Weeping willow — the nature of the beast

A year ago I wrote a post on dappled willows (Salix integra ‘Hakuro Nishiki’), comparing one rigorously maintained specimen and one planted-and-forgotten specimen. Two takeaway points from that post (I hope): 1) plants in a garden usually require at least some maintenance — more or less, depending on the genus and its role in the garden; and 2) willows really want to grow.

Here’s a photo illustrating the second point. This willow — I think it’s an old weeping willow (Salix babylonica) — clearly had started to break apart, and had apparently become fairly hazardous. Its owner whacked the entire top off, and the willow responded with this explosion of shoots. Willows grow fast and grow weak, but they’re vigorous enough to continue growing even if they break up, fall over, are pruned to the nth degree, or are cut down, which is what makes them such great coppicing plants. But that’s a topic for another post…In the meantime, enjoy the photo, which I took in a New Hampshire seacoast town.

Cartoon character or tree? Weeping willow growing into a new form after having been topped.

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Thriving live hemlock

That last post made a good point — sometimes the leftovers in a landscape can be used as a feature in and of itself — but I much prefer the photo here. This hemlock is very much alive, and lives outside of Boston on private property. Carl Cathcart, Consulting Arborist, took me to see this wonderful tree last July, and you can see more photos of and information on the tree at Taking Place in the Trees.

To get an idea of the scale of this tree, look just to the right of the tree's center; Carl Cathcart is standing on the ground under the tree's canopy, and his legs are just visible.

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Boston hemlock

The other day I was on Beacon Hill and spotted this mostly dead hemlock tree, completely swathed in Boston ivy:

Though this hemlock tree on Beacon Hill is dead, its stripped-down structure maintains usefulness, as Boston ivy covers it entirely with foliage.

Perhaps the owners were simply neglecting their courtyard garden, but I like to think that they saw the mature tree’s size as an asset to the place, and decided to use the deadwood as an armature for another plant, and to use the resulting ‘hybrid’ as a garden element.

I have seen this strategy used with other trees; an ancient, mostly dead apple through which a vigorous rose climbs and blooms, tiny dead crabapple that hosts a clematis vine, and a couple of thriving Norway maples through whose canopies wind equally thriving wisteria vines.

We see bittersweet and poison ivy taking advantage of the height and sun exposure offered by trees; why not use that principle and foster the growth of ornamental vines over dead trees, or, as in the case of the Norway maples and wisteria, let one aggressive species provide a platform for another aggressive species?

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Hemlock root flare excavation

It has been a while since I’ve written about root flares. I got some photos from my friend Carl Cathcart the other day, showcasing the excavation of a hemlock root flare. This tree is one of a hedge of 7-8′ tall hemlocks planted two years ago. Its owner had noticed that while the hedge wasn’t failing, it wasn’t exactly thriving, either. He called Carl, a Consulting Arborist, in to inspect the situation.

Carl zeroed in immediately on the base of the tree, and with a little hand excavation discovered that the hemlocks were sitting at least four inches too deep in their root balls. It has been customary for years to plant balled and burlapped trees so that the top of their root balls sits at or slightly above the finish grade around them. Cultivation practices in the growers’ nurseries have changed since that technique became the standard, though, and now it is necessary to check each root ball to make sure that root ball soil is not covering a tree’s root flare. A buried root flare — whether it is buried with root ball soil, compost, or an excess of mulch post-planting — spells trouble for a woody plant, and can be the cause of a tree’s failure to thrive. Small leaves, shorter-than-normal annual twig extension, and thin foliage can all be symptoms of a buried root flare. Root flares are not roots and are not adapted to life under the soil surface; they are part of the tree’s aboveground trunk, and typically need to be exposed to the air.

The in-field solution to this problem (should the excess soil not be removed in the nursery) is to excavate the root flare onsite during project planting. This task should be done before the tree is planted, so that the flare is planted at the correct grade; unfortunately, many contractors are not even aware of the issue, and will not have included time for root excavation in their bid. Here’s where landscape architects can make a major difference in the longevity of their project’s woody plants, and where contractors can distinguish themselves from the competition; LAs aware of the need to excavate root flares should include that requirement in their bid sheets for contractors, and contractors aware of that need (whether they are in a bid situation or not) can use this task, and the benefits it brings to the planted landscape, as a compelling selling point.

When root flare excavation doesn’t take place when the plants go in the ground, the signs of tree stress will likely show up within a year or two. At that point, hand excavation is still possible, but air-tool excavation usually will be more efficient.

When Carl identified the problem, he advised the homeowner to have air-tool excavation done. Matt Foti of Matthew R. Foti Tree and Landscape sent over a crew to carry out the work; Carl’s photos illustrate this post-planting process nicely.

The arborist has tied up the hemlock's branches for easier access in to the root ball. In this photo some of the soil has been blown away already.

A compressed air tool blows off the root mass. Just visible behind the tree is a plywood barrier that helps keep airborne soil from covering the surrounding plants.

The root flare has been uncovered; note the soil line about four inches up from the root mass. When you see side branches at, just above, or even emerging from below the soil level you can suspect a buried root flare. Carefully scraping away soil at the tree's trunk will indicate if further excavation is necessary. Now that the root flare is exposed, it is possible to see the girdling root that has formed on the trunk's left side.

The girdling root has been cut off, preventing any further vascular constriction in the root coming off the trunk and heading toward the photo's lower left corner.

