Gardening 101: Crassulas

Crassula, Crassulaceae: Blue Ribbon Houseplants

When I see Crassulas, I think of the Philadelphia Flower Show. If you’ve ever been courageous enough to brave the crowds, you know that one of the joys of that venerable exhibition is the display of prize-winning house plants. Every year I have visited the show, I have seen astonishing specimens that are unique and memorable, elegantly arranged on spacious shelves where they can be studied from all angles. One of the most popular types in the competition is succulents, with Crassulas being a big favorite. This is a large genus filled with a varied array of extraordinary looking plants, some bearing clusters of tiny flowers, seemingly custom made to attract the attention of ribbon-bearing judges.

The Flower Show website features an extensive botanical database, which lists the names of more than 20,000 plants that have been entered in the show over the years.  Type in “Crassula” and you get more than 150 entries.  They range in form from the mottled pointy-leaved Crassula alba to Crassula “Buddha’s Temple” with its thin gray-green leaves stacked like poker chips to Crassula perfoliata, also known as “Airplane” or “Propeller Plant” for its whorls of flat leaves. And, of course, there are numerous examples of Crassula ovata or jade plant, the most popular Crassula, which is a ubiquitous resident of sunny windows in homes and offices everywhere.

Read on to learn everything you need to know about this family of succulents:

To better survive in the semi-arid areas most of them call home, these mainly South African natives developed an ingenious method to conserve water, which is known as Crassulacean Acid Metabolism or CAM.  Most plants take in carbon dioxide for photosynthesis during the day, which causes a significant loss of moisture in the process. Crassulas, however, are able to absorb carbon dioxide at night, enabling them to retain more of the water they store in their leaves, stems, and roots to better endure times of drought. Despite their unusual forms, Crassulas are relatively easy to care for and are especially appealing as house plants.

Cheat Sheet

• Because they store water in their leaves, many Crassulas are top-heavy. Plant them in substantial clay pots instead of flimsy plastic to avoid damaging tip-overs.
• In order to flower, many Crassulas need a period of rest with short days, long nights, no fertilizer, and minimal water.
• Crassulas are remarkably easy to propagate from leaf or stem cuttings.
• Add a top dressing of grit or limestone chips around the stems of these plants to make sure moisture does not linger and cause rot.

Keep It Alive

• Good drainage is vitally important to Crassulas so use a potting medium such as a cactus mix that contains sand or grit.
• Over-watering can be fatal. Water thoroughly and then allow the soil time to dry to the touch before watering again.
• Crassulas like warmth and most need to be moved inside if outdoor temperatures fall to below 50 degrees.
• When growing outside, avoid sites with very hot direct afternoon sun which can cause leaf scorch.

The jade plant is beautiful but there are at least 150 species of Crassulas, so you really owe it to yourself to explore other members of this genus. And, while most Crassulas do make wonderful house plants, they don’t necessarily have to be limited to the interior of your home.

For instance, Crassula capitella ‘Campfire’, which is hardy in USDA growing zones 9 to 10, makes a wonderful warm-climate ground cover.  Its fleshy, stacked rosettes of  pointed leaves turn from green to a startling bright red and in summer they produce tiny fragrant white flowers.  For a different look, there is Crassula tetragona, a tree-like evergreen shrub that can grow to more than 3 feet in height and is hardy in USDA zones 9 to 11.  Let your inner garden artist run free and consider adding some of these unusual beauties to your landscape.

N.B.: For more of our favorite succulents, see:

• Succulents & Cacti: A Field Guide for Planting, Care & Design.
• Field Guide: Aloe.
• Steal This Look: Succulents Garden.