Plant the seeds in high-drainage soil. Whether you bought seeds or harvested them from an existent cactus, you'll want to plant them in clean, shallow containers filled with suitable soil. Moisten the soil thoroughly before planting but do not allow any standing water to remain. Next, spread the seeds across the top of the soil (don't bury them). Finally, lightly cover the seeds with a very thin layer of soil or sand. Cactus seeds only have a small amount of stored energy and if planted too deeply will not reach the surface before they run out.
It's important to use a high-drainage soil for planting your cactus,especially if you're dealing with desert varieties. Since desert cacti aren't used to receiving high amounts of water in their natural habitat, they can be susceptible to root diseases if the moisture in the soil is not allowed to drain. Try using a high-quality potting mix with a high pumice or granite content for exceptional drainage.[3]
If the soil you use for planting hasn't been pasteurized (it should say whether or not on the packaging), you may want to consider heating it in the oven at 300o F (about 150o C) for half an hour. This kills any pests or pathogens in the soil.///
Allow cacti to recover from repotting in the shade. As the visible, above-ground portion of your cactus grows, its roots will as well. As your cactus becomes larger and larger, which can take years, it may need to be repotted multiple times. However, because the transplantation process can be stressful for plants, it's important that you allow your cactus to "recover" after each time you repot it. Instead of keeping the repotted cactus in a location where it receives a good amount of sunlight, try keeping it in a shaded or partially-shaded area until its roots re-establish. Gradually re-introduce the cactus to sun over a period of a month or so. ///// Water infrequently. Established cacti have less vigorous watering requirements than most other potted plants. Though they do require some water, their reputation as hardy desert survivors is well-earned. Most varieties of desert cactus require little water once they're fully established. Though individual species of cactus may differ in the amount of water they require, a good general rule is to let the soil dry out completely before watering. Depending on the temperature, this mean waiting a month or longer between waterings.
Remember that cacti experience slow, gradual growth. Thus, they don't need very much water. Watering more frequently than is necessary can lead to to problems for the plant, including root disorders that can cause the eventual death of the plant.
Tropical cacti are something of an exception to this rule, as they are naturally acclimatized to more humid environments than desert cacti. While you can get away with a little more watering if you have a tropical cactus, you should still wait until the soil dries out before each new watering.ๅๅๅ Avoid phototoxicity by limiting sun exposure after using pesticides. If you've ever noticed that you've gotten an especially-bad sunburn after being in water, you've experienced something similar to phototoxicity, a harmful malady that can affect your plant. After applying an oil-based pesticide to a plant, the oil from the pesticide remains on the surface of the plant, acting as a sort of "tanning lotion" by increasing the intensity of the sun's rays. This can cause the portions of the plant on which the oil is present to become burnt, grey, and dried-out. To prevent this, place the cactus in a shaded location for a few days until the oil-based pesticide has done its work before returning it to the sun.