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Bulbs for Garden Habitatsby Judy Glattstein
Some of us tend to fall heir to this casual, automatic association: If plants are bulbs, they come from Holland and bloom in the spring. If they come from Holland and bloom in the spring, they must be bulbs such as tulips, daffodils, and hyacinths. Circular reasoning won't take us very far. Geophytes that happen to originate close to home are, for whatever reason, given the primary classification of "wildflower" or "native plant." It is not that wildflower and geophyte are mutually exclusive terms. Simply put, some wildflowers are geophytes. And given a suitable site, they can add grace and beauty to the woodland garden or, indeed, to any shaded garden. "Native" is another term with a somewhat ambiguous or tenuous definition. The dictionary applies it to animals or plants occurring naturally in a region or place. The puzzlement comes to me when I try to decide how big a region or what place. State boundaries are artificial constructs that fail to impress plants or animals. If a plant grows in one town but not the next community, is it native only to the first? When I add something to my garden that was not growing there but could have been found there historically, I suppose I could claim it is native. I don't really know the answer to the "What is a native?" question but will continue to rely on field guides and floras to provide an answer.
Shade is a shady concept. It is not as easy to define as its antonym: a sunny garden receives a minimum of eight hours of sunshine per day — that's during the growing season, of course, as winter day length is much shorter than its summer counterpart. All sorts of expressive terms are used for shade: dappled, partial, moderate, and more. But they are descriptive rather than quantifying. Just keep in mind that a single small tree, such as a flowering dogwood, Cornus florida, planted in the middle of a lawn provides much lighter shade than a copse or grove of dogwoods. Majestic canopy trees such as oaks (Quercus species) and tulip poplar (Liriodendron tulipfera) contribute more shade, especially if understory trees such as dogwoods nestle beneath them. Certain deciduous trees such as Norway maple (Acer platanoides) and American beech (Fagus grandifolia) create conditions of Stygian gloom. As well, both of them have moisture-sucking roots that compound the problem. Evergreen conifers produce year-round shade and, again, dry soil conditions. Fortunately for gardeners, the spring-blooming geophytes are tolerant of shade. After all, their performance is in early spring before the leafs' canopy closes in. Further, their life cycle naturally sends them down into dormancy while shade in summer is at its peak. These woodland-tolerant geophytes do not need the sunny summer baking that tulips and crocus from the steppes of Central Asia prefer. Our native woodland geophytes call the forest home. Only in northern climates, where temperatures are cooler and overcast weather more common, will sunny rather than shady conditions be acceptable.
In common with many other shade-tolerant geophytes, many of our "homegrown" spring-flowering genera are ephemeral. They emerge in early to mid-spring, quickly produce flowers, mature their seed, and return to dormancy until the next spring season arrives. Squirrel corn, Dicentra canadensis, is one such example. Such fugacious plants need to be partnered with others that provide interest when they are dormant. Additionally, by covering otherwise bare ground, these perennials and/or ground covers protect the dormant geophytes from inadvertent damage caused by an eager gardener digging around and looking to shoehorn in yet another plant. Other native geophytes, such as bloodroot, Sanguinaria canadensis, maintain their foliage through the summer. Since the majority of shade-tolerant plants flower early in the growing season, foliage is the more useful aspect. Their partnerships should focus on plant associations that provide an attractive contrast of foliage, with perhaps the bonus of fruiting effect for later interest. Bloodroot's broad leaf would pair nicely with a lacy-leaved plant such as astilbe, or a fern.
