Garden Notes

It's show time for the iris

flowering tuliptree
The flowering tuliptree can be found around our Island, such as this one at Heather Gardens. Photo by Susan Safford

By Abigail Higgins - June 21, 2007

The summer solstice is upon us, the splendid time of light and growth in the natural world, and the official start of summer in the human one. From here on out, the quality of light shifts slowly and imperceptibly, and initiation of bloom and seed formation takes the place of spring's green growth of leaf and shoot. Everything is light-driven.

Now it is just regular caterpillars of all stripes making their seasonal appearance; the infestation phase of the fall cankerworms and their inchworm cohort is diminishing. With trees in numerous places around the Island having been defoliated repeatedly, there are going to be some dead trees.

If you have a tree needing to be taken down, I would like to suggest replacing it with a tuliptree, a magnificent tree worthy of filling the empty spot. Liriodendron tulipifera is a member of the Magnoliaceae. It is native to and is one of the tallest trees of the eastern North American mesic forest. The one other member of the genus is native to China. Cabinetmakers and builders know the wood as yellow poplar, straight-grained and blemish-free.

The liriodendron's majestic stature requires a larger scale site, making it less suitable for the small lot; but if space is available, heed Michael Dirr's words in his "Manual of Woody Landscape Plants." He calls it "truly an aristocratic tree" and writes further: "as a specimen ...it has great beauty; perhaps most handsome in large groupings or groves where trees develop a spire-like habit." He also cites the splendor of its yellow autumn coloration.

The tuliptree grows best in an open sunny situation where the soil is deep, moist and loamy. Don't despair if that doesn't sound much like the typical Vineyard soil; you can choose the site carefully and mulch and amend the soil. There are a number of tuliptrees successfully growing on the Island: at the Polly Hill Arboretum (PHA), the grounds of the West Tisbury town office, and Heather Gardens (see photo), to mention just three.

Liriodendron leaves are a smooth bright green; the lobes give them a somewhat square shape of about six inches. The large beautiful flower is a chartreuse tulip-like blossom, up to two inches; the outside of the tepals is painted with a splash of soft orange and is stuffed with stamens and plentiful nectar. They are bee pollinated.

There are a number of interesting cultivars available, some with different foliage variegations, leaf shapes, or having different habits of growth. Among the more useful are 'Compactum,' a dwarf form; 'Fastigiatum,' a narrow upright form; 'Ardis' and 'Little Volunteer' are each diminutive forms.

Since "all things are interconnected," the habitat changes -more sunlight due to widespread tree defoliation and death - are sure to provide an opportunity for spectacular understory growth. Not only does this provide a chance for saplings, which eventually replace the lost trees, to accelerate, but also other understory elements like viburnum, winterberry, sheep laurel, lowbush blueberry, grapevines, and poison ivy.

Unhappily, invasives such as oriental bittersweet, multiflora rose, Japanese honeysuckle, garlic mustard, and autumn olive also proliferate in the increased light. As with any weed, it is far easier to spot and eliminate these nuisance plants when they are small than when they have taken over.

In a recent Polly Hill Arboretum talk on Invasive/Exotics, PHA executive director Tim Boland mentioned the role of disturbed soils in the spread of weed plants. You don't want areas of open dirt if you can avoid it. (As I view the path of our un-mulched waterline trench, now hairy with bindweed, I sigh: fac quod dico, non quod facio!)

Should it become necessary to remove a dead tree, whether due to caterpillars or other causes, simply cut off the trunk flush with the ground. Perform stump removal or grinding only if exactly the same spot is needed for another tree; otherwise, plant alongside or nearby the original position. The New England Wild Flower Society has an excellent web page of information on this topic at http://www.newfs.org/conserve/invasive.htm, as well as print materials. I urge all gardeners and property owners to avail themselves of the information and learn to ID the undesirables.

Changes in habitat have also led to disastrous changes in bird populations. Ornithologists and the National Audubon Society have recently released figures showing spectacular declines in many bird species. "Some of the most common birds seen and heard in American back yards are becoming a less frequent sight and sound in much of the United States," according to a study released by the National Audubon Society. "Twenty common birds - including the northern bobwhite, the field sparrow and the boreal chickadee - have lost more than half their populations in the past 40 years, according to the society's research."

Factors include: agriculture, habitat loss, pesticides, invasive species, and global warming. "The focus isn't really on what's happening to these 20 birds, but what's happening to their environment," said Greg Butcher, the society's conservation director. The health of a bird population is often a harbinger of the health of other wildlife and humans.

As with all things we as individuals care about protecting - whether butterflies, birds, fish, or wild flowers - we can at least do what is within our own means. And all of us can at the very least educate ourselves about problems and try to reduce our individual role in their causes.

Speaking of poison ivy and learning to ID undesirables, one of the signature features of poison ivy at this time of year is the red coloration and three leaflet arrangement of its new growth. I find it amusing that the excellent modern climber rose, 'Dublin Bay,' seems to mimic poison ivy with similar shining, red-hued three-leaflet new growth; it has caused me to nickname it the "poison ivy" rose. When I work with them, trained on a long fence in an up-Island garden, my peripheral vision constantly receives a subliminal poison ivy warning. Its glowing blood-red buds and flowers, produced continuously, however, contradict my nickname. Sadly, there is little rose fragrance.

Roses are burgeoning. Satisfy their hearty appetites with a monthly side dressing of organic food: dehydrated manure, organic fertilizer or compost. Dry or starved roses are more apt to receive the unwanted attentions of pests: sawfly larvae are about and Japanese beetles soon will be. Sawfly larvae, which look like green caterpillars but are not, are controlled by applications of insecticidal soap, sprayed early or late in the day to avoid foliage burn.

It is now or never for pinching back branching perennials such as phlox, Montauk daisies, garden mums, and asters. The reasons for doing this are threefold: to promote bushiness and more flower heads, reduce need for staking, and retard bloom time.

PHA presents Clematis for Your Garden, with Dan Long, June 27. Call 508-693-9426 for more information.