Eric’s Pet Plant: Carpet Weed (Cheiridopsis purpurea)

In this post, our friend Eric over at Yale’s Marsh Gardens reports on his new pet greenhouse, which will include  – finally! – a proper environment large enough to house the significant collections of desert plants. The cheiridopsis, an iceplant-relative that like most of them is only a weed in warmer climes, is about to be one very happy camper. (Eric, too, once the dust clears.)

the (currently somewhat cramped) carpet weed

the (currently somewhat cramped) carpet weed

New Desert House and Carpet Weed
Cheiridopsis purpurea

By Eric Larson
The construction work here at the garden is starting to wind down, with occupancy dates being bandied about. The greenhouse itself is complete, while the ancillary link area, the rest of the wiring and the ‘charging’ of the hot water heat system are all awaiting our attention. As well as some work in the driveway for those of you who have visited us and lost their Volkswagens in one of the potholes.  We will now have not one but two uni-sex (if that’s the right word) toilets here in the greenhouse, a small room for storage of gear, a new office for Chris* and a better sink for our events.  Hallelujah!

Since the greenhouse is done, we started installing the stone retaining walls for the new desert display, which takes up the last bay of this new facility.

At present, our desert collection is growing in a cramped and very wet bay in the oldest greenhouse here at the garden.  (We call it our “desert in a bog” ). We are growing a good number of these plants in pots or in raised beds on benches to keep them above the wet humid floors.

Desert in bog, about to be history

Desert in bog, about to be history

In the new house we are constructing retaining walls to hold the soil mixture (part sand and part ‘grit’ or quarry dust, and in some isolated areas there will be some rather more organic constituents), so that we can grow these magnificent plants to more like their representative stature. By growing in pots, we have to prune the tops heavily to keep the plant’s top and root system in proportion.

Dave’s** enthusiasm for this project is beyond measure. He has joined in the very physical work of moving and stacking the stone, and then beginning the back fill process with gravel. We put in a three-inch layer of gravel, then install a geo-textile filter fabric, then add the sand/grit mix on top of that.

The most important aspect of our design is that the plants thrive in the environment we create, hence the attention to soil drainage from the beginning. We also have continued the standard practice of separating the plants by nativity: one half the room will be Old World plants, mostly from Africa, and the other half of the room will be plants from the New World, North, South and Central America.   We will have an area devoted to chaparral plants, which will be the first that I have heard of in a conservatory in our area.  There will also be a special collection of the plants of Madagascar, which has a distinct and quite unusual set of plants endemic to only that island off the east coast of Africa.

Cheiridopsis or Carpet Weed is a succulent plant native to South Africa and Namibia.  It is a member of the Aizoaceae (formerly Mesembryanthemacae) family, commonly called Fig-marigold or Ice-plant family.  There are 135 genera of Mesembs (the shortened name of the family from its previous appellation) and almost two thousand species.  The genus name comes from the Greek for ‘like a hand,’ as the plants there in have a growth pattern that makes the leaves look like fingers clustered together.

Dave could give you a world of information on the culture of these plants, but I will outline a bit what it takes to grow them.  They go dormant in the summer, so it is best to withdraw water at that time, only starting to water when the leaves begin to show signs of growth.  They will withstand a light frost, so in our climate it is best to grow them in the greenhouse. But you can keep that section cool in the winter.  It is best to grow them in a mixture of sand and grit, as we do, with little or no fertility in the soil.  We provide them with some extra light in the form of fluorescent grow lights in the winter.

The leaves are blue-green, soft and rubbery, as we would expect a succulent’s foliage to be.  The flowers are purple and quite showy, with a daisy-like form, but more tightly held.  This plant gets only a few inches tall, but when happy, it will spread outward with alacrity (hence its common name).

* Christopher Bolick, Horticulturist-in-training.
**Dave Garinger , Curator of Greenhouse Plant Collections.

Home stretch on the desert to be

Home stretch on the desert to be

Disclaimer: The opinions and views expressed herein are the sole responsibility of the author.  Yale University and Marsh Botanical Garden and Leslie Land are not responsible for the inane and sometimes off the chart craziness of this publication.

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  • Annette Said,

    This is not carpetweed. It maybe couper’s ice plant though.

  • Eric Larson Said,

    The stems on Delosperma are more elongated than Cheridopsis, and the flowers size tends to be larger (both of these are admittedly somewhat subjective observations) so I would still go with my original identification (which is also borne out by the curator of indoor plant collections here at Marsh Botanical Gardens) of Cheridopsis. Common names are bothersome: this doesn’t look like the carpet weed that bedevils us poor temperate zone gardeners here in the States, but Azoaceae is referred to as the ‘Carpet-weed family,’ probably from the common name where it is native.
    Annette, I would never argue with anybody’s life on the line about a plant about which I didn’t have complete certainty. So I won’t in this case. Do visit our web-site ( and send me an e-mail, and we can figure our disagreement out. You may be right, but I don’t think so. The typical liberal waffling, I’m afraid.

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