CPC Plant Profile: Harbison's Hawthorn
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Plant Profile

Harbison's Hawthorn (Crataegus harbisonii)

Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Rosaceae
  • State: TN, GA, LA
  • Nature Serve ID: 819851
  • Date Inducted in National Collection:

The Harbison hawthorn is one of the rarest woody plants in the United States. After many years of research into its history, distribution, and taxonomy, several points have been made clear. The entity is distinct from other hawthorns, being closely related only to two other species in the genus. The entity has become progressively rarer in its endemic range, seemingly due to habitat changes brought on by the proliferation of exotic plant competition and fire control. The entity is currently known to be represented only a few individuals in its natural range, and by several hundred cultivated individuals. As Lance (2000) notes, this species has had an interesting history. Early accounts of Crataegus harbisonii implied that it was endemic to Tennessee, and the Nashville area specifically, as all early collections were made from that area. An accurate image of the natural status of C. harbisonii at its time of description is difficult to substantiate, but was alluded to as "common" by Sargent (1905, 1922, 1947). Beadle (1899) reports "numerous examples" of C. harbisonii "observed at intervals during the past summer". By 1950, no further reference to abundance in the Nashville area, or in Tennessee, is noted in the literature until 1978, when the species was included in the list of "Rare Vascular Plants of Tennessee", and in 1982, when Paul Somers referred to it as "endangered" and "possibly extirpated" from its type locality in his element ranking form for the Tennessee Natural Heritage Inventory. Between 1993 and 1998, only two living specimens were discovered after extensive field searches. As of 2001, only 1 living specimen of C. harbisonii is known to remain in the type locality. However, recent searches have discovered a handful of this species in the near vicinity.

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Updates
  • 10/05/2020
  • Propagation Research

Cultivation efforts (from grafts) at the North Carolina Arboretum found that this species can not tolerate

  • 10/05/2020
  • Genetic Research

Ron Lance compared this taxon with other closely related, similar, or even synonymous taxa or specimen using isozymes and found that C. harbisonii contains a unique allele, supporting the need for this taxon to be recognized as a species rather than just a morphological variant of a more common Crataegus species (C. triflora). He also found C. harbisonii to differ from the also rare C. ashei, which is often considered synonymous with C. harbisonii, while C. ashei did not differ from the common C. triflora. (Lance 2000a, 2000b)

Nature Serve Biotics
  • 05/02/2017

When treated in the strict sense (excluding Crataegus ashei), Crataegus harbisonii is known extant only at one site in central Tennessee, consisting of just one sterile tree within the ever-increasing metropolitan area of Nashville. Until this site was discovered in 1993, the species had not been documented in Tennessee since 1948. Including C. ashei material (as is done in this record) adds another 12 or so occurrences in Mississippi (8) and Alabama (4), but all of these are very small, with the largest containing no more than 30 trees. Known occurrences of C. ashei are threatened by vegetation succession, red cedar rust, and competition from exotic plant species.

Ron Lance
  • 01/01/2010

The invasive shrub (Lonicera maackii) has altered the understory of the forests where this species was once found, likely inhibiting recruitment of this and other species. (Lance 2000a) Like most hawthorns, C. harbisonii is susceptible to a number of

Ron Lance
  • 01/01/2010

A number of plants were recently found in the wild near the type location, but all were in an area with a heavy canopy that blocks sunlight and appears to be keeping the individuals from flowering and producing seed. A number (over 100) of individuals are in cultivation at North Carolina Arboretum (Lance 2000a).

Ron Lance
  • 01/01/2010

Ron Lance compared this taxon with other closely related, similar, or even synonymous taxa or specimen using isozymes and found that C. harbisonii contains a unique allele, supporting the need for this taxon to be recognized as a species rather than just a morphological variant of a more common Crataegus species (C. triflora). He also found C. harbisonii to differ from the also rare C. ashei, which is often considered synonymous with C. harbisonii, while C. ashei did not differ from the common C. triflora. (Lance 2000a, 2000b) Cultivation efforts (from grafts) at the North Carolina Arboretum found that this species can not tolerate

Ron Lance
  • 01/01/2010

For now, the individuals in the wild are protected within a registered State Natural Area of Tennessee and a municipal property of Nashville. The Natural Resources Staff of the park are aware of the location and significance of the plant, as are the Tennessee Natural Heritage Inventory botanists. (Lance 2000a)

Ron Lance
  • 01/01/2010

Removal of adjacent competing exotic plants, and thinning the overhead canopy to allow for admittance of sunlight to C. harbisonii specimens. (Lance 2000a)

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Nomenclature
Taxon Crataegus harbisonii
Authority Beadle
Family Rosaceae
CPC Number 1099
ITIS 24566
USDA CRHA2
Common Names Harbison hawthorn | Harbison's hawthorn
Associated Scientific Names Crataegus harbisonii | Crataegus ashei
Distribution Found only in one population in Tennessee outside of Nashville.
State Rank
State State Rank
Georgia SNR
Louisiana SNR
Tennessee S1
Habitat

Found in the area surrounding Nashville, Tennessee, on dry limestone outcroppings and soil overlying limestone in natural hardwood forests. (Sargent 1905; Lance 2000)This species is found in the understory. Canopy associates include Ulmus, Fraxinus, Celtis, and Juniperus, with increased incidence of Quercus and Acer saccharum in more mesic conditions. Understory trees and shrubs such as Viburnum rufidulum, Cornus florida, Cercis canadensis, Frangula caroliniana, or Forestiera ligustrina may be common in the natural sense, but exotic Lonicera frequently dominates many sites today. (Lance 2000a)

Ecological Relationships

Fire may play a role in the survival of this species...Although individual Crataegus tend to have bark that is poorly resistant to fire, regrowth from root systems and development from seed is rapid, and continued colonization of burned lands is a reasonable expectation for the plants. (Lance 2000a)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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