How to Grow Astrophytum Asterias from Seeds

Fill a cactus planter or a similar wide, shallow container with cactus potting mix. To prepare your own blend, mix 1 part perlite with 1 part sphagnum peat moss. Plan to sow the seeds when the night temperature holds at 65 to 70 degrees F.

Sow the star cactus seeds on the soil surface. Cover the seeds with a thin layer of sand, about 1/8 inch thick.

Place the pot inside a plastic tub. Add water to the tub until it is halfway up the cactus planter. Leave it in the tub for the soil to suck up the moisture through the drainage holes. Go to the next step after the water reaches the soil surface.

Cover the planter with a piece of plastic film to retain moisture and heat.

Transfer the pot outside where the seeds can be exposed to bright but indirect sunlight. Cactus seeds germinate within three weeks. Lift part of the plastic film as soon as you spot a sprout. Remove the plastic film completely two or three days later.

Irrigate the star cactus seedlings with a spray bottle or a mister attached to the garden hose. Let the soil dry somewhat but not completely before misting the plants.

Transfer 1/2-inch to 1-inch-tall seedlings to individual pots filled with cactus soil. Water the plants. Allow the soil to become mostly dry before irrigating it again.

Begin to feed star cactus after it reaches 1/2 an inch in height. Dilute a soluble 20-20-20 fertilizing formula to half strength and water the plant with it once a week.

Grow young star cactus under morning sunlight and afternoon shade. Use two indicators to increase or decrease sun exposure: Yellowing of the skin on the side that faces the light indicates that the plant needs less sun. A star cactus that begins to grow into a shape other than round -- elongated, for example -- requires more time in the sun.