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Home > Plants, Pests & Pest Control > Pest Management > Noxious & Invasive Weed Program > NWAC > Risk Assessments > Morrow's Honeysuckle

Morrow's Honeysuckle Risk Assessment

Common Name: Morrow’s honeysuckle
Latin Name: Lonicera morrowii

Morrow's honeysuckle plants
Plants in bloom, photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Morrow's honeysuckle berries
Berries, photo by Stacey Leicht, University of Connecticut, Bugwood.org


  • Laura Van Riper
  • Tim Power


  • Minnesota Department of Natural Resources
  • Minnesota Nursery and Landscape Association

Date: 08/28/2014
File #: MDARA00033MOHS_8_28_2014

Final Results of Risk Assessment

Review Entity-Outcome

  • NWAC Listing Subcommittee - List as a Restricted Noxious Weed.
    Subcommittee agreed with the risk assessment that L. morrowii should be listed as a restricted noxious weed.
  • NWAC Full-group - Restricted Noxious Weed
  • MDA Commissioner- Not yet reviewed


Box Question Answer Outcome
1 Is the plant species or genotype non-native? Yes. Native to Japan (Munger 2005). Go to Box 3.
3 Is the plant species, or a related species, documented as being a problem elsewhere? Yes. Naturalized in states in the eastern and midwest United States (Love et al. 2009, McCusker et al. 2010, Wisconsin Department of Natural Resources 2007). Regulated as noxious/invasive in CT, MA, NH, and VT.
USDA Plants accessed 3-26-14. http://plants.usda.gov/core/profile?symbol=LOMO2
Restricted in Wisconsin NR40.
Go to Box 6.
6 Does the plant species have the capacity to establish and survive in Minnesota?    
6A Is the plant, or a close relative, currently established in Minnesota? Yes. Morrow’s honeysuckle has been found in many counties in Minnesota, especially in the southeast and central portions of the state (EDDMaps 2014). There are not many reports in the northwest portion of the state and limited reports in the southwest. Go to Box 7.
7 Does the plant species have the potential to reproduce and spread in Minnesota?    
7A Does the plant reproduce by asexual/vegetative means? “Research on asexual reproduction for the bush honeysuckles is sparse. In the commercial trade greenwood and hardwood cuttings are used to propagate stocks of bush honeysuckles” from Wisconsin DNR 2007. Go to Box 7B.
7B Are the asexual propagules effectively dispersed to new areas? Not likely. The main method of spread to new sites is likely through seeds. Go to Box 7C.
7C Does the plant produce large amounts of viable, cold-hardy seeds? “Information about seed production is sparse, but it is apparent that some bush honeysuckles are capable of producing substantial numbers of seeds. Barnes indicates Bell's honeysuckle produces consistent annual seed crops. A single "typical" Bell's honeysuckle shrub, about 6.6 feet (2 m) tall, growing in southern Wisconsin, produced 3,554 berries in 1 year. Numbers of seeds/fruit, sampled from several shrubs at this site, averaged 5 to 7, indicating that a "typical" plant may produce >20,000 seeds annually” from Munger 2005. L. morrowii is a parent plant of Bell’s honeysuckle. Go to Box 7F.
7E Is this species self-fertile? Not known (Munger 2005). 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. Birds can vector honeysuckle fruits and seeds (Drummond 2005, McCusker et al. 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? Yes. L. morrowii has hybridized with the non-native L. tatarica to form the hybrid L. x bella which is widely distributed in Minnesota.
Other hybrids have been formed although they are not widely escaped:
Lonicera × minutiflora Zabel (bunchberry honeysuckle), a cross between L. morrowii and L.× xylosteoides.
Lonicera × muscaviensis Rehd. (Muscovy honeysuckle), a cross between L. morrowii and L. ruprechtiana. (Munger 2005)
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, that are documented to effectively prevent the spread of the plant in question? No controls native to Minnesota exist.
“Although not purposely introduced for the purposes of biological control, Hyadaphis tataricae is a nonnative aphid that feeds on a variety of bush honeysuckles in North America (for an analysis of taxa-specific susceptibility see Herman and Chaput [72]) [183,184]. H. tataricae feeding results in dwarfing and folding of terminal leaves, stunted terminal growth, and development of "witches brooms" [23,24,107,183]. This lowers plant vigor and may prevent flowering and fruit development [23,24,184]. Voegtlin and Stoetzel [184] indicate that it is not expected to provide widespread, effective control of bush honeysuckles. However, according to U.S. Geological Survey Northern Prairie Wildlife Research Center [23,24], H. tataricae is still expanding its North American range and "may eventually reach levels that will provide control" from Munger 2005.
There is a honeysuckle leaf blight that has been observed on Morrow’s honeysuckle in Iowa, Ohio, and Pennsylvania (Boyce et. al 2014).
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.  
8A Does the plant have toxic qualities, or other detrimental qualities, that pose a significant risk to livestock, wildlife, or people? Not known. Dense infestations of the related Amur honeysuckle can increase the incidence of tick borne diseases to humans (Allan et al. 2005). Go to 8B.
