• facebook
  • twitter
  • YouTube
  • RSS feed
  • 651-201-6000
  • 800-967-2474
  • 711 TTY
  • PARKING

NodeFire Save Document
Home > Plants, Pests & Pest Control > Pest Management > Noxious & Invasive Weed Program > NWAC > Risk Assessments > Tree of Heaven

Tree of Heaven Risk Assessment


Common Name: Tree of Heaven
Latin Name: Ailanthus altissima

Ailanthus is clearly a problematic invasive species in other parts of the United States. It is present in Minnesota, but not naturalized, and whether or not it can currently thrive in the state is debatable. Discussion should focus on whether or not it could thrive in Minnesota now or in the near future.

Reviewer: Ken Graeve
Affiliation/Organization: Minnesota Department of Transportation

Date: 08/25/2014
FILE #: MDARA00037TOHV_8_25_2014

Final Results of Risk Assessment

Review Entity | Outcome

  • NWAC Listing Subcommittee: Regulate as a Restricted Noxious Weed.
    Comments: Eradication is possible but may not be necessary because the one known plant in MN is female and without a male plant nearby is unlikely to produce viable seed. No other plants have been found in unmanaged wooded sites in the immediate vicinity. It is unlikely that this species can currently grow well enough in MN for it to be very aggressive. However, its nationwide distribution is right on the edge of plant hardiness zone 4, and it is likely to become better able to thrive and spread in MN as the climate warms. The primary concern with this would be that the species is allowed to be moved around the state for horticultural purposes in the meantime, leading to a much more widespread problem when it finally does become invasive in MN. Restricting the sale and movement of the species now will prevent future problems.
  • NWAC Full-group: Regulate as a Restricted Noxious Weed.
  • MDA Commissioner: Not yet reviewed.
Box Question Answer Outcome
1 Is the plant species or genotype non-native? No. (Global Invasive Species Database, 2005; Fryer, 2010; USDA NRCS, 2014).
Ailanthus altissima is native to Taiwan and central China, and was first introduced to North America in the late 1700s for horticultural reasons (Fryer, 2010).
Go to Box 3.
3 Is the plant species, or a related species, documented as being a problem elsewhere? Yes. Reported as invasive in New England, the mid-Atlantic States, California, the Pacific Northwest, and the Southwest. It is weakly invasive in the middle and southern Great Plains, and spreading in the South (Fryer, 2010).
Listed as invasive in 38 states by other sources (Global Invasive Species Database).
Go to Box 6.
6 Does the plant species have the capacity to establish and survive in Minnesota? Yes. The species is present but not naturalized. Minnesota may or may not be just outside the range of Ailanthus altissima, but because this species is so invasive in other places and since it might be right on the edge of being able to survive in MN, this is a situation in which it is worth considering future climate in assessing risk. Future climate projections indicate that MN will be warmer in the future, with plant hardiness zones shifting up to a full zone every 30 years (US Global Change Research Program, 2009), and there is already some data showing that the current plant hardiness zones may already be outdated (Krakauer, 2012). In considering climate projections for this risk assessment, the question to be examined is how quickly will changing climate allow Ailanthus survival in MN, and is that soon enough to necessitate it being regulated by the current noxious weed law. One important concern is the plausible scenario in which a species is able to survive but not thrive in Minnesota and is therefore not regulated. Without regulation it could become more widespread through horticultural use or inadvertent spread, and by the time changes in climate allow the plant to become invasive (and thus subject to regulation) it will have already become widely distributed and gone through its lag phase, and we will have missed the opportunity to prevent it from becoming a problem in MN. See Box 6A.
6A Is the plant, or a close relative, currently established in Minnesota? Yes. The one known Ailanthus altissima plant in Minnesota is in a somewhat sheltered site in St Paul. In this sheltered site within the heat island of a large metropolitan area, it suffered some die-back in the cold winter of 2013-2014 (see photos) and is suspected of having died back in earlier winters. While this site is somewhat sheltered, the die-back seems to occur on the branches that extend above a sheltering wall, where they are exposed to cold winter winds that might have a desiccating effect on the branches. If it weren’t for the wind, could it thrive in a place like St Paul?  If cold, desiccating winter winds are the limiting factor, then could it survive in sheltered valleys in far SE MN, which would be less windy than street canyons in the city and also possibly warmer, lacking the urban heat island effect but being located on the edge of hardiness zone 5a?
