By early June, when the growing season seems to be just getting up to speed, some of our most beautiful woodland wildflowers will have already come and gone. To find any sign of trout lily, spring beauty, squirrel corn, Dutchman’s breeches, dwarf ginseng, or toothwort in July, you will have to do some digging, for by then their leaves will have shriveled up and disappeared.
Though these plants are often called “spring ephemerals,” which suggests that they are short-lived, all of these are hardy perennials with underground storage organs that live throughout the year. They exploit a niche, like everyone else, but for these plants the niche is a temporal one: between snowmelt and the time when deciduous trees leaf out. During this period, the forest floor is moist, nutrient-rich, and so sun-drenched that it warms quickly.
Although the length of this spring niche varies from year to year, depending mostly on the amount of snow, it is always very brief. The ephemerals’ growth is limited by low temperatures at the beginning and by increasing shade in late May. When hardwood leaves come out, it is like pulling a window shade on the forest floor.
At that point, spring ephemerals close up shop, but, like a successful toy shop at Christmas, they will have amassed enough working capital to make it to the next season. They shut down before losing money, and they stash their savings underground. Also, like the toy shop, preparation for the hectic season begins well before the new infusion of income is at hand. They spend the winter preparing and by spring are ready to make the most out of the sun and warmth of early spring days.
All the ephemerals have conspicuous, insect-pollinated flowers, but you don’t have to be a honeybee to appreciate them. They all are beautiful and bloom at a time of year when there is not a lot of floral competition.
Trout lily is the most common spring ephemeral. The pale yellow flowers with five curled-back petals are small for lilies, only about one inch across. The leaves are sort of trout shaped, as well as having a mottled, trout-like pattern of brown splotches.
Only about one half of one percent of the individual plants in a bed of trout lilies will flower in a given year. Normally, it takes many years for a plant to accumulate enough resources to be able to produce a flower, and most never do, persisting in a sub-flowering state for years before dying.
Trout lilies have been dug up, weighed, measured, and analyzed at all times of the year, and some of the statistics gleaned from these depredations are eyebrow raising. In one study, the average dry weight of the plants increased by over 250 percent in just 12 days. Over the whole growing season, which was 37 days in the year of the study, the dry weight increased by nearly 450 percent.
Even so, trout lilies won’t win any prizes for being the world’s fastest-growing plants. They do, however, photosynthesize and grow considerably faster than forest floor plants that stay green throughout the summer. Weight losses during the long non-photosynthetic period can equal or exceed the dramatic gains of spring.
Although trout lilies make up only a very small fraction of the biomass of the forest, their capacity for extremely rapid growth over a short period plays a significant role in preserving the nutrient capital of the forest ecosystem. The greatest soil nutrient losses occur in spring because, until the trees leaf out, their roots do not absorb nutrients. In spring, seepage from the nutrient-rich soil is more likely to be carried away from the forest ecosystem and into streams than at any other time of year.
But it’s trout lilies to the rescue, for this is when they are growing most actively. They temporarily accumulate nutrients, especially potassium and nitrogen, when these elements are in abundance and when other growing plants are in short supply. Trout lily leaves contain more nitrogen than summer green plants, an indication that they take advantage of the higher soil nitrogen levels in spring.
About seven weeks after trout lily leaves have unfurled, the green parts begin to die. Some of the nutrients are transferred from the leaf to the corm. The rest are released as the leaf decomposes. But by this time, the roots of trees and other plants are actively growing and can make good use of them.
It is satisfying to think that these beautiful little plants, plants that you might think could get by just on their good looks, are also making a contribution to the trees that tower over them. Look for them this month on your favorite hardwood hillside.