Things You'll Need
20-20-20 liquid fertilizer
Avoid over watering. Using the spray bottle will enable you to mist the cactus rather than dumping water at the base of the plant. Cacti can grow disproportionately when planted in overly rich soils or given too many nutrients. This can potentially ruin their unique aesthetic and also lead to unbalanced growth that may be dangerous to the plant. Your homemade fertilizer system, with a well balanced soil blend below and diluted fertilizer mist above, will give the plant the gradual supply of nutrients that helps it grow best.
Cacti are members of the succulent family of plants, and as such have some special requirements. Most (but not all) cacti require a sandier, coarser soil. Fewer nutrients and less moisture are ideal, and full sun is almost always welcome. Fertilizers can be used, but you can successfully fertilize your cactus by making a soil blend that already has the fertilizing ingredients in it.
Take two parts soil and two parts sand and blend them together thoroughly. Use a high quality, rich potting soil as the cactus will glean nutrients from this blend gradually over many weeks.
Add one-half part peat moss, bone meal and limestone. Follow the manufacturer's directions on the package for properly dosing the bone meal and limestone. These two ingredients have a wide range of concentrations and strengths, and failure to duly note your particular kind's special instructions could result in overly acidic or alkaline soil, or otherwise create a less than hospitable environment for your cactus.
Mix one part liquid fertilizer with four parts water in a spray bottle labeled as fertilizer for your cactus. This will prevent you from using this specially diluted blend on other plants that have a greater need for fertilizer.
Josh Roberts has three years of experience as a writer in a variety of genres including fiction, creative nonfiction, nature, and technical writing. Graduating from Belmont University with a Bachelor's of Arts in English, he received the Carl Chaney Award for Excellence during that time. His work has appeared in Belmont's Literary Journal, and received honorable mention in the Nashville Scene's 2004 Writing Contest.