What Makes A Species Invasive?

Yarrow is a biodynamic accumulator.

Bullying and oppression are all too common throughout the planet, especially in our natural settings, where theres little regulation. We, as humans, are responsible for being the largest spreaders of other species and have the opportunity to understand and help out our terrestrial communities.

Invasives come in many forms, including plant, animal, insect, fungi, and diseases. They affect the health of our forests, prairies, parks, urban areas, and more. Theres only so much space on the planet, and what's generally healthiest is a polyamorous culture of things: plant, insect, microorganism, and tree diversity. Without this diversity, were left with degraded habitats and ecological damage. With this diversity, we have endless bounty and health to our ecosystems, and to us.

In the land of classification of species, things tend to fall into one of a few categories: endangered, threatened, common, prolific, or invasive. But then theres also terms like native, aggressive, and beneficial. This is greatly determined by where these species are and just how successful they are at being there.

Some plants get a bad reputation as being invasive, and a common reflex is to utilize chemicals. But theres other cultural approaches one can employ. Some plants arent actually invasive; they just have such aggressive tendencies that its hard to tell the difference. Pesky plants, like dandelions, lambs-quarter, chickweed, and thistles, have sincere jobs to do. They are the biodynamic accumulators that recycle carbon; bust up tough earth to upcycle nutrients, making them available for others; and they grow quickly and die quickly, so they provide a lot of organic matter back to the soil. Other plants and species are hardy perennials that have the ability to reproduce at astounding levels, holding ground long term and very quickly.

Invasive means a plant or species that is both nonnative and able to establish on many sites, grow quickly, and spread to the point of disrupting plant communities or ecosystems. Other indicators would be super-fast growth, rapid reproduction without inhibition, high dispersal ability, phenotype plasticity (the ability to alter growth form to suit conditions), and tolerance over a wide range. Well, wouldnt that be the dandelion and thistle? Not exactly because the other main considerations include how well they play with others (strangulation and starvation methods), what they provide or do long term (negative chemicals and hormones or beneficials and mycelium), and how hard removal is of said species. Species that dont play nice and are harder to remove warrant more concern and are more invasive. Invasive species alter the soil and terrain and very quickly lead to conditions with high risk to disease, erosion, devaluing of property, and loss of habitat and wildlife.

There are invasive species all along the taxonomy ranks, but some plague many more of us than others. The plant kingdom in Madison is most threatened by just a few: buckthorn, honeysuckle, bishops weed, creeping bellflower, Japanese knotweed, and Norway maple among the most notable invaders. Chemicals are often reached for in the presence of these yard perpetrators, but there are other approaches that work. The biggest goal is interrupting the cycle, keeping it from being so successful. Removing seed heads on rapid spreaders, like creeping bellflower, and repetitive short mowing can starve roots out on plants, like bishops weed. Employing a goat method of repeated cuttings on woody species, like buckthorn and honeysuckle, and digging seedlings to remove spreading roots can be highly successful management.

Chemicals can sometimes look like they work faster, but they often dont do a thorough job and leave the ground burnt, scorched, and starved, making it more likely for our biodynamic communities to move in (thistles, dandelions). All plants release hormones and mycelium from their roots; some of these are beneficial for other entities and some are extremely harmful. Knowing what goes on below the scenes is extremely helpful in determining a course of action. Identifying the issues on site and restoring native plant communities will benefit everything from the ground up.

Karina Mae is the designer and team leader at Garden Search & Rescue.

Garden Search & Rescue
Madison, WI

Invasive Madison Fauna
Common Rabbit, [Oryctolagus cuniculus]
Bighead, Silver, Grass, and Black Carp, [Cyprinus carpio]
Zebra Mussels, [Dreissena polymorpha]
Jumping Worm, [Amynthas agrestis]
Brown Marmorated Stink Bug, [Halyomorpha halys]

Ten Extremely Common Invasive Plants in Madison
Buckthorn, [Rhamnus cathartica]
Honeysuckle, [Locinera periclymenum]
Bishops Weed, [Aegopodium podagraria]
Creeping Bellflower, [Campanula rapunculoides]
Reed Canary Grass, [Phalaris arundinacea]
Japanese Knotweed, [Fallopia japonica]
Norway Maple, [Acer platanoides]
Common Orange Day Lily, [Hemerocallis fulva]
Japanese Barberry, [Berberis thunbergii]
Multiflora Rose, [Rosa multiflora]

Ten Bio-Dynamic Accumulators
Amaranth, [Amaranthus]
Birch, [Betula]
Borage, [Borago officinalis]
Chickweed, [Stellaria media]
Chicory, [Cichorium intybus]
Comfrey, [Symphytum]
Dandelion, [Taraxacum]
Lambs Quarters, [Chenopodium album]
Nettles, [Urtica dioica]
Yarrow, [Achillea millefolium]