Issue: January 26, 2002

Repotting Christmas cactus

I am ready to re-pot my Christmas cactus and am wondering what the proper soil is for it. Would it be best to use a potting soil such as Miracle-Gro, or would it need a more acidic soil such as that for African violets?

ow is a good time to repot Christmas cacti (Schlumbergera spp.). Following flowering they should have begun growing, or will begin soon. The soil into which you transplant them is important, but the Christmas cactus is tolerant of various conditions. It is very important that the potting soil be well drained. This is one of the plants that will not tolerate soggy conditions - it needs air around its roots. Having said that, I have seen Christmas cacti growing very well in garden soil used as potting soil. The ideal potting soil will contain a high proportion of organic matter such as peat or well-decomposed compost. Addition of coarse sand, or even aquarium gravel, will provide the necessary drainage and aeration. There are commercially available cactus potting soils that are designed to be well-drained soils. The reason for such a need for aeration is that these plants are native to tropical rain-forests where they grow as epiphytes high in the trees. The "soil" in these locations is just composted tree leaves and whatever else gets caught in this "compost pile." There is a distinct dry season, but even in the wet season when it rains daily, the location of these plants high in the trees causes drying of the compost around the roots each day. Roots in a pot will not dry as completely, but a well-drained potting soil allows adequate aeration for healthy root growth.

Making potting soil

Can I make my own potting soil by taking soil from the garden?

Garden soil works best in the garden but can be used in potting soil. In the confined environment of a pot, addition of certain amendments is helpful. Compost, peat, or other organic matter is a good addition to garden soil. If the garden soil is quite sandy, organic matter may be all that is required. If the garden soil has a lot of clay, perhaps some coarser material such as coarse sand or aquarium gravel should be added, depending on the plants to be grown. Another consideration is the presence of fungi and bacteria in all garden soils. In the confined environment of a pot, these are more likely to damage plants. You can pasteurize the soil by heating it to a temperature of 160 degrees for 30 minutes. Heated soil does not smell good, so if you can pasteurize the soil outside, it is advisable. You can use a portable oven or barbecue for outdoor soil pasteurization.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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