Closet Cactus Care-By Michael S. Smith

Starting from Seed

For the non-professional cactus lover, starting cacti from seed can be a daunting task, especially for those without a greenhouse and experience. But growing these beautiful specimens of the plant kingdom should not be limited to those who are mass producers. Everyone should have a chance to start their own cacti from seed and slowly watch them as they grow and form into mature specimens. With the right resources and techniques the closet cactus enthusiast should find success.

Seeds and Soil

Of course, first thought must be given to what seeds to grow. There are a number of very reputable cactus plant and seed dealers, my own favorite being Mesa Gardens of Belen, New Mexico. This company has thousands of different species of seed to choose from, many of ethnobotanical interest. Many other seed sellers can be located at the Cactus and Succulent Mall Home Page. Since many individuals will be interested in the most famous species of cacti, Lophophora williamsii, it may be necessary to order from companies in Europe, but if your interested in Trichocereus species you can find American sources easy enough. Sadly the USA is one of the only countries in the world with laws against the Lophophora genus. If this is the prize you seek, act wisely, shipping to the USA is not illegal, but reception of any Lophophora species here is.

Soil choice among  professionals can be quite an intricate endeavor. Many cacti have very specific ecosystems that they have evolved in, but until you become much more involved in cacti care you can simply use the general cactus soil that can be purchased from your local nursery or garden center. If you are looking for a nicer soil I would recommend ordering from Bob Smoley’s Garden World, or many of the other cacti dealers found at the Plant Mall.

Getting Started

Other needed supplies are small 4” plastic pots, a regular sized spoon, 2 deep microwavable bowls with lids (preferably glass, one large and one small), a set of tweezers, a can of disinfectant spray, a bottle of bleach, and, depending on how many pots are to be used, large or small unused ziplock baggies.

Getting the soil ready and killing off all contaminates is the first step. Make an estimate of how much soil is going to be needed to fill the number of pots that are going to be used (remember, seeds should be set in the soil no less that 1/2 apart, but an inch is best). Take the soil and put it in the large glass bowl and slowly add water and mix till it is minimally wet, then microwave for about 1 minute for each cup of soil. The soil should not be so wet as to make it difficult to work with, the heat and steam created by the small amount of liquid should be enough. Just try to make sure there are no dry spots in the soil. Use the small glass bowl to do the same procedure with sifted soil, but this time use only about 1/4 the original soil amount. This will be the soil which will top off the pots and allow for the seeds roots to dig in. After microwaving the soil let it cool. I recommend letting it cool with the lids on since it will help the soil avoid picking up airborne spores. This may of course take some time, so get cleaning.

Disinfect all the pots and tools by placing them in the sink with a gallon of warm water and a few tablespoons of bleach. Let them sit for awhile. If they are previously used they should be scrubbed with a clean unused sponge, being careful to remove all dirt and mineral buildup. This step will most likely save you from the horror of fungus engulfing your seeds and seedlings. Many simply avoid this step by using a fungicide in the soil, but often this will lessen seed germination rates, something that the closet cactus grower cannot afford. Finish up by using lysol on the counter top and placing the clean pots and tools out to dry on a clean towel. I am of course trying to stress that all items used the process, from towels to tweezers, need to be thoroughly clean and free of mold and fungus spores.

Sowing the Seed

Once the fine topsoil is ready and slightly warm (80 to 85 degrees), start by filling each pot 3/4th full with regular soil and 1/4 sifted soil on top of that. Gently press the soil down with your spoon, but not too much, it needs to stay rather loose. Give a spraying from a misting bottle to settle and even out the top layer of soil. Make sure the soil is relatively wet but in no way sopping wet. Now just take your tweezers and place the seeds on the soil and press them halfway into the soil. Give about an inch between seedlings as you should probably keep them in these containers for at least a year.

Now you are ready to bag them up. One pot fits nicely into a small ziplock bag, while two fit comfortably into a large one. The trick in bagging them is to make the bag like a tent. This will cause the condensation buildup within the bag to run down the sides and collect at the base of the pots, possibly to be sucked back into the pots through the bottom holes. If a horizontal ceiling is above the pots, droplets of condensation may fall directly on top of the newborn seedlings, often displacing the seedlings or causing them to rot more easily. The easiest way to make such a tent is to place the pots directly on the crease that is at the bottom of the bags. This means that the the ziplock is directly above the pots.

