For optimal results, seeds should be aged a year before trying to germinate them. They should dried and preferably pulp free before planting. They require very little water.
You can start seeds outdoors is in the spring, but it is best to start them in flats. Be sure to use cactus soil.
Cactus soil is a potting soil with a coarse material added for drainage. Commercial blends are usually peat or shredded bark, however too much peat will clump up into soggy balls when watered. These clumps once solidified are difficult to re-hydrate, water runs right off them.
The best cactus soil is a sandy loam blended with perlite, I prefer to blend in some coco coir as well. Some people use sphagnum moss. A thin top layer of fine gravel is also advisable as it retains moisture and helps to prevent clumping.
Using a flat or seed tray, fill it with commercial cactus soil and sow the seeds directly on the soils surface and gently add a fine layer of sand on top of them.
The next step is to mist the soils surface with a fine spray of water. Covering the tray with a plastic lid or dome his advantageous only until they germinate. Be certain that if you do use a lid to allow for aeration / ventilation by cutting a holes in the plastic.
Place the pots in a sun drenched area or window sill. If you have suitable artifical lighting or grow lights that will work well also. Soil temperatures should be at least 70 F. Mild temperature fluctuations are acceptable. Remember in the desert to which they are indigenous, night time temperatures are chilly while day temperatures are oppressively hot.
With cactus there is a thin line between watering and over watering. You should never allow the soil to become saturated - never. A fine mist over the soils surface is all it takes, a very fine mist. Water your barrel cactus weakly weekly in the summer. In the winter cut back to about every once monthly, as the barrel cactus doesn’t require much water during its winter dormancy.
You might notice condensation building up on the inside of the plastic lid if you chose to use one. That condensation can also be deadly, it creates an overly moist environment for the cactus and promotes fungus, mold, bacteria. Remove the lid periodically to allow for better air circulation.
Fertilizer is also low on the Barrel Cactus regimen, once a year in the spring is sufficient. A low nitrogen fertilizer is best.
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