Official Assessment of Japanese Honeysuckle (Lonicera japonica)

in Indiana’s Natural Areas

Answers are underlined and in bold; italicized text indicates discussion points


Members of assessment subcommittee:  Ellen Jacquart, Mike Cline, Phil O’Connor, Brian Abrell, Jim Gerbracht, and Tom Good.

Contents of the Assessment:

Section I – Invasion Status. Pages 1 - 2.  Determines whether the species being evaluated is invasive in Indiana.

Section II – Ecological Impacts of Invasion. Pages 2 - 3. Evaluates the significance of impacts of the species.

Section III – Potential for Expansion.  Pages 3 - 4.  Evaluates the actual and/or potential expansion of the species.

Section IV – Difficulty of Management.  Pages 4 - 5.  Evaluates how hard it is to control the invasive species.

Section V – Commercial Value. Page 5.  Evaluates how valuable the species is economically in Indiana.


Questions in Sections I – V may direct you to one or more of the following sections for particular invasive species:

Section A. Page 7.  For species which have impacts limited to a few sites, assesses the potential for further spread.

Section B. Page 7.  For species which have medium impacts but high value, assesses whether species could be used in specific circumstances that would prevent escape and invasion.


A worksheet for use with the assessment is found on page 7.

[comments] Taylor Prof (Paul?): Potential for expansion—not yet invasives in IN, Handling twice? Sec A  or 1B4 (persistance)  Redundancy

Automatic Exemption From the Assessment

Is this species listed on any federal or state noxious, or prohibited plant lists?

If YES then do not proceed with assessment but indicate a conclusion of

Do not use this plant on the front of the response form.


If NO then go to Section I.

Section I            Invasion Status

1-a Current Invasion in Indiana


1. Does this species occur in any natural areas in Indiana?

If NO then go to Section III-c (page 4).

If YES then go to 1-a 2.

2. Does it ONLY occur in natural areas of Indiana because it has persisted from its previous cultivation (e.g., in abandoned farmland or homesteads)?

If YES then go to Section III-c (page 4).

If NO then go to Section 1-b (below).


1-b Invasion Status in Indiana


Evidence of invasion (forming self-sustaining and expanding populations within a plant community with which it had not previously been associated) must be provided.  If not available in a published, quantitative form, this evidence must include written observations from at least three appropriate biologists.


1.        Is species invasive ONLY when natural disturbance regime and scale have been altered? (e.g. where frequency, extent, or severity of fires have been reduced by human activity).

If YES then go to questions 1-b 2.

If NO – the species is invasive, go to Section II (below).


2.        Has this species ever been known to persist, following colonization, when the natural regime is resumed and the natural flora/communities recover? (e.g., is not an early successional species that only temporarily invades disturbed sites.)

If YES (or unknown) - the species is invasive, go to Section II (below).

If NO (known not to persist) the species is currently not invasive in Indiana.  Go to Section III-c (page 4) to assess the species’ potential for future invasion.

Section II   Ecological Impacts of Invasion Impact Index

II-a                Known Impacts at WORST SITE(S) (without, or before, any control effort)


Add up points for ALL impact statements (i through vi) that are true at the worst affected site(s) in that zone then go to question II-b.   Evidence of impacts must be provided.  If not available in published, quantitative form, this evidence must include written observations from at least three appropriate biologists, including specific locations of observations.  Scientific names of impacted species (e.g., State-listed or native species with which hybridization occurs) must be included on the response form.  If there is no evidence of an impact, then assign 0 points unless the impact is considered very likely (e.g., fixes N2 in low nutrient soil that can change the flora) or the impact (except vi) has been demonstrated in similar habitats in other zones or outside the states.   In these cases assign 0.5 points.


i)  Causes long-term, broad alterations in ecosystem processes changing the community as a whole (e.g. invasion of cattails changes hydrology, drying the site and allowing open aquatic systems to become forested).          15


ii) Has negatively impacted Indiana State-listed or Federal-listed plants or animals (choose one of the following):

Displacement, death or hybridization has been documented AND occurs in at least 20% of known locations of the listed species, OR these effects occur in less than 20% of known locations of the listed species, but at least 4 different listed species are affected. (15 plants, three animals)               12


