What Causes a Cactus to Bloom?

Age of Cactus

• A cactus must be mature before it can bloom. The age of flowering depends on the species of cactus. A cactus may reach mature size at 2 years of age, while another may take 10 years. Once it is old enough, the cactus should flower every year. Buying a cactus that is already blooming is one way to assure the plant has reached mature size.

Sunlight

• Provided that the cactus is old enough to flower, proper sunlight is the most important bloom-producing condition. Finding a suitable location can be difficult to achieve indoors. During the growing seasons, which include spring, summer and fall, a cactus needs abundant light. Most species bloom better if the light is lowered in the winter then increased in the spring. Changing light intensity causes the cactus to bloom by stimulating bud growth.

Dormancy

• A dormant period causes a cactus to bloom. During the winter, the cactus needs rest in order to store energy needed for blooming. Too much sunlight and heat during dormancy causes the plant to expend energy for survival instead of resting to make flowers. Keep the cactus cool, dry and out of direct sunlight.

Water

• Proper watering causes a cactus to bloom. However, watering requirements must be adjusted seasonally. Water frequently when plants begin to show new spring growth, but allow the soil to dry out between watering. Give the plant small amounts of water in the summer. From late summer to early fall, increase the amount of water slightly. Stop watering the cactus during the winter resting period. Wet soil in the winter causes rot and other fungal infections.

Soil and Potting

• The soil must be coarse and well-drained to grow a healthy cactus capable of blooming. Purchasing a soil specifically for a cactus is an easy way to get the proper blend. Also, modifying a commercial potting soil with gravel or sand is a satisfactory alternative. Put the cactus in a suitable pot that is not too large. Otherwise, the plant expends energy growing to the size of the pot instead of blooming.

Fertilizer

• Fertilizing the cactus may give the plant a better potential for blooming. When fertilizing a cactus, feed it about every third watering. A cactus-specific fertilizer may be used. Another choice is a highly diluted plant fertilizer that is low in nitrogen and high in phosphorus and potassium. Tomato fertilizer, which is high in potash, may also be substituted.