A Detailed Guide to Fertilizing and Propagating Succulents by Cuttings

  Many friends have asked how to fertilize succulents and how to mix soil when repotting. Actually, succulents themselves do not really need much fertilizer. So if you do want to fertilize, how should you go about it? The following summary should be useful to everyone:

  1. Potassium fertilizer is very important; most commercially available compound fertilizers are not suitable for growing cacti and succulents. Phosphorus fertilizer comes second, especially when flowering and fruiting. With compound granular fertilizers, it is sometimes really hard to say exactly what specific ingredients they contain. Traditional chemical fertilizers are still more reliable.

  2. Potassium chloride can be used in small amounts temporarily; the main issue is that it leaves chloride ions behind in the soil. Likewise, potassium sulfate should not be used in large amounts either.

  3. Chemical fertilizers that can be mixed together: potassium nitrate, monopotassium phosphate, plant ash, potassium chloride, etc. Among these, potassium nitrate and potassium chloride are neutral.

  4. Acidic pesticides and fertilizers all carry a line: forbidden to mix with alkaline pesticides and fertilizers. Acidic fertilizers refer to salts that show acidity when dissolved in water, mainly ammonium salts of strong acids such as ammonium nitrate, ammonium sulfate and ammonium chloride, and acid salts such as monopotassium phosphate and superphosphate (whose main component is monocalcium phosphate). The reason they cannot be mixed with alkaline pesticides and fertilizers is that: ammonium salts break down into ammonia gas when they meet alkali, and superphosphate reacts with alkali to form calcium phosphate, which is extremely poorly soluble in water. Monopotassium phosphate should not fall into this category, because when monopotassium phosphate is neutralized by alkali, the products dipotassium phosphate and potassium phosphate are both soluble in water.

  Conclusion: monopotassium phosphate should be able to be mixed with plant ash.

  5. Calcium is very important for some cactus globes, especially for those such as Astrophytum that originate from limestone soils. You can use gypsum, and it is best to use raw mineral gypsum. If you do not have any, then use superphosphate. Note that at this time you must not mix in alkaline substances such as plant ash; for the reason, see 4… I feel that using peeled eggshells is also quite good, provided the soil is on the acidic side.

  6. Regarding nitrogen, globe-shaped cacti generally do not need urea; the fertility is too strong and hard to control, and the bit of nitrogen in potassium nitrate is enough. Everyone must pay attention to this: too much nitrogen fertilizer will make the globes burst open. This includes types such as Mammillaria and Astrophytum; apply a handful of urea, and within a few days the globes will split… Ammonium-form nitrogen fertilizer lasts longer in the soil than nitrate-form nitrogen fertilizer; nitrate ions are easily washed out through the bottom of the pot along with water. Ammonium salts, being cations, bind with soil particles and are more lasting. If the soil is on the acidic side, use just a little ammonium dihydrogen phosphate, or a single granule of urea, and it will act over a longer period. Note: just a little bit of urea.

  Summary:

  Formula 1: Use monopotassium phosphate + potassium nitrate as a top dressing, at a very low concentration. Mix gypsum or superphosphate or eggshells into the soil. Then everything is just fine.