By Rebecca Jepsen
for the Mercury News
August 1, 2009
Invasive plants are on the march throughout California, with well-meaning gardeners unwittingly aiding in the assault.
According to the California Invasive Plant Council, invasive species costs our state billions of dollars every year, with an estimated $82 million spent on control, monitoring and outreach alone.
Experts say invasive plants threaten wildlife and biodiversity, increase wildfire potential, reduce water resources, accelerate erosion and flooding, and contribute to crop loss.
Invasive species reproduce themselves through self-seeding or by rapidly spreading root systems. Once these pests get started they are very difficult and costly to control.
Often gardeners looking for drought-tolerant, water-wise plants or easy-to-grow options will be directed to invasive species by well-meaning but uninformed employees at garden centers. More than 30 varieties are available today through wholesale and retail nursery centers.
This is a difficult issue to stay on top of, because a particular species may be invasive in one geographic area and not in another.
A growing problem that is literally taking over California is the purple-flowering ice plant (Carpobrotus edulis). Now extending from the Bay Area to Mexico, ice plant was introduced in the early 1990s for dune stabilization. It steals water and blocks light from other plants and makes the soil inhospitable by dramatically increasing salt content. Although it is still available in
nurseries today, better choices would be beach strawberry or woody strawberry (Fragaria chiloensis or F. vesca) or ground cover myoporum (Myoporum parvifolium 'Prostratum').
Troublesome brooms, including Scotch, Spanish, French and Portuguese varieties, have invaded more than a million acres in California and have become a fire hazard. Better options would be forsythia (Forsythia x intermedia) or yellow bush daisy (Euryops pectinatus).
Jubata grass (Cortaderia jubata), a cousin of pampas grass, is extremely invasive. Its lightweight seeds can be carried by wind for miles. Instead, opt for giant rye (Leymus condensatus "Canyon Prince"), deer grass (Muhlenbergia rigens) or sedge (Carex spp.).
We can avoid contributing to the demise of native plants and animals by making smart choices with our plant selections. Instead of periwinkle (Vinca major) try hardy geranium (Geranium 'Rozanne') or star jasmine (Trachelospermum asiaticum).
Go for Seaside daisy (Erigeron glaucus) vs. Mexican evening primrose (Oenothera berlandiere), Forget about forget-me-not (Myosotis sylvatica) and opt instead fpr impatiens.
When planting bamboo, look for clumping types like Bambus multiplex, B. olhamii, Fargesia nitida) or New Zealand flax (Phormium tenax); avoid giant reed (Arundo donax), which resembles bamboo.
For a good list of beautiful, vigorous and appropriate plant recommendations for your area (and the invaders to avoid), go to www.plantright.org.
Q I have a wall of ivy that I want to remove; I then want to paint the wall. How do I remove the tendril residue from the wall? I am considering power-washing and using a stiff brush.
A You are on the right track. The best bet is to power-wash the wall and then use metal bristle brushes to remove the remaining tendrils.
Rebecca Jepsen is a Santa Clara County Master Gardener.