Cactus plants are adapted to drought and extreme temperatures. One of the adaptations that allows them to survive their native desert conditions is slow growth. Saguaro cacti, for example, grow only 1 inch in the first eight years of life. These massive plants are usually 35 years old before they produce flowers, and at least 75 years old before they produce side arms.
Growing cactus from seed is an exercise in patience since the seeds may take up to a year to germinate. Once the seeds begin growing, it may be at least two or three years before the plant flowers. Sow the seeds in a sandy potting mix and keep the soil at 70 degrees Fahrenheit. Cover the seed tray with plastic wrap to conserve moisture and warmth. Keep them in the starting tray until the plant stands 2 to 4 inches high, which may take up to two years.
Many nurseries and garden centers sell small cacti as houseplants. These plants grow very slowly and can remain in the same pot for two or three years. The plants grow during the spring and summer, followed by a dormant period in the fall and winter.
To encourage reasonable growth, plant your cactus in a shallow pot with a coarse sand and soil mixture or a potting mix made specifically for cacti. Place the cactus outdoors in full sun during the summer, but bring it indoors in the winter. Water it every two weeks or so during hot weather. Provide water in the winter every three to four weeks. Cacti are prone to root rots and fungal diseases in damp conditions. Gradually move the plant each spring and fall to help it acclimate to its new surroundings. Moving it abruptly outdoors after a winter inside may scorch the plant.
Cacti vary in their growth rate, depending on the species. Try Christmas cactus, golden barrel or fire barrel cactus as houseplants. Other succulent plants that are often classified as a cactus, such as aloe, agave and sedums, may grow more quickly.