Pondkeeper's How to...

Aquatic plants for all garden ponds

Aquatic plants breathe somewhat differently to us. Typical aquatic plants breathe in carbon dioxide during the day (and breathe oxygen out) Aquatic plants breathe in oxygen during the night (and breathe carbon dioxide out)

Aquatic plants introduction:

All aquatic plants behave as follows in a pond and are thus able to add real value to that environment:

Aquatic plants convert carbon dioxide in the atmosphere to oxygen in the water and the aquatic plants use this carbon dioxide to produce energy in the form of sugars - photosynthesis.

All aquatic plants consume nitrogen chemicals (mainly nitrates and phosphates) that build up in the water. Floating aquatic plants and oxygenator (submerged) aquatic plants are best for aquatic aeration. Water cress is often used for this purpose.

Aquatic plants have a limited filtering effect.

Some aquatic plants are particularly good at oxygenating the aquatic water. Oxygenators is generic name for these aquatic plants

Select aquatic plants for around a pond to blend in with the garden. Refer to the diagram in the pond plants or aquatic plants links on this page to see a diagram that will help you decide on aquatic plants for around a pond.

Another use for aquatic plants is to provide shade for fish. Aquatic plants used for this purpose also inhibit algae growth by reducing light transmission into the pond.

How many aquatic plants for your pond?

Here is a rule of thumb for deciding how many aquatic plants to add to your pond. To each square metre of pond surface (10 square feet):

2 bunches of oxygenating aquatic plants

1 Water lily - there is a massive range of these aquatic plants to choose from

1 Bog plant - these aquatic plants can also be planted around the perimeters of garden ponds.

You would of course combine aquatic plants into areas and not space them according to this rule of thumb.

Planting aquatic plants

Bear in mind that aquatic plants do get bigger so don’t over-plant your pond. For good water lily care remember water lilies do not like splashing water or rapidly moving water. Aquatic plants of the water lily type often tend to like water deeper than 60cm.

When you plant aquatic plants use baskets or plastic pots into which specially formulated aquatic plants compost has been used – low in phosphorous and nitrogen. Only ever use fertilizers made for aquatic plants and even with these be careful of using too much. Low organic (preferably nil) soils are best for planting most aquatic plants.

An alternative to baskets for aquatic plants are normal plastic planting pots. Cover the top of the pot with pebbles or gravel to prevent fish disturbing the soil and roots of the aquatic plants – especially if you keep koi.

For placing aquatic plants in those specially made planting areas in preformed ponds use coco mats or coir as a means to hold the plant in position. You can also place a bit of special compost together with the coir for these aquatic plants. Place pebbles on the mat to keep it submerged.

Here is a clever trick I learned from Peter J May for aquatic plants where you already have a pond and it is fairly deep and you want to place largish aquatic plants in the pond. Get a second person to help and between you hold two ropes in parallel stretching across the pond. Allow the ropes to be placed beneath the ridge of the aquatic plants pot as if the pot was in a sling or hammock and then gently lower it into the pond.