Garden Notes: Summer winds down

Now is a good time to assess your garden.

Polly Hill’s Oxydendrum arboreum, an appropriate species for Island planting. — Susan Safford

“We’re in the countdown,” the frequent greeting heard around mid-August, “only two and a half weeks to go!” Summer is winding down, and for many here, not a minute too soon.

Rudbeckias for late summer

Some of the easiest to grow flowers in late summer are the golden Rudbeckia family. To the novice these are collectively nick-named “black-eyed Susans,” but according to Allan Armitage in “Herbaceous Perennial Plants,” Rudbeckia consists of about 30 species of annuals, biennials, and perennials, all native to North America. Most are plants of sunny places, tolerating greater to lesser amounts of moisture.

Years ago, I bought and planted a six-pack of so-called Gloriosa Daisy (Rudbeckia hirta). This species behaves variably as annual, biennial, or short-lived perennial, as they self sow around. Investing in that six-pack was serendipitous.

Through many seasons, diversity inherent in those original six small plants has expressed itself in golden variety: all yellow; yellow with deeper golden center; yellow with chocolate brown center; yellow with two-tone crimson/brown center; and a dramatic bleed-through with all red/brown flowers. Plants are usually not browsed by deer and tolerate dry sites. Stems are long, sturdy, and straight, perfect for cutting.

I leave the brown seed head cones standing at the end of the year as food for wildlife. Now offspring of the six-pack are distributed throughout several different planting areas, having required no effort from me. I only edit out the ones that planted themselves in the wrong spot.

Many gardeners know and love Rudbeckia fulgida var. sullivantii ‘Goldsturm.’ Its bold golden mounds can be seen from one end of the Island to the other now, lending structure and presence to airier plants, such as perovskia, phlox, and goldenrod.

Although formerly a vegetative clone, eventually ‘Goldsturm’ demand outstripped supply and seed propagated plants were sold as ‘Goldstrum.’ Plants strongly increase under good garden conditions: weed out, or make divisions. However, these are not the only useful rudbeckias. If you have room, taller rudbeckias are effective border backdrops and screening. R triloba, R laciniata, and R maxima and their cultivars and clones all contribute gold to gardens of late summer.

We need trees

Do you see the trees on your road or in your local park? Can you identify them? Do you have a favorite tree or species? Pictured is a favorite species of mine, the magnificent oxydendrum specimen on Polly Hill Arboretum grounds along State Road. In autumn it becomes a flaming tower of scarlet.

In hot weather the shade of trees makes itself invaluable. The Vineyard is being cleared and deforested at an accelerating rate, the urban/suburban heat-island effect fast materializing. (July ’21: Earth’s hottest on record!). Overheated bodies can tell the difference between tree shade and shade from buildings: while structures may cast shade, unlike trees their roofs are radiating heat.

Replacement, tree-for-felled-tree, is unlikely to occur. However, individuals can educate themselves about quality trees for Island locations and plan to plant as many as their property can accommodate. The mission of Polly Hill Arboretum includes advising the public on tree matters.

Qualities could include deep-rootedness, drought and salt tolerance, wind resistant structure and timber, and enduring lifespan. Many candidates would be oaks.

The recent heat events have caused many trees, shrubs, and plants to shed leaves. As long as adequate moisture exists and new growth is showing, this is not serious, just the plant’s way of handling stress of too many leaves transpiring too much moisture at a certain point. Sadly though, since we need every tree we have, some, such as trees growing in marginal conditions or stressed by road heat and exhaust pollution, will fail.

In the garden

Lavenders gone woody do not survive well in winter. Lavender also requires a well drained, dry, and sunny location to thrive. Trim and prune now to help plants produce new growth that is hardened off by autumn, giving attention to overly woody growth and stems, and remove debris from around plants’ crowns. Applies also to other grey-leaved plants, such as santolina, stachys (“lamb’s ears”), and salvia.

The Vineyard has an extended fall growing season; the only thing diminishing is light, weakening until the winter solstice. Even if your garden suffers with lower light levels, work in gardens can include soil improvement.

Cover crops mixes and green manures of various plants produce differing results in vegetable gardens, depending on conditions. Buckwheat is a great favorite, being easy-kill but also attracting pollinators, adding silica to soil, and germinating fast.

Winter rye, ryegrass, several different clovers and legumes, grains, and radish are others used as cover crops and green manures. Shop locally or check Johnny’s Selected Seeds and Pinetree Garden Seeds for wide selections of New England adapted soil holders and improvers.

Chasing perfect

As the season races along, take a minute to assess your garden. Gardens, unlike “landscaping,” are not static. Plants grow and crowd, taking more space; or grow and must be pruned, spread out, or divided. The year after the garden seems “perfect” is often the year it requires lots of work.

I have a small bed where the shrub rose placement is wacky. They need to be dug and repositioned so the look is less unbalanced. A couple of other things are off-kilter as well. Sometimes placement is simply unsatisfactory, even if it is off by mere inches.

Color schemes do not always work out as envisioned. Light conditions may have changed as trees and shrubbery grow but then leave them unable to flower or thrive. Perennials need division. Even walkways and stepping-stones may need re-routing.

Mark locations and photograph the layout. It helps when autumn arrives: you are ready to start, but plants offer fewer identifying clues.