Indoor Cactus Gardening 101

Congratulations! You have entered (or are interested in) the wonderful world of indoor gardening. Succulents are plants that store water in their specialized stems and leaves. Cacti are succulents, too, except they store water only in their specialized stems, and they have no leaves. Most succulents and cacti are pretty easy to grow indoors because they thrive on neglect. All you need to do is check on them and give them water about twice a month -- and that’s it! These are plants that grow in some of the harshest climates in the world, and they therefore are pretty hard to kill. The most common cause of cactus or succulent death is actually overwatering! We’ll talk about why later on. But let’s start with some of the basics:

THE PLANTS

Some plants are better suited for indoor life than others, and the same goes for cacti and succulents (C&S). I've found that cacti are better suited for indoor life than most succulents. Here are my top picks for indoor cacti and succulents:

This plant, also called the “Domino Cactus” or “Sea Urchin Cactus,” is extremely well suited for indoor life. It can tolerate temperatures down to 35 Fahrenheit and does best in filtered light and shade rather than direct light. They stay pretty small, so they’re a good choice for windowsill gardeners. They also flower as houseplants, which is rare among cacti. These guys prefer east-facing or west-facing windows.



This plant has been on my windowsill for a while now and absolutely loves it. They can tolerate temperatures down to about 50 Fahrenheit, and they need full sun to partial shade, so they’ll do great in a south-facing window (east and west-facing windows work, too). They will bloom indoors if conditions are right, but they have a tendency to get kind of big, so you may need to cut them back occasionally.

Biznaga Partida Mocha (Coryphantha retusa)

These plants also do well indoors. They stay pretty small, and they do best with a little bit of direct light and some indirect light. However, these plants won’t flower too well indoors.

Moon Cactus (Gymnocalycium cultivar)

These plants, commonly found at Lowe’s or Home Depot, have a green base and a brightly colored, spiky top part. This top part is actually another cactus grafted onto the green base. These guys grow well in bright indirect light and stay pretty small. Sometimes these cultivars will flower indoors. These cacti can’t live forever, however. The top part has no chlorophyll and cannot survive on its own, so it leeches nutrients from the green part below. After some time, the green part will not be able to support the colorful top, and the colorful part will die. When this happens, simply chop off the top part with a clean knife, let the green part of the cactus heal, and you will be able to keep the green part for much longer. The base is a Hylocereus cactus, and the top is a Gymnocalycium.



Jade plants are the easiest succulents to grow indoors. They do best in temperatures above 40 Fahrenheit and prefer bright light (they will tolerate indirect light and shade as long as they’re kept drier). These plants are very popular as houseplants, and they come in many varieties and colors. They’re resistant to drought, but they need more water than the cacti listed above, and they will die of underwatering. They’re resistant to bugs, and are super easy to propagate.

Of course, there are more plants than these.

Check out http://windowsillcactus.com/ or the forums here on All Things Plants to get some more information on some of these plants and other plants for growing indoors.

BUYING YOUR PLANTS

Buying the plants is an exciting experience. There are, however, several things to look for.

The first thing you want to do is to go to a reputable grower. I recommend calling around to local nurseries to see whether they sell C&S. Lowe’s, Home Depot, and Walmart also sell C&S, but some locations take better care of their plants than others do. I usually recommend Lowe’s over Home Depot and Walmart because I have found that Lowe's plants are less likely to be diseased.

The second thing to do is to make sure the plant you have your eye on is healthy. Inspect the trunk, the leaves, the spines, and the base of the cactus or succulent to ensure that there are no off-color spots and no squishy areas. If you can, try to dig a little below the dirt line on the base of the plant to check for mushy, brownish spots that could indicate rot. Tap the pot lightly and see whether any small gnats fly about. All of these could be signs of disease. Avoid all browning and mushy cacti -- they are not healthy. Don’t be afraid to ask one of the shop attendants about the condition of a particular plant.

Third, check the label on the plant. Look at the recommended growing conditions and make sure you can fulfill the plant’s needs. My apartment does not have south-facing windows, and I cannot give plants direct sun. That means that buying a high-light plant is not a great idea for me. Also check the size of the plant. You probably don't want a three-foot cactus on your windowsill.

LIGHT

Cacti and succulents (C&S), just as all other plants, need light in order to grow. Because C&S in particular are native to very hot, dry areas, they need LOTS of light. Place them on a windowsill in your house or apartment with a southern exposure, if possible. A western or eastern exposure will work if you don’t have any other options, but keep in mind that C&S with high light requirements may not thrive. Some people choose to move their indoor C&S outdoors for the summertime to give them more light during the growing season.

That said, some cacti do not need a lot of light, and they will scorch or “sunburn” if exposed to too much light. Usually this is not a problem in indoor gardening, as most of the light will be filtered by your window. Be careful if you decide to put your cacti outside for the summer. They will be used to filtered indoor light and will have a high probability of scorching. If you do decide to move your plants outdoors, be sure to gradually move them into the light. Don’t just stick them in full sun right away.

TEMPERATURE

C&S often grow in hot, arid environments, and they need to be kept in temperatures well above freezing. Most cacti can tolerate temperatures no lower than 40 degrees, but this can vary based on the species of plant. This usually is not a problem for houseplants, as most homes are well above 40 degrees Fahrenheit. Make sure your windows don’t have too much of a draft, and always be sure to check what your individual plant needs.

