Botanical family: Cactaceae
Desert Cacti come in numerous forms and sizes. They form interesting houseplants and are especially popular with beginners. Desert Cacti have many adaptations for water conservation. The native habitat of Desert Cactuses is subject to drought; many live in extremely dry environments like the Atacama Desert. Desert Cacti are succulents which means they have thickened, fleshy parts adapted to store water. Most species have lost true leaves, retaining only spines, which are modified leaves. The spines are produced from specialized structures called areoles; woolly or hairy areas on stems. Areoles are the identifying feature of cacti. The areoles also give rise to flowers.
The odd one out is Pereskia spp which bears thin stems and true leaves. The flowers look like wild roses and hence the common name Rose Cactus. It grows to a height of 6 ft. Desert Cacti have shallow root system that quickly absorb any water reaching the soil surface. Their stems are ribbed or fluted which allows them to expand and contract easily for quick absorption of water. The leafless, spiny stems are succulent which is an adaptation to store water. The surface of the stem may be smooth or covered with protuberances of various kinds, usually called tubercles. Most Desert Cacti employ the CAM (Crassulacean Acid Metabolism) mechanism. CAM plants are plants that harvest Carbon dioxide at night and use it during the day to make their food. As they make their food they store the oxygen they produce in the process and release it at night. This is an adaptation of CAM plants to their drought-prone climate which enables then survive the harsh climate. Desert Cacti require plenty of sunlight, free-draining, sandy soil and to be kept on the drier side. Another group of Cacti are the Forest Cacti which are native to the tropical rain forests. They are so different in form and requirements from the Desert Cacti. The popular ones include Christmas Cactus, Easter Cactus and Orchid Cactus.
Desert cacti prefer bright light to full sunlight; at least 2-3 hours of sunshine per day. Turn the pot a quarter turn every few days to ensure the plant receives light from all sides. Avoid exposing the plants to too hot sunlight before acclimatizing them as they can get sun scorched. Learn how to ensure your plant receives the correct light in this guide on understanding light for houseplants
Water Desert Cacti moderately during the growing season and allow the top 2 in. of soil to dry out between waterings. Reduce watering during the cold period to maintain the soil barely moist. Avoiding wetting the plant as it can lead to rotting. Watering from the bottom is safer. Use room temperature water to avoid plant shock. Avoid waterlogging as it can lead to rotting. Learn more on how to water houseplants.
Average warmth between 16-280C during the growing season is ideal for Desert Cacti. Learn more on temperature for houseplants.
Average room humidity is ideal for Desert Cacti. They have no need for high humidity. Ensure good air circulation for Desert Cacti to prevent fungal diseases.
Feed Desert Cacti monthly during the growing season with a phosphorous (for root development) and potassium (to enhance flowering) rich fertilizer. Withhold feeding in the dormancy stage. Find out more on how to feed houseplants.
Repot Desert Cacti annually during the growing season for the young plants. Repot mature plants only when the plant is pot-bound. Use a shallow rather than a deep pot; they have shallow roots. Use a pot 1 size larger and one that has a drainage hole to prevent waterlogging as it can lead to rotting. Be careful not to bury the stems to prevent rotting. The best soil should be loose and free-draining.
Desert Cacti can be propagated at the beginning of the growing season from offsets which form at the base of the plant or stem cuttings.
Propagating Desert Cacti from offsets
Seperate the offsets from the mother plant. Allow the offsets to dry for 1-3 days before potting. Place each offset on the top of the soil in its individual pot in moist free-draining soil. Water sparingly, only when the soil is dry and avoid waterlogging as it can lead to rotting.
Propagating Desert Cacti from stem cuttings
Take a 3-4 in. stem cutting from a healthy Cactus plant. Allow the stem cuttings to dry for 1-3 days. Insert the cutting into moist soil. Place in a warm well-lit place. Maintain the soil moist by light misting until the Cactus is well established.
Elongated stems in Desert Cacti are caused by too little light; Desert Cacti prefer bright light to direct sunlight. Too little light will cause the plant to grow elongated stems in an attempt to reach the light source.
Overwatering is the cause of shrivelled stem tip and soft rot in Desert Cacti. Water Desert Cacti moderately during the growing season while allowing the top 2 in. of soil to dry out between waterings. Ensure the soil is free-draining and the pot has a drainage hole to avoid waterlogging.
Rotting plant base and stems collapse in Desert Cacti is an indication of basal stem rot disease which is brought about by overwet conditions. Avoid overwatering during the cold season. Use the upper stem to propagate new plants and discard the infected parts.
Brown soft patches in Desert Cacti are an indication of stem rot. Cut out infected tissue and water with a fungicidal solution. Avoid wetting the foliage and improve air circulation.
Corky patches on the surface in Desert Cacti are due to three reasons. One reason is underwatering; water Desert Cacti moderately during the growing season while allowing the top 2 in. of soil to dry out between waterings. Ensure the soil is free-draining and the pot has a drainage hole to avoid waterlogging. The second reason is physical injury; keep the plants away from the line of traffic. The third reason is chilling; Desert Cacti can not tolerate chilling temperatures. They prefer average warmth with a minimum of 150C therefore they need to be protected from cold draughts and low temperatures.
Improper watering is the reason for no growth in Desert Cacti; water Desert Cacti moderately during the growing season while allowing the top 2 in. of soil to dry out between waterings. Ensure the soil is free-draining and the pot has a drainage hole to avoid waterlogging.
Desert Cacti are non-toxic to humans and pets. However, some have spines and thorns, though they are not poisonous it is advisable to wear gloves while handling to avoid injury. They are safe to grow indoors.