01/10/2024
If you look at a Tulip Poplar (Liriodendron tulipifera) in winter, you’ll see something resembling flower petals splayed out against the background of the sky. What!? Flower petals…in winter!? They’re not petals. Rather, these are the bottom scales from the fruits that have dropped their seeds. The formation of these fruits started back in early spring. Images A - G show this annual process from flower bud to mature fruit in one of our most popular hardwood trees, the Yellow or Tulip Poplar.
A: Flower buds appear in spring, often around mid-April where I live in the Upstate of South Carolina. Green sepals cover the developing flower bud.
B: Tulip Poplar flowers open in late April to June in the southeast. The large (1.5-3“ wide) yellowish-green flowers have six petals in two overlapping whorls of three each. There is an orange patch near the base of each petal. Below the petals is a whorl of three pale green, leaf-like sepals. These formerly enclosed the flower bud and now provide some support for the overlying petals.
C: Looking inside the flower, there is a light green, spear-like structure in the middle. It consists of a central stalk (the receptacle) covered in dozens of fused pistils. Each pistil is a female structure on the flower. As pollinators visit the flowers, they brush against a sticky stigma at the tip of each pistil. This deposits pollen from other tulip poplar flowers the pollinators visited for nectar.
But where does the pollen come from? Look peripheral to the pistils. The light brown and yellow tubes that resemble stretched out matchsticks are the stamens. These male structures (stamens) produce pollen within the light-brown anthers at the top half of each stamen. Thus, each Tulip Poplar flower has both male and female parts, but the flowers are cross-pollinated for the best fruit set. A wide range of bees, flies, and beetles serve as pollinators. Tulip Poplars are also a good native tree for caterpillars. Check out the pictures in the comments.
D: As the flowers wither, the petals and sepals drop, along with the stamens and their pollen-producing anthers. What doesn’t drop, though, is the large central spear covered in fused pistils. Following pollination, each pistil will develop over the summer into a dry, winged fruit called a samara. I know that name resembles one of the Girl Scout cookies, but trust me, this isn’t where the Girl Scouts get them, although these cookies are quite “poplar.” 🍪🤦♂️
E: Once the petals, sepals, and stamens have dropped, all that remains is the large spear of pistils fused onto the central receptacle running down its core. Where I live in the Upstate of SC, this starts to happen around mid-May.
F: By early autumn, the dry fruits have developed and they resemble a splayed out pine cone. Each spike is a ~1.5” long winged samara with a seed at its base. As the samaras drop, they blow in the wind or float away in a stream to new habitats where a Tulip Poplar might grow.
G: I dissected this fruit open to show you the individual samaras attached to the central core, the receptacle.
This tall native tree grows in bottomland forests, yards, and parks across the eastern United States. Despite being called a poplar, it’s actually in the magnolia family (Magnoliaceae). Tulip Poplar wood is used to make furniture and cabinetry and their long, straight trunks once made them prized for building log cabins and canoes. It’s easy to see why Tulip Poplar is the state tree of Indiana, Kentucky, and Tennessee!