Go to Box 7.
6B Has the plant become established in areas having a climate and growing conditions similar to those found in Minnesota? It is said to occur in USDA hardiness zones 4-8 in North America (Fryer 2010). Ailanthus is said to be able to survive temperatures of -27F (NatureServe, 2014) to -38F (Fryer 2010), which may mean it could survive in zone 4b to 3a, which have average annual extreme minimum temperatures of -30 to -25F to -40 to -35F (USDA ARS, 2014), theoretically allowing it to extend across much of the state. Its seedlings are said to be vulnerable to cold, but older plants are more tolerant, meaning that it could get established in cold regions that get occasional multiple-year periods of milder winters (Fryer, 2010). However, most locations of infestations on EDDMaps seem to be in zone 5a or warmer (see maps), which raises the question of whether or not it can survive and thrive in MN. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7 Does the plant species have the potential to reproduce and spread in Minnesota? If Box 6 is affirmative, then yes. See Box 7A.
7A Does the plant reproduce by asexual/vegetative means? Yes. Vegetative sprouting is common in Ailanthus altissima, even in trees with uninjured stems, and root sprouts can appear up to 50 to 90 feet from the main stem (Fryer, 2010). Go to Box 7B.
7B Are the asexual propagules effectively dispersed to new areas? No. Dispersal of asexual propagules would probably require mechanical transport by human activity or possibly movement of soil from hillsides or stream banks during flooding. Go to Box 7C.
7C Does the plant produce large amounts of viable, cold-hardy seeds? Yes. Ailanthus has been observed to have seed production rates 40 times higher than the next-highest producing species in a Connecticut hardwood forest, with 12” DBH trees producing 400,000 and 2 million seeds per tree in two different years. Seed viability rates are said to be high (Fryer 2010).  Go to Box 7F.
7D If this species produces low numbers of viable seeds, does it have a high level of seed/seedling vigor or do the seeds remain viable for an extended period? Seedling establishment has been reported as low, but nevertheless Ailanthus does frequently spread by seed (Fryer, 2010). Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7E Is this species self-fertile? Ailanthus altissima is dioecious (Fryer, 2010). Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7F Are sexual propagules – viable seeds – effectively dispersed to new areas? Yes—Fryer cites many studies showing infestations establishing from seedlings (2010). Go to Box 7I.
7G Can the species hybridize with native species (or other introduced species) and produce viable seed and fertile offspring in the absence of human intervention? No. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7H If the species is a woody (trees, shrubs, and woody vines) is the juvenile period less than or equal to 5 years for tree species or 3 years for shrubs and vines? Ailanthus altissima trees can begin seed production early, producing seed by 1 to 10 years of age. Trees in one study averaged 4.8” DBH at first seed production (Fryer, 2010). Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7I Do natural controls exist, species native to Minnesota, which are documented to effectively prevent the spread of the plant in question? No. Researchers in Pennsylvania are studying a native fungus that causes wilt and high mortality in Ailanthus trees but more information is needed on its effectiveness, host specificity (Nisley, 2014), and cold hardiness. However, this research is preliminary. Go to Box 8.
8 Does the plant species pose significant human or livestock concerns or has the potential to significantly harm agricultural production, native ecosystems, or managed landscapes? Yes. See Box 8A.
8A Does the plant have toxic qualities, or other detrimental qualities, that pose a significant risk to livestock, wildlife, or people? Can be toxic to humans, and can damage buildings, foundations, and water facilities (Fryer, 2010 and Global Invasive Species Database, 2014). See Box 8B.
8B Does, or could, the plant cause significant financial losses associated with decreased yields, reduced crop quality, or increased production costs? Has been said to endanger forest regeneration and restoration efforts in West Virginia, Ohio, and Pennsylvania (Nisley, 2014) and considered a “dangerous weed” in forest plantations (NatureServe, 2014). See Box 8C.
