The Ultimate Guide to Fertilizing Plants Growing in Water

A fun and easy way to enjoy houseplants without soil is to grow them in water, which is also known as hydroponics. You only need a vase or glass jar, water, and a cutting from your favorite plant. But plants can’t get the nutrients they need to grow without soil. That’s where fertilizers come in.

When using fertilizers for hydroponics, there are a few key things to keep in mind:

Types of Fertilizers for Hydroponics

There are two main types of fertilizers used for plants grown in water:

• Liquid fertilizers are weak fertilizers that are mixed with water. They give you extra nutrients right away, but you have to keep applying them. Popular options include fish emulsion and seaweed extract.

• Slow release fertilizers – These provide a constant supply of nutrients over an extended period of time, Osmocote is a common slow release pellet fertilizer used in hydroponics

Nutrients Plants Need When Growing in Water

Plants need three main nutrients when grown hydroponically:

• Nitrogen (N) – For healthy, green growth
• Phosphorus (P) – For strong roots and flowers
• Potassium (K) – For disease resistance and sturdy stems

Also, they don’t need as much iron, zinc, magnesium, calcium, or magnesium. All of these are in the right amounts in a balanced fertilizer.

How Often to Fertilize

How often you need to fertilize depends on a few factors:

• Type of fertilizer – Liquid feeds may need reapplication every 1-2 weeks while slow release feeds can go 2-3 months between applications.

• Plant growth rate – Fast growing plants use up nutrients quickly and need more frequent feeding. Slow growers can go longer between fertilizing.

• Water changes – Fresh fertilizer should be applied after each water change, around every 2-4 weeks.

In general, fertilize half as much as the package says to every two weeks or whenever the water changes. Watch for signs of not getting enough nutrients, like leaves turning yellow or slow growth, and increase the amount of times you do this as needed.

7 Best Fertilizers for Hydroponic Plants

Here are some of the best fertilizer options for nourishing plants grown in water:

1. Fish Emulsion

Made from fish byproducts, this organic liquid feed provides a quick dose of NPK, plus beneficial microbes. The fishy smell fades quickly. Use 1⁄4 strength weekly.

2. Seaweed Extract

Seaweed is a natural source of potassium, magnesium, iron, zinc and other trace elements. It’s especially good for promoting healthy roots and stress tolerance. Use every 2 weeks.

3. Compost Tea

Steeping finished compost in water creates a mild, nutrient-rich fertilizer. Compost tea also contains beneficial microorganisms. Brew a batch every 2-4 weeks.

4. Worm Castings Tea

Like compost tea, worm casting tea is filled with nutrients and good microbes. Brew up a batch using worm castings and use it to fertilize plants every 2-3 weeks.

5. Banana Water

Simply submerging banana peels in water creates a liquid fertilizer high in potassium and magnesium. Let peels soak for a day or two before using the water.

6. Epsom Salts

Dissolve a teaspoon of Epsom salts in water to provide magnesium and sulfur. This can help plants develop lush foliage and beautiful blooms. Use every 3-4 weeks.

7. Aquarium Water

Siphon water from a freshwater aquarium to give plants a dose of nitrogen and micronutrients. Make sure tank water tests safe before using.

Troubleshooting Nutrient Deficiencies

Here are some common nutrient deficiencies to look out for:

• Yellowing leaves – Nitrogen deficiency
• Spotted or curled leaves – Calcium deficiency
• Poor flowering/fruiting – Phosphorus deficiency
• Weak stems – Potassium deficiency

Target fertilizers to the specific nutrient needed or use a balanced, hydroponic blend to correct deficiencies.

Growing plants in water can be an incredibly rewarding process. Pay close attention to their nutritional needs by fertilizing regularly with hydroponic blends. This will keep plants thriving for months or even years without soil!