Can I Combine an Old Christmas Cactus and a New One at the exact same Pot?

Christmas cactus (Schlumbergera x buckleyi, formerly Zygocactus x buckleyi), which grows outdoors in U.S. Department of Agriculture plant hardiness zones 11 through 12, is a true cactus, native to Brazil and often sold around the winter holidays. Grown for its bright, tubular flowers, Christmas cactus is a low-maintenance plant that suffers from few pests and diseases. An old Christmas cactus can be combined in a single pot with a new plant, as long as neither plant is suffering from disease or pest infestation.

Rot Issues

Before combining two Christmas cactus in a single pot, check on both plants to get one of the most usual diseases: stem or leaf decay. This condition is usually caused by overwatering and leads to dead, dying or waterlogged stems near the ground line. Affected stems may drop off. To treat decay, remove the affected plant parts with sharp clippers, disinfecting the blades with a mixture of 9 parts water to 1 part chlorine bleach between cuts. Repot in new potting medium and don’t water unless the soil is dry to the touch. Wait a few months prior to hooking up treated plants alongside new plants.

Cactus Pests

Although decay is the most frequent problem that will prevent potting old and new Christmas cactuses together, it’s also wise to check for pest infestations. Look carefully at leaves and stems of both the new and established plant for the existence of the most usual Christmas cactus pests: aphids, mealybugs, fungus gnats, soft brown scale insects and spider mites. A good treatment for these pests is to wash the plant thoroughly with a solution of 1 to 2 teaspoons dishwashing liquid mixed in 1 gallon of tepid water. Rinse leaves and stems thoroughly and monitor for indications of further infestation. Repeat if needed.

Potting Two Cactuses

Christmas cactuses bloom best when they are slightly pot bound, so opt for a container to the 2 plants that’s only slightly larger than the combined root balls of them both. Make sure the new container has adequate drainage holes. You will probably need to add a little more permeable medium. Use a mixture of 40 percent perlite and 60 percent permeable soil for good drainage. Put the repotted plants in bright, indirect light. After the soil surface becomes dry, water and fertilize simultaneously, using a balanced 20-20-20 fertilizer diluted to half power, usually 1/4 teaspoon in 1 gallon of water.

Christmas Cactus Considerations

Always check fresh Christmas cactus plants for signs of pests and disease. It’s a good idea to isolate them from different houseplants for a month to monitor for problems. If an established Christmas cactus plant is severely affected with decay, it could be better to root a cutting and establish a new plant which may eventually develop along with a second Christmas cactus. To do this, cut several healthy stem sections, add them cut side down in moist vermiculite and enclose the container in a sealed plastic bag. The cuttings should root in three to eight weeks.

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