Amaranth Hot Biscuits in Wave Hill’s Flower Garden. (Adrian Higgins/The Washington Post)
Gardening columnist

If you want some pointers on how to keep the garden humming along in a dry autumn, you should make your way to Wave Hill, the 28-acre estate overlooking the Hudson River in New York.

Long known as a gardener’s garden because of its high level of horticulture, it’s a quiet and unexpected oasis in the Bronx whose stone mansion has been home to such creative souls as Mark Twain and Arturo Toscanini. New Yorkers know it as a place to spend a quiet hour sitting on the lawn, gazing beyond its arbor to the river and the stone cliffs of the Palisades on the Jersey side.

I always seem to show up at Wave Hill late in the season, which is great because I get to see how others dress the garden for the final act. Two gardens here in particular focus on September and October but — instructively — in markedly different ways.

The first is splashier. The Flower Garden sits alongside the ornate conservatory, where paths, fences and arbors form a framework for a loose and cheerful display of flower power.

In general, the garden in early fall relies less on blooms than the late-spring version, drawing instead on the power of ornamental grasses and the shapes and textures of foliage plants. But even at this reduced pitch, the Flower Garden is awash in blossoms — salvias, helianthemums, dahlias, amaranth, nicotianas. If this is soon to crash with the first frost, neither the flowers nor the bees seem to know or care.

In the red border, rose hips and amaranth entwine in a late season embrace. (Adrian Higgins/The Washington Post)

This garden peaks in June and again in early fall. As such things as spent foxgloves and other biennials are yanked out after the first show, the holes are filled with plants destined to perform three months later.

“The garden consists of about 40 percent perennials, 20 percent self-sowers, and the rest are things we grow and add,” said Harnek Singh, the gardener. The beds radiate from a central circle, arranged by color.

For the end-of-season show, Singh employs a few tricks. One is to delay starting dahlia tubers until late spring — a month or more later than usual. Those planted in May, he argues, have run out of steam by now. One of his dahlias, the crimson-flowered Bednall Beauty, should be grown for its foliage alone: Dark, cutleaf and small, it presents a dahlia with uncommonly fine texture.

Another tactic is to start annuals later as well. “I was still sowing seed at the end of June,” he said. Candidates for such tardiness include cosmos, zinnias and, notably here, nicotiana and amaranth. The deep-plum-red nicotiana Nicki Red is gorgeous and became another name jotted in the notebook.

With its dark-red foliage and tresses of crimson flowers, the amaranth is an annual full of Victorian melodrama — no wonder it’s sometimes called Love Lies Bleeding. I find amaranth to be an acquired taste. Fortunately, I have acquired it. One plant was held in the arms of a rose bush, itself full of orange-red fruit, and together they resembled star-crossed lovers at the end of a bleak opera.

Most amaranth flowers are red, but some are a tan brown, conspicuously a group of towering plants in the central bed named Hot Biscuits. It is hard to grasp that a plant so beefy started life just a few weeks earlier from a seed that would fit on a pinhead.

One of Singh’s beds is full of the basil-like — but purple-leafed — perilla, an annual he pinches back regularly in summer to delay flowering and keep its principal ornament, the foliage, looking fresh.

The Flower Garden at Wave Hill offers an oasis of calm and color away from the New York bustle. (Adrian Higgins/The Washington Post)

Another foolproof way to enliven the fall garden is to plant lots of salvias. They are tender plants, and the largest of them function by August as shrubs with presence. Others are more slender and can be squeezed into places where there otherwise would be seasonal gaps. Singh has planted 42 varieties in the Flower Garden and points out a large, magenta-flowered beauty named Mulberry Jam, growing at the base of an aster that is yet to bloom. My own Mexican bush sage began to flower only last week. Other species start earlier but carry on through to the first frost.

The second special autumn display occurs in the Wild Garden, which is a hillside with topography, gravel paths and plantings that scream more “dry” than “wild.” I love such arid landscapes because you can assemble so many interesting plants that otherwise struggle or rot away. The key, apart from a sunny aspect, is to make sure that the soil is as free-draining as it looks and that you are fastidious with your plant selection. Spring bulbs love these environments, by the way, and such a garden would be a haven for snowdrops, irises, crocuses, miniature daffodils and species tulips.

Much of the garden is now a composition of forms and textures of perennials and small shrubs that are given spice through a series of self-sowing annuals. The gardener, Gelene Scarborough, has the real fun of pulling these annuals from unwanted areas, to leave others to emerge in just the right places, in the nooks and crannies between permanent plants. Because these annuals have chosen their sites themselves, the effect is natural, if not quite wild.

Gomphrena, here the richly hued variety QIS Carmine, is a delightful presence in this environment. Scarborough has grown it in and around the dainty thistle-like blossoms of the tassel flower, Emilia coccinea. Other self-sowing annuals include the sculptural and wiry Verbena bonariensis and the phlox-like Silene armeria. They are joined by clumps of garlic chives, which are handsome in their September white flowers, though a challenge to keep in check.

Scarborough took me to the heights of the garden, where a couple more unusual self-sown annuals had created a real presence. Euphorbia cyathophora is low and wide, with holly-like leaves, red flower bracts and clear echoes of its relative, the poinsettia. Its common name is fire-on-the-mountain. Fittingly, its cousin, Euphorbia marginata, grows nearby and is called snow-on-the-mountain. It is tall and slender, with creamy variegated leaves and white blossoms. It lends a cool freshness to the garden when it is most needed, at the end of a hot summer that managed to be both humid and in want of rain at the same time.

@adrian_higgins on Twitter