Creating the Right Environment – Heat and Light

Now that the seeds are bagged up, it’s important to create the right growing environment of heating and lighting. This is possibly the most critical aspect of growing your own cacti from seed. My own method is to place the baggies onto a reptile heating pad that can be purchased from a pet store. I have forgotten the brand I use, but it is very thin (as opposed to the ones that are thick, white, and rather puffed up) and black with a clear lamination on it. There are a couple different sizes available, but they are rather expensive, approximately $40 for the larger one. You may want to place a small thermometer (sterilized) within one of the bags to make sure the internal temperature does not get excessive. Best germination is at about 80 to 85 degrees, but a night temperature around 65 to 70 degrees is also necessary. I simply have my heating pads and lights on a timer. A 12 hour cycle of light and heat is good.

For lighting I use 3’ long shop lights with plant/aquarium bulbs. These are elevated about 2’ above the seed containers. This is usually fine for the germination phase but may turn out to be too much light for best growth. It must be kept in mind that though cacti are typically desert plants they germinate and have much of their initial growth in cracks and crevices in the soil or under the shade of other plants. A clear sign that there is too much light is that the seedlings will stop growing and get a reddish/brown color. If this occurs you can take a layer of cheesecloth and lay them over the bags as needed. As I said before, put the lights and heaters on a 12 hour timer. Germination should take anywhere from a week to nearly a month, so be patient and avoid opening the baggies and letting in contaminates. After about two months you can remove the pots from the baggies and keep them under the lights and on the heating pad cycle. If necessary also reapply the cheesecloth.

One additional measure I take to help recreate a natural environment indoors is to add a small fan onto my timing system. I place the fan directly above the cacti on low and allow it to blow throughout the area of my exposed cacti. Not only will this help limit any fungus growth but it will also help with the all too common gnat problem. Another way to limit gnats, as well as retain soil moisture, is to apply a layer of fine sand around the seedlings once they are big enough.


Once the cacti are out of the baggies watering will become important. Seedlings will need much more water than mature cacti, but they also stand a better chance of getting root rot. That is why I recommend the the top layer of soil should come close to being dry before re-watering. When watering is needed the pots should be placed in a dish of semi-warm water, allowing the water to rise from the bottom till the top is moist. One can also regularly apply a fine mist with a water bottle. If you decide to use sand as a top cover it may be necessary to learn how to use pot weight as an indicator of watering time. Do this by learning the weight of the pots when fully watered. When the pot becomes noticeably lighter be sure to water.

Though my technique does not often afford rapid growth it should lessen the chances for rot, thereby ensuring that the small closet cacti grower has his or her limited amount of seed succeed. Following the directions of a good 1-7-6 fertilizer such as Sudbury Cactus Juice may possibly increase survival rates by strengthening the plant’s natural defenses. With any fertilizers it is necessary that they be fed from the bottom only, otherwise mineral deposits will built up on the cacti themselves, which can possibly burn them.

Growing Seedlings Outdoors

Since I am in a Northern clime I find it best to start my seedling by the above method indoors in the Spring or Summer with the anticipation that I will put them outdoors after a years growth. It is very important that when placed outdoors the seedlings receive no direct sunlight, but are instead placed in a nice shady spot which gets diffused light. As with artificial lights, too much sunlight will be readily recognizable by the reddening of the cacti. In this case the cacti can be moved to a less bright spot or else a mesh can be created to diffuse the light. My own method is to use replacement screening for screen doors and windows which can be cheaply purchased from your local hardware store in rolls. This screening can be doubled up until the needed level of protection is attained. Such porous screening also allows for needed air circulation as well.


Once your seedlings have grown to about a half inch to an inch you might want to consider transplanting them to a new container with fresh soil. Let the soil first dry out a little. It is best that the soil is not fully wet, but also not fully dry, at which point it might harden up and encase the roots, causing the young rootlets to tear off when removing from the soil. With most clumping desert cacti, such as Ariocarpus and Lophophora, a deep container that does not extend more that an inch from the cacti is recommended. Many species have their best growth in a relatively root bound environment.

Once the seedlings are transplanted to a new container and are healthy and on their way to maturity it is time to start testing out their natural sunlight capabilities. As with all cacti a sudden move from shade or partial sun to full sun is not recommended. Such a sudden shift in environments can cause the plant to get unsightly sunburn marks. It is best to slowly move them into more sunlight over the period of a few weeks, taking care to watch for browning. Immediately move the plant back into more shade if this occurs. Also be informed that though your cacti received strong artificial light indoors they still might not be capable of handing a rapid shift to natural light.


Reprinted with permission from Growing Cacti From Seed