January 19, 2021

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How to choose the right conifers for any outdoor space

Evergreens fall into two basic categories: broadleaf trees and shrubs, such as hollies and camellias; and the needled cone bearers, the conifers. It is tempting to go overboard with both, to cling to screening and ornament in the gray months ahead. But this would be a mistake, especially with conifers. It is the deciduous, woody plants that give a place its sense of seasonality and vitality. If the Tidal Basin were planted with cherry laurel instead of cherry trees, well, there would be no tour buses flocking to the Cherry Laurel Festival.

A garden overstuffed with conifers seems to me to be static and lifeless, ironically, and the surfeit of pointed shapes against the sky is unsettling in some indefinable way. On the other hand, single conifers have a capacity to dazzle as sublime specimens or to drag a landscape down. A mature Japanese red pine, stiff-bristled and ruddy-barked, is a work of art. A mature Norway spruce, to my eye, is morose and drab.

This gets to another point: Many conifers are large trees, and the best of them deserve to be placed with great care — not just to give them elbow room with their neighbors, but to surround them with the empty negative space they need to set them apart. You would need such a considered spot for something as special as a China fir, Himalayan pine or Japanese umbrella pine.

Another large and underused conifer is the Alaska cedar, one of those rare Western conifers that adapt to the heat and humidity east of the Rockies. The most oft-planted Alaska cedar is a branch-drooping variety named Pendula, though other, less pendulous types also convey that garland effect. It is one of the favorite conifers of Smithsonian horticulturist Rick Shilling, who is also a fan of the gray-green and feathery deodar cedar. He commends a variety named Shalimar, with an upright growth habit and bluish needles.

The Japanese cedar, or Cryptomeria, is one of those rare conifers that gets big — it soon reaches 20 feet and then keeps going — but can be squeezed into a relatively tight spot, especially if the lowest branches are judiciously removed.

One of the strangest aspects of these garden conifers is that the same species can exist as a large, towering evergreen or as a tiny one. This is down to the long-standing desire of conifer connoisseurs to discover branch mutations and from them propagate slow-growing versions known as dwarf conifers.

What is needed in today’s smaller gardens is a conifer that sits somewhere between a giant specimen and a miniature version, functioning as a small tree or a large shrub. These exist, but you have to seek them out.

The thing to remember is that conifers can only take limited amounts of pruning, so you can’t just cut them back hard to fit a space, says Joe Meny, horticulturist of the Gotelli Conifer Collection at the U.S. National Arboretum.

There are many varieties of the hinoki false cypress, Chamaecyparis obtusa, for example. It’s a matter of picking one you know (in time) will fit its allotted space. Meny suggests one of the yellow forms, Elmwood Gold, which, after a few years, might reach six feet high and across (though the mature specimen at the arboretum is twice that size).

In the quest for moderately sized conifers, I am always drawn to the Korean pine — long-needled and stately without being huge. Shilling favors the variety Morris Blue, selected for its pyramidal habit and silver-blue needles. Yes, it will reach 40 feet, but only after many years.

The Atlantic white cedar is a useful native conifer, especially for wet areas, but it gets big. Meny suggests the compact, dense variety named Rubicon, which has the bonus of turning an attractive plum-purple in cold winters.

There are some upright and useful varieties of the native eastern red cedar, perhaps undervalued because of its weediness in the wild. Look for Emerald Sentinel, and if you want something even more narrow and upright, get Taylor, which will grow to 20 feet or more but will stay just four feet wide.

People who crave quick evergreen screening seem to be turning less to the problem-prone Leyland cypress in favor of the arborvitae Green Giant, a better plant but suffering now from overuse. Deanna Curtis, curator of woody plants at the New York Botanical Garden, recommends another variety, Atrovirens, which is more contained, with a neater branch architecture.

The dark green, fine-textured oriental spruce remains a choice conifer. Skylands is favored for its more compact nature and golden color. Curtis likes one named Gowdy, which is smaller and easier to fit in a contained landscape. Meny suggests Firefly, which has bright yellow foliage and grows to just 10 feet or so.

Two of the finest conifers — the dawn redwood and the bald cypress — lose their needles in winter. The sacrifice is worth it, though, not only for the beauty of the trees, with fine-textured foliage and peeling red trunks, but also for the spectacular autumn color. They, too, come in an assortment of shapes and sizes.

Many conifers traditionally used on the East Coast were marginally adapted to the sticky climate, and in an age of milder winters and hotter summers, we should steer clear of firs, at least, not to mention larches and the more coldblooded pines. No more Colorado blue spruces, please. Climate shifts offer the opportunity to try more southern species, however. In the Bronx, Curtis is trying the spruce pine and the graceful longleaf pine, both native to southern states.

Finding named varieties can be a challenge, but the online world opens channels, albeit to plants that tend to be young and small. Independent garden centers should have large selections and may be willing to special-order your choice. Beware of substitutions; the variability is too great.

Tip of the Week

Leaves are too precious a soil amendment to bundle, bag and discard. Chop up as many as you can with the lawn mower, and either leave them to break down on the lawn or spread them on growing beds.

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