Are you starving your plants? Just like how people need water for hydration and food for fuel, so do our cacti. But what kinds of fertilizer should we be feeding our plants, and how often do they need to eat?

In this guide, we’re going to talk about why you should feed your cactus, what kinds of food/fertilizer to use, and how much and how often to use them.

Why Feed Your Cactus

Feeding your cactus isn’t strictly necessary for survival, but if you want it to thrive, you need to start feeding your plants. With proper feeding, cacti grow stronger, look better, and reach their full growth potential. Well-fed plants also tend to be more resilient, with increased resistance to pests and disease. 

The difference isn’t always instant. Cacti have a slow metabolism, so nutrient deficiencies (or excesses) can take a while to show. But over time, feeding makes a visible impact on overall health and appearance.

That said, feeding only works when the conditions are right. Cacti need adequate light and active growth to actually use those nutrients. Fertilizing during low-light or dormant periods can cause etiolation or other potential issues, so always pay attention to your growing conditions.

Kinds of Food

When it comes to what to feed your cactus, there’s a lot of information out there, and honestly, much of it makes things more complicated than they need to be. Compost and other at-home additives can work in theory, but they can be hard to measure and inconsistent. 

We find that the simplest and most effective approach is to use a fertilizer with a balanced NPK ratio. Anything in the range of 10-10-10 to 20-20-20 works well for cacti when diluted properly. Avoid anything too nitrogen-heavy, which can push excessive vertical growth without the structural strength to support it. A balanced fertilizer provides essential macronutrients like nitrogen, phosphorus, and potassium, as well as essential micronutrients, like calcium and magnesium, which support overall plant health.

You can use liquid fertilizer, you can use granular/slow-release, whatever you prefer, but make sure to go for fertilizers that have a guaranteed analysis. That means they’re lab-tested and you actually know what you’re giving your plant. We make a point to be as science-based as possible, and we want you to be on the lookout for products that make promises without backing them up with proof, or products that seem too good to be true. 

Liquid Recommendation

We use GrowMore at 200 parts per million (Most growers in San Diego County use this!). But whatever you find, as long as the ratio seems balanced, try it out and go for it. 

Granular Recommendation

Our recommendation for granular fertilizer is Osmocote Smart-Release Plant Food for flowers & vegetables.

When to Fertilize

How often you fertilize is tied to your growing season and light conditions. The better your conditions and the more light your cactus gets, the more frequently it can safely use those nutrients. For most setups, that means feeding anywhere from every watering to every other watering during active growth. We’ve personally found that we can do every watering and it’s been no issue.

It is important to use slow-release fertilizer early in the growing season so that it works during plants' active growth - you don’t want to use it too late and have it bleed into dormant seasons.

When NOT to Fertilize

Do not feed your cactus during dormancy in the Winter or extreme Summer temperatures. When growth naturally slows or stops, nutrients should stop too; otherwise, you risk problems like etiolation from pushing your plant to grow when it doesn’t want to. If you do water in the Winter, then only use water - cut all nutrients so that you’re not giving the plant stored nutrients to work with.

How to Fertilize

How To - Liquid Fertilizer: You should be able to follow the directions on the container to determine how much fertilizer to mix with the appropriate number of gallons of water. Wearing gloves, fill up a large container with water and pour in the appropriate amount of fertilizer, then mix or agitate the water until you are confident that the fertilizer has dissolved. You can either connect this to a pump and water your plants with a hose or use a good old-fashioned watering can, whatever suits you and your budget.

How to - Slow-release/granular: For slow-release fertilizer, you should also be able to follow the directions on the container for the amount of granules to use per square foot of soil. Sprinkle the proper amount of granules evenly on the top 1-3 inches of soil. You may then water regularly, and the fertilizer should start to work.

Tips

• Don’t worry too much about compost in potting mixes. Compost has generally low concentrations of 1-1-1 NPK and won’t be strong enough to affect the growth of the plant. If your potting mix has leave-in fertilizer, that might be stronger, and you can wait a little longer before fertilizing.
• A lot of generic, store-bought fertilizer isn’t usually strong enough for cacti specifically, so go with anything in that range of 10-10-10 to 20-20-20 NPK.
• If you’re new and your plants have never gotten fertilizer, start with a lower ratio or higher dilution and start with a gradual increase to see how they respond.
• Synthetic vs Organic - both work!
• If you don’t want as much growth (limited space), then reduce your feeding schedule either in amount or in frequency.

Summary

It’s time to stop starving your cactus! Feeding your cacti during their natural growth cycles supports healthy, resilient plants that will look better and feel stronger. Remember, it’s important to feed under the right environmental conditions, look for fertilizers that have a balanced NPK ratio, and make sure they have a guaranteed analysis for the best results.