One disadvantage of some perennials is that they are invasive--they spread where you don't want them and are difficult to control and keep in gardens. They may spread by roots, as in the case of mints, or by seeds, as in the case of Purple Loosestrife. Those spreading by roots can be useful if in a confined situation, or used in rough areas, such as slopes, to control erosion. In perennial beds, the root-spreaders can kill less vigorous species and take over most the bed. Those spreading by seeds may be useful--as with many field wildflowers--yet some, such as Purple Loosestrife, colonize wet areas, eventually destroying them and the wetland wildlife habitats. Purple Loosestrife and other similar invasive perennials are banned from sale in many states for this reason.

The invasive nature of perennials is relative. Many on the following list may not even be hardy in certain areas, therefore acting neither as perennials nor problems in these areas. Or they may be hardy, though not vigorous or a problem, in many areas. Others, especially the root-spreaders, may be less or not invasive, depending on factors such as culture and soil types. Those invading by seed may not be a problem in northern areas if the short growing season keeps them from going to seed (such as some silver grasses).

The term "invasive" is itself relative. To some, this means any plant spreading at all. To others, an invasive perennial is one that not only spreads but is also quite vigorous and difficult to control. Those that spread but can be controlled by yearly cultivating or dividing are termed either "spreading" or "aggressive," depending on how fast they spread.

Other than cultivating, dividing and weeding out seedlings, root-spreading perennials may be controlled by planting them in containers either in or on the ground. If in the ground, make sure roots do not exit the drain holes or go over the top. If you want to keep these perennials from year to year, they may need to be divided and repotted annually to keep them from dying out. Systemic herbicides may also be used to control root-spreading perennials; several applications may be necessary to provide control. Herbicides that act by merely burning back the foliage are not very effective with vigorous perennials, which merely resprout from the roots. If using any herbicide, read and follow all label directions.

The following list is only a beginning of some of the more common perennials listed as invasive by some, in some areas of the world. Others, especially those that "self sow" once they go to seed, may be in this group as well. Some species or cultivars of a perennial may be invasive, and others not--the listing of a genus below does not mean that all of its members are invasive. This list should be used only as a "red flag" to check closer into a particular plant or genus of perennials before planting.

Scientific Name

Common Name

 

Adenophora liliifolia
Aegopodium
Ajuga
Alcea
Allium tuberosum
Anemone x hybrida
Angelica
Artemisia ludoviciana and cv's
Arundinaria
Aster (certain species e.g., ericoides)
Borago
Campanula punctata
Campanula rapunculoides
Campanula takesimana
Carpobrotus
Centaurea montana
Convallaria
Cymbalaria muralis
Elymus
Euphorbia amygdaloides var. robbiae
Filipendula rubra 'Venusta'
Fragaria
Freesia
Helianthus
Houttuynia
Hypericum calycinum
Lamium maculatum
Leucanthemum vulgare
Lychnis coronaria
Lysimachia
Lythrum
Macleaya
Mentha
Miscanthus
Monarda
Oenothera
Ornithogalum umbellatum
Oxalis
Persicaria virginiana 'Painter's Palette'
Phalaris arundinaceae var. picta
Phlox paniculata
Physostegia
Polygonum
Rehmannia
Sedum (some spp.)
Spartinia
Stacys byzantina
Symphytum
Tanacetum
Tovara (see Persicaria)
Tradescantia
Tropaeolum peregrinum
Verbena cultivars (e.g., Homestead Purple)
Vinca minor
Viola

Ladybells
Goutweed
Bugleweed
Hollyhock
Garlic Chives
Hybrid Windflowers
Archangel
Western Mugwort
Bamboo
Aster
Borage
Bellflower
Creeping Bellflower
Korean Bellflower
Hottentot Fig
Mountain Bluet
Lily-of-the-Valley
Kenilworth Ivy
Lyme Grass
Euphorbia
Queen-of-the-Prairie
Strawberry
Freesia
Perennial Sunflower
Chameleon Plant
Creeping St. John's Wort
Dead Nettle
Ox-eye daisy
Rose Campion
Loosestrife
Purple Loosestrife
Plume Poppy
Mint
Silver Grass
Bee Balm
Evening Primrose
Star-of-Bethlehem
Wood Sorrel
Persicaria
Ribbon Grass
Gardon Phlox
Obedient Plant
Knotweed
Rehmannia
Stonecrop
Cordgrass
Lamb's-ears
Comfrey
Tansy

Spiderwort
Canary-bird Vine
Perennial Verbena
Periwinkle
Pansy, Johnny-jump-up, Violets

Adapted from Leonard P. Perry, University of Vermont Extension, 2000