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What Are the Best Fertilizers for Geraniums (Pelargoniums)?

Janet has been passionately growing pelargoniums since a child. She's a member of the Geranium and Pelargonium Society.

Discover the best fertilizers for geraniums (pelargoniums)

Discover the best fertilizers for geraniums (pelargoniums)

Not All Fertilizers Are Created Equally

Feeding geraniums with the right geranium fertilizers requires some knowledge about this plant’s specific requirements. Despite what you may have heard, geraniums are heavy feeders that crave the right nutrients in order to thrive.

Sure, many geraniums grow well even without feeding them much, but unless you live in the perfect climate with the perfect soil, chances are, your geraniums will just survive rather than thrive. Not all fertilizers are created equally, and therefore, it's important to know what to look for in order to have healthy and happy geranium plants.

The Importance of Feeding Geraniums the Right Food

As with several other plants, geraniums need more than just water to thrive. When you place a geranium in a pot filled up with soil or in a flower bed, chances are, the soil will lack important nutrients or may not have them in the correct amount.

Hence, the importance of finding optimal fertilizers to make your geranium happy.

The Importance of Primary Nutrients (Macronutrients)

Most geranium plants need primary nutrients such as nitrogen, phosphorous, and potassium. Each of these nutrients plays a fundamental role in growth. Let's take a closer look.

  • Nitrogen is essential to help plants grow and attain that nice green foliage.
  • Phosphorous is responsible for stimulating stronger bud and flower development while also strengthening young roots, giving them an excellent start.
  • Potassium helps with strong stem development and helps the plant become more resistant at times of drought and disease.

The Importance of Secondary Nutrients (Micronutrients)

On top of the above primary nutrients, secondary nutrients are also needed. Micronutrients are needed in small amounts (usually in parts per million) and include boron, chlorine, cobalt, copper, iron, manganese, molybdenum, nickel, and zinc.

Pick the best fertilizer for your geranium.

Pick the best fertilizer for your geranium.

The Right Geranium Fertilizer

Choosing the right geranium fertilizers can be tricky because the ideal type may vary based on what nutrients you already have in the soil and several other factors. It may help to have your soil tested.

You can buy a home soil test kit or ask your local cooperative extension office to test it for you.

The folks working there should be able to suggest to you the ideal fertilizer based on your soil’s results, whether you are growing in pots indoors or outdoors, and the type of plant you are planning to plant (most likely geraniums, if you are on this page!).

Deciphering the Numbers in Fertilizers

Generally, many commercial fertilizers used for geraniums consist of a water-soluble 15-15-15 fertilizer. What do these numbers mean? Each number represents the percentage of nitrogen (N), phosphorous (P), and potassium (K) the fertilizer contains. With a 15-15-15 fertilizer, you are therefore getting 15 percent nitrogen, 15 percent phosphorus, and 15 percent potassium.

The fertilizer must be diluted in water in the correct proportions. Never pour it straight out of the bottle! Failure to dilute may lead to the fertilizer burning the plant, which may end up killing the plant! Liquid fertilizers are fast acting, and geranium plants absorb the nutrients quickly through the roots.

Products Crafted With Geraniums in Mind

For those looking for products specifically crafted for geraniums, there are several options.

Jack's Professional Geranium

This is a water-soluble fertilizer crafted specifically for geraniums. This product's high phosphorus content promotes strong roots and bud set while minimizing nutritional toxicities. Jack's Professional geranium fertilizer is sold in a 25-pound bag and is a 15-15-15 fertilizer.

EZ-GRO Geranium Fertilizer

Similar to Jack's, this is a 15-15-15 fertilizer. It works well for both indoor and outdoor plants. It's designed to be used instantly as it's a liquid fertilizer. Its high phosphorous levels promote a strong root system and bud set, allowing for an increase in the number and size of blooms.

The product is blended with a micronutrient package for optimal nutrition leading to large eye-appealing blooms.

Algoplus Geraniums

Algoplus offers a liquid fertilizer that delivers 12 essential nutrients plus trace elements. Although this fertilizer has lower numbers compared to commercial types, the company claims that this is just the needed amount that can be used from March to October.

Algoplus Geraniums is my favorite fertilizer so far as it has been able to make my geraniums finally produce those striking snow-ball blooms often seen on seed packets and magazines!

