Home & Garden Columns

One more scary invasive exotic plant has shown up in the East Bay. Susan Schwartz of Friends of Five Creeks issued a bulletin:  

I’m hoping you will help look for the bright-yellow, leafless, parasitic vine shown in the attached photo. If you find it, please inform Vince Guise of the Alameda/Contra Costa Weed Management Area (vguis@ag.cccounty.us) and me [F5creeks@aol.com]. California has many dodders, but no other forms these bright yellow tangles in broad-leaved trees. 

This plant is Japanese dodder, Cuscuta japonica. It is a new invader in California—our restoration site at Adams Street on Cerrito Creek is apparently only the third reported instance. But the second was at an apartment building in San Pablo, so there may well be others. That is why I’m asking your help. 

This parasite can infest a wide variety of trees. At Cerrito Creek, it’s on willow, plum, and elderberry; at San Pablo it infested pittosporum. It spreads by seed and vegetatively, by bits and pieces—the long, succulent tendrils break off easily. Once it finds a host, it sends root-like structures called hausatoria into limbs, sucking the host plant’s water and nutrients. It forms dense tangles and weakens or eventually kills the tree or bush. 

The plant has herbal uses in Asia and may be being brought in for that reason. There is a Department of Agriculture quarantine, but those are often ineffectual. Like many invasives, it has the potential to spread rapidly and widely in wild lands, gardens, and orchards.  

Department of Agriculture advice is to inform them rather than try to eradicate it yourself. If you do try, their advice is to remove the entire tree or bush down to the ground, double-bag everything down to small fragments, and make sure the bags are deeply buried in landfill (that is, do not compost). 

The usual sort of dodder is easy enough to see now, especially in pickleweed salt marshes along the bay. It looks like a big skein of orange thread, tangled in the succulent marsh plants. Dodders, native or imported, are officially agricultural pests: as parasites, they reduce crop size and health. The new one is attacking gardens, too—pittosporum is a genus of commonly used ornamental shrubs and small trees. In wildlands, the nutrient balance can be even more precarious than a small farmer’s financial balance, so the imported species wouldn’t exactly be welcome there either. 

This new one is not just any wildland invader; healthy trees have had to be destroyed to get rid of it— it spreads fast, as Schwartz notes above, and can make a whole stand of trees sicken and die, if such harsh measures aren’t taken. You can imagine how this affects creek restoration and flood control efforts—kill the trees and the banks erode and the winter floods wash away our wild neighbors’ homes along with ours—and breaks the hearts of the people, many of them volunteers, who are actually getting out there and sweating on those efforts.  

Lots of restoration work, especially along creeks, involves the hard, repeated, sometimes years-long labor of removing Algerian ivy. You can tell that from English ivy—which is a wildlands pest too—by Algerian’s bigger leaves and red petioles (leaf stalks). It’s more vigorous than English ivy, and it’s been planted as a droughty, cheap, low-maintenance ground cover for years.  

It’s going out of style lately, thank Flora, for several reasons. A big one is that it harbors rats—Norway rats, roof rats, the kind you’d really rather not have close to home. One ivy-killing project I know of involved cooperative neighbors, some of whom were alarmed at the apparent influx of rats in their yards. Of course, it wasn’t that the newly bare spaces were attracting rats; it was that the rats that had been there along were suddenly visible.  

Ivy of all sorts can climb, smother, strangle, and kill trees, even though it’s not a parasite. Sometimes it’s like a local version of kudzu. It’s a skin irritant, especially its juices; for some of us it’s a serious allergen. (Me, for example.)  

If you have some, get rid of it before it murders you in your bed. At least cut off the mature parts, where the berries grow, before it gets spread farther in birds’ droppings. Plant some snowberry for the birds instead.  

And if you see yellow dodder, e-mail the addresses above or call the county weed control folks fast! 

Photograph courtesy of Freinds of Five Creeks