Planting A Pond: A Beginner's Guide
What kinds of pond plant are there?
Pond plants are traditionally divided into four categories – marginal plants, oxygenating plants, floating plants, and deep-water plants. There is some overlap between the categories, but they are still useful.
Marginal plants grow around the edges, or margins, of the pond where the water is shallow. They usually have their soil and their crown (their growing point) underwater, and sometimes their lower foliage as well. They are generally placed on shallow planting shelves within the pond, but if you don’t have shelves their pots can be stood on things such as house bricks to raise them up to the correct height. In order to be considered a true marginal pond plant, the variety must be able to tolerate fully waterlogged soil or water over its crown all year. A plant which will tolerate permanently moist soil but will not tolerate water over its crown or foliage, is considered a marsh plant. There is a huge range of marsh plants available, but a much smaller range of true marginal plants. Unfortunately, many marsh plants are sold as marginal plants, but they will not survive in a pond in the long term.
Marginal plants usually have recommended planting depths - these refer to the depth of water over the crown, or growing point, of the plant (which is about the same thing as the depth of water over the soil level). So a plant with a recommended planting depth of 0 - 4 inches, should be grown anywhere from wet or waterlogged soil (0 inches) up to 4 inches of water over its crown. You can actually grow most marginals in less water than this if you need to, such as in an ordinary flowerbed, provided that their soil is not allowed to ever completely dry out. However, you should never grow them in deeper water than the recommended maximum.
Good examples of marginal plants would be water irises, and marsh marigolds. Most people consider marginal plants essential to make the pond look natural and attractive, and they also provide cover and habitats for all kinds of wildlife.
Oxygenating plants are plants that have all their foliage under the water. They may live on deeper shelves or on the bottom of the pond, or even float suspended in the water – they will grow at any depth where there is light. They are the plants that are sometimes called 'pond weed'; they usually have fine, delicate foliage. Good examples would be spiked water milfoil, or hornwort. They are generally fast-growing and can take up food through their leaves as well as their roots, which means that they are good at absorbing excess nutrients from the water. This can help 'starve out' algae and blanketweed and keep water from going green. These plants also provide important habitats for aquatic invertebrates, and spawning sites for amphibians and fish. In addition, because all plants give off oxygen, their submerged vegetation will increase the oxygen levels in the pond during daylight hours. This is where the name comes from, although because the oxygen is lost at night this is actually not an important function. They also give a very natural and pleasing look to the pond, with their luxuriant underwater foliage. Unlike marginal plants, oxygenators can't usually be grown outside of the pond in a flowerbed or similar place.
Floating plants, as the name suggests, are any plants that float freely in the water and do not have true roots. Some of these plants are also oxygenators (having fine foliage under the water, such as hornwort), while others are more like waterlilies (such as frogbit) and have all their foliage on the water surface. Floating plants are quick to put in to the pond because they don't need potting, and quick and easy to remove if they ever need thinning out. They also provide shade for the pond and, because they take up some of their nutrients directly from the water, they will compete with algae and blanketweed and help keep these in check. Floating plants, like oxygenating plants, can't be grown outside of the pond.
Deep-water aquatic plants are plants that grow on deep shelves or on the bottom of the pond, but unlike oxygenators, most of their foliage is on, or above, the water surface. This category would include waterlilies (although for convenience, waterlilies are usually listed separately in plant catalogues). Apart from waterlilies, good examples would be flowering rush or floating four-leaf clover. Aside from their attractive appearance, these plants can also provide shade for the pond (which can help with green water) and cover for fish and pond wildlife. Because they start fairly deep under the water and then emerge up into the air, they are also the best plants for dragonfly and damselfly larvae to crawl up. Like oxygenating plants and floating plants, deep-water aquatics also won't grow outside of the pond in, for example, a damp flowerbed or bog garden - they need water over their soil in order to grow.
Where should I site my pond?
Most pond plants like full sun to partial shade - not many will grow well in shade, or if they grow they will not flower, so bear this in mind when deciding where to place your pond. Sunny sites also attract more bees and dragonflies/damselflies. The pond will look most natural if placed at the lowest point of your garden or where water would collect naturally - most people know a pond placed somewhere high looks wrong even if they can't tell why it does. It's also worth considering what you would like the pond to achieve - if you want to sit by it with a cup of tea, is it close to your house? Check that you can access the pond to thin plants or clear debris when needed. If you want wildlife to benefit, will they be easily disturbed and does the pond have cover to allow them to approach unseen? And finally, if the pond is close to trees or bushes, these will shed leaves into it, which is not actually a severe problem but can smother plants and be inconvenient.
When should I plant my pond?
People often contact us asking if it is too early or too late to plant up their pond, but in fact you can plant up your pond at any time of the year. The optimum time for most potted pond plants is late winter/early spring, as this means that they go in their new pots with fresh soil and food just before they start to grow, so they get the most benefit from this. However, this is preferable, not essential, and it also depends on what qualities you have chosen the plant for. For example, if you have chosen a plant which flowers in very early spring, it may be better to get it planted up and established the previous autumn so that it is not moved and trimmed while the flowers are forming. Or if you are planting a natural pond with a soil bottom instead of using pots, it will be pleasanter to plant, the water will be more shallow, and the plants will establish faster, if you plant in late summer or early autumn when the soil and water are warm.
