Garden Notes: Hybrid hibiscus steal the show

Garden Notes: Hybrid hibiscus steal the show

Red Mallow. — Susan Safford

Abigail-HigginsThe sun is falling steadily lower in the sky. It signifies not summer’s end, but tells us that it is drawing nigh. This amazing season has given gardeners much to appreciate and be thankful for. The heat waves experienced elsewhere did not materialize, despite predictions, and there have been few Japanese beetles and mosquitoes. Nights have been cool. Rainfall has been sufficient and often at night.

Scene-stealers in the August garden are the hybrid hibiscus now in bloom. Those unfamiliar with the theatrical plants’ dinner-plate sized flowers and stature are literally stopped in their tracks by them. What a floral tour de force!

The question of the August garden has become more perplexing, with height-of-bloom times speeding up almost yearly: stars of high summer such as oriental lilies and some phlox cultivars are almost passé by the beginning of the month. Fortunately, hibiscus hybrids seem to have resisted this speeding-up process, and still reliably take center stage in mid-August.

According to “Herbaceous Perennial Plants,” Allan M. Armitage’s big book of perennials (Stipes Publishing LLC), many of the garden hybrids were bred from Hibiscus moscheutos (“mos-KEW-tas”) a North American native, along with other vigorous members of the genus. Islanders know the beautiful pink stands of them, along our brackish coves and salt ponds, as “marsh mallows.”

Hybrid hibiscus plants share the hardy nature of their wild ancestors and the brilliant colors of their tropical relatives. (Armitage mentions the outstanding work done by the three Fleming brothers of Lincoln, Nebraska, in this hybridizing.) Many are patented plants and not always available in small local nurseries, but finding and growing them is worth the effort for the show they put on. The color range is white through pinks/lavenders to red and beyond red, to an almost black; one, ‘Old Yella,’ is a buttery primrose.

Space them out

The heights of hardy hibiscus hybrids vary from compact to super-sized, but most require plenty of room and air space. Do not try to shoehorn a hardy hibiscus into that small blank space that “just cries out” to be filled. Hardy hibiscus hybrids prefer full sun and fertile, well-drained soil. They appreciate adequate moisture but, unlike our beautiful, Island “marsh mallow,” they do not need to be planted in a swamp! Figure two to three feet wide and about four feet high for spacing most, with some becoming one to two feet taller where happy.

Hibiscus plants are categorized as woody shrubs. They are one of the last perennials to break dormancy and emerge in the spring. In the gardens where we care for them, we leave the woody stems until next year’s growth is well up, to avoid disturbing new shoots by cultivating. These woody stems are sturdy enough to be pressed into service to support the current year’s growth, a sort of built-in, self-grown, staking system.

You may encourage sturdier, bushier growth by pinching hardy hibiscus when the shoots are about six to eight inches tall. They benefit from fertilization, but hold off after the third week of June, or you may encourage vegetative growth at the expense of blossoms. Excessive feeding by Japanese beetles or hibiscus sawfly may indicate plants that are stressed; step up efforts at soil improvement.

Turk’s cap lilies

An emblem of Island roadsides and quiet shaded spots in August, the turk’s cap lilies have shone in recent weeks. While there are some people whose aesthetic prevents them from welcoming these towers of elegant orange into their premises, most of us are enchanted with their bright presence, easiness, ability to reproduce and increase on their own, and general resistance to the red lily beetle. So I am dismayed to see that many — though not all — are suffering from browning and loss of lower leaves. Am hoping to learn the cause of this disfigurement.

In the garden

Check grafted trees and shrubs, such as roses, for suckers originating from below the graft union. If they are not removed, eventually the entire plant will revert to whatever species supplied the rootstock.

Watering is paramount now. The afternoon sun is especially hot. The sun’s wavelength shift towards the infrared causes solid matter to heat up and hold heat differently than when the wavelength is primarily ultraviolet. Pots and garden seedlings may need watering twice daily. Keep plants looking good with a liquid feed.

Lift and divide bearded iris. Choose young, strong sections of rhizome. Trim off foliage and roots by two thirds and one third, respectively, and replant about one foot apart, with rhizome just at soil level.

I have seeded beets, carrots, more zucchini ‘Romanesco,’ Swiss chard, sugar snap peas, radicchio, and Portuguese kale but could have done much more — nothing ventured, nothing gained. Continue to weed and cultivate in vegetable gardens. The uncultivated crust that forms accepts less water, including dew, than cultivated soil does. Reemay over my three seeded rows of carrots will, I hope, hold in the moisture the seedlings need to grow well and keep out the bunny that has wormed its way through my fencing.

Parts of well-established clematis vines have succumbed to clematis wilt in my garden, and in others too. It is always a disappointment: to go for years without wilt, and then, in an otherwise satisfying season, to have it appear — “for no good reason,” as we always say. (Well, there is a reason, probably, but it’s not apparent to the gardener.)

If there are empty spots in your vegetable garden, or if you are clearing it out preparatory to departure, mulch them or sow with a green manure (cover crop) of some sort. If nothing else, it occupies the space and prevents the blown-in seeds of weeds becoming established.