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The Homeowners Column
Space Invaders – The Sequel
Extension Educator, Horticulture
Rebellious teenage plants are twittering to all the other insurgents about their plans to make me crazy. The plants I want to scorch from the face of the earth bounce around my yard with the glee of a kid in a playground. But then again maybe the heat has ignited my paranoia.
Last week's column I discussed the ways plants spread: seed, stolon and rhizome. Beyond my deep seeded belief that plants enjoy their pestiferous nature, a plant's purpose in life is to go forth and procreate. True to their nature some plants are over-achievers.
Perennial plants with rhizomes, because of their stealthy underground behavior, are the hardest to monitor and control as the mass gets wider every year. A few options exist if you just can't say no to these temptresses. One method is to maintain a mulched plant-free perimeter around the misbehaving plant. This method requires persistence and regular monitoring to quickly eliminate any plant prisoners that jump the guarded mulched area. Another less time consuming method is to sink into the garden a 12-inch or larger diameter plastic pipe or plastic pot with the bottom cut out so it is at least 18 inches below ground and one inch above ground. Then plant the defiant plant in the corral. Or just plant all the pesky plants together and let them fight it out.
Perennials with stolons are a bit easier to control. Even though they spread, the underground stems are closer to the surface and easier to pull out or dig out with a garden fork. The same methods for perennials with rhizomes can be used for stoloniferous plants.
Reseeders may be annual or perennial plants. These space invaders produce vast quantities of seed that germinate into a carpet of baby plants in any bare space. As with the other spreaders reseeders are not always bad. With cottage gardens or prairie restorations we want reseeders.
Here are just a few over-achieving plants:
Perennials with rhizomes
- Chameleon plant Houttuynia cordata
- Lily-of-the-Valley Convallaria majalis
- Yarrow Achillea millefolium
Perennials with stolons
- Goutweed Aegopodium podagraria
- Loosestrife, Yellow and Gooseneck Lysimachia spp.
- Obedient plant Physostegia virginiana
- Periwinkle Vinca minor
- Ribbon Grass Phalaris arundinacea 'Picta'
- Silver King Artemesia Artemesia ludoviciana
- Yellow Archangel Lamiastrum galeobdolan
- Black-eyed Susan Rudbeckia spp.
- Celandine Poppy Stylophorum diphyllum
- Dame's Rocket Hesperis matronalis (biennial)
- Garlic Chives Allium tuberosum
- Northern Sea Oats Chasmanthium latifolium
- Purple Coneflower Echinacea purpurea
- Sweet Autumn Clematis Clematis ternifolia
- Brazilian Verbena Verbena bonariensis
- Moonflower Datura spp.
- Sweet Annie Artemesia annua
Sometimes we want plants to spread as a groundcover. A garden's soil and environmental conditions will affect how much a plant spreads. It may be a weed in my garden but not in yours. Weeds are plants out of place no matter whether they came with a price tag or not.
If a garden plant is popping up all over your garden and yard, a red flag should unfurl and smack you in the face declaring this plant has no boundaries and has the way and the will to go beyond your garden into natural areas. A prime example is crown vetch. These rebellious plants should be avoided and deserve immediate removal. Some garden plants are on the hit list of exotic weeds and are illegal to grow such as Japanese Honeysuckle and Purple Loosestrife (Lythrum salicaria).
By understanding a plant's nature to wander we can make educated decisions on their usage.
Fact sheet from Purdue "Spreading Ornamental Plants: Virtues & Vices" http://www.hort.purdue.edu/hort/ext/pubs/hla/hla_001.pdf Stop by our office or call (217)333-7672 for a copy.