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Invasive Plants Revisited

Every year, more than $80 million dollars from our taxes are spent on invasive plant removal. Invasive plants are a threat to our environment, crowding out native plants, clogging our waterways, degrading our drinking water, and driving many species of flora and fauna to extinction. These plants are perfectly suited to their native habitat because they have natural enemies that keep them controlled but, when transplanted to another area, they can spread unchecked and take over. The biodiversity of millions of acres in California have been compromised by the spread of non-native species of plants.

Yellow star thistle (Centaurea solstitialis), for example, rapidly invades and out competes native plants. This reduces the biodiversity, wildlife habitat, and forage of an area. It is a major problem in rangelands and is toxic to horses. They develop a disorder called “chewing disease” that is fatal once the symptoms develop. It has invaded more than 14 million acres of California rangelands and pastures. It has a taproot that is so deep that it siphons off all the water that native plants depend on to thrive. It can even be embedded in grass seed sold at nurseries. Only certified grass seed should be purchased when putting in a lawn.

Scotch broom (Cystisus scoparius), as well as numerous other brooms, were introduced into the Sierra during the gold rush by the pioneers. It quickly established itself in the foothills and has steadily moved up the mountains ever since. Brooms have invaded over one million acres in California. The flowers produce thousands of seeds that build up in the soil and create dense thickets that obliterate entire plant and animal communities. It grows so quickly that it creates a hazard in residential landscapes.

A very invasive water plant sold in nurseries for backyard ponds is water hyacinth (Eichhornia crassipes). It is invasive in California, Texas, Louisiana, Georgia, and Florida. One of the fastest growing plants known, water hyacinth reproduces primarily by way of stolens, or runners, which eventually form daughter plants. It produces large quantities of seeds which can live as long as thirty years. It is a vigorous grower known to double its population in two weeks. These plants are so vigorous that they can clog whole waterways and divert streams. Although it is great for purifying water in ponds, and is a good choice in states where it is not invasive, we need to keep it out of our ponds in California.

It is important for our Sierra Nevada environment that we all become responsible gardeners. When planning a garden or pond it is essential to be aware of the plants that may spread outside the borders of your property and invade the surrounding countryside. In a previous article I gave a number of alternatives to invasive plants to produce the same aesthetic effect. These can be found on the following Internet sites: www.plantright.org. and www.cal-ipc.org.
If you pull up an invasive plant in your garden or want to get rid of one from your pond:

Remember: don’t throw them out with garden waste because they will propagate! Instead, let them dry out in the sun and then put them in a plastic bag and throw them in the garbage. You can also burn them but some non-native plants actually need to be burned by fire to propagate.

I have made a list of some of the more invasive plants in our area. Print this article out and carry it in your wallet the next time you go to a nursery. It is hard to remember all the names – especially the Latin ones. Some varieties of a plant can be invasive and others can be quite safe. The Latin name is the clue, so I’ve included their complete names.

If you are interested in attending a Yellow Starthistle Control workshop in your neighborhood or hosting a yellow starthistle presentation at your service club or home owners’ association, please call the UC Cooperative Extension office in Tuolumne County at (209) 533-6993.

List of invasive plants to avoid

  • Arundo, giant reed (Arundo donax)
  • Blue gum eucalyptus (Eucalyptus globulus)
  • Brazilian water weed (Egeria densa)
  • Brooms: Scotch, Striated, French, Bridal Veil, & Spanish broom
  • Capeweed (Arctotheca canendula)
  • Chinese tallow tree (Sapium sebiferum)
  • English ivy (Hedera helix)
  • Foxglove (Digitalis purpurea)
  • Green fountain grass (Pennisetum setaceum)
  • Myoporum (Myoporum laetum)
  • Pampas grass (Cortaderia jubata & selloana)
  • Parrots feather (Myriophyllum aquaticum)
  • Periwinkle (Vinca major)
  • Russian olive (Elaeagnus angustifolia)
  • Saltcedar (Tamarix ramosissoma)
  • Scarlet wisteria (Sesbania punicea)
  • Tree of Heaven (Ailanthus altissima)
  • Water hyacinth (Eichhornia crassipes)
  • Yellow iris (Iris pseudacorus)

Francie McGowan is a Bay Area transplant to the Sierra Nevada is a Master Gardner