Garden Notes: Don’t plant that!

But try these, in the late-season garden.

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Late flowering Salvia azurea var. pitcheri, here with gaura, is among the bluest of flowering plants. —Susan Safford

In the Sept. 27 Garden Notes, I mentioned the role our own taste plays in garden choices: Mostly what we plant is nobody’s business but our own. However, the garden and nursery industry owes its buying public a responsibility to point out plants and situations where information and planting caution are called for.

Interstate (and global) commerce leaves us vulnerable. Many plants we buy here are sourced from Southern growers. Inevitably, kudzu is going to be present in those rootballs (see Sept. 27th’s “Kudzu crops up in West Tisbury”); and plants that are wonderful in one respect may be unusable in another.

Even with knowledge and expertise, invasions of egregious plants occur. Pyrus calleryana cultivars such as ‘Bradford,’ ‘Aristocrat,’ ‘Redspire,’ and ‘Autumn Blaze’ have gone rogue and reverted, and are now a horror spreading throughout the Middle Atlantic states, and heading our way.

We see this truly awful invasive sited on Clough Lane, Vineyard Haven, and in Edgartown’s fanciest landscapes. A heavily hyped introduction of our National Arboretum, the ‘Bradford’ pear (a cultivar of Pyrus calleryana) and its ecological consequences are the subject of a recent Washington Post article, “Scientists thought they had created the perfect tree. But it became a nightmare,” by garden writer Adrian Higgins (no relation).

The late garden

It might be useful to describe plants other than asters for fall gardens. Loss of light is a factor we can do little about, one that is separate from climate or plant selection. Otherwise, though, on the Vineyard we are different; our marine climate extends fall and prolongs garden life.

In open, sunny locations, colorful dahlias will keep on until felled by frost, and are a source of cut flowers, not to mention joy. The first really frosty night puts an end to them, however. Garden chrysanthemums will soldier on in spite of frost; or at any rate, can be cleaned up a little so they still look presentable, even under snow.

Look for the particularly good Autumn Crescendo series of daisy-flowered ’mums: ‘Bolero,’ ‘Rhumba,’ ‘Overture,’ ‘Samba,’ and ‘Harmony.’ With lovely colors, they are trouble-free and floriferous, their mounding habits making a splash in the garden.

The following three are North American natives:

  • Woodland tobacco (Nicotiana sylvestris) is hard to beat for stature and dramatic effect in the late garden. It not only tolerates cold, but also is deer-resistant. Once introduced and located in the garden, the plant self-sows, since it spreads its dustlike seed and reliably germinates the following year.
  • Gaura (Oenothera lindheimeri) adds movement and brightness to the late garden: ‘Whirling Butterflies’ with its hints of pale pink; all white ‘So White,’ and ‘Siskiyou Pink,’ to name three. Individual plants may not survive winter, but gaura also self-sows freely.
  • Sprawling Salvia azurea var. pitcheri is among the bluest of flowering plants. It saves itself for the end of the season. Plant in sunny, dry locations with good drainage — it can be marginally hardy.

 

The other spot of “true blue” for the late garden is ceratostigma, or hardy plumbago. This creeping groundcover loves to weave itself harmlessly through stonework and dry-laid retaining walls, the green foliage sporting rosy red leaves as autumn wears on.

Gleaming white Montauk daisies have become iconic autumn perennials for Island gardens, and with good reason. Their mounding forms are shrublike in their presence, and lend a crisp, designed look to gardens. Pinching several times before early July is crucial for achieving a tidy shape; unpruned plants splay open laxly.

Verbena bonariensis needs no introduction these days, yet it was not very long ago that its glowing violet flowers atop pencil-thin stems were scarcely known to Island gardeners. Much like woodland tobacco, plant it once in your garden and you will never need to replant; it is an excellent self-sower and carries through until the garden’s finale.

Annuals do their part too, and many, such as snapdragons, salvias, and petunias, resurrect themselves with cooler weather. Ageratum ‘Blue Horizon’ is excellent until the very end, and is avoided by deer.

Trapping photons — more light! — is usually critical for late-season gardens, but for the late garden in part shade, try aconitum and anemone. Seasonal garden owners who must leave before these beauties’ season of bloom may find them vexing plants; but the late garden would be a sad place without them.

For unknown reasons, lately the white Anemone x hybrida ‘Honorine Jobert’ has achieved towering heights, despite not needing staking even so. Normally it grows about 36 to 40 inches high. ‘September Charm’ is a beautiful light pink, with the petals’ reverse a deeper purplish rose. The recently introduced shorter hybrid, ‘Wild Swan,’ is sensational, producing nonstop white flowers with steel blue petal reverses. All the anemones derive much charm from their centers of golden stamens.

Kirengeshoma palmata, the waxbell, is a lovely long-lived perennial from Japan for holding down a spot in shade gardens, gradually achieving the stature of a small shrub and coming into bloom only after Labor Day. Its large pendant flowers are pale yellow.

Partners to the above suggestions, in what used to be called the mixed border, are deeply colored grasses, such as panicum or schizachyrium, compact shrubs that color or berry well, and foliage plants that age with tawny colors, such as geranium, tiarella, hosta, and ferns, and let’s not forget roses.

With enough light, and thoughtful plant selection and maintenance, in some years an island garden may be colorful right up until Thanksgiving and beyond.

 

In the garden

A bumper year in squirrels is interfering with mainland Massachusetts agriculture, according to UMass Vegetable Notes. Island roads are littered with squirrel roadkill. Wait until asparagus tops (“ferns”) have turned yellow to cut them down. Leave a short stub, about two inches, of stem; then weed the bed and mulch it with well-rotted manure, if available, or compost. Harvest fallen leaves for leaf mould.