The Mountain Gardener: Keep pesky invasive plants from taking hold
by Jan Nelson
Jun 06, 2013 | 2805 views | 3 3 comments | 246 246 recommendations | email to a friend | print
A bull thistle, one of several invasive plant species that can ruin a garden in short order if not addressed. Courtesy photo
A bull thistle, one of several invasive plant species that can ruin a garden in short order if not addressed. Courtesy photo
slideshow
A vinca major, one of several invasive plant species that can ruin a garden in short order if not addressed. Courtesy photo
A vinca major, one of several invasive plant species that can ruin a garden in short order if not addressed. Courtesy photo
slideshow

We can't control those pesky weed seeds that blow into our gardens and take hold. There are ways to keep them from taking over, however. But what about those invasive plants that are already in our gardens like ivy and vinca major? What's the best way to deal with them? Then there are plants we buy ourselves that can invade natural areas. Are there better plants to use that are just as attractive and useful? Here are some solutions to make your garden happy.

 

Bull thistle eradication

One invasive thug that can take over is bull thistle, a relative of the edible artichoke. The seeds of this vigorous exotic take hold in disturbed areas including your beautiful garden soil, and if not controlled can become a solid mass of impenetrable thistles in just a few seasons. Bull thistle only reproduces by seed, so removal of the flowering stalks at this time of year will prevent them from spreading. The flowering heads must be discarded in a plastic bag and destroyed to keep them from forming viable seed. Because this weed is biennial you also need to dig out the first year plants that have not formed stalks. You can also mow thistles close to the ground a couple of times before they form stalks to reduce the population over time.

 

‘Too successful for their own good’

As a landscape designer and consultant, I'm often called upon for advice for an area covered with vinca major or ivy. Both of these invasive species are too successful for their own good, smothering native plants and harboring pests such as rats and snails. Vinca major also serves as a host to the bacteria that causes Pierce's disease in grapevines. For your information, vinca minor has not been found to be invasive in California so far

You can choose organic methods to control vinca and ivy rather than chemical herbicides. Hand removal is labor-intensive but the results are good if all the root nodes and stolons are removed. Work inward from the perimeter of the patch and pull the plants back. You will need to do this every three months during the first year to remove re-sprouts but native plants may re-colonize the area and reduce the chance that other weeds will move into the area following the disturbance caused by the removal activities.

Replanting with another more desirable groundcover is another solution. For shady areas, try planting wild ginger (Asarum caudatum), Catalina perfume (Ribes viburnifolium), creeping snowberry (Symphoricarpos mollis), yerba buena (Satureja douglasii), bear's foot hellebore (Helleborus foetidus), winter saxifrage (Bergenia cordifolia), pachysandra, Serbian bellflower (Campanula poscharskyana) or Asian jasmine.

Good substitutes for vinca or ivy in sunnier spots include groundcover types of manzanita and ceanothus. Also attractive are Taiwan raspberry (Rubus pentalobus), California fuchsia (Zauschneria), or beach strawberry (Fragraria chiloensis).

 

Good plants gone wrong

Some plants even though purchased from a nursery can cause problems. You wouldn't buy a Scotch or French broom knowing how invasive they can be. Forsythia, Japanese kerria, golden currant and Jerusalem sage all provide that beautiful spring butter yellow color in the garden.

The licorice plant (Helichrysum petiolare) gained popularity for its deer resistance and foliage color many years ago. Unfortunately, it self sows wildly and the spreading branches will root at any point of contact with the ground. Try instead better behaved plants like California natives salvia leucophylla or eriogonum giganteum. Teucrium germander or Powis Castle artemisia also work well in the same area.

Another good plant gone wrong is cotonester  lacteus (parneyi). The red fall berries are spread by birds and with their rapid growth and competitive roots they can overtake the garden and wild areas. Fortunately there are many other plants to use instead that provide food for birds and are beautiful, too. Try planting toyon (Heteromeles arbutifolia) a California native with delicate white flowers and large clusters of brilliant red berries. Pineapple guava is another good substitute as is strawberry tree (Arbutus unedo).

These are just some of the suggested alternatives for invasive garden plants for this area. Don't give an invasive an inch; it can take over your garden, the neighbors and our wild lands.

- Jan Nelson, a landscape designer and California certified nursery professional, will answer questions about gardening in the Santa Cruz Mountains. E-mail her at janis001@aol.com, or visit www.jannelsonlandscapedesign.com to view past columns and pictures.

Comments
(3)
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Theryl
|
June 26, 2013
Wow, this is by far the best Press-Banner garden article in a while. Ivy, Himalayan Blackberry, and Periwinkle are so incredibly invasive and most definitely need to be addressed.

Along the rail side of E. Zayante Rd you can see remnants of houses because someone decided to plant ivy or periwinkle. 50 years later there is no sign of a house save a small concrete foundation, but the invasive plants thrive and continue on.

My parcel is full of Ivy and Blackberry and I have spend years trying to nurse the natives back to life. Man what a chore! Please give more tips!!
JHA
|
June 11, 2013
How do I get rid if the blackberries?
Jan, TMG
|
June 11, 2013
Same way as vinca. Labor intensive and more thorns but the process if essentially the same.



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