Hackberry trees, belonging to the genus Celtis, are common deciduous trees found across North America. Valued for their shade and resilience, their subtle flowers are often overlooked. However, these inconspicuous floral components play a significant role in the tree’s life cycle and the broader ecosystem.
Characteristics of Hackberry Flowers
Hackberry flowers are small, typically about 1/4 inch across, with a greenish-yellow or greenish-white coloration. Unlike showier blossoms, they lack distinct petals, a characteristic known as apetalous. Instead, their structure is formed by four to six spreading sepals. These flowers can appear singly or in small clusters. Hackberry trees are usually monoecious, meaning both male (staminate) and female (pistillate) flowers are present on the same tree. Male flowers typically form in clusters near the base of new branchlets, while female flowers are found singly or in pairs in the axils of developing leaves.
Flowering Season and Pollination
Hackberry trees typically flower in early spring, often in April or May, coinciding with or just before leaf emergence. The exact timing varies by geographical location, blooming earlier in southern regions. Due to their lack of bright colors, nectar, or strong fragrance, hackberry flowers do not rely on insects for pollination. Instead, they are primarily wind-pollinated. Male flowers release pollen into the air, which is then carried by wind currents to the receptive female flowers on the same or neighboring trees.
From Flower to Fruit
Following successful wind pollination, female hackberry flowers develop into small, round fruits known as drupes. These pea-sized fruits, typically 1/4 to 1/2 inch in diameter, ripen from green to purplish-red, dark purple, or nearly black through late summer and fall. Each hackberry fruit contains a thin, sweet, yellowish flesh surrounding a single, large, hard seed. These fruits often remain on the tree through the winter months and sometimes into the following spring, providing a sustained food source.
Ecological Role
Hackberry flowers and their subsequent fruits contribute to the local ecosystem. While primarily wind-pollinated, the pollen can still provide a food source for some generalist insects that visit the trees in early spring. The fruit plays a prominent role, serving as a winter food source for a wide array of wildlife.
Various bird species consume the persistent berries, including:
- Cedar waxwings
- Robins
- Flickers
- Quail
- Pheasants
- Wild turkeys
Small mammals also forage on the hackberry fruits throughout the colder months, such as:
- Raccoons
- Squirrels
- Opossums
- Skunks
- Foxes
Beyond sustenance, hackberry trees serve as host plants for the caterpillars of several butterfly species, including:
- Hackberry Emperor
- Question Mark
- Mourning Cloak
- American Snout
- Tawny Emperor
Although hackberry pollen is wind-borne and can contribute to seasonal allergies in sensitive individuals, it is generally considered less allergenic compared to some other wind-pollinated tree species.