8B Does, or could, the plant cause significant financial losses associated with decreased yields, reduced crop quality, or increased production costs? High densities of honeysuckles may constrain timber regeneration which could have negative financial impacts for the timber industry (e.g. Schulte et al. 2011). Go to Box 9.
7C Can the plant aggressively displace native species through competition (including allelopathic effects)? Can reach high densities, for example density of Morrow’s honeysuckle was 67,920 ± 4,480 shrubs/ha in a study in Pennsylvania (Love and Anderson 2009).
There are reports of dense stands of non-native honeysuckles forming monocultures in forest understories (Batcher and Stiles 2000, Munger 2005, Webster et al. 2006, Wisconsin DNR 2007, NatureServe 2014).
Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7D Can the plant hybridize with native species resulting in a modified gene pool and potentially negative impacts on native populations? No hybridization with native species known. Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7E Does the plant have the potential to change native ecosystems (adds a vegetative layer, affects ground or surface water levels, etc.)? Adds a shrub layer (Munger 2005). Bold/italic text is provided as additional information not directed through the decision tree process for this particular risk assessment.
7F Does the plant have the potential to introduce or harbor another pest or serve as an alternate host? No evidence of this. 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?    
9A Is the plant currently being used or produced and/or sold in Minnesota or native to Minnesota? Not aware of any Minnesota nurseries producing Morrow’s honeysuckle for sale. There are nurseries selling the similar looking L. tatarica cultivars. (Tim Power, Minnesota Nursery and Landscape Association, May 12, 2014). Plant is not native to Minnesota. 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? The plant is an introduced species. Its spread cannot be easily controlled. It produces abundant seeds which can be vectored by birds. It is a woody plant so control is cost and labor intensive. 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.
There are native honeysuckles than can be alternatives:
Diervilla lonicera [dwarf bush honeysuckle; note this is not a true honeysuckle (Lonicera)], Lonicera canadensis (fly honeysuckle), L. oblongifolia (swamp fly honeysuckle), L. villosa (mountain fly honeysuckle); the three true honeysuckles (Lonicera sp.) are not commonly grown commercially. There are ornamental non-native honeysuckles (Lonicera xylosteum cultivars) sold that have not had their invasive potential assessed. Alternatives listed in MIPN Landscape Alternatives brochure (note that not all are hardy in Minnesota) (http://mipn.org/MIPN%20Landscape%20Alternatives%202013.pdf):
Amelanchier spp. (serviceberry), Heptacodium miconioides (seven son flower), Kolkwitzia amabilis (beautybush), Calycanthus floridus (Carolina allspice), Sambucus canadensis (American elderberry), Sambucus pubens (American red elderberry), Lonicera dioica (red honeysuckle), Lonicera involucrata (twinberry), Stephanandra incise (cultleaf stephanandra) Viburnums (Viburnum spp. – V. acerifolium, V. lentago, V. rafinesquianum, V. trilobum), the ninebarks (Physocarpus opulifolius), and the dogwoods (Cornus spp. – C. alternifolia, C. racemosa, C. sericea) can also be alternatives.
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?    
10A Is the plant currently established in Minnesota? Yes. Go to Box 10B.
10B Does the plant pose a serious human health threat? No. 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? No. There are methods that can be used to control Morrow’s honeysuckle, but they are cost and labor intensive. Morrow’s honeysuckle is widespread throughout the state. The plant likely cannot be reliably controlled on a statewide basis using existing practices and available resources. Control of Morrow’s honeysuckle is cost and labor intensive. Love and Anderson (2009) reported costs including: $770/ha (for foliar herbicide treatments), $4880/ha (for cutting plants), $9330/ha (mechanical removal with an axe), and $9620/ha (for cutting plants and treating the stump with herbicide).
Love and Anderson’s (2009) implications for practice were:
  • Mechanical removal in spring was most effective, and a foliar application of 2% glyphosate solution in spring was the second most effective method to reduce density of Morrow’s honeysuckle.
  • Foliar application of 2% glyphosate was the cheapest treatment method and required the least amount of labor.
  • Mechanical removal of Morrow’s honeysuckle resulted in the highest metrics for herbaceous diversity.
  • Shrub density, rather than percent shrub cover or stem density, proved to be the most reliable indicator of treatment success.
  • An adaptive restoration approach, including follow-up treatments, planting of native seedlings and herbs, and deer control, will need to be enacted to meet restoration goals.
List as a Restricted Noxious Weed.


