Don’t Share These Plants

Spring is a time of year when gardeners start to grapple anew with plants that are growing beyond their intended space – or growing where they aren’t wanted at all.

These are not exactly “weeds” but rather flowers and groundcovers that just turned out to be more aggressive than the planter thought.

Dug-up divisions of plants from other gardeners’ yards don’t always make good gifts. Photo by George Weigel

“Surplus plants” is a nice way to describe them.

But since gardeners tend to be benevolent and nurturing souls, they often have a hard time digging and tossing these frisky extras.

And so lots of gardeners – dug-up rootballs in hand – can be found in spring looking for foster parents for their botanical castoffs.

Sometimes these plants end up at plant sales, plant exchanges, and yard sales.

This doesn’t mean you should run the other way when you see a neighbor heading your way with a mystery clump.

Sometimes pass-along plants turn out to be welcome gifts. If the culled-out plants aren’t invasive and match a site in your yard, this is a great way to fill or expand garden space at no cost. And the digger-outer feels as if he/she has saved a plant’s life while doing a good deed for a friend.

Seeds from these morning glory vines have sprouted in the lawn below. Photo by George Weigel

The down side

On the other hand, sometimes these plants merely transfer an invasiveness issue from one yard to another.

In other words, people tend to dig and get rid of what’s turned out to be overly aggressive for them.

The trick is sorting out the good stuff from the Trojan horses.

If you’re not familiar with an offered plant, ask the giver the key questions of how much it spreads and how often he or she has to thin it out.

Also, ask how freely the plant might seed. Some plants churn out seedlings all over the yard for years, such as nigella (love-in-a-mist), morning glories, hardy ageratums, and bronze fennel.

With any luck, the giver will know the name of the plant so you can at least look it up in a good garden book or online before planting. Be wary if any descriptions mention words such as “invasive,” “aggressive,” or catalog-writers’ favorite code word, “vigorous.”

You might also check your state’s Noxious Weed List to make sure you’re not accepting something in the worst-of-the-worst category.

Where you decide to plant a pass-along can make a difference as well.

Example: A neighbor may have a planting of variegated bishop’s weed or ajuga that looks to be reasonably well behaved under a big shade tree. But if you take divisions of those same plants home and put them in good soil in a perennial border, they can become thugs.

Beyond the invasiveness issue, decide if you even like the look and habit of the plant. Ask yourself if there’s a spot in your yard where it’ll fit in and make sense. Don’t ruin an otherwise nice design with a newcomer just because it came free.

Top 10 plants you might not want to share

A plant’s invasiveness can vary from region to region, but some are aggressive just about everywhere.

Chameleon plants are attractive with their pink-variegated leaves, but it’s a species that can quickly colonize into unwanted areas.

Here are 10 to watch out for:

Chameleon plant (Houttuynia). A short groundcover with beautiful multi-colored leaves. Problem is, it sends out runners everywhere.
Bamboo. Some types are fairly well-behaved clump-formers, but the spreading types can put out runners that go under a driveway and come up on the other side.
Ribbon grass (Phalaris arundinacea var. Picta). A white-edged grass that spreads mercilessly, especially in damp soil.
Purple loosestrife (Lythrum salicaria). Banned from sale in some states, this long-blooming perennial with the spiky pink-purple flowers seeds rampantly and chokes out most everything else, especially in damp areas.

Purple loosestrife is an upright, purple-blooming perennial that some states have banned for its invasive seeding.

Lemon balm. The lemony scent is nice, but this herb creeps and seeds and roots to the point where most gardeners end up ripping it all out.
Spearmint. Another nice-smelling herb that’ll creep for miles if you let it. If you get a division, grow it in a big pot, not in the ground.
Bishop’s weed (Aegopodium podagraria). The variegated leaves are attractive, but it’ll usually spread out of control in even marginal conditions.
Lily-of-the-Valley. Sweet-smelling flowers but forms dense colonies in shade.
Creeping Bellflower, Deep, persistent roots make it very difficult to eradicate.
English Ivy. Spreading vine that can take over trees, fences, and garden beds.

