– Lithops (2019)

By Bob Williams (January 2019)

In writing articles for the Plant of the Month series in 2018, my theme was caudiciforms. When I was looking at my spreadsheet of all the Plant of the Month articles on our website, inspiration struck.

For 2019, my articles will be based on the last time an article was written on a plant or genus. Plants from the oldest articles will be featured first. This month’s article is on Lithops, last featured in 2004.

Lithops are fascinating plants and popular at our annual show and sale. There are very few, if any, left by Sunday afternoon. This is understandable. Lithops are small. A single plant is only 1 inch in diameter. You can put them in a 3-inch pot and let them go.

The markings on the plant are unusual and attractive. The flowers are big for the size of the plant and attractive. However, even though almost all of the information I have read on lithops says they are easy to grow, most people kill them in a short period.

Lithops is a genus of succulent plants in the ice plant family, Aizoaceae. The name is derived from the Ancient Greek words “lithos,” meaning “stone,” and “ops,” meaning “face” – referring to the stonelike appearance of the plants. The formation of the name from the Greek means that even a single plant is called a lithops.

They avoid being eaten by blending in with surrounding rocks and are often known as pebble plants or living stones. They also have a few more colorful names, including belly plants (because you need to crawl on your belly to see them), beeskloutjies “little cow hoofs” and, in Namibia, ombuma yombwa or dog testicles.

The first scientific description of a lithops was made by botanist and artist William John Burchell in 1811 while on a botanical expedition to South Africa. He went to pick up an interesting stone and discovered that it was a plant. For the first 100 years, the plants were listed as Mesembryanthemum species. In 1922, the Mesembryanthemum genus had become so large that plant taxonomist Nicholas Edward Brown decided it was time to break up the species, and Lithops was born.

Even then, little was known about lithops. Then in the 1950s, Desmond and Naureen Cole began to closely study the plants. During their visits to the wild, they collected over 400 different species of Lithops. In 1988, Desmond Cole published a book on Lithops titled Lithops – Flowering Stones. Even today, this book is considered the go-to publication on lithops. HSCSS has a copy in the club library.

Lithops grow in the arid and semi-arid regions of Namibia, Botswana and South Africa. If you have been to one of Dan Mahr’s presentations, you’ll know that these areas may get 2 inches of rain in a good year. Sometimes a year or more goes by without any meaningful rain. The rainy season in these areas is in the fall, when the temperatures cool. What these areas do get is occasional morning fog. This is a clue that overwatering can be a problem. What these plants do receive in abundance is heat and sun.

The whole function of the plant is to store water. Lithops consist of a taproot and only two leaves. That’s it. Because of the harsh environment in which they live, any more than two leaves would waste water. The top of the plant barely grows above ground level. Again, if the plant grew any taller, the plant would lose too much water.

When growing lithops, a well-draining soil mix is a must. It may be advisable to add a little extra grit or pumice to your normal mix.

These plants are not winter growers per se. The growing season starts in late August into September. At this time, the leaves begin to separate. This is the time to water. Lithops can take a good initial drenching, then maybe every other week. If the plant is old enough (3 to 5 years), a flower bud may appear. White, yellow, orange and red are the common flower colors.

After flowering, new leaves will appear. When this occurs, cut way back on watering. What is happening is that the old leaves are being used by the new. The new leaves absorb the water and nutrients from the old ones. This process continues until the spring, when the old, dried-up leaves can be taken off.

I have seen information that water should be completely stopped in the winter, while some literature says very little watering should occur (some even just misting) to keep the fine roots from dying. In the spring, watering can resume until the weather gets hot. Summer is the dormant period for this plant. Watering should be cut way back to just enough to keep the fine roots alive.

Even though lithops survive in a hot, sunny environment, they do not do well in full sun in cultivation. If you have them outside, they should be in an area where you control the watering and sunlight. Five to six hours of sunlight per day is adequate. It is better if you can give the plant early or late sun. The reason is that in habitat, the taproot stays cooler than it can in a 3-inch pot that gets eight to 10 hours of full sun. Too much direct sun can sunburn and even kill lithops.

Everything you read says that lithops cannot survive freezing temperatures. When Marge and I visited Leo Chance in Colorado Springs last year, we found lithops growing in his back yard that had been there at least six years. They have a southern exposure and grow under the overhang of his house. I do not remember him saying that he puts any protection over the plants.

Temperatures can get below zero for extended periods of time in Colorado Springs. The area gets very little snowfall and almost no freezing rain. If lithops can be winter-hardy here, they may be able to take the temperatures, but not the moisture. Some sort of “hot box” may be needed to grow them outside in Missouri.

These plants are readily available from many vendors on the Internet, and there is a wealth of information on their history and care. My hope is that now I may be able to buy some and get them to live.

Sources:
Wikipedia – https://en.wikipedia.org/wiki/Lithops
Lithops – http://www.lithops.info
Lithops/Flowering Stones – http://floweringstones.co.za
The Biogeography of Living Stones, San Francisco State University Department of Geography – http://online.sfsu.edu/bholzman/courses/Fall99Projects/lithops.htm