Wednesday, December 1, 2010

Viscum minimum: a Dwarf African Mistletoe

Viscum minimum fruit emerging from its host.

Parasitic plants, which obtain some or all of their water and nutrients by attaching to a free-living host plant, seem to be unusually well represented in the floras of desert regions. Mistletoes (genus Viscum), probably the most familiar of vegetable parasites, may be encountered in arid places (and elsewhere) in the old and new worlds. Mistletoes are usually hemiparasitic, meaning that they extract water and minerals from their host, but are green and can manufacture some of their own nutritional needs via photosynthesis, like ordinary plants.

Viscum minimum is a minuscule mistletoe endemic to South Africa, where it grows inside of the succulent stems of euphorbias. Most of the time, V. minimum grows internally, with no indication of its presence on the exterior of the host plant. However, when it reproduces, the mistletoe’s greenish flowers and showy orange-red berries break through the euphorbia’s skin, in order for pollination and seed dispersal to take place.

Old plant of Euphorbia polygona ‘Snowflake.’

Viscum minimum is one of the few types of mistletoe that is ever cultivated outside of its native land. The host plant, usually Euphorbia polygona, is an easy to grow and attractive addition to a greenhouse or windowsill succulent collection. The mistletoe, which can be acquired either in the form of an infected euphorbia cutting or by smearing fresh, sticky seeds onto the surface of a suitable host, doesn’t cause significant harm to its host plant, and will produce crops of colorful fruit in time for the holidays year after year.

6 comments:

Julie said...

WOW! How interesting. whouda known??? Another euphorbian weirdness.

Matt said...

There are a lot of strange plants out there!

Alex said...

I just found this blog yesterday. I see that postings are becoming less frequent, which is a little sad because they are great! As a fellow plant nerd, I hope you will be able to find time to continue to show off plant oddities. Thanks for your efforts thus far.

Matt said...

Thanks, Alex. My usual pace of postings is about 1 per month, and I'll probably keep that up for the foreseeable future, anyway.

Alex said...

I'm glad to hear it! Do you happen to know any nurseries that are selling infected clones of Euphorbia polygona? That thing would be great for a parasitic plant lesson/display. With what appears to be largely internal growth, I presume it is a holoparasite. Or can it photosynthesize under the surface?

Matt said...

Alex: I think it's a holoparasite, though the exposed parts are sort of greenish, so I'm not certain. Our Viscum minimum originally came from the Huntington Botanical Garden, through their annual ISI sale. I don't know of any nurseries that offer it on a regular basis, unfortunately.