Floating plants are not usually available in the winter as they disappear down to small buds or shoots on the bottom of the pond and we don't sell them as we think people might be disappointed with how they look. If you want these plants, you will usually have to buy them between April and September.
All of our plants here are used to living outside in the British climate, and can be put into your pond at any time of the year. However, like most nurseries, our stock is mostly available in spring and early summer. This is partly because this is when demand is highest, and partly because we need a quiet period to propagate new stock for the following year, since we do not buy in our plants from dealers but grow them all from scratch ourselves.
How many plants do I need, and what types?
There is no 'right' way to plant your pond - like planting up a flowerbed, it depends on your own personal preferences. However, here are a few things to consider:
- For a pleasing and conventional look, aim to have one-third to two-thirds of the water surface covered by oxygenating plants and plants with floating leaves such as waterlilies, and the rest clear. Aim to have marginal plants around one-third to two-thirds of the pond edge, and the rest open. This rule is also optimum for keeping fish, which do not like either completely bare ponds, or completely covered ponds.
- Around the edge of the pond, aim to have a mix of taller and shorter marginal plants. Don't space plants evenly around the edge, as this won't look natural - plant in clumps. For larger ponds, you can buy several of the same plant and place together in one larger pot.
- Pick the plants you would like, then work out how many feet of water surface or of pond edge you want to cover. On each plant's page on our website, we suggest an approximate planting density. This density should give you a nice look for that area in two to three years. From this you can work out how many of each plant you would need. (Please remember that planting densities are just a guide, and growth rates will vary depending on how sunny or deep your pond is, what soil or fertiliser you use, where you are in the UK, what varieties of plant you choose, and, especially, on the size of pot you use. Pond plant growth rates are more variable than those of standard garden plants). For most people, budget will be the main limiting factor in how many plants they buy when setting up their pond. Don't forget to allow in the budget for any pots or soil that you might need. There is advice on choosing pots and soil on our page here.
- As mentioned above, the majority of pond plants like a position that is sunny to partial shade. If you plant them in deeper shade, they will usually survive but will not flower well or at all. If you have an area of full shade, consider non-flowering plants such as grasses or ferns like Japanese rush, corkscrew rush, or water horsetail - they will tolerate fairly deep shade and their evergreen foliage actually looks better when grown in a sheltered location. Ivy-leaved duckweed is a floating plant which does extremely well even in deep shade, and in this situation will look fresher and cleaner than it does in sun. Creeping plants such as marsh pennywort, water speedwell, and water mint, will generally produce nice-looking foliage in shade even if they don't flower. Rather surprisingly, oxygenating plants will also grow in shade, albeit more slowly. If your shade is due to deciduous tree cover and is absent in the spring, marsh marigolds, a spring-flowering plant, are a good choice. Apart from these, it may simply be a case of experimenting until you find what works in your location. Plants to avoid if you have a shady pond would be waterlilies (consider water hawthorns instead), water irises (unless you don't mind if they don't flower), and cottongrasses.
- Consider choosing plants that give different colour flowers and/or flowers at different times of the year (marsh marigolds for yellow flowers in spring, loosestrife for pink flowers in early summer, pickerel plants for blue flowers in late summer etc). Foliage is also important – try to choose one or two things that are evergreen, such as Japanese rush or water horsetail, so that the pond has some winter interest. For a balanced look, choose both tall slender plants and low bushy plants. If you are trying to hide the edge of the pond, choose plants with creeping stems and a scrambling habit, such as water speedwell, marsh pennywort, water mint, or bog pimpernel. These grow in wet soil and shallow water and also 'raft' out onto the surface of deeper water, covering it. They can also be used as underplanting (planted around the base of taller plants) to hide the edges of pots (but do thin them out if they begin to swamp the taller plant). Plant heights, flower colour and flowering times are all given on this website on each plant's page.
- The more oxygenating plants and plants with floating leaves you have, the less algae you will get. These are also the best type of plants to give cover to fish.
- If you want to use plants to encourage wildlife, the single most important thing is to choose plants from each category so that you have a range of habitats within the pond - plants with underwater foliage, such as oxygenating plants, plants with floating leaves, and marginal plants around the edge. It is also helpful to emphasise British native plants, as they are overall more likely to be useful to our local wildlife. If you specifically want to encourage dragonflies and damselflies, make sure you have some marginal plants with tall stems that the larvae can crawl up as they emerge from the pond before flying away. If you are interested in butterflies and bees, try to choose plants that are on the RHS 'Perfect For Pollinators' list, such as loosestrife or spearwort (you can search our website using the keyword "perfect" or the keyword "pollinators"). For frogs, toads, small mammals, and birds, try to place some of your marginal plants and marsh plants around the pond’s edge in such a way that it blends with the vegetation of rest of the garden, to give cover so that small animals can enter or leave the pond without coming out into the open.
Finally, remember that is it normal for new ponds to go green. There is more information on algae and blanketweed on our page here.
And once your pond is planted up, just like mowing a lawn or tending a flowerbed, it will need routine maintenance. There is more information on seasonal pond care on our page here.