How to Fertilise Pond Plants: A Simple Guide to Healthy Growth

Want lush foliage, stronger roots and more flowers in your water garden? Feeding your pond plants is one of the easiest ways to encourage healthy growth, and it doesn't need to be complicated.

Just like plants growing in your garden beds, aquatic plants need nutrients to thrive. During the warmer growing months, a regular feed can help potted pond plants produce fresh leaves, develop healthy roots and put on a beautiful display.

At We Know Water Gardens, we've been growing and caring for aquatic plants for years, so we know that a little regular attention can make a real difference.

In this guide, we'll explain when to fertilise pond plants, how to apply fertiliser tablets, how much to use in different pot sizes and what to look for if your plants aren't thriving.

When should you fertilise pond plants?

In most parts of Australia, spring and summer are the main growing seasons for many pond plants. As temperatures rise and new growth appears, plants begin using more nutrients.

For potted pond plants, we recommend feeding monthly from September through March, using a suitable aquatic plant fertiliser and following the product directions.

During autumn and winter, many aquatic plants slow their growth or become dormant. They generally need less feeding during this time, so avoid adding fertiliser simply because the calendar says it's time.

A simple rule to remember: Feed actively growing pond plants during the growing season, and reduce or stop feeding when growth slows.

What is the best fertiliser for pond plants?

The most important thing is to choose a fertiliser specifically formulated for aquatic plants.

Ordinary garden fertilisers aren't necessarily suitable for ponds. Nutrients can leach into the water, potentially contributing to excessive algae growth and affecting water quality. This is particularly important in ponds containing fish, frogs and other aquatic life.

We recommend Pond Plantz Time Release Fertiliser Tablets. These easy-to-use tablets release nutrients gradually and are formulated for pond and water garden plants. This pond fertiliser is safe for fish and other aquatic visitors.

When used as directed, they help support:

• Healthy new foliage and vigorous growth.
• Stronger root development.
• Better flowering in suitable flowering varieties.
• Consistent plant growth throughout the growing season.

The tablets are designed for use in the growing medium of potted aquatic plants, rather than being scattered loose into the pond water.

How to fertilise pond plants in pots

Feeding your pond plants is a quick job. Here's how we do it.

Step 1: Check your plant

Look for fresh growth and check the condition of the leaves. Remove any dead or yellowing foliage while you're there, and check that the plant isn't overcrowded in its pot.

Step 2: Add the fertiliser tablet

Push the tablet into the potting medium, around 5–10 cm below the soil surface where possible. Cover it with the growing medium so the nutrients are released around the roots rather than directly into the water.

Step 3: Use the correct amount

For Pond Plantz Time Release Fertiliser Tablets, our recommended quantities are:

• 7 cm pot: Half a tablet.
• 12 cm pot: One tablet.
• Larger pots: Multiple tablets may be suitable, depending on the pot size and product directions.

Always follow the instructions on the fertiliser packaging and avoid using more than recommended.

Step 4: Return your plant to its pond

Place the pot back into its usual position and continue your normal pond care routine. Make a note of when you fed it so you can keep track of the next application.

That's it! A few minutes of care can help set your pond plants up for a productive growing season.

See the difference a little plant care can make

We recently gave our Lebanese Cress (Aethionema cordifolium) a quick tidy-up and a feed in its patio pot.

We removed the yellowing leaves, added a fertiliser tablet and put the plant back in place. Three weeks later, the transformation was impressive: fresh, deep green foliage, no more yellow leaves and plenty of healthy new root growth.

The roots were also helping keep the water in the patio pot clear.

It’s a great reminder that plant care doesn't have to be complicated. Regular feeding, a quick tidy-up and suitable growing conditions can go a long way.

Watch our video: Lebanese Water Cress | Drab to Fab in 3 Weeks!

Why are my pond plant leaves turning yellow?

Yellow leaves can be a sign that a plant needs attention, but fertiliser isn't always the answer.

Here are a few things to check.

Nutrient deficiency: If your plant has been growing actively without a feed, it may benefit from an appropriate aquatic fertiliser.

Seasonal changes: Some plants naturally lose older leaves or slow their growth as temperatures change.

Water depth: A plant positioned too deeply or too shallowly for its needs may struggle. Check the recommended growing depth for your particular variety.

Light conditions: Too little light can affect growth and foliage colour, while excessive heat and strong sunlight can stress plants in small containers.

Crowded roots: A plant that has outgrown its pot may need dividing, repotting or fresh aquatic planting medium.

Start by checking the growing conditions and removing damaged leaves. If you suspect a nutrient deficiency, use a suitable aquatic fertiliser according to its directions rather than adding extra tablets in the hope of a quick fix.

Can fertilising pond plants cause algae?

It can, if fertiliser is used incorrectly or excess nutrients enter the pond water.

Algae naturally occur in ponds, but excess available nutrients can encourage unwanted growth. This is why it's important to use a fertiliser designed for aquatic plants and apply it at the recommended rate.

For potted plants, insert the tablet into the growing medium and cover it properly. Avoid dropping fertiliser directly into the water or increasing the dose to make plants grow faster.

Healthy plants can contribute to a balanced pond environment, but fertilising alone won't guarantee clear water. Fish numbers, feeding, sunlight, filtration and overall pond maintenance all play a part.

Do all pond plants need fertiliser?

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