Displacement, death or hybridization occurs in less than 20% of locations of the listed species OR impacts are considered likely because the listed and invasive species closely co-habit (e.g., compete for light).              4


iii) Displaces or precludes native vegetation (affecting mortality and/or recruitment) by achieving infestations in the zone state that have at least 50% coverage of this species (as defined in the glossary) in the affected stratum that meet any of the following criteria:

a) collectively add up to at least 10 acres

b) are 5 infestations of at least 0.25 acres

c) are 5 infestations that cover an entire localized community

(e.g. sinkhole, seeps, fens, bogs, barrens, cliffs)

d) are 5 infestations some of which are at least 0.25 acres and others of which cover entire localized communities.          128


iv) Changes community structure in ways other than vegetation displacement (e.g., alters wildlife abundance, adds a new stratum, or increases stem density within a stratum by more than 5-fold).  Adds new stratum – a carpet across the forest floor.  Also, this species has been shown to suppress growth and increase mortality of adult trees and seedlings.  It may also lead to a decline or alteration in abundance in songbird populations (see management abstract for literature citations).        4


v) Hybridizes with native Indiana plants or commercially-available species.        4


vi) Covers over 15% of invaded stratum (but if 12 points were assigned for statement iii, do not assign points here) on > 10 acres in the state.        31

        Total points (place in worksheet page 7):        28       


II-b  Range of Habitats in Which Species is Invasive


Forest:             1)Dry upland, 2)Dry-mesic upland, 3)Mesic upland, 4)Mesic floodplain, 5)Wet-mesic floodplain, 6)Wet floodplain, 7)Bluegrass till plain flatwoods*, 8)Boreal flatwoods*, 9)Central till plain flatwoods, 10)Dry flatwoods*, 11)Sand flatwoods*, 12)Southwestern lowland mesic flatwoods*


Savanna:                 13)Mesic savanna*, 14)Dry sand savanna*, 15)Dry-mesic sand savanna*


Barrens:             16)Limestone bedrock*, 17) Sandstone bedrock*, 18)Siltstone bedrock*, 19)Chert*, 20)Gravel*, 21)Sand*, 22) Clay*


Prairie:              23)Dry-mesic prairie*, 24)Mesic prairie*, 25)Wet prairie*, 26)Dry sand prairie*, 27)Dry-mesic sand prairie*, 28)Wet-mesic sand prairie*, 29)Wet sand prairie*


Wetland:             30)Marl beach*, 31)Acid bog*, 32)Circumneutral bog*, 33)Fen*, 34)Forested fen*, 35)Muck and Sand flats*, 36)Marsh, 37)Sedge meadow*, 38)Panne*, 39)Acid seep*, 40)Calcareous seep*, 41)Circumneutral seep*, 42)Forest swamp, 43)Shrub swamp


Lake:                  44)Lake, 45)Pond


Stream:            46)Low-gradient creek, 47)Medium-gradient creek, 48)High-gradient creek, 49)Low-gradient river, 50)Medium-gradient river, 51)Major river


Primary:             52)Aquatic cave*, 53)Terrestrial cave*, 54)Eroding cliff*, 55)Limestone cliff*, 56)Overhang cliff*, 57)Sandstone cliff*, 58)Lake dune*, 59)Gravel wash*


Is this species known to be invasive in at least four habitat-types (note – rare habitat-types are marked with a * and count as 2 when adding) OR does it occur in at least one habitat-type of each of the terrestrial and palustrine/aquatic lists (palustrine/aquatic habitats are shown in bold)  4 common communities (4 pts.) plus 6 rare communities (12 pts.) = 16 pts.


If YES then multiply total score from II-a by 1.5
then go to Section II-c  (Below)

If NO then multiply total score from II-a by 1
then go to Section II-c (Below)

Place point total in worksheet, page 7. 28 x 1.5 = 42.


II-c  Proportion of Invaded Sites with Significant Impacts


Of the invaded sites, might any of the worst impacts [items i-v in section II-a] only occur under a few, identifiable, environmental conditions (i.e., edaphic or other biological conditions occurring in 1-10% of the sites)? Documentation of evidence must be provided for a YES answer.