Dutchman's breeches and squirrel corn
Bleeding heart, Dicentra spectabilis, from Japan, is probably the most familiar species in many gardens. The perennial with husky, thonglike roots is popular with gardeners for its sprays of pink, heart-shaped flowers, dangling like a string of lockets from a chain. A big plant, growing 3.5 feet (1 m) high and wide, it makes an untidy mess when its foliage weakens, turns yellow, and collapses as the plant goes dormant in early summer. This is quite a contrast to our two eastern woodland natives, which are far daintier in scale. Dutchman's breeches, D. cucullaria, grows from a cluster of small, white scales crowded together into a tiny bulb. Generally less than 1 foot (30 cm) tall, the slender stem supports 3 to 12 nodding white flowers, with twin spurs that provide the fanciful resemblance to pants hung out to dry. Clusters of lacy, glaucous leaves form an attractive mound. Making its appearance in early spring, plants make themselves at home in woodlands and along shady roadsides, on slopes under deciduous trees. Where happy, Dutchman's breeches can make a frothy blanket of white under the trees' still-bare branches. When they quietly fade away in late spring, it is without fuss or muss. Though happiest with shallow planting, bulbs should have a covering of humus-rich soil. If exposed to sunlight, they will "sunburn" and turn red. Propagation can easily be managed though division of the little scales, loose to begin with. Since they are so small, it is helpful to line them out in a flat and grow them on for a season or two before planting out in the garden.
Most gardeners find that Dutchman's breeches flower quite well under cultivation, but that often its cousin squirrel corn, Dicentra canadensis, does not. The bulbs of squirrel corn look like a loose collection of golden yellow grains of corn. They should not be buried deeply, but rather just lightly pushed into the surface of the soil. The "grains" are so loosely attached to each other that any disturbance leaves some that have separated. They can be pressed into the soil and new plants should develop. Squirrel corn has white, heart- or locket-shaped flowers with a touch of yellow at the tips of the nodding flowers. It, too, flowers in spring and then goes dormant soon afterward.
Dog's tooth violet
Dog's tooth violets do indeed have a bulb that looks like a dog's canine tooth. The pendant, nodding flowers look more like little Turk's cap lilies, with recurved petals. Other common names run the gamut from fawn lily and trout lily to adder's tongue. Different species are found on the American east and west coasts, and even in between. One species is native to Europe and Asia — Erythronium dens-canis, with rose-pink to purple flowers, and occasionally with a white form. Several cultivars include rich violet 'Frans Hals' and self-descriptive 'Lilac Wonder', 'Pink Perfection', and 'Rose Queen'. Splitters allow E. japonicum its own species, while lumpers consider it merely a variety of E. dens-canis.
Erythronium americanum is the species found from New Brunswick to Florida, and from Ontario and Minnesota south to Arkansas and Oklahoma. This is the species commonly seen in Connecticut and New Jersey. Early in spring, it forms large patches of attractively mottled, shiny leaves, with here and there an occasional yellow flower, the petals strongly buff colored on the reverse. That is generally the way of it — patches in the garden increase each year, but generally only two or three flowers are produced.
Driving along one spring day, I noticed a rocky outcrop with a ledge positively yellow from the number of flowers in bloom. Quickly pulling to the side of the road, I hopped over the guardrail for a closer look. As best as I could figure out, the bulbs had become so wedged into the soil-filled hollow that they had nowhere else to go. A brief pause here for a botanical digression. Erythroniums, being true bulbs, make offsets. In the majority of species, the daughter bulbs cluster close to the original parent bulb, similar to narcissus, hyacinths, tulips, hippeastrum, and what have you. Erythronium americanum, on the other hand, sends out a long dropper root about the thickness of a strand of thin spaghetti that eventually produces a daughter bulb, but at some distance from the parent bulb. Look carefully at one of those sizable but sparse-flowering patches of trout lily, and you'll realize that many of the plants are sending up only a single leaf. All the flowering plants, however, are sending up a pair of leaves. Clearly, the new bulbs need to bulk up. Only when they store sufficient reserves to produce a pair of leaves are they then also vigorous enough to produce a flower. Wedged into the outcrop's ledge, the bulbs could descend only so far before they hit an impenetrable barrier. Since they couldn't go down, they bulked up and flowered. The metaphorical cartoon sound bite with a light bulb flashing and "Eureka!" went off above my head. When planting trout lily bulbs, dig them a nice hole. Set a largish flat rock, a piece of slate, or some other sufficient barrier on a slant at the bottom of the hole. (The slant allows better drainage than flat.) Toss in some leafs' soil, set your bulbs, and finish filling the hole; then water and mulch. Not the next year, but starting the year after that, the bulbs will flower better and better. Fortunately, the general run of other, readily available dog's tooth violets flower quite nicely without such heroic measures. I've seen mention of a similar situation in a woodland area a few miles from Columbus, Indiana, where large patches of E. americanum were absolutely covered with bloom. The assumption in this instance was that the dense mass of tree roots had inhibited increase and the plants had used their energy to produce flowers.
