Our plant evaluation process

Invasive plants

JLBG adheres to the Botanical Garden and Nursery Codes of Conduct as adopted at the 2001 St. Louis Summit on Invasive Plants and encourages other institutions to do the same.

Understanding the problem

In addition to studying adaptability of new plants, we are also keenly focused on evaluating their potential garden weediness as well as their proclivity to become invasive species. New plants are carefully evaluated at JLBG and at other cooperating sites. JLBG adheres to the Botanical Garden and Nursery Codes of Conduct as adopted at the 2001 St. Louis Summit on Invasive Plants and encourages other institutions to do the same.

JLBG also understands, that while a species may be invasive, cultivars within that species may not exhibit those undesirable traits. Current ornamental breeding is focused on this direction. While the invasive plant issue is a great area of concern here at JLBG, the regularly proposed bans of non-native plants is very concerning, since it is based on emotion and not science. Years ago, there was a movement to implement a nationwide ban on plant species that are only problematic in Hawaii or South Florida.

Realizing it is impossible to completely predict invasiveness in every ecological region of the country, JLBG implores gardeners to watch for plants that show true invasive potential and to report those findings back to JLBG, and to your County Extension Service. As with all vices, JLBG believes moderation, common sense, and responsibility are the key to good outcomes.

Most people don’t understand that re-seeding around the garden is very different from being an invasive species. On-line articles about invasive plants show a complete lack of understanding between the two. In the plant world, the scientific definition of an invasive species is a “non-native” plant that when left alone will invade a functioning natural ecosystem, displacing native plants once population equilibrium has been reached, causing economic harm.

So, let’s breakdown the terms within the definition:

Non-native – an often used, but intellectually indefinable term, since “native” is a place in time and not a place in location.

Functioning Natural Ecosystem – The definition here boils down to your definition of “natural”.  Some people consider the species Homo sapiens to be “un-natural”.  This reflects a need to “bucketize” a world by putting everything into one of two buckets….good/bad or black/white. Some people classify Homo sapiens that arrive across the Pacific Ocean as good and thoughtful, while those who arrive across the Atlantic Ocean as bad and greedy. Every habitat that exists is a functioning ecosystem. These include: a home garden, a highway right of way, any inner city, and even a farm. The question becomes, are these habitats then “natural”? Many North American prairies, which were formed by the climate at the time, were modified and maintained by early Homo sapiens as open hunting grounds for large mammoths.

Population Equilibrium – when a new species is added to a population where the climate is favorable for its growth, the result is a population spike. The plants previously growing on the site will usually rebound, and the number of the newly added species will decline. Population equilibrium may take a few years, or perhaps centuries, depending on the ecosystem processes (hydrology, soil conditions, and species competitiveness).

Economic Harm – this is how the cost of an impact of a new plant on the ecosystem is measured. Many figures are tossed around about the cost to control invasives, but if you examine the reporting criteria, those numbers are usually so inflated to be quite worthless. The number of dollars spent to control weeds, includes plenty of native weeds, as well as properties that weren’t remotely “natural.”

Phytolacca americana 'Silberstein'
Phytolacca americana ‘Silberstein’

Weedy natives

Some of the worst weeds in our Zone 7b NC garden include these current North American natives below:

Acalypha rhomboidea (three-seeded Mercury)
Ambrosia artemisiifolia (ragweed)
Apocynum cannabinum (Indian hemp)
Baccharis halimifolia (groundsel tree)
Chenopodium album (Lambsquarters)
Elephantopus tomentosus (common Elephant’s foot)
Equisetum arvense (common horsetail)
Euphorbia maculata (prostate Spurge)
Euphorbia hirta (giant spurge)
Eupatorium capillifolium (dog fennel)
Geranium carolinianum (wild geranium)
Linaria canadensis (Canadian toadflax)
Phytolacca americana (pokeweed)
Rumex hastatulus (dock)
Solanum carolinense (horse nettle)
Solidago canadensis (Canada goldenrod)
Toxicodendron radicans (poison Ivy)
Viola bicolor (field violet)
Viola cucullata (marsh blue violet)

Weedy ornamentals

Then, there are terribly weedy native plants, considered ornamental, that spread so fast in the garden that we’d never let them near our garden beds:

Asclepias syriacus (common milkweed)
Oenothera speciosa (pink evening primrose)
Prunella vulgaris (self heal)
Pteridium aquilinum (bracken fern)
Pycnantheum muticum (mountain mint)
Rhus copallina (winged sumac)

We can’t imagine that anyone would intentionally want to introduce a new weed or an invasive plant, but we feel that it is incumbent on those who introduce new plants to properly do their assessment homework.

Oenothera speciosa
Oenothera speciosa
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