If NO or NO SCORE on items i to v in section II-a
then go to Section III

If YES then go to Section A (page 7)

Section III Potential for Expansion.     Potential Index

This section evaluates a species’ actual and/or potential for expansion in Indiana.

III-a  Potential for Becoming Invasive in Indiana


1.     Is information available on the occurrence of new populations of this species in Indiana over the last 5 years?

If YES then go to section III-b

If NO go to Section III-c to estimate potential for expansion based on the biology of the species.


III-b. Known Rate of Invasion.


1.        Was this species reported in more than two new discrete sites (e.g., lakes, parks, fragments of habitats at least 5 miles apart) in any 12 month period within the last 5 years?

If NO then P = Low; then go to Section IV

If YES then P = High; then go to Section IV


III-c. Estimated Rate of Invasion.  This section is used to predict the risk of invasion for species that are 1) not currently invasive in the state, and 2) invasive in the state but for which no data on current rate of spread exists. These questions are based on Hiebert et al. 1995.


1.            Does this species hybridize with any State-listed plants or commercially-important species? (E.g., exhibit pollen / genetic invasion.)

If YES then go to Section B (page 7)

If NO then go to question III-c 2.


2.             Add up all points from statements that are true for this species.            Points  

i. Ability to complete reproductive cycle in area of concern

a. not observed to complete reproductive cycle    0

b. observed to complete reproductive cycle      5


ii. Mode of reproduction

a. reproduces almost entirely by vegetative means                                1

b. reproduces only by seeds                                                                3

c. reproduces vegetatively and by seed                                                5

iii. Vegetative reproduction

a. no vegetative reproduction                                                                0
b. vegetative reproduction rate maintains population                                1
c. vegetative reproduction rate results in moderate increase in

population size                                                                                                3
d. vegetative reproduction rate results in rapid increase in

population size                                                                                                5

There was discussion whether c. or d. was the appropriate response; we agreed it was a fast grower, but unless it has full sun its vegetative reproduction would be moderate.

iv. Frequency of sexual reproduction for mature plant

a. almost never reproduces sexually in area                                                0
b. once every five or more years                                                                1
c. every other year                                                                                3
d. one or more times a year                                                                5


v. Number of seeds per plant

a. few (0-10)                                                                                                1
b. moderate (11-l,000)                                                                                3
c. many-seeded (> l,000)                                                                                5

We discussed how we define ‘plant’ a single rootstock could have dozens of vines coming from it.  We used a reference in the management abstract that noted 11-200 seeds per plant.  This is probably low, but may represent an average value for sun/shade plants.

vi. Dispersal ability

a. little potential for long-distance dispersal                                                0
b. great potential for long-distance dispersal                                                5

vii. Germination requirements

a. requires open soil and disturbance to germinate                                0
b. can germinate in vegetated areas but in a narrow range or in

special conditions                                                                                                3
c. can germinate in existing vegetation in a wide range of

conditions                                                                                                5

Can find seedlings growing in very undisturbed forest
viii. Competitive ability

a. poor competitor for limiting factors                                                0
b. moderately competitive for limiting factors                                3
c. highly competitive for limiting factors                                                5

We agreed that the limiting factor for this species is generally light; in low-light conditions it is a poor competitor.  In high light conditions it is highly competitive.  We chose moderately competitive as an average value.

                Total points for questions i – viii (place in worksheet page 7):                 34

Section IV                   Difficulty of Management    Management Index

IV    Factors That Increase the Difficulty of Management


Add up all points from statements that are true for this species then go to Section V (page 5).  Assign 0.5 point for each statement for which a true/false response is not known.



i) Control techniques that would eliminate the worst-case effects (as listed in Section II) have been investigated but none has been found.          15

ii)  This species is difficult to control without significant damage to native species because: it is widely dispersed throughout the sites (i.e., does not occur within discrete clumps nor monocultures); it is attached to native species (e.g., vine, epiphytes or parasite); or there is a native plant which is easily mistaken for this invader in: (choose one)

³ 50% of discrete sites in which this species grows;        10

25% to 50% of discrete sites in which this species grows.        7

Dormant season treatment of this species is possible, but in forest conditions it still results in non-target damage to the plants the vines are draped over (some sedges and other plants stay green into winter).  In glades and barrens it is possible to do dormant season treatments with little or no non-target damage.  About ½ of the areas to treat are glade/barren, and half are forest.

