Hamamelis virginiana L.
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Basis for Listing
Hamamelis virginiana (witch-hazel) is a fairly common forest shrub farther east, but it is quite rare in Minnesota, where it reaches the northwestern periphery of its range. Extensive searches have discovered surviving plants to be clustered in only about a half dozen habitat fragments in the southeastern counties (Paleozoic Plateau). There is concern that these fragments may not have retained the ecosystem processes that are necessary to assure the perpetuation of this species. In light of this, intensive management such as manual removal of invasive species or the creation of habitat buffers may be needed.
When H. virginiana was listed as special concern in Minnesota in 1984, only 4 populations were known in the state, and it was hoped that unexplored potential habitat would produce more records, once further surveys were conducted. A comprehensive botanical survey of the region has now been completed by the Minnesota Biological Survey, and only 8 additional populations were discovered, indicating this species is even rarer in Minnesota than previously believed. Furthermore, the threat from invasive species has increased, as new invaders are identified nearly every year. For these reasons, the status of H. virginiana was elevated to threatened in 2013.
Hamamelis virginiana is a large shrub, with multiple stems that may reach heights of 6 m (20 ft.) and diameters of 8 cm (3 in.). The branchlets are brown or gray and have stellate hairs. The bark is brown or gray-brown and rough. The leaves are simple, alternate on the stem, and deciduous. They are broadly elliptical to nearly circular in outline, 6-15 cm (2.4-5.9 in.) long, and 4.5-10 cm (1.8-3.9 in.) wide, and the margins are irregularly wavy. The flowers are bisexual, 4-merous, and sessile in axillary clusters. The petals are yellow, ribbon like, and 1-2 cm (0.4-0.8 in.) long. The fruit is a woody capsule, 1-1.4 cm (0.4-0.6 in.) long that matures in autumn, one year after pollination. It opens explosively and disperses seeds forcibly (Smith 2008).
Hamamelis virginiana occurs in the understory of dry to moist deciduous forests, typically with Quercus spp. (oaks), Acer saccharum (sugar maple), or Tilia americana (basswood) (Mesic Hardwood Forest). It easily survives and reproduces in a closed-canopy forest, but growth and flowering are reportedly increased under small canopy gaps (Hicks and Hustin 1989). These habitats are usually integral parts of large, complex forest systems that possess considerable topographic relief and varying edaphic conditions.
Biology / Life History
Hamamelis virginiana is peculiar in that the flowers open in the autumn; usually peaking about the time the leaves are falling. This may happen after the first frost, yet flying insects are still active and manage to pollinate the flowers. Although pollination occurs in the autumn, actual fertilization does not occur until the following spring (Flint 1957), so the fruits develop during the summer, like those of most spring-pollinated species. When the fruits are ripe in the autumn, they burst open, forcibly ejecting 2 smooth, black seeds a distance of up to 10 m (33 ft.) (Meyer 1997). Most seeds remain dormant in the soil for 18 months, germinating after 2 winters (Gaut and Roberts 1984).
Conservation / Management
The main conservation consideration for H. virginiana is the continued maintenance of ecosystem processes within its forest habitat, which may come into conflict with consumptive uses such as logging, livestock grazing, and residential development. For a number of reasons, livestock grazing in native forests is widely recognized as unwise land management and is therefore not nearly as prevalent as in the past. However, logging and residential development seem to be increasing. They have the effect of directly reducing available habitat, and at the same time increasing exotic species invasion. Rhamnus cathartica (common buckthorn), and Lonicera spp. (Eurasian bush honeysuckles) are perhaps the most destructive exotic shrubs in forest habitats. There are, however, a dozen or more additional species that also cause serious problems, and that number is increasing almost yearly.
A search for H. virginiana can be conducted whenever the leaves are present, from mid-May through mid-October. When the leaves have fallen, the flowers and fruits should still be present until early November.
Conservation Efforts in Minnesota
A relatively small population of H. virginiana is known to occur in a State Park where it is protected from commercial logging and residential development. There is another cluster of records on state-owned forestland that is managed for timber production. No effort has been made to assess the conservation needs of any of these sites.
Author: Welby Smith, MN DNR, 1988
Revised: Welby Smith, MN DNR, 2008 and 2016