Vitis aestivalis (Summer Grape)
|Also known as:||Silverleaf Grape|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; average to dry; deciduous woods, thickets, wooded bluffs|
|Plant height:||to 70 feet|
|Wetland Indicator Status:||GP: FAC MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Cylindric clusters up to 6 inches long opposite the leaves of this year's new branches. Separate male and female flowers are typically on different plants, both 1/8 inch across or less with 5 green to yellowish petals that drop off early. Male flowers have 5 or 6 long, pale, erect to ascending stamens around a tiny button center. Female flowers have a bottle-shaped style and 5 short stamens that are usually sterile and somewhat contorted. The calyx cupping the flower is minute; flower stalks are minutely hairy and often red. Flowers are fragrant.
Leaves and stems:
Leaves are 4 to 8 inches long and about as wide, mostly broadly heart-shaped in outline, shallowly to deeply lobed with 3 or (usually) 5 major lobes and a broad gap between the 2 basal lobes. Deep sinuses between major lobes are often well-rounded. Edges are toothed, the teeth mostly rounded with a minute point at the tip.
The lower surface is covered in a whitish, waxy bloom, which is often obscured by reddish-brown, cobwebby hairs; major veins are also densely hairy. The upper surface is dark green and hairless or becoming so. Leaf stalks are 2 to 6 inches long, often reddish, hairy, more densely so near the leaf blade and more sparsely near the stem.
New branches are yellowish-green to reddish and hairy, the nodes covered in a waxy bloom. Forked tendrils develop opposite the leaves on first year branches, usually skipping every third leaf, and become woody with age. Older bark is brown to reddish-brown, hairless and shredding, peeling in long strips. A mature plant may have a trunk as much as 8 inches in diameter at breast height (dbh). Plants may climb high into trees or crawl over shrubs and lower vegetation.
The flower clusters become dangling as fruit develops. Fruit is a round berry ¼ to ½ inch in diameter, ripens from green to blue-black, and is covered in a white bloom. Inside a berry are 2 to 4 slightly flattened, egg-shaped seeds. Berries are often sour until after a frost, then turn more sweet-tart.
Summer Grape a rare species in Minnesota, limited to a few southeast counties along the Wisconsin border, where it reaches the extreme northwest edge of its range. Across its range, it's found in upland hardwood forest and forest edges, dunes, fencerows, and wooded bluffs, often in sandy soil and in areas of disturbance (natural or man-made). According to the DNR, biological surveys in the southeast over the last 20 years have only found 1 new location, bringing the total to 11 known populations, one of which was unintentionally destroyed in an effort to manage specific canopy trees. This illustrates the problem of managing an entire ecosystem as component parts rather than as a whole. Its habitat preferences in MN are not well understood and it was listed as a Special Concern species in 1996, elevated to Threatened in 2013.
It can resemble the related Riverbank Grape (Vitis riparia), which has leaves with sharply serrated edges, lacks the cobwebby hairs and waxy bloom on lower leaf surfaces, and is ubiquitous in floodplain forests and woodlands throughout the state, where Summer Grape prefers drier habitats. Summer Grape leaves may also resemble another vine, Common Hops (Humulus lupulus), which does not have woody stems or tendrils, has opposite leaves, and a cone-shaped fruit rather than berries. There are 3 recognized varieties of Vitis aestivalis, distinguished by fruit size, degree of hairiness, the amount of waxy bloom and other traits; var. bicolor, a.k.a. var. argentifolia, is present in Minnesota. Note that the population we encountered had sparse glands on at least some new stem growth, but there is no mention of glands or glandular hairs in any of the available references.
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- Summer Grape vine
- high-climbing vine
- vine climbing over shrubbery
- sparse glands on new stems
- sparse hairs on lower leaf stalks
- more leaves
- budding flower clusters
- new stem growth with red tendrils
- leaf shape can be quite variable
Photos courtesy Peter M. Dziuk taken in Houston County.
Have you seen this plant in Minnesota, or have any other comments about it?