Tag Archives: parasitic plant

Plant of the day: oak mistletoe

It is Christmas Eve, and bundles of yellowish-green leaves hang over the doorway–an invitation for lovers and friends to stop and smooch. According to legend, it was actually an obligation to kiss if you met under the mistletoe. A pale white berry would be plucked for each kiss that happened, until the berries were gone and the obligation was ended. Nowadays there seems to be no limit on kisses though–the berry plucking tradition has faded away.

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Of course, these bundles are mistletoe, a classic holiday ornament. There is no single species of mistletoe–it’s a general name for a group of parasitic plants that grow on trees. In Europe, the smooching mistletoe is generally Viscum album. Here in the California, the native oak mistletoe (Phoradendron villosum) is the most common holiday decoration. You can see it growing on oaks, pepperwoods and other trees throughout California. Look for a round clump of foliage on a tree limb, looking like a nest or a shadow or a strange stuck balloon. If you go closer you’ll see the leather, oval leaves and the pale greenish-white berries. The roots of the plant go straight into the branch of its host tree; the two often seem to be indistinguishable, one merging into the other rather like lovers enjoying a holiday kiss…

HAPPY CHRISTMAS EVE!!! I hope everyone is having a great holiday.

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Plant of the day: saltmarsh dodder

Bright orange patches dot the green swath of a salt marsh. Look close and you will see what looks like a mat of fishing line or straw. Hundreds–thousands–of narrow orange threads are wrapped tightly around bright green pickleweed stems. Copious white flowers often bloom off the threads. This is saltmarsh dodder (Cuscuta salina), a parasitic native plant that mooches nutrients off its host plant. Instead of photosynthesizing its own food, it sinks tiny root-like organs (called haustoria) into the flesh of the plant. Once it taps into the vascular system it can suck out all the water, minerals and carbohydrates that it needs.

Dodder seeds are scattered by wind, tides and animals so there is no guarantee that they will germinate near a suitable host plant. But they die if they can’t find one quickly. It sounds impossible for a  brainless, eyeless, noseless  plant to do, right? Nope–not if a host is anywhere close. They can detect the volatile compounds emitted by the host (basically, its smell) and then they grow towards it.

There are a lot of species of dodder in the US, and some of them are parasitic to some of our favorite crops like alfalfa, potatoes and petunias. Though the group is much maligned as a result, some ecologists make a case for the role that parasitic plants can play in the natural environment. Species like dodder or mistletoe don’t decimate their hosts’ population, but they do create patchiness. And in ecology, patchiness tends to lead to diversity, which is a good thing!

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