Garden Notes: Tips on our dry gardens

And looking ahead to fall plantings.

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We had a couple of rainfall apéritifs. Thankfully, it was enough to lay the dust, although drought conditions persist.

Checking in with various gardens, it is clear that even long-planted, established material is feeling the drought, and trees and shrubs recently planted are much more vulnerable. (At yesterday’s up-Island garden, the soil was dust-dry 10 inches down.) Keep in mind that trees with large, extensive root systems will take the available soil moisture from the punier ones of shrubberies and flowerbeds.

One can see this in lawn-browning patterns — indicators of dry soil. However, as the “Vineyard lawn” has proven over generations, grass greens up when rains and cooler weather return. Set sharpened mower blades higher, mow less often or not at all, and give the underlying soil a chance to avoid baking.

Looking droopy and shedding leaves are reactions to drought, lessening plants’ moisture loss. Watering is the instinctive response, but there are other moisture-retaining measures. Apply a layer of mulch around root zones to trap that water, and to enhance soil infiltration of what there is.

Apply an antidesiccant spray to foliage, bark, and stems (follow label directions). Even if there has been significant leaf drop, this will help protect next year’s buds. If mulching with compost, horticultural charcoal, known to increase material’s moisture-holding capacity, is a possible additive to home composting.

The weed scene

An unsought side effect of irrigation: Almost every weed seed that falls on irrigated soil germinates, increasing the need for regular maintenance. (And crabgrass, neon green on roadsides, does not even need watering to thrive!) In garden beds, there they are, lurking under the canopies of perennials and blurring neat edging — seemingly overnight phenomena, like mushrooms.

Many gardeners overly obsess about the problem of weeds and weediness, and crabgrass is not the only unwanted plant; it has plenty of company. Purslane, nutsedge, horsetail, and more — they all love August. Try employing a dust-mulch approach, and cut back on water use if excessive weediness seems a problem.

Not all weeds are bad. If plants support pollinator or bird life, you may expect profuse reseeding. Some have eco-importance; others may serve as trap plants for unwanted insect life, like Japanese beetles on evening primrose. Some seedlings may be from desirable garden plants that self-sow easily (thinking echinacea, various rudbeckias, various asclepias, Peegee hydrangeas, even trees such as hollies and kousa dogwood). So important to wildlife, various briars, brambles, and more sprout: cat-briar, wineberries, dewberries, blackberries, pokeweed, poison ivy.

Trying for balance in gardens and encouraging tolerance for “all this” is part of eco-awareness in our gardens. It is a wonderful thing for other life to find sanctuary in them, just as we do.

Dry garden? Try vitex and tiger lilies

Parched and wilting hydrangeas need not supply blue in your dry August garden. Checking in with various gardens and driving around neighborhoods allows me to observe conditions. A standout, even in the drought, is spectacular lavender blue vitex, of Mediterranean origin, also known as chaste-tree and, confusingly, summer lilac. (Stick with “vitex” — this is not a lilac, nor is it reliable with chastity.) Butterfly-covered Vitex agnus-castus is at peak bloom now, and is loving the heat.

Until recently this large, spreading shrub was not dependably hardy on the Island, and would die back to the crown over the winter, limiting its size and impact. I had one here, which failed over one cold winter, but not before a play-date child asked if it was a marijuana plant. The divided grayish-green, compound foliage is aromatic, and does somewhat resemble cannabis.

With the new weather cycles, Island vitex appear to be achieving their potential. Deer-resistant, they become towering mounds of intensely lavender blue flowers in gardens dry enough to have difficulty mounting more classic August displays. Deadheading of flower panicles extends bloom time: Flowering is on new growth; soil and water requirements are moderate.

Available vitex cultivars exist in shades from white to pink to purple. However, since rose of Sharon supplies plenty of pink to rosy reds in the dry August garden, it is hard to top intensely lavender blue forms in full flower.

‘Shoal Creek’ is one of the best, but ‘Abbeville Blue,’ ‘Mississippi Blues’ and ‘Montrose Purple’ are also highly rated by Michael Dirr, citing Longwood trials. First Editions’ purple flowered ‘Flipside’ is an intermediate grower, at six to eight feet. Proven Winners’ ‘Blue Diddley’ is a dwarf selection, growing from three to six feet, but dying back each winter.

A contrasting accompaniment to lavender blue vitex is the tiger lily, Lilium lancifolium, also able to thrive on its own in unirrigated gardens. L. lancifolium (now the official name) is mostly left alone by deer, differing from many other bulb lilies, which they often decapitate. The tall stems, four to six-plus feet depending upon location, are punctuated by the shiny black bulbils that mature and fall to the ground, effortlessly creating colonies of showy, orange-flowered plants. (Indeed, some consider L. lancifolium invasive.) They attract stupendous extravaganzas of equally showy butterflies.

In the garden

Continue to sow fall crops, being mindful of lessening light levels. Useful in fall vegetable gardens is a good selection of kale. The need for spraying against cabbageworms recedes; frost sweetens the leaves; add them to soups and good on their own, like collards. My current favorites are ‘Beira,’ tronchuda or Portuguese kale, and ‘Redbor,’ Russian kale.

Dividing perennials: Cut back and puddle in well. Better yet, wait until September. Last call to trim back lavender and santolina, thyme, and — maybe — rosemary. Having rosemary winter over here is still novel; much of their care will be trial and error. Trim back wisteria shoots to two or three brown buds. Use dehumidifier water on plants.

Tick check every night.