Growing from Seed

Growing from seed is not as hard as one might think. With the right supplies and a cactus seed packet from the local nursery or hardware store, one could have cactus seeds sprouting in a little over a week. Seed packets are typically filled with cactus seed that readily and easily germinate.

Supplies Needed

Seed Starting Soil Mix
The one that work best for me for starting cactus is 'Whitney Farms Seed Starter'. It has higher concentrations of sand and perlite mixed in with peat moss compared to other seed starter mixes helping to keep the soil damp but not sopping wet.

Container
A shallow pot is perfect for germinating seed. Shallow pots are sometimes called "bulb pans" and the decreased depth allows the soil to dry a little bit faster. If more segregation of seed is needed, then "six packs" may be a better choice. These are the cheap, thin plastic containers that annual flowers or vegetables are sold in at a nursery. A more elegant way of segregating seeds is to buy a mini greenhouse. Mini greenhouses come with 36 or 72 sections for planting and a removable clear plastic cover.

Covering the air space above seeds is very important, since cactus like a humid environment for germination. Most cactus in the wild germinate under other plants, often under their leaf litter where they are protected from direct sunlight and dessication. While mini-greenhouses come with a clear plastic cover, pots and six-packs do not. The solution? Use something like Saran wrap as a covering. Some brands of clear plastic cling and some do not. If it doesn’t cling, use a rubber band to cinch it down around the pot. Poking a few holes in the plastic will allow a tiny bit of air flow. For a mini-greenhouse, offset the top a little to allow some air flow.

Tips For Growing Cacti From Seed

Watering
Water so that the seeds and seedlings are not disturbed. A fantastic way of watering is with a spray bottle. Another way of watering is from below. Putting a pot/six packs in a pan of water or pouring water into the bottom of the mini greenhouse will allow water to creep up via capillary action.

Heating Mat
A heating mat helps the growing season start a little earlier. In fact, my 2007 crop of seeds were started in January with the aid of a heating mat and a grow light. The hope in starting so early is that the plants will have a long first growing season. It seems that most of my problems with seedlings that are less than one year old is that they tend to rot in their first winter.

Some heating mats have thermostats and some do not. Those that do will do their best to maintain a desired temperature. Mats that do not will have to be monitored to make sure they don't get too hot on warmer days.

I used a heating mat underneath a mini-greenhouse in 2006 and it worked out great except for one thing. The warmth and humidity within the mini-greenhouse made for quite a bit of condensation on the inside of the clear plastic cover. As a result, the runoff from the cover ran down the sides and into the planting cells along the perimeter causing those cells to remain too wet. The solution was to offset the top slightly which resulted in less condensation due to a little air flow coming through.

Placement
Cactus seed like to have warmth more than light to germinate. Select a place that will be warm (65 degrees Fahrenheit or higher) 24 hours a day and make sure that at no time direct sunlight or strong diffuse sunlight shine upon the seeds. I have started out seeds underneath a plant table in the greenhouse and have had relatively good luck there. A window in a house is a good place as long as no direct sunlight falls upon the seeds. If it does, cover the top with a paper towel or two to help limit the amount of light that gets in. About two weeks after the last of the seeds have germinated; remove the plastic cover for it will no longer be needed. But keep misting the plants to help keep the soil damp and seedlings from being dislodged. Slowly introduce seedlings to more and more light. Slowly. If any start to turn red, give them to less light.

Repotting Seedlings
When seedlings start to crowd one another, it's time to repot them individually. The aforementioned six-packs are about the right size for seedlings as are the cells in a mini-greenhouse. 2 or 2 1/2 or 3 inch pots will suffice for seedlings. If the roots are entangled, gently tease them apart. When repotting, try to plant in a cactus potting soil. Peat moss is great for short term plantings, but not long term.