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For best results when growing cactus, a lot of fertilizer isn’t necessary. Cacti need very little fertilizer, in fact, and do well with a minimum of fuss or additives as long as their basic needs are met, including abundant sunshine. An application of cactus fertilizer is needed only during the plant’s active growing season, and even then it only needs one or two applications because cacti are not heavy feeders in their native desert habitat. Like other plants, cacti need a fertilizer that contains phosphorous, nitrogen and potassium, but cactus growers should be sure the content of the fertilizer they are using has a higher proportion of phosphorous, and less nitrogen.
Phosphorous and nitrogen have opposite purposes. Phosphorous works below the soil to promote healthy roots. Nitrogen works above the soil to promote growth of the plant and, in the case of plants other than cacti, leaves. The third fertilizer ingredient, potassium, promotes flowering as well as strength in the cactus’ interior.
Cactus fertilizer is sold online and in garden shops, and it is manufactured specifically for cacti and succulents. If a gardener prefers to use a standard type of fertilizer instead, a minor adjustment needs to be made. This type of fertilizer should be watered down to half-strength. It is also important to be sure the standard fertilizer contains trace elements that include manganese and magnesium.
If cacti are kept as houseplants, the conditions they’ll be growing in might require a bit more cactus fertilizer, but again, it won’t be a lot. With cactus fertilizer, it is better for a gardener to err on the side of too little rather than too much. The reason cacti might need to feed more indoors is that the average home’s interior does not resemble a cactus’ native conditions. Cacti kept as houseplants should do well with a fertilization schedule of every other watering during the warmer growing season.
Not all cactus plants need abundant doses of sunshine. Because there almost 2,000 different varieties of cacti, some of them shade-loving, a home gardener may need to adjust the feeding schedule to year round for a shade-loving plant. Shade lovers do not enter dormancy and will continue to grow throughout the year.