To compound the issue, the native plant garden at The New York Botanical Garden has several large patches of Erythronium americanum behaving as it generally does — lots of leaves, very few flowers. At the far end of the garden in some rather mucky soil are several clumps of yellow trout lilies that are much bigger in both leaf and flower than the usual ones. What's more, these make large clumps with lots of flowers. I have asked if perhaps these are E. umbilicatum, a different but still yellow-flowered native species, only to be assured that no, it is also E. americanum. When I grew E. umbilicatum in Connecticut, it freely made offsets that huddled close to mother, resulting in an attractive display each spring. One distinguishing characteristic taxonomists are apt to focus on is the seed capsule, which is not pointed, rounded, or beaked in E. umbilicatum as it is in E. americanum. Also, in E. umbilicatum the stem bends after flowering, depositing the seed capsule on the ground.
Other dog's tooth violets can be found across the United States. Erythronium albidum is a charming species native found in woodlands from southern Canada down to Texas. The narrower, lightly mottled leaves make a subtle background to the solitary white flowers lightly flushed with a hint of blue or pink on the outside. Yellow anthers are a color echo of the yellow center at the base. Yellow-flowered E. tuolumnense is rather localized, found in California's Tuolumne County. Large, pale green, unmarked leaves splay out beneath one to four bright yellow flowers. Increasing freely, this is perhaps the easiest to grow of the yellow-flowered dog's tooth violet species in cultivation. Another delightful West Coast species is E. revolutum, found in forests and in damp sites from California up to Canada's Vancouver Island. Attractively mottled leaves and ease of cultivation are two attributes that, coupled with its lovely, deep pink flowers, make this an excellent choice for the shady garden. 'White Beauty' is a selection of E. revolutum that has (as you would expect) white flowers, accented by brown spots at the base of the petals. Vigorous in growth, it has mottled leaves.
A certain amount of deliberate hybridization has given us several cultivars, some of relatively recent origin, that are popular with gardeners and often more available than their parent species. Erythronium 'Jeanette Brickell' is a cross between E. tuolumnense and E. oregonum, with lightly mottled leaves and as many as seven icy white flowers. Though selected in England in 1956, for some reason it took another 20 years before it was named, in 1978. 'Jeannine' was introduced by W. P. Van Eeden of the Netherlands in 1984. Sulfur-yellow petals with a brighter yellow interior give the flowers a bright, sunny appearance. 'Kondo' is an E. tuolumnense and E. revolutum cross, with lightly mottled leaves and sulfur-yellow flowers accented by a brown ring on the inside. 'Pagoda' has the same parentage, with a stronger yellow flower and somewhat stronger mottling on the leaves.
Given their early spring period of bloom, numerous choices are available for partnering perennials. Perhaps my favorite "marriage" matches dog's tooth violets with hellebores, particularly the Lenten rose, Helleborus orientalis, with its large, buttercup-shaped flowers in apple-green, white, and pale pink through deep rose to plum, the lighter colors sometimes speckled or freckled with darker spotting and other times clear of any markings. The earlier blooming, somewhat smaller flowered hellebores in the Early Purple Group with their deep plum-colored flowers and ivory stamens are also a pleasing choice.
Dog's tooth violets really dislike being out of the ground. They get soft and flabby very quickly, become moldy, and even if they consent to grow will often refuse to flower in the year following disturbance. When purchased, the dormant bulbs should be received packed in some protective wood shavings, both as cushioning and to reduce desiccation. If you are moving dog's tooth violets around in the garden, prepare the new site, dig and divide the healthy clump, and then sprint to deliver them to their new location. Deer sample but do not devour them. Often the tips of an emerging set of leaves are nipped off, after which they expand into an oddly squared-off appearance and will manage to flower.
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