8C Can the plant aggressively displace native species through competition (including allelopathic effects)? Yes. Ailanthus can crowd out native vegetation, reduce diversity of native plants, and alter natural ecosystem succession because of its allelopathic effects, high degree of shade tolerance and very rapid growth rates (Fryer, 2010 and NatureServe, 2014). Because Ailanthus is most invasive in disturbed sites, some sources consider it to be only slightly or moderately invasive. However, because of its allelopathy, altering effects on soil chemistry and litter layers, interference with natural succession and forest regeneration, and ability to  invade and alter riparian ecosystems it is considered highly invasive and a serious ecological threat by many others (Fryer, 2010 and NatureServe, 2014). Go to Box 9.
8D Can the plant hybridize with native species resulting in a modified gene pool and potentially negative impacts on native populations? No. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
8E Does the plant have the potential to change native ecosystems (adds a vegetative layer, affects ground or surface water levels, etc.)? Yes. Ailanthus can reduce the leaf litter layer, decrease soil carbon:nitrogen ratios, increase susceptibility of ecosystems to invasion by other species. It also alters natural ecosystem succession by invading early succession habitats and crowding out native vegetation with rapid growth rates and allelopathic compounds (Fryer, 2010 and NatureServe, 2014). Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
8F Does the plant have the potential to introduce or harbor another pest or serve as an alternate host? No. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
9 Does the plant species have clearly defined benefits that outweigh associated negative impacts? No. See Box 9A.
9A Is the plant currently being used or produced and/or sold in Minnesota or native to Minnesota? No. However, the concern is that it could be sold, which would lead to problems in the future. Go to Box 10.
9B Is the plant an introduced species and can its spread be effectively and easily prevented or controlled, or its negative impacts minimized through carefully designed and executed management practices? Yes, it is introduced and no, its spread cannot be easily prevented or controlled. No, its effects cannot be minimized through carefully designed and executed management practices. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
9C Is the plant native to Minnesota? No.  Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
9D Is a non-invasive, alternative plant material commercially available that could serve the same purpose as the plant of concern? Yes.  Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
9E Does the plant benefit Minnesota to a greater extent than the negative impacts identified at Box 8? No.  Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
10 Should the plant species be enforced as a noxious weed to prevent introduction &/or dispersal; designate as prohibited or restricted? Restrict the sale to prevent the spread of the species and therefore prevent setting the species up for rapid spread when climate changes enough to allow its survival. See Box10A.
10A Is the plant currently established in Minnesota? Yes. Present, but there are no records of naturalized populations. Go to Box 10B.
10B Does the plant pose a serious human health threat? No. Minimal threat, except possibly to those working with the plant to control it (Fryer, 2010). Go to Box 10C.
10C Can the plant be reliably eradicated (entire plant) or controlled (top growth only to prevent pollen dispersal and seed production as appropriate) on a statewide basis using existing practices and available resources? Yes, because of its very limited distribution. Flow chart says to list as prohibited, but see comments from Listing Subcommittee above.

References:

EDDMapS. 2014. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Accessed July 17, 2014.

Fryer, Janet L. 2010. Ailanthus altissima. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Accessed July 17, 2014.

Global Invasive Species Database, 2005. Ailanthus altissima. Accessed July 17, 2014.

NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Accessed: July 17, 2014.

Nisley, Rebecca G. 2014. Ailanthus: A Nonnative Urban Tree Is Causing Trouble in Our Forests. Research Review, No. 22. USDA Forest Service Northern Research Station. Accessed July 17, 2014.

U.S. Global Change Research Program. 2009. Global Climate Change Impacts in the United States. Accessed July 21, 2014.

USDA, NRCS. 2014. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA. Accessed July 17, 2014.

USDA, ARS. 2014. USDA Plant Hardiness Zone Map. Accessed July 17, 2014.