Botanical family: Cactaceae
Desert Cactus come in numerous forms and sizes and they form interesting plants which are especially popular with beginners as they can tolerate some level of neglect.
They have many adaptations for water conservation. The native habitat of Desert Cactus is subject to drought; many live in extremely dry environments like the Atacama Desert.
Desert Cactuses 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.
These 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.
Pereskia spp (Rose Cactus)
The odd one out of the Desert Cacti 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.
Most Desert Cacti employ the CAM (Crassulacean Acid Metabolism). 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.
Forest Cacti are so different in form and requirements from the Desert Cacti. The popular ones include Christmas Cactus, Easter Cactus and Orchid Cactus.
Desert Cactus thrives in bright light to full sunlight with at least 2-3 hours of sunshine per day, average warmth and humidity and moderately moist, well drained soil coupled with monthly feeding during the growing season.
Young Desert Cacti require repotting annually during the growing season while mature plants are repotted when pot-bound. Keep reading for more on these growth conditions and how to provide them.
Desert Cactus grows best in bright light to full sunlight with at least 2-3 hours of sunshine per day.
If the light is too low the plant will grow elongated stems in an attempt to reach the light source.
Rotate the pot a quarter turn every few days to ensure that the plant receives light from all sides for even growth.
Avoid exposing it to too hot sunlight before acclimating it as it can get sun scorched.
Desert Cactus can also grow under a grow light where natural light is not sufficient.
Water Desert Cactus liberally during the growing season and allow the top 2-3 in. of soil to dry out between waterings to keep the soil moderately moist.
Lessen watering during the cold season to maintain the soil barely moist but do not let it dry out completely.
Avoiding wetting the foliage as it can lead to rotting. Watering from the bottom is safer.
Use room temperature water to water to avoid plant shock as it can lead to reduced growth.
Ensure the pot has a drainage hole to prevent the soil from getting soggy as it can lead to rotting.
Average warmth between 16-280C during the growing season is ideal for these Cactus. Keep it away from cold drafts to avoid sudden drops in temperature which can cause reduced growth.
Average room humidity is ideal for Desert Cactus. They have no need for high humidity but they require good air circulation to prevent fungal diseases infestations.
Feed Desert Cactus monthly during the growing season with a phosphorous (for root development) and potassium (to enhance flowering) rich fertilizer. Do not feed during the dormancy stage (cold season) as growth is minimal at this time.
Repot Desert Cactus 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 as they have shallow roots. Use a pot 1 size larger and one that has a drainage hole to prevent the soil from getting soggy as it can lead to rotting.
Be careful not to bury the stems of to prevent rotting. The best soil for Desert Cactus should be loose and free-draining to avoid waterlogging of the soil.
Desert Cactus can be propagated at the beginning of the growing season from offsets which form at the base of the plant or stem cuttings.
Seperate the offsets from the mother Desert Cactus plant and allow the offsets to dry (callus) for 1-3 days before potting.
Pot each offset in its individual pot in moist, free-draining soil while being careful not to bury the stems to prevent rotting.
Water sparingly, only when the soil is dry and avoid waterlogging the soil as it can lead to rotting.
Take a 3-4 in. stem cutting from a healthy Desert Cactus and allow the stem cuttings to dry (callus) for 1-3 days.
Insert the cutting into moist soil and place the set up in a warm well-lit place.
Maintain the soil moist by light misting until the new Cactus is well established after which you can begin routine care.
Desert Cactus problems indoors include elongated stems, corky patches, rotting, shrivelled growing tips, lack of growth, pests and diseases among others. Keep reading for more on these problems and how to fix them.
Elongated stems (leggy growth) in Desert Cactus are caused by too little light as they grow best in bright light to direct sunlight.
Too little light will cause the plant to grow elongated stems in an attempt to reach the light source.
Position the Cactus in a brightly lit spot where they can also receive bright light with some direct sunlight or instal a grow light where the natural light is not sufficient.
Corky patches on the surface in Desert Cactus are due to three possible reasons. One possible reason for corky patches on the surface is underwatering.
Water the Cactus liberally during the growing season while allowing the top 2-3 in. of soil to dry out between waterings.
Ascertain that the soil is free-draining and the pot has a drainage hole to avoid soggy soil.
The second possible reason for corky patches on the surface in Desert Cactus is physical injury. Keep the plants away from the line of traffic.
The third possible reason for corky patches on the surface in Desert Cactus is chilling; they can not tolerate chilling temperatures.
They prefer average warmth with a minimum of 150C therefore they need to be kept away from cold drafts like windy doors, drafty wndows and low temperatures.
Shrivelled stem tip and soft rot in Desert Cactus are caused by overwatering or soggy soil (too wet soil).
Maintain the soil moderately moist during the growing season and slightly moist during the cold season but never let it be soggy.
In addition, ensure that the soil is free-draining and the pot has a drainage hole to prevent the soil from getting soggy.
Rotting plant base and stems collapse in Desert Cactus is an indication of basal stem rot disease which is brought about by overwet conditions.
Avoid overwatering during the cold season to keep the soil slightly moist. Use the upper stem to propagate new plants and discard the infected parts.
Brown soft patches in Desert Cactus are an indication of stem rot due to wetting the foliage coupled with poor air circulation.
Cut out the infected tissue and water the plant with a fungicidal solution. Avoid wetting the foliage and improve ventilation to ensure good air circulation for the plant.
Lack of growth in Desert Cactus is due to improper watering; either underwatering or ovewatering.
Water the plant thoroughly during the growing season while allowing the top 2-3 in. of soil to dry out between waterings.
Decrease watering in the cold season to keep the soil slightly moist but do not allow the soil to dry out completely.
Always make sure that the soil is free-draining and the pot has a drainage hole to prevent the soil from getting soggy.
Common diseases in Desert Cactus are crown and stem-rot and root-rot disease. Isolate the affected plant to prevent spread to other houseplants and treat the plant with a fungicidal solution.
Common pests in Desert Cactuses are Mealy Bugs, Scale Insects and Spider Mites. Isolate the affected plant to prevent spread to other houseplants and treat it with a horticultural oil as per the manufacturer's recommendations.
Desert Cactuses 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.