Growing from Seed

Growing from see is not as hard as one might think. With the right supplies, some hints on what to do, and a seed packet from the local nursery or hardware store, one could have cactus seed sprouting in a little over a week. One nice thing about a seed packet is that they're full of seeds from plants that readily germinate, so you'll have an idea if you're doing it right in a relatively short amount of time. There are species of cactus seed that take a longer time to germinate, but before trying those try a seed packet. The focus of this page is on growing cacti from seed rather than succulents since most of my experience is with cactus.

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 drain 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 for when seedlings need tending.

Covering the air space above seeds is very important, since cacti like a humid environment for germination. Most cacti in the wild germinate under other plants, often under leaf litter where they are protected from direct sunlight and drying out. 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. Poking holes in the mini-greenhouse cover is not needed since there’s enough air flow where the cover meets the container.

Tips For Growing Cacti From Seed

Watering
Water so that the seeds and seedlings are not disturbed. One way to water is to set the pot in pan of water and let it soak in from the bottom. Another way of watering is with a spray bottle. Any method so that the seeds and seedlings don't get dislodged.

Heating Mat
A heating mat helps the growing season start a little earlier. In fact, the 2007 crop of seeds were started in January with the aid of a heating mat. 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 have a thermostat tend to keep tray about 10 to 20 degrees warmer than the air temperature where the tray is located. For example, if it's a 50 degree room, the temperature of the seeds/seedlings is 60 to 70 degrees. If it's an 80 degree room, the temperature of the seeds/seedlings is between 90 and 100 degrees, so be mindful if you use a heating mat without a thermostat and the weather turns warm. Typically though, if it's 80 degrees in the room, there is little need for a mat.

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. It resulted in less condensation and a little more air flow which the young plants seem to like.

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 does 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.

Succulent seeds are a different matter. Many new plants will start off on the wrong foot if they're not given enough light. The seeds will sprout and immediately start looking for light. If necessary light isn't available, they'll start to stretch out and bend toward available light. Because of their higher light requirement, it's probably best to start out cactus seeds and succulent seeds in different trays. Succulent seedlings should be kept out of direct mid-day sun, but will likely benefit from sunlight from sunrise to about 10 a.m. and/or from about 2 p.m. to sunset. If midday is the only time sunlight is available, a screen will help diffuse the sun's strong rays.

Repotting
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, but anything over that size might be an issue. The term 'over potting' comes from having a pot being too big for a plant since the plants roots can't take advantage of all the extra soil. When there's too much soil and not enough roots, the soil tends to stay too damp for too long and this can lead to problems, namely rot. Of course plants need to be put into bigger pots so they have room to grow, but if given too much room, problems can arise.