WATER

Water is the number one killer of C&S. These plants are designed to live in places where there is very little rain, so they conserve water within their tissues. Too much water will cause the plants to pull too much water into their tissues, making them burst. This will kill the plant.

Water combined with a warm environment allows for bacteria to grow in the soil. C&S are highly sensitive to bacteria, and they easily get infections. “Root rot” is a type of bacterium that grows in water-rich soil and infects the roots. It usually will kill the plant slowly. It is therefore incredibly important NOT to overwater C&S.

The general rule is to water these plants only when the soil is completely dry. Allowing the soil to completely dry out between waterings prevents bacterial and fungal growth within the soil, and it lets the plant use up some of its stored water before you replenish it. This mimics the natural environment of the C&S, where the plants will go weeks before it will rain and water them. Your C&S will need less water in winter than in summer, so you will see them take longer to go dry in the winter months than in the summer months. I usually water my plants about once a month in winter, and two to three times per month in summer.

SOIL

C&S need soil that drains quickly to prevent bacterial and fungal growth in the soil and to help keep the plant dry. Most commercial C&S soils (such as Miracle-Gro Cactus, Palm and Citrus Soil) work well for indoor plants, but most hobbyists prefer to make their own mix. What I've found to work best is a commercial cactus potting soil mix with some added perlite or lava rock chunks to improve drainage. I use 2 parts store-bought mix to 1 part lava rock chunks. Doing a little Googling on the subject of Cactus and Succulent potting mixes will bring up a ton of possible options. Some people use sand, bark, and other things in their mixes, too, but for just getting started, going with a 2:1 ratio of store-bought soil to perlite or lava rock chunks will work just fine.

POTTING

Potting plants with spikes can be very painful. To prevent getting poked, I will usually put a towel over the top of my plant so that I can hold it without getting injured. You will want to re-pot your plant when it starts looking too big for its pot (touching the edges or causing the pot to tip over) or when the roots start coming out of the bottom of the pot.

For top-heavy C&S, such as thick aloes or Jade plants, ceramic or terra cotta pots are best because they are heavy enough to keep top-heavy plants from falling over. Plastic pots are useful for plants that are low and globular. I usually buy my pots for windowsill gardening at Walmart or Target. Walmart usually has a good selection of small, cheap ceramic pots small enough to fit on a windowsill and large enough to hold a pretty good-sized plant. Target sells some awesome plastic pots for a dollar that will fit nicely on a windowsill. The only rule for buying a pot is that it MUST have good drainage holes. Too little drainage can cause water to build up within the pot and rot your plant.

As for how to pot a cactus, follow the technique in these videos:
Part 1: https://www.youtube.com/watch?...
Part 2: https://www.youtube.com/watch?...

See also: https://garden.org/ideas/view/...

PROPAGATION

Most C&S are super easy to propagate. Most of the time, in the case of succulents, fallen leaves left in the pot will simply take root and start growing baby plants. Cacti will often sprout “pups," or baby cacti on their sides. These can be separated from the main plant and grown as separate plants. These methods of propagation will result in “clones” of the mother plant.

Below is a picture of some Sedum "Pork and Beans" leaves sprouting new plants.



CACTUS DISEASES

No good introduction to C&S is complete without touching on the common diseases of C&S. The most common diseases are:

“Root Rot” -- This is a catch-all term for bacterial and fungal infections of the soil, leading to infection of the roots and rotting of the whole plant from inside out. In most cases, in the early stages of rot, the plant can be saved by chopping off the rotted portion and allowing the remainder to scab over and grow new roots. However, most cases are not caught early, and the plant will die. Symptoms include yellow to brownish (and, in severe cases, black) spots that are mushy and oozy on the cactus. Rotted roots will be mushy and will break easily.

Fungus gnats -- These guys are more of a nuisance than a plant-threatening problem. They are teeny gnats that lay eggs in moist soil and fly around your plants. They can infect other plants, causing more flies to spawn. The larvae in the soil rarely feed on the plant (they feed on fungi in the soil), so usually these gnats are just annoying and won’t threaten the integrity of the plant. The symptoms are gnats, and lots of them. To get rid of them, let the soil dry out completely between waterings and sprinkle organic cinnamon on the soil to kill the fungi the larvae feed on. Cinnamon is a natural antifungal, and it will not harm the plant. To control the flies, use commercial gnat traps and swat them at will.

Scale -- Scale builds up on the surface of the cactus and can appear in many different forms. Look for discolored spots on the cactus that can be scraped off gently with a fingernail -- that’s usually scale. If you believe you may have some type of scale, try doing a Google image search to identify it.

Mealybugs -- Mealybugs are the bane of cactus and succulent owners. They appear on the cactus as small fuzzy patches with little bugs (about 1/10’’) near them. Those fuzzy patches are excretions from the bugs. The bugs feed on the plant, and this can cause leaves to drop and the plant to eventually yellow and die. If you suspect a mealybug infestation, wash them away with a steady stream of water. Repeat this as many times as necessary for light infestations. You can also use special soaps and insecticides if the infestation is really bad.

LASTLY…

Above all else, research the plant you want before you buy it. The Internet has a wealth of information on C&S, and this can help you decide whether you can meet the needs of your individual plant indoors. Not all C&S are suitable for indoor growth, and no two C&S are the same. This guide was intended to be an introduction to indoor C&S gardening. Enjoy learning about your plants and growing them.