Growing and Buying Aquatic Plants and Grasses

Grasses for the Water Garden

Grasses are grown for their foliage, as a foil for other plants and as an attraction in their own right. Between them there are dozens of species that are perfectly at home either in the pond itself (true aquatics), or in the moist conditions of the bog garden. All have definite characteristics that make them worthy garden plants, but not all gardens are suited to the very idiosyncratic forms the plants take.

Ornamental grasses

When browsing through plant catalogues even just a few years ago you would have come across only a mere handful of decorative, ornamental grasses listed. Now that they have become fashionable, there is a bewildering array of species and varieties to choose from, such as the architectural pampas grass and the clump forming smaller forms, like Festuca.

Grasses and grass-like plants are perfect for growing in and around a pond. Their slender stems form elegant vertical clumps that make an ideal contrast to the bold lines of formal ponds, as well as blending and contrasting with other plants in an informal pond. Some also have attractively variegated or coloured foliage that provides colour and interest from spring to autumn.

Although some members of the grass family grow in the water (rushes and sedges), most of the smaller ornamental species prefer a moist but free-draining soil.


Ferns are grown for their foliage. These shade-loving plants are perfect for the waterside, with their delicate, fresh green leaves (more correctly, ‘fronds’). Few plants suggest the prehistoric quite like the fern. They have been around since the age of the dinosaur, which means that they are sturdy, durable and hardy. More often than not they grow in damp places although, it has to be said, a dank atmosphere is as important to them as a wet soil. Indeed, it is quite a common occurrence for the crown and roots of outdoor ferns to rot in consistently wet soil.

Choosing and Buying Aquatic Plants

Mid-spring to early summer is the best time to plant up a pond. Consequently, most garden centres will be stocking a wide range of aquatic and moisture-loving plants during this period. Specialist water garden nurseries tend to offer better quality plants, and in a wider range of forms. The prices of plants can vary, too, with specialist centres often selling plants at as much as half the price you would have to pay at a general garden centre. Also, specialist aquatic nurseries can provide customers with good, informed advice; not all general centres can provide this.

Why are spring and early summer the best times to plant? Because the pond water will be sufficiently warm to provide a receptive environment for new plants. These plants will have the whole of the summer and autumn to become established before the onset of winter. You can usually buy aquatic plants through until late summer or even autumn, however.

Plants are sold either bare-rooted or grown in containers. The former will be sold to you in plastic bags for planting as soon as you get home. The latter can be left in their containers until you are ready to plant them — but do not let them dry out. Keep them submerged in a tray of water, or in the pond itself.

How to Recognize Healthy Aquatic Plants

When you purchase aquatic plants, there are certain things you should look out for (sadly, many garden centres and nurseries do not look after their water gardening section as well as they should).

Aquatic plants you are considering for purchase, should look fresh and healthy with plenty of new growth: avoid any with a lot of dead leaves that could have already spread disease through the entire plant.

Floating lilies, the sun light showing its del...

Take a good look around the aquatic plant display area. Marginal plants and deep-water aquatics are usually displayed in trays of water, which should be reasonably clean.

The soil into which aquatic plants are planted must be permanently and consistently moist, so avoid any which have been allowed to dry out.

All plants should be clearly labelled, but do not buy any with badly faded labels — a clear indicator that they have possibly been neglected for some time, and been sitting around for a very long time.

Buying Mail Order Aquatic Plants

If you are not happy with your local source of aquatic plants, it is worth considering placing an order with a specialist mail order supplier. You will often find choice and even rare plants with these companies, and many of the plants will have been propagated and grown by them as well. The proprietors are the real water gardening experts, and they are usually happy to impart good advice.

Modern packaging —tough polythene bags and polystyrene packing — and reasonable postage costs mean that the plants generally arrive in good condition, and at an affordable price. It usually compares favourably when you take into account the cost of driving to a garden centre and then paying what can sometimes be inflated prices.

The downside to mail order buying is that you cannot see the quality of the plants before you buy them, which is why it is important for you to use only companies with a good reputation, or which offer a full money-back guarantee for peace of mind.

What to Do Before You Plant Your Water Garden Plants

Once you have got the plants home, you should try to plant them straight away. If planting is delayed, make sure to keep the plant continually moist. Ideally, oxygenators and deep-water plants should be submerged in pondwater or rainwater.

These plants can survive in this state for a good two to three weeks, after which time their condition will begin to deteriorate.

Waterlilies, in particular, will benefit from a little preparation before they are planted. If any of the roots are damaged, or are excessively long, use a sharp knife or a pair of secateurs to cut them back to within 5cm (2in) of the tuber. Remove any leaves that have unfurled close to the base, ensuring that you are careful not to damage any new growth. Do not interfere with any young, tightly rolled leaves that are still growing; as they will soon reach the water surface of their own accord.

Do’s and Don’ts for Choosing Water Garden Plants

Do allow new ponds, filled with fresh tap water, to stabilize before planting. It is always a mistake to rush in to planting up a brand new pond. If you have just filled it with tap water, allow it to stand for a few days so that the temperature of the water stabilizes.