Although this product may seem costly compared to the cheaper fertilizers you often see on sale in garden centers or grocery stores, it lasts long and delivers results. As the saying goes, "you get what you pay for.'' Just think that just one liter of concentrate yields 450 liters of fertilizer. That's about 115 gallons!

This is overall my personal favorite fertilizer for ease of use and results. See the video below on Algoplus and how it benefits geraniums.

The Power of Magnesium

Geraniums may benefit from the addition of a little bit of magnesium every now and then, especially if the soil the plant is in happens to be slightly deficient in magnesium.

You don’t have to go to the garden center in order to add a touch of magnesium. Instead, you can provide some magnesium to your geranium plants by giving some Epsom salts, which is often found in households. Epsom salts are simply a source of magnesium sulfate. To be precise, Epsom salts are composed of about 10 percent magnesium and 13 percent sulfur.

Every third or fourth watering, add 1 teaspoon of Epsom salts to one gallon of water. Mix thoroughly, and water your geraniums with this solution.

How does magnesium sulfate help geraniums? This mineral is helpful in keeping the foliage nice and green. Indeed, a lack of magnesium or sulfur is often the cause of yellow, dull-looking leaves. On top of that, magnesium helps improves a geranium plants’ uptake of nitrogen, phosphorus, and sulfur.

The Power of Liquid Seaweed

Liquid seaweed has been used for a long time, but now it seems more and more gardeners are re-discovering its beneficial effects. And this is not at all surprising, this product contains more than 70 minerals, vitamins, and enzymes, and a little of this product goes a long way.

Not only does seaweed add nutrients to the soil, but it also strengthens the plant's defenses. Boosting your plants' defenses means that they're more resistant to diseases and injuries. The benefits of liquid seaweed for geraniums, therefore, include better resistance to frost, better resistance to stress, and deterrence of pests and diseases.

Many gardeners use liquid seaweed for soaking seeds, as a rooting solution, as spray to encourage vigorous growth of leaves and buds, and added to the watering can for the general purpose of growing healthier, stronger, and more disease-resistant geranium plants.

The ratio of liquid seaweed to water varies depending on the brand and its concentration. As mentioned, a little goes a long way!

The right geranium fertilizer can really make a difference

The right geranium fertilizer can really make a difference

What About Natural Fertilizers?

Some geranium lovers prefer to rely on natural do-it-yourself fertilizers. Often, these consist of "food" that comes from animals. Let's take a look at some examples of natural fertilizers that may turn helpful to geraniums.

Animal Manure

From chicken manure to cow and horse manure, these are what it sounds: animal poop. Animal manure has been used for many centuries as a fertilizer prior to the invention of the commercially prepared ones. It supplies primary nutrients (nitrogen, phosphorus, and potassium) and micronutrients to geraniums, in addition to being a source of organic matter.

Manure should be used carefully. For example, chicken manure is very high in ammonia and, therefore, can readily burn plants when over-applied. On top of this, it may supply too much phosphorous, so you may want to have your soil tested to prevent excess build-up of phosphorus, suggests the University of Wisconsin-Madison Division of Extension.

Other risks are nitrate leaching, nutrient runoff, and, depending on the type of manure, salt damage.

Worm Castings

Worm castings is the polite term used to depict the end product of a worm's digestion. Worm poop has such a great reputation, that some gardeners have decided to raise their own worms just to harvest their poop.

What's the "scoop" on worm poop?

Studies have found that castings are rich in organic matter and microorganisms, providing essential plant nutrients. On top of this, they also help improve the structure of the soil, improving aeration.

The humus in earthworm castings helps increase soil's water retention, improve soil aeration, and anchor plant nutrients that would otherwise leach away with water. Castings also feed beneficial soil microorganisms that produce, store and slowly release plant nutrients into your soil to feed plants.


  • Earthworm Castings as a Substrate Amendment for Chrysanthemum Production Pablo R. Hidalgo' and Richard L. Harkess, Hortscience 37(7): 1035-1039. 2002
  • University of Wisconsin-Madison Division of Extension, Using Manure in the Home Garden
  • Principles of Horticulture by C.R. Adams,K.M. Bamford,M.P. Early

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Janet Rolla