Allan, B.F., H. P., Dutrac, L. S. Goessling, K. Barnett, J. M. Chase, R. J. Marquis, Genevieve Pang, Gregory A. Storch, Robert E. Thach, and John L. Orrock. 2010. Invasive honeysuckle eradication reduces tick-borne disease risk by altering host dynamics. Proceedings National Academy of Sciences, vol. 107 (43) 18523–18527.

Batcher, M. S. and S. A. Stiles. 2000. Element Stewardship Abstract for Lonicera maackii Maxim (Amur honeysuckle), Lonicera morrowii A. Gray (Morrow’s honeysuckle), Lonicera tatarica (Tatarian honeysuckle), Lonicera x bella Zabel (Bell’s honeysuckle), The Bush Honeysuckles. Accessed May 29, 2014.

Boyce, R. L., S. N. Brossart, L. A. Bryant, L. A. Fehrenbach, R. Hetzer, J. E. Holt, and B. Parr. 2014. The beginning of the end? Extensive dieback of an open-grown Amur honeysuckle stand in northern Kentucky, USA. Biological Invasions DOI 10.1007/s10530-014-0656-7. Published online February 16, 2014.

Drummond, B. A. 2005. The selection of native and invasive plants by frugivorous birds in Maine. Northeastern Naturalist 12(1): 33-44.

EDDMapS. 2014. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Accessed May 30, 2014.

Love, J. P. and J. T. Anderson. 2009. Seasonal effects of four control methods on the invasive Morrow’s honeysuckle (Lonicera morrowii) and initial responses of understory plants in a Southwestern Pennsylvania old field. Restoration Ecology 17 (4), 549–559.

McCusker, C. E., Ward, M. P., and Brawn, J. D. 2010. Seasonal responses of avian communities to invasive bush honeysuckles (Lonicera spp.). Biological Invasions 12:2459–2470.

Munger, G. T. 2005. Lonicera spp. Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Accessed May 7, 2014.

Nature Serve 2014. Nature Serve Explorer: Lonicera tatarica. Accessed May 29, 2014.

Schulte, L. A., E. C. Mottl, and B. J. Palik. 2011. The association of two invasive shrubs, common buckthorn (Rhamnus cathartica) and Tartarian honeysuckle (Lonicera tatarica), with oak communities in the midwestern United States. Canadian Journal of Forest Resources 41: 1981–1992.

Webster, C. R., Jenkins, M. A., and Jose, S. 2006. Woody invaders and the challenges they pose to forest ecosystems in the Eastern United States. Journal of Forestry 104 (7): 366-374.

Wisconsin Department of Natural Resources. 2007. Lonicera morrowii Literature Review. Accessed May 29, 2014.