Plants to Think Twice About Sharing

Plant	Category	Notes
Obedient Plant	Perennial	Spreading perennial that can form large colonies.
Evening Primrose	Perennial	Self-seeding perennial that spreads easily.
Mint	Perennial Herb	Aggressive spreading herb; best grown in containers.
Spearmint	Perennial Herb	Very vigorous mint that spreads by underground runners.
Lemon Balm	Perennial Herb	Seeds and spreads freely in many gardens.
Lily of the Valley	Perennial (Rhizome)	Fragrant groundcover that spreads aggressively in shade.
Tawny Daylily	Perennial	Hardy daylily that naturalizes quickly.
Snow-in-Summer	Groundcover Perennial	Fast-spreading groundcover for sunny areas.
Creeping Bellflower	Perennial	Deep-rooted perennial that is difficult to remove once established.
Gooseneck Loosestrife	Perennial	Spreads by underground runners in moist soil.
Tansy	Perennial	Spreading perennial herb that can become invasive.
Yellow Flag Iris	Perennial (Rhizome)	Moisture-loving iris that spreads aggressively in wetlands.
Crown Vetch	Groundcover Perennial	Often used for erosion control but spreads rapidly.
Bishop’s Weed	Groundcover Perennial	Variegated foliage plant that spreads vigorously.
Ribbon Grass	Ornamental Grass	Fast-spreading grass, especially in damp soil.
Bamboo	Grass	Some species spread aggressively via underground runners.
English Ivy	Groundcover / Vine	Aggressive evergreen vine that can spread rapidly.
Sweet Autumn Clematis	Vine	Vigorous climber that can reseed heavily.
Purple Loosestrife	Perennial	Invasive wetland plant banned in some states.
Dame’s Rocket	Biennial	Self-seeding flower that spreads readily.
Honesty	Biennial	Attractive seed pods but spreads by reseeding.
Johnny-jump-ups	Short-lived Perennial / Annual	Small violas that reseed freely.
Sweet Annie	Annual	Aromatic annual that self-seeds heavily.
Borage	Annual	Self-seeding herb that can reappear each year.
Butterfly Bush	Shrub	Ornamental shrub that spreads by seed in some regions.
Burning Bush	Shrub	Invasive shrub in many regions due to prolific seeding.
Barberry	Shrub	Thorny shrub that spreads into natural areas.
Rose-of-Sharon	Shrub	Seeds prolifically and produces many volunteer seedlings.

Tip: Before accepting a pass-along plant, ask how quickly it spreads and whether it produces lots of seedlings. A little research can prevent years of garden headaches.

Safer Pass-Along Plants

Plant	Type	Why Gardeners Share It
Bearded Iris	Perennial (Rhizome)	Easy to divide and rarely spreads beyond where planted.
Daylily (hybrid varieties)	Perennial	Clump-forming and simple to divide every few years.
Peony	Perennial	Long-lived plant that expands slowly and divides well.
Hosta	Perennial	Shade-loving plant that forms neat clumps.
Shasta Daisy	Perennial	Easy to divide and spreads at a manageable pace.
Black-eyed Susan	Perennial	Tough, reliable bloomer that rarely becomes invasive.
Coral Bells (Heuchera)	Perennial	Attractive foliage plants that stay in tidy clumps.
Garden Phlox (upright types)	Perennial	Popular cottage-garden plant that divides easily.
Astilbe	Perennial	Well-behaved shade perennial with clumping growth.
Sedum (upright types)	Perennial	Drought-tolerant plant that expands slowly.
Coneflower (Echinacea)	Perennial	Pollinator favorite that spreads modestly.
Siberian Iris	Perennial	Graceful clumping iris that rarely runs.

Tip: The best pass-along plants are usually clump-forming perennials that need dividing every few years. They share easily without taking over a garden.