Ashlyn and I find ourselves on our local hiking trails frequently, especially during peak plant seasons. This means we don't hike much during the winter since there is not much to see, but that doesn't mean there aren't cool plants to be found in the cold months. One plant we look forward to seeing in the winter is a lesser-known plant called the cranefly orchid (Tipularia discolor). The cranefly orchid is, in fact, an orchid! It belongs to the family Orchidaceae and is one of many terrestrial orchids native to our area. This orchid was the first species that spurred my interest in all of the different orchid species native to the Eastern U.S. - and there are more than you would think!
The cranefly orchid is very unassuming and can be hard to spot. I'm sure we walked passed this plant many times before we knew what is was simply because we did not know what to look for or our timing was in line with one of its two dormancies within a year.
First off, this plant grows in deciduous hardwoods forests, usually surrounded by maple, oak, beech, sweetgum, etc. It grows in moist but well drained soil with high organic matter. And like many orchids, it associates with mycorrhizal fungi in the soil. Therefore it is usually found around decaying wood since the fungi it associates with also happens to decompose fallen trees.
It takes advantage of its environment by entering its leaf stage in autumn when the forest floor gets more sunlight. It produces a single leaf - green on top, purple on the underside - and that leaf will remain active until spring. For this reason it is known as a hibernal leaf, only active during the winter.
When the leaf dies back, the plant enters its first dormancy until the middle of summer when a flower stalk emerges. The single stalk can contain up to a couple dozen small orchid flowers. The flowers are pale pink to almost brown in color, camouflaging itself with the leaf litter surrounding it. One common characteristic found within the orchid family is that most flowers are bi-laterally symmetrical (zygomorphic), meaning if a line is drawn down the middle, the left and right sides are mirror images of one another. However, this is not the case with the cranefly orchid. Its flowers are actually asymmetrical (cannot be divided equally). Another interesting trait is that the pollen is contained within sticky sacks called pollinia. These unique traits play a roll in how this plant gets pollinated.
The primary pollinators of the cranefly orchid are not craneflies but nocturnal moths. Like some other orchids, these flowers contain a spur off the back of the flower that contains nectar, which these moths are after. The flowers are also slightly fragrant to help attract these moths during the night. Due to the asymmetrical design of the flowers, the moths have to orient themselves in a certain position to access the nectar. This lines them up with the pollinia which gets attached to the moth's eyeballs. The pollinaria (entire pollen sack structure containing the pollinia) gets broken off and the moth transports the pollen to another plant, inducing cross pollination.
After pollination, the flowers will then produce seed pods containing dust-like seeds. The seeds lack endosperm, which is what feeds an embryo to start the germination process. Without this, cranefly orchid seeds rely on a symbiotic relationship with fungi in the soil to aid in the germination process. After seeds have been formed, the plant enters its second dormancy until late fall when a new leaf appears.
The "powerhouse" of the cranefly orchid is an underground corm. This is the food storage structure (similar to a bulb) that stores the energy it produces during the winter and supplies that energy during the summer for flowering. Since there is no leaf during flowering, the flowering process relies entirely on the corm for energy. In many cases, plants will not flower two years in a row simply because it does not have the energy stored to do so. New corms can be produced and are connected to previous corms like beads on a string. The older corms remain dormant unless divided from the others, in which a new plant is produced.
As you can see, the cranefly orchid is a well-adapted plant. From its leaf taking advantage of sunlight during the winter months, the flower structure aiding in pollination, and the fact the pollen is contained in sacks, all play a role in its will to survive.
Rasmussen, Hanne N., and Dennis F. Whigham. IMPORTANCE of WOODY DEBRIS in SEED GERMINATION of TIPULARIA DISCOLOR (ORCHIDACEAE). 1998.
Smith, Julie L., and Richard B. Hunter. GENETIC VARIATION in the TERRESTRIAL ORCHID TIPULARIA DISCOLOR. 2002.
Snow, Allison A., and Dennis F. Whigham. COSTS of FLOWER and FRUIT PRODUCTION in TIPULARIA DISCOLOR (ORCHIDACEAE). 1989.