Don’t buy poor quality plants. Do not be tempted to buy water plants if the trays they are standing in contain lots of dead or rotting vegetation, weed or algae. This is a sure sign that they have been neglected.

Do rinse bare root aquatic plants before you plant them or pot them. This is to ensure there are no unwelcome pests (such as leeches) or weeds (such as duckweed) lurking between the leaves or fibrous roots. Duckweed is the main offender here. It is a minuscule, bright green floating plant that tends to sneak in quietly but can soon carpet the entire surface of the pond.

Don’t collect plants from the wild. Firstly, it is likely to be illegal, and second, it is definitely inadvisable, as they may be suffering some disease or virus. The plants may also be harbouring pests, or you might be bringing in to your garden something that is so invasive it will outgrow everything else around the pond.

Installing Pond Plants Where You Want Them to Grow

Before plastics were commonly used, most pond plants were set directly into the mud in the bottom of the pond. You can, of course, still do this today, and it is usually carried out in large ponds where many plants need to be planted and there is room for them to develop without restraint. It is ideal for a large wildlife pond, where the planting is, for the most part, left to its own devices.

If you want to do this with your own pond, place a layer of soil about 15cm (6in) deep onto the base of the pond liner. Plant directly into this soil and then fill the pond very slowly — even for a period of over a week or more — so as to avoid stirring up the soil with the water.

The main problem with this method is that eventually the plants will grow into each other, with more vigorous varieties smothering their neighbours. You will need to control plants on a regular basis, and weeding a murky pond is not an appealing task.

Suitable Soils

Special aquatic composts can be purchased, although ordinary garden soil (sifted to remove twigs, roots and stones), is perfectly acceptable. Use a heavy loam, such as the fertile top layer taken from your pond excavation. Do not add peat, as this will float out into the pond, and do not incorporate garden compost or manure to the soil, as this is far too rich and will pollute the water.

Planting Aquatics in Mesh Containers

Aquatic plants are best planted in hessian cloth inside plastic mesh containers, as this will both retain the growing medium under-water and will allow the roots of the plant to ‘breathe’. The pots come in a range of shapes and sizes. Some retailers now sell plants already in mesh pots, which can be placed directly in the pond.

Planted containers can be positioned in the pond at any desired point, and they can easily be moved when cleaning or maintenance is necessary. A particular advantage of planting individual plants in containers is that each one is shown off at its best.

Do not plant two or more different varieties in the same basket, as plants grow at different rates and to different sizes, so one is almost bound to smother the other(s).

The planting procedure is straightforward. When planting up tall marginal plants, place stones in the base of the container for added stability.

Line the plastic mesh container with hessian (sack) cloth. Put a layer of soil in the hessian at the base of the container, and then position the plant in it, ensuring that its existing soil level is just below the rim. Fill with soil to within 2.5cm (1 in) of the top of the container and gently firm the soil.

Add a layer of fine gravel to just below the rim of the pot. This stops soil floating out of the pot, prevents fish from nosing around and stirring up the soil, and provides an attractive finish. Then water the plants thoroughly, using a can with a fine rose-end; soak the compost, which will drive out surplus air.

Installing Plants Around the Pond

Setting out the plants

The next thing to do is to place the plant into the pond. Marginal plants can be placed directly in their final positions. Deep water aquatics — plants that need a depth of at least 20cm (8in) in order to grow well (most forms of waterlily come into this category) — need to be ‘acclimatized’ gradually to their eventual planting position and level. Do this by placing the planted container on a base of bricks — one to four bricks deep, depending on the desired depth. The plants’ foliage at this planting stage should be just below the surface of the water. Remember to place some padding under the brick so that the liner does not become damaged. Remove the bricks, layer by layer, over several weeks as the leaves each the surface.

For larger ponds, suspend plants in the water by running a line of stout string on either side of the basket and anchoring it on both sides of the pond. Gradually lower the plant as the leaves extend until it reaches its final position, when the string can be removed.

Planting oxygenators

Most oxygenating plants are sold as bunches of unrooted cuttings with a weight at one end. To plant these, simply drop them in to the pond. Sometimes a stone attached to the bunch with an elastic band will help to carry them to the bottom where they will root well. If you wish, you can loosely fill a container with soil. Insert about 7.5cm (3in) of the weighted end of the cuttings into the soil, firm gently, add gravel and place into the pond. These plants should be sited in water that is 30-60cm (12-24in) deep.

Planting a Bog Garden

Plant your bog garden plants in spring or autumn (container plants are usually available from garden centres all year round). Mesh baskets are not necessary, so plant them directly into the soil. However, take care not to compact the wet soil when walking over it.

Do not add fertilizers or handfuls of rotted or concentrated manures that may run in to the pond water. Finally, plants growing in moist soil usually grow vigorously (think of the giant rhubarb, Gunnera, and ornamental rhubarb, Rheum). Therefore you should give new plants plenty of space in which to spread. Do not overcrowd a bog garden.

10. April 2012 by Dave Pinkney
Categories: Water Garden Plants | Tags: , , , , , , , | Comments Off on Growing and Buying Aquatic Plants and Grasses


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