Maidenhead Aquatics Topical Tips - May 2010
Well, the barbeque is sheltering from the rain and the mornings have been cold. Weathermen are looking apologetic and the weeds are growing like crazy – it must be summer!
Outside
As sunshine warms the depths of the pond, plants start back into life. Lilies are slowly sending new growth to the surface and oxygenators are putting on lots of growth. Like any form of gardening, water gardening requires a knowledge of when to do nothing and when to get your hands dirty. Generally speaking, pond plants have much in common with the hardy perennials in your flowerbeds and will happily grow for years with minimal attention but share a need for nutrients and the right position. Like those hardy plants they will grow and flower far better if they receive a bit of attention.
Depending on their preferred depth, pond plants are divided into a number of groups:
Marginal plants dip a toe in the water and range from being species that will grow in a moist flowerbed to types that tolerate up to a foot of water over their crowns. Some, such as Siberian Iris (Iris sibirica) like to be wet in the summer and drier in winter, whereas the dazzling Lobelia ‘Queen Victoria’ will fare better if submerged, away from the winter weather. Marginal plants often include the flowering ‘star performers’ of the water garden and in a dry summer will add a verdant lushness that is absent elsewhere. Many of these are improved forms of native plants or their close counterparts from Asia or North America and can be great for wildlife. Marginal plants can be used to scramble between the land and water, thus hiding the liner and disguising the artificial nature of your pond. When growing in the soil surrounding the pool, these plants are often referred to as ‘pond side plants’ – just make sure that the soil next to your pond remains moist enough to satisfy their needs.
Deep marginal plants are a fine example of ‘doing what it says on the tin’ and include some terrific choices such as Water Hawthorn (Aponogeton distachyos) which flowers through the cooler months. Some great native plants also fall into this category such as Water Fringe (Nymphoides peltata) and the imaginatively named ‘Pond Weeds’ in the genus Potamogeton. All of these will flower and add greatly to the value of a pond for wildlife and human observers.
Water Lilies are the real class act of the water garden and thanks to the artist Monet, are an almost essential purchase. Bred from a number of pure species, these plants are extremely versatile but all hate shade and having their leaves splashed by fountains or moving water. Lilies are greedy plants and flower best when re-potted regularly in nutrient rich aquatic plant compost. Water lilies come in four main colour groups – white, yellow, pink and red (deeper pink!) and in various growth forms from miniatures such as the yellow ‘Helvola’ to enormous plants suitable for lakes such as ‘Albatross’ or the native species Nymphaea alba. When purchasing a lily, try to think of it in the same way as you would a shrub or tree – if it takes a long time to grow it’ll spend a long time in the nursery. This is why pygmy and medium water lilies can look so expensive compared to the big boys which will be bigger, cheaper and a lot more work to keep on top of! The right lily will bring years of ornament rather than hours of pruning and dividing in cold, wet mud. When adding a new lily to your pond, make sure that at least some of the leaves/pads are on the surface, otherwise the plant will drown. Lower your new purchase gradually to the appropriate depth or buy a plant when it’s dormant and looking like an expensive basket of mud, that way the new leaves will grow straight to the surface. As I mentioned above, site your lily away from fountains and waterfalls and if you have a shady, deep or moving situation, consider the native Yellow Pond Lily (Nuphar lutea) or one of its smaller relatives. These ‘pond lilies’ are generally sold as deep marginals and are tough, cheap and undemanding with large buttercup flowers.
Oxygenating plants are one of the most misunderstood plant groups available and although essential can be a