back (don’t compost; put in the garbage). For the following year, consider replacing with disease- and pest-resistant varieties like the Tought customers mentioned below.
- Although many hostas are prone to slug damage, pest- and disease-resistant cultivars have thicker, waxier leaves. Good bets include Hosta ‘Blue Wedgwood’, ‘Canadian Shield’, ‘Northern Halo’, ‘Krossa Regal’ and ‘Sum and Substance’.
- Mildew-resistant summer phlox (Phlox paniculata) cultivars include ‘David’, ‘Delta Snow’ and P. maculata ‘Natascha’.