With the root flare exposed and girdling roots removed, planting soil is blown or shoveled back into the excavated area at the correct grade.

The last step, before untying the branches, is to water the excavated area thoroughly, to rehydrate roots and to eliminate any air pockets in the root mass.

Project site: Private Residence, Sudbury, MA

Consulting Arborist: Carl Cathcart, A Plant Healthcare Consultant
Arborist for root flare excavation: Matthew R. Foti Landscape and Tree Service, Inc.

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Dappled willow

About ten years ago, I noticed a mild fad rev up in the gardening world; all the garden centers around here started carrying Salix integra ‘Hakuro Nishiki’, usually trained into standard form with a 3-4′ high stem and a pompom of foliage at top. Hakuro Nishiki, also known as Dappled Willow, is a fast-growing, twiggy large shrub/small tree with variegated white and light green to pink leaves, and it lights up a garden with its foliage, which is profuse and almost aggressively healthy-looking.

I’m fond of these plants, though they certainly need to be placed with care. They like full sun, but can deal with some shade. Because they grow so vigorously, it’s a good idea to commit to pruning them every year or so, to keep them in bounds. Actually, I can see how sculpting them in various ways each year might be an interesting exercise — not something you’d want to do with most plants, but this one seems malleable enough to allow some experimentation.

I have written earlier about L. and A., my excellent clients on the North Shore, who enjoy developing and fostering their landscape. Several years ago L. bought a Dappled Willow for her perennial garden. It’s not a standard form; instead, she’s keeping it pruned low, to keep it in scale with other elements in the garden. Here’s a photo of it in leaf:

This plant is about thirty inches high and wide, and is kept as a mounded shrub with pruning.

And here’s a photo of how L. prunes it to keep it contained to this form:

Every year L. cuts this Dappled Willow back hard, to keep its vigorous growth contained in a form that works for her perennial garden.

I have wondered what these plants look like unpruned, and last week got to see one. If the willow in L.’s garden looks like a contained explosion, this one looks as if the top blew off the container:

Perhaps the owner of this plant didn't realize what level of attention Hakuro Nishiki was going to require annually.

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It’s that season

Last week a friend mentioned seeing a yellow-flowering shrub on the VFW Parkway in Boston. It reminded me of the show of Hamamelis that used to appear outside of the Harvard Business School’s Baker Library back in the early 80s; when I first saw it (this was a few years before I became a landscape architect and learned what Hamamelis was) I thought a bank of Forsythia was blooming in February.

Saturday I was in Cambridge, and drove down a street that used to be on my route home from work at CRJA. As I turned the corner, this sight greeted me.

This street runs roughly east-west, and with buildings on both sides gets a slice of sun in the middle of the day. The sycamore maples further along the street add a bit of dappled shade to that slice, too. These Witch Hazels don’t seem to mind. And they have the room they need to spread and fill out their characteristic fountain habits.

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Deskside greenery

Cattleya in bloom; Ripsalis in background

Another grey and cold day in a long, cold month. Going to my desk and working is a good antidote to the gloominess, especially when the Cattleya next to my drawing board blooms (as it did last fall), or the Ripsalis in the window each January reliably turns from a mop of green string into a mop of green string and yellow confetti. Each plant has its own delicate flower fragrance, which rests quietly in the air until someone walks through the room and stirs up faint currents of deliciousness. It’s a good reminder to use scented plants in the landscape.

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Aster

So we’ve started down this path, which in a time typically relatively quiet in plant color may not be such a bad thing. These Purple Dome asters gave a great show on one of my projects this fall, and enlivened the scene when other plants were fading to gold and rust.

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Blue

On a gloomy day, after a cranky post, perhaps a little visual break is in order:

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Small-space gardening

We’ve all seen photos of grand mixed and perennials borders on old country estates (Gertrude Jekyll, Vita Sackville-West, Beatrix Farrand),

Vita Sackville-West, Sissinghurst White Garden. Photo by bestfor/Richard on Flickr.

and of sweeps of perennials, grasses and shrubs by the contemporary designer Piet Oudolf and landscape architects Wolfgang Oehme and James van Sweden.

They’re dramatic and luxurious-looking, and it’s easy to envision being right there, surrounded on all sides by space and uninterrupted swathes of glorious texture and color.
Sometimes the only space available is quite a bit smaller and more constrained. This past weekend I was walking down a suburban Boston street and found this planting, in which a narrow bed — bounded by fence on one side, driveway on the other — hosts a garden that shows off in every season.

This plant bed can't be any more than three feet wide, but there is a lot going on in it.

In this climate, plantings that flank a driveway have to be tough. Snow gets shoveled and plowed on top of them, and sometimes it’s best to stick to herbaceous perennials that will die back to the ground and be unharmed by wayward plows.
This garden has a fairly simple palette — Hydrangea, ‘The Fairy’ Roses, Korean Chrysanthemums, Sedum ‘Autumn Joy’, and a carefully pruned collection of crabapples — that works well here. Even if the hydrangeas and roses get clobbered by the plow they’re likely to recover; the sedums and chrysanthemums can be cut back to the ground, and the crabapples are trained to hug the fence, out of the way, making what could have been a winter drawback into a fine asset.
It’s refreshing to see this kind of resourcefulness in what often seem only to be incidental places on a property. This strip isn’t a place in which you’d want to (or could) lounge away the hours, but it shows how varied and texturally exciting even a small space can be.

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