How to Grow a Cactus

When the first spines show, allow the plant to ventilate. In the weeks after you plant your new cactus seeds, your seedling should begin to germinate. Cacti typically grow fairly slowly, so this can take a month or more. Eventually, you should be able to see the first tiny emergence of your cactus's spines. When this happens, start giving your cactus a chance to breathe by removing the transparent cover during the day. As the cactus grows, you may leave the cover off for longer periods of time until the plant is well-established and no longer needs the cover.

• It's worth noting, however, that this will increase the rate at which water evaporates from the soil. This means that you'll need to start watering. Try to do so cautiously — don't let the soil dry out completely, but don't ever leave standing water in the container from over-watering.
• Note that many tropical cacti won't have spines, so in this case simply remove the cover once the seedling sprouts up through the soil.

Repot your cacti when they are well-established. As noted above, cacti grow fairly slowly. Depending on the type of cactus you have, it should take about 6 months to 1 year to grow to roughly the size of a large marble. At this point, it's a wise idea to repot the cactus in a different container. Like most potted plants, keeping a cactus in a container that's too small for it can cause the plant to become nutrient-starved, inhibiting its growth and even killing it.

• To repot your cactus, use sturdy gloves or a spade to remove the entire plant, roots and all, from its growing medium. Place it in a new, larger container with a the same type of soil, pack the soil around the cactus, and water.

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 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.

Fertilize young plants during the growing months. Though cacti grow slowly, their growth can be supplemented during the growing months of spring and summer with the light application of fertilizer or plant food. Cacti generally require less fertilizer than other plants — try using a diluted solution of liquid fertilizer once a month. Mix a small quantity of liquid fertilizer with an equal volume of water. Use this mixture to water your cactus every second or third watering.

• The precise amount of fertilizer you should use can vary based on both the species of cactus you are growing and its size. Specific information should be on the fertilizer's packaging.

Prevent rot by avoiding over-watering. One of the most common problems when it comes to potted plants is fungal rot (also called root rot). This affliction typically occurs when the roots of a plant are held in contact with moisture that is unable to properly drain, which becomes stagnant and encourages fungal growth. This can happen to most potted plants, but desert cacti are especially susceptible as they naturally require only a small amount of water compared to other plants. The best cure for rot is a preventative one: simply avoid over-watering in the first place. As a general rule, it's better to under-water than to over-water when it comes to cacti. You'll also want to use a good-quality potting soil with a high level of drainage for all cacti.

• If your plant has rot, it may appear swollen, soft, brownish, and/or decayed, with the possibility of splits in its surface. Often, but not always, this condition moves from the bottom of the plant up. The options for treating rot after it has set in are limited. You can try to remove the cactus from its pot, cut away any slimy, blackened roots and any dead tissue above ground, and re-plant it in a new container with clean soil. However, if the damage to the roots is extensive, it may die anyway. In many cases, it's necessary to discard plants with rot to prevent the spread of the fungus to other adjacent plants.^[3]

Gradually increase exposure to sunlight to treat etiolation. Etiolation is a condition in which a plant experiences pale, sickly growth because it is not exposed to enough light. Cacti with etiolated growth will often have a thin, flimsy quality and a pale, light-green color. The etiolated portion of the plant will grow towards a nearby light source, if there are any. While etiolation is permanent in the sense that any sickly growth that has already occurred cannot be reversed, future etiolation can be curbed by ensuring the plant receives a sufficient amount of sunlight.

• However, you won't want to throw a cactus with etiolated growth into intense, direct sunlight immediately. Instead, gradually increase the amount of sun the plant receives each day until you notice that its growth has become normal. Exposing any plant to drastically increased sunlight can be stressful for the plant, while exposing an etiolated cactus to such levels of sunlight can be fatal.

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.