iii) Total contractual costs of known control method per acre in first year, including access, personnel, equipment, and materials (any needed re-vegetation is not included)

$2,000/acre (estimated control costs are for acres with a 50% infestation)          5

Brian noted that a contract at Wesselman Woods N.P. for Japanese honeysuckle control cost $1200/acre several years ago.  There was general agreement the current cost would be $1000-$1500/acre.

iv) Further site restoration is usually necessary following plant controldeath to reverse ecosystem impacts and to restore the original habitat-type or to prevent immediate re-colonization of the invader. Generally not; most species are suppressed under the vines rather than entirely displaced and will reestablish themselves.        5


v) The total area over which management would have to be conducted is: (choose one)

³ 500100 acres; No question on this!            5

< 500100 but > 50 acres.            2

>< 50 but > 10 acres.            1

><10 acres            1/2


vi) Following the first year of control of this species, it would be expected that individual sites would require re-survey or re-treatment, due to recruitment from persistent seeds, spores, or vegetative structures, or by dispersal from outside the site: (choose one)

at least once a year for the next 5 years;            105

one to 4 times over the next 5 years;            6

regrowth not known            22


vii) Occurs in more than 20 discrete sites (e.g., water-basins, parks, fragments of habitats at least 5 miles apart).        3


viii) The number of viable, independent propagules per mature plant (e.g., seeds, spores, fragments, tubers, etc. detached from parent) is > 200 per year
AND one or more of the following:

A.                 the propagules can survive for more than 1 year;

B.                 the propagules have structures (fleshy coverings, barbs, plumes, or bladders) that indicate they may spread widely by birds, mammals, wind or water;

C.                 the infestations at 3 or more sites exhibit signs of long distance dispersal. Some possible indicators of long distance dispersal include: the infestation has outlier individuals distant [>50 yards] from the core population; the infestation apparently lacks sources of propagules within ¼ mile.        3

ix) Age at first reproduction is within first 10% of likely life-span and/or less than 3 months.  We couldn’t make a compelling case that this was true; didn’t count.          2

                Total points (place in worksheet page 8):

Section V         Commercial Value                 Value Index


V-a                Commercial Value


Does this species have any commercial value?   

If response is NO then V = 0 and Go to Conversion of Index Scores to Index Categories

If response is YES then go to Section V-b Dave Gorden reported that there are 3 main cultivars in the trade: ‘Halliana’, ‘Aureo-reticulata’ (in one reference they say this is ‘less aggressive than the species’), and ‘Purpurea’.  Locally, Hobbs, Brehobs, and Cunninghams all list at least one cultivar. Outside of Indiana, some major national suppliers listing the plant include North Coast, Klyn, and Willoway (all in Ohio) and Bluebird in Nebraska.


V-b          Factors that Indicate a Significant Commercial Value


Add up all points from statements that are true for this species.  Assign 0.5 point for each statement for which a true/false response is not known.



i) This species is sold in national or regional retail stores ( e.g., WalMart, Home Depot, Publix).        10


ii) State-wide there are more than 20 commercial growers of this species.        7


iii) More than five growers in Indiana rely on this species as more than 10% of their nursery’s production.        3


iv) This species has provided a crop, turf, or feed source (e.g., forage, nectar) that has been, or resulted in, a significant source of income for at least five farmers for over 20 years.        3


v) This species is utilized statewide        3


vi) There are more than 100 retail seed outlets statewide        3

              Total points (place in worksheet page 8):    13

Section A (from Section II-c)

A1                Can the habitats in which the worst-case ecological impacts occur (items i to v in Section II-a) be clearly defined as different from invaded sites where there are no such impacts (e.g., defined by edaphic or biological factors)?   (If ecological impacts include negative effects on a State-listed species, then the specific habitats in which that State-listed species occurs must be clearly distinguishable from habitats in which it does not occur.)

If NO then return to Section III (page 4)

If YES then Go to question A2 and prepare such a site definition


A2                Can an estimate be made of the maximum distance that propagules (or pollen if hybridization is a concern) might reasonably be expected to disperse?


