Why Aggressive Plants Might Actually Be Your Friends

Plant tags increasingly replace "aggressive" and "spreading" with the friendlier "naturalizes." Our gut reaction is to run, but rhizome-stretching, self-seeding marauders have a place. Some native plants I love to see have at it. I'll always advocate natives for insects and wildlife, and in areas covered in aggressive exotics, exuberant natives can help fight back. Let's examine the contentious nature of fast-spreading plants.

The Difference Between "Aggressive" and "Invasive"

Not equal. "Invasive" means crowding out local natives, depriving them of sun and nutrients, permanently changing the environment. Some exotics change soil structure via root microbes, making it impossible for natives to grow (common on prairies). "Invasive" carries connotations of severe ecological detriment.

Yes, aggressive natives may form monocultures, but: 1) In wild nature, plants colonize in drifts and masses (New Perennial movement mimics this); 2) Aggressive natives are often part of native ecology—other natives get their turn as climate and herbivore patterns evolve; 3) Aggressive natives can crowd out exotic invasives and restore ecological balance.

Obviously, this changes in smaller gardens—aggressive plants are a bad idea in urban gardens or foundation beds.

How They Spread

Rhizome Spreaders

Predictable—research reveals speed and distance given soil and light. Unlikely to pop up 50 feet away in one year.

Self-Seeders

Produce lots of seed, sprout readily, fly everywhere. Birds eat and disperse seeds miles away—different ballgame than rhizomes.

Why Plant Aggressive Natives

1. The Tough Spot

Whether flooding then drying like brick, or dry brick in full shade, finding the right plant for difficult places is annoying. Years of trial and error get expensive for large areas—let plants colonize. Perfect for hillsides to prevent erosion.

2. Clean Design

General rule: smaller bed, fewer species. 100 sq ft? Maybe 10 or fewer species—even five or less. Letting plants spread in drifts creates modern, calming design. Too many species in small space screams "weedy mess."

3. Less Fuss

Tracking which plants need what, which have mold, attract plagues, need water, division—too many species complicates maintenance. Let thugs have their way, easier to see what's going on.

4. Support Wildlife

Sunflower patches are nirvana for insects, birds, mammals—high-class buffets. Same for showy milkweed, grasses providing nesting cover. Thousands of square feet of sedge around a pond purifies water. "Aggressive" doesn't mean "bad," especially for natives adapted to local conditions and coevolved wildlife. Exotics become invasive partly because they lack natural predators here.

Native Plant Suggestions

Some better for smaller areas, some for larger—plan and research accordingly.

• Wild bergamot (Monarda fistulosa): Native to almost every U.S. state and Canada. Moist to medium soils (clay to loam), full sun, 2–4 feet tall, summer bloom. Bee magnet, especially long-tongued bumblebees. Less showy than hybrids but attracts more insects, long-lived. Self-sows; small seeds don't travel far, spread by rhizomes (easily divided).
• Cup plant (Silphium perfoliatum): Native from Great Plains east. Square stems, leaves form cups catching rainwater for birds. 6–8 feet tall, high summer bloom, medium to wet soil (especially clay)—good for large rain gardens. Aggressive, spreads by rhizomes and seeds (birds eat, wind carries).
• Queen of the Prairie (Filipendula rubra): Native to upper Midwest, Great Lakes, Northeast. Sweetest, most fantastic scent—like roses when roses had scent. Perfect for rain gardens or moist areas. Moves moderately by rhizomes, ~4 feet tall in full sun to partial shade.
• Blue Mistflower (Conoclinium coelestinum): Native from central U.S. to East Coast. Relative of Joe Pye Weed, blooms late summer into fall, 2–4 feet tall. Sun to partial shade, medium soil (adaptable, moist best in full sun). Runs and spreads moderately fast. Diverse insects feed on nectar—great for butterfly gardens.
• Goldenrod (Solidago spp.): Many species, none cause hay fever. Aggressive self-sower Canadian goldenrod (S. canadensis) common on roadsides. Stiff goldenrod (S. rigida) less aggressive; shorter, better-behaved species like grassy Riddell's (S. riddellii) and Zigzag (S. flexicaulis). All highly attractive to beneficial pollinators.

Before You Plant Aggressive Natives

Know Your Plants

Research is key—plant tags don't constitute research. Check local extension offices and state/county noxious weed lists. Research via Latin name for accurate horticultural info and others' experiences. Think long and hard about 5–10 year garden vision and what you'll deal with. "Knowing is half the battle."

Consider Your Neighbors

If planting a rhizome-spreading native, don't plant along the fence where it'll invade neighbor's space in a year or two. Buried containers? No container holds back a plant from being itself. No "safe," "sterile," or "seedless" plant stays that way forever—reproduction is a plant's primary drive.