Choosing the best cactus seeds for the garden, greenhouse or indoor houseplant depends on factors like climate, soil conditions, humidity and pests. There are over 3000 species of cacti and succulents, giving the gardener many choices. Growing cacti from seed is not difficult as long as some basic guidelines are followed. Gardeners should remember that different types need different growing conditions, so do some research before purchasing seeds.
Cactus plants can also be propagated from cuttings taken from mature plants, but using cactus seeds are an inexpensive and easy option. The only disadvantages are that it may take years before the plant reaches the blooming stage — some cacti take a year before they flower while others can take three years. Seedlings are generally more sensitive than adult plants, and are vulnerable to temperature and light variations and pests.
Soil conditions are perhaps the most important consideration to take into account when buying cactus seeds. Some species such as Cereus, Echinopsis and Harrisia are water tolerant and can deal with wet conditions but don't tolerate soil that is a hard substrate or clay heavy. Others will not deal well with wet soil at all and need to be placed in free draining soil or substrates like sand, grit or rocks that do not absorb a lot of water.
Some adult cacti thrive under full sun conditions and others require shade at least some of the time. Carefully consider the light the mature plants will receive. Seedlings, however, burn easily in the sun so until they reach a mature age, they need to be protected from direct sunlight. It is important that they have a lot of indirect light in order to grow.
Cacti come in many different shapes and sizes so before deciding on which cactus seed to buy, landscaping needs to be considered. Columnar cactus such as the sahuaro, or Carnegiea gigantea, can grow up to 50 feet (15 meters) tall and the Mexican fencepost, or Stenocereus marginatus, can produce multiple stems of up to 12 feet (3.5 meters) tall. Barrel cactus such as the golden barrel, or Echinocactus grusonii, grows up to 3 feet (1 meter) tall and three feet wide so space is a consideration. Smaller cacti such as the Echinocereus engelmannii, a hedgehop cactus, grows up to 1 foot (30.48 cm) so it would suit smaller spaces better.
