Runaway Beauties: Managing Aggressive Garden Plants

No sooner are you thrilled that a certain plant is thriving than it pops up unexpectedly where you didn't plant it. Before long, it has merrily spread through your garden.

Some reproduce easily by seed, thanks to birds and breezes. Others spread aggressively by stolons (stems that creep along soil surface, rooting and forming new plants at intervals). Eventually stoloniferous plants can choke out neighbors. Pulling or hoeing barely fazes them; any stolons left in soil resprout. The upside: they make good soil binders for slopes and grow where nothing else will.

The nursery plants below have aggressive tendencies that can make them nuisances for meticulous gardeners. Encourage seed-spreaders where you want them, pull unwanted ones. Restrain stolon-types by planting in raised beds or soil pockets surrounded by paving. Regularly dig out unwanted shoots.

Runaways to Watch

Savvy gardeners develop strategies for using runaway beauties to advantage, letting them spread only where desired. Some plants cannot be safely controlled. In some regions, ornamentals have jumped the garden fence and threaten native species or choke waterways. Scotch broom (Cytisus scoparius) with pretty yellow flowers, and purple loosestrife (Lythrum salicaria and related species) are examples. Good source for invasive plant info: Federal Noxious Weed Program website (www.aphis.usda.gov/ppq/weeds). Native plant societies in many states also maintain problem plant lists.

Seed-Spreaders

• Forget-me-nots (Myosotis) – Demure blue flowers persist for years self-sowing. Easy to pull where unwanted.
• Johnny-jump-up (Viola tricolor) – Petite-flowered viola clan member, relentless reseeding. Easy to pull or hoe.
• Jupiter's beard (Centranthus ruber) – Self-sows prolifically via dandelion-like parachutes. Plant in fringe areas; cut old flowering stems to prevent self-seeding.

Stolon-Spreaders

• False dragonhead, obedient plant (Physostegia virginiana) – Pink flower spikes resemble snapdragons; "obedient" only in that blossoms stay when twisted. Divide clumps every two years in spring to keep in bounds.
• Garden asters – Hardy, small-flowered hybrids quickly lace soil with stolons and send up shoots everywhere. Curb in pots or raised beds.
• Indian mock strawberry (Duchesnea indica) – Trailing ground cover with wiry stems that root; thrives among open shrubs or small trees. Yellow single flowers; small, nearly tasteless berries. Can be rampant invader. If grown, confine to big pots with saucers on paved patio.
• Matilija poppy (Romneya coulteri) – 6-ft gray-green stems produce yellow-centered white flowers resembling fried eggs. Plant in marginal areas like hillsides; keep away from less vigorous plants. Withhold summer irrigation to check growth.
• Mexican evening primrose (Oenothera speciosa) – Pink, poppy-like flowers bloom profusely spring and summer. Grows downhill following water. Grow in raised beds or planting pockets surrounded by paving.
• Periwinkle (Vinca major) – Blue-flowered ground cover with trailing stems that root wherever they touch (useful on banks). Extremely invasive in sheltered forested areas; on noxious weed lists in some states. Dwarf periwinkle (Vinca minor) is less invasive.
• Russian sage (Perovskia) – In mild climates, woody perennials with blue spires spread rapidly even in arid soil, sending up whiplike shoots of silvery leaves difficult to pull.
• Sweet violet (Viola odorata) – Heart-shaped leaves and demure purple flowers belie boldness; quickly carpets moist, semishaded ground. Easy to pull.
• Sweet woodruff (Galium odoratum) – Low ground cover with pretty green leaves and fragrant white flowers. Spreads rapidly in moist, shaded gardens; can become pest if unchecked.