Growing a cactus tree is relatively easy. It needs only the three basic requirements to grow: soil, water and light. Most cacti prefer soil with good drainage, such as a rocky soil that is rich in nutrients. When potting small or baby cacti, you can use a mixture of pearlite, pumice, potting soil, rocks, sand, peat, coir and gravel to provide a well-draining mix.
Re-pot cacti every two years, graduating in pot size as the cacti grows bigger. Since it takes a long time for cacti trees to grow, potting them during the growing years is a good method to watch and control the growth of cacti trees. However, cacti trees grow in the wild, so planting directly outside is a good way to get it acclimated into the soil conditions from the start.
Water cacti trees when the soil is dry. In most dry areas, such as in Nevada and Southern California where the temperatures rise above 100 degrees F during the summer, it is advisable to water cacti trees at least once week. Do not assume that cacti trees do not need water, even when they can survive during drought season. Their ability to survive comes from being able to convert and store water in their tissues. Avoid over-watering in order to prevent rotting.
It is advisable for cacti trees planted directly outdoors to get full sunlight all day long. For potted small plants, seedlings or rooted plants, moving them around to get full sunlight at least half a day would be good to get help them establish and grow. Avoid moving potted cacti trees outdoors when it is very hot, this is because the pots can heat up higher than the soil, which may kill the root system. If there is not enough sunlight, such as in the fall and winter, you can use a full-spectrum fluorescent lamp to provide the potted cacti trees with their daily dose of light indoors.
As mentioned in the previous section, cacti trees will grow in pots and directly in the soil outdoors. It is best to sow seeds when the weather condition is good, well before winter comes. When the seedlings appear, re-pot them about 1-inch apart from each other.
When planting in a greenhouse where you can use a small, heated propagator, it is possible to sow the cacti seeds at the end of January or early February. Maintain the heat between 40 to 45 degrees F will help the young plants considerably. If you do not have a heater, then it is best to wait until late April or early May to sow the seeds. Cover the sown seeds with paper until the seedlings appear to get some light.
Planting directly outdoors can be a challenge for areas that experience extreme cold weather. Avoid sowing seeds so deeply in order not to hamper germination. The farther away from wintertime is the best time to sow seeds to help the seedlings establish in October, or right before the start of fall. Place some wooden stakes around the seedlings and place a plastic cloak to help in preventing too much rain and cold air from penetrating the soil when the rainy season begins.
Preventing Diseases Caused by Pests
It is important to ensure that the planting area is free from pests. The most common problem pest is the mealy bug. At the first sign of mealy bug presence, kill it promptly. Apply an insecticide containing Malathion with a fine brush on the affected areas. Some cacti succulents may have a negative outcome or even die because of Malathion formula present on insecticide; for these cacti species, choose a formula containing Imidacloprid instead.
Remove soil and destroy when you suspect root mealy bug infestation. Wash the roots thoroughly using methylated spirits and then rinse it off completely after treatment. Re-pot or re-plant in clean and fresh soil that is free from pests. When using the same potting tools used when removing infected soil, it is important to wash them with soap and warm water and sterilize with denatured alcohol prior to use to prevent transfer of the disease.