If NO then return to Section III (page 4)

If YES then prepare instructions for Specified and Limited Use based on maximum dispersal distance (e.g., may be acceptable for use in specific areas but not near habitats where impacts are high.)   Reassess if the incidence of worst-case impacts increases above 10% or within 10 years, whichever is earlier.   THEN resume the assessment at Section III to provide scores for the other indices.

Section B (from Section III-c or if Value = High and Impact = Medium)

B1                Are there specific circumstances in which this species could be used that would not be expected to result in escape and invasion?  (E.g., foliage plants that are only used indoors and which can be reasonably prevented, by conspicuous labeling, from use or disposal in the landscape.)


If NO, then retain the previously derived Conclusion.

If YES, then Acceptable for Specified and Limited Use where regulations and educational programs for penalties and enforcement of misuse exist.  Reassess this species every 2 years.

Worksheet for Assessment

Section I:

Follow directions to different sections.

Section II:

Impacts Point Total: _28_____ X (1 or 1.5) =                ____42_____ Impacts

Section III:

Potential = High Medium or Low                ____34_____ Potential for Expansion

Section IV:

Difficulty of Management Point Total:                ____24_____ Difficulty of Management

Section V:

Commercial Value Point Total:                ____13_____ Value

Conversion of Index Scores to Index Categories

Using the following table, determine the appropriate category (Low to High or Very High) for each index. 



Potential for Expansion

Management Difficulty


Low (L)

< 12



£ 6

Medium (M)

High (H)

Very High (VH)

12 – 25



20 – 30


15 – 25






Anthropogenic disturbance.  Human-induced disturbance (e.g., mowing) or human-induced changes in natural disturbance regime (e.g., changing the frequency, extent, or severity of fires).


Coverage.  Visual or quantitative estimate of the relative amount of area in a stratum where the canopy of the non-native species intercepts the light that would otherwise be available for other species in or below that stratum. Estimated cover may be dispersed or continuous in a site. Cover is usually measured when foliage is fully expanded. In the case of species that form a dense, continuous mat of rhizomes or stolons, the percent of the soil surface or upper level occupied by that root mat can be estimated as soil, rather than canopy, cover.


Disturbance.  Mechanisms that limit biomass by causing its partial or total destruction.


Discrete sites.   Disjunct habitat-types or fragments of habitats at least 1 mile apart that support invasive plant populations that likely arose by separate long-distance dispersal mechanisms.


Documentation of evidence. One publication including relevant, original research will suffice if data are specific to the taxon and zone(s) under evaluation. If such documentation is not available or needs to be up-dated, at least three individuals who have the expertise on the particular species and zone in question must be identified.


Federal- or Indiana -listed.  Species that are listed by Federal laws or Indiana statutes or rules as threatened or endangered within the State of Indiana.  This list with notes is available at


Formal Risk Benefit Analysis.  Detailed economic studies of impact and  management costs and commercial value for present and future infestations.


Invasive.  A species that forms self-sustaining and expanding populations within a natural plant community with which it had not previously been associated (Vitousek et al. 1995).


Long-term alterations in ecosystem processes.  Examples of ecosystem processes that could be altered: erosion and sedimentation rates; land elevation; water channels; water-holding capacity; water-table depth; surface flow patterns; rates of nutrient mineralization or immobilization; soil or water chemistry; and type, frequency, intensity, or duration of disturbance.  For further explanation see Gordon (1998). 


Native.  Species within its natural range or natural zone of dispersal (i.e., within the range it could have, or would have, occupied without direct or indirect introduction and/or care by humans. Excludes species descended from domesticated ancestors) (Vitousek et al. 1995).


Natural areas. Natural areas: Areas with native plant communities supporting native plant and animal species, with long undisturbed soil systems, and hydrological regimes relatively intact or under restoration. Edges of historically or currently disturbed areas  (roadsides, trails, adjacent to historically disturbed locations, etc.) should not be included in the assessment of invasion into natural areas. That invasion may have been facilitated by the edges, but has to have extended into the native communities for inclusion in this category.


Pollen or genetic invasion. When a native species is displaced by a non-native species through hybridization.


Stratum.   A distinct layer in the architecture of vegetation (e.g., tree canopy or understory shrubs).