Grow Cactus from Seeds
A Bay Weekly reader who has tried and failed many times asks how to grow cactus plants from seeds.
It’s possible. Here’s how.
For growth, cactus plants need full sun, dry conditions except for a few days of rain in the spring, sandy rather poor alkaline soil that’s hot in the day and cool at night. These are exactly the same conditions you must satisfy to be successful in germinating seeds.
To prepare a seed germinating mix, blend one-fourth cup of garden soil with two cups of play sand and one rounded teaspoon of agricultural grade dolomite limestone. Moisten with water and mix thoroughly. Place the mix in a metal or Pyrex pan and bake at 200 degrees for one hour, cooling in the oven. By doing this, you are pasteurizing the soil to kill all weed seeds and living organisms that are not common under desert conditions. Put two tablespoons of the sterilized soil in a clean, sterile container or plastic bag. Place the rest of the sterilized soil in a clean, shallow four- or five-inch pan with drainage holes in the bottom.
Uniformly scatter cactus seeds over the surface of the mix, allowing one-eighth to one-fourth inch between them. Cover the seeds with the saved pasteurized soil using a tea strainer. Water the seeds carefully with a rose bulb or fine sprinkler until water drips from the bottom of the container. Place the pot near a window facing south where it will obtain full sun all day and cool temperatures at night.
Commercially, cactus seeds are germinated in lighted cycling chambers with 80 degrees of bottom heat for 12 to 15 hours under grow lights and nine to 12 hours of darkness at temperatures 60 to 65 degrees. You can best achieve the commercial germination chamber with a gooseneck lamp with a 40-watt incandescent light bulb. Adjust the light to 10 to 12 inches above the pot and place both in the middle of a room. Turn the light on soon after you rise in the morning and turn it off before going to bed at night. The heat and infrared rays of the incandescent light bulb will not only provide light but also warm the soil during the day. When the light is off, the soil will cool.
Most packets of cactus seed contain several species, so germination is very erratic, anywhere from a few weeks to a month or more. Check for soil moisture daily. If the soil feels warm, irrigate lightly. If the soil feels cool, withhold irrigation.
Ask The Bay Gardener your questions at [email protected]. Please include your name and address.