Perhaps the word “forest” should be a verb, not a noun. From the first tiny Black locust trees pioneering an old field, to a centuries old Sugar maple and Beech forest, there is continual change. Disturbance of course accelerates the process, and this little forest has been changing on the fast track over the past ten years, thanks to invasive plant removal and the Emerald ash borer.
Both the canopy and understory layers have been opened up to sunlight in a very short time, leading to an explosion of fast growing opportunists like Pokeweed. This tall, widely branching perennial is a huge berry producer, at this season dangling its wares over the trail at head height – nourishment for frugivorous birds, turkeys, mice, deer, coyotes, box turtles and many more.
In contrast to Pokeweed, many forest fruits are borne on shrubs and vines. Though we tend to think of forests as mostly composed of trees, the eastern forest understory is home to quite a few shrubby, berry producing species that depend largely on birds for dispersal. Some, like the ubiquitous blackberries, raspberries and grapevines, establish on edges and early successional sites with lots of sunlight. But in this forest, interior light filled gaps resulting from invasive shrub removal and dying ash trees are also filling with fruiting species like Pawpaw, Spicebush, Elderberry, Wahoo, Coralberry and Greenbriar.
This new openness is both an opportunity for understory revival and a challenge. Urban forest management in particular is complicated by the presence of so many woody and climbing invasive plants. The ongoing task is to keep the understory revival on track by planting where needed, and carefully monitoring and removing the faster growing non-native woody species that could easily overwhelm the recovery.
I think of invasive plant management as a replacement program. The non-native shrubs and vines that took over the understory of this little forest did so by producing massive amounts of berries, and letting the birds do the rest. Undoubtedly these plants provided food and habitat for frugivorous birds and other animals. But they also created a species monoculture and dense shade that excluded most native plants. Thanks to the forest steward’s intensive work over the past decade, the berries of invasive Bush honeysuckle, Privet and Wintercreeper – once providing over 90% of forest fruit – are now in very short supply. Yesterday I enjoyed watching a mob of robins fill up on the first ripening Spicebush berries, and it was gratifying to know they were dispersing a keystone native shrub!
Timing helps explain the great diversity of fruiting plants in eastern forests. If a plant’s fruit is ripe at a season when little else is available, chances of disperal are better. Though forest fruit season peaks in late summer and fall, there is a progression of ripening berries beginning in early summer with Red mulberry and Red x White mulberry hybrids.
This first fruit is heralded by noisy, joyous flocks of robins and Cedar waxwings converging on the berry laden trees. I have stood beneath such a tree with bits of berries and bird droppings splattering down around me!
Black elderberry fruits are the next to ripen, following pollination of the broad flat-topped corymbs of tiny white flowers. Like other berry producers, this plant provides twice – nectar and pollen for insects, and fruits for birds, mammals and box turtles.
Midsummer brings the bramble fruits Black raspberries and blackberries, mostly on the forest edge but also in sunny gaps.
Though in the same genus, Cornus, shrubby dogwoods are less well known than their lovely cousin, the understory tree Flowering dogwood. These thicket forming species with late summer ripening white or blue berries include Gray, Silky, Red osier, and Roughleaf dogwoods. If protected from heavy deer browsing, the dense thickets provide great habitat for migrating frugivores like thrushes, Gray catbirds and Brown thrashers.
Early fall brings another red berry besides Spicebush, the somewhat uncommon Wahoo, or Eastern burning bush (Euonymus atropupureus). As one of the common names suggests, it’s closely related to the non-native, invasive Burning bush (Euonymus alatus) so often planted for its red fall foliage. Wahoo would likely be more common in this forest, but for the fact that deer browse it heavily (most Euonymus are highly deer preferred).
Some forest fruits are seldom noticed since they’re borne on vines high up in the canopy, and only seen when they fall to the ground. Wild grapes are easy to recognize, but the fruits of vines like Virginia creeper, Poison ivy and Greenbriar (Smilax spp.) are less well known and equally important to wildlife.
Even on the forest floor, fruits can be found – Mayapple, Jack in the Pulpit, and its close relative Green dragon are all becoming more abundant since they’re shunned by deer.
The largest native fruit in North America is the Pawpaw, which grows on a tree of the same name, the only member of the tropical family Annonaceae found in eastern forests. It’s abundant in this forest and becoming one of the main understory trees. Though delicious to humans and other animals, the two to three inch banana-like fruit with large seeds may be an anachronism in ecological terms. Large fruits growing in places where large animals are now extinct (think mammoths, giant sloths) are likely not getting dispersed in the manner orginally intended. Rather than ingesting the whole fruit and depositing its seeds in a nice pile of poop, smaller mammals tend to nibble them and ingest fewer seeds. But not to worry,it only takes one seed to start an entire clonal Pawpaw patch!(Pawpaws are ripening now and can be found on the ground under large “patches”).
The much smaller Persimmon tree fruits fare better with mammal dispersal; though the tree is uncommon in this forest, I notice the seeds in fox and coyote scats in late fall.
Sumac berries are among the last fruits of the year. The dense clusters at the end of branches will persist through the winter, providing food for birds when little else is available. For this reason, and the valuable cover they provide, the forest stewards have been planting Shining sumac, since sumac patches no longer existed at the forest edges. The fruit in the pic above is part of the first crop produced by a patch we planted two years ago. Now well established, the original plants are taller than me, and the patch will spread clonally over time. When restoration plantings succeed this well, I feel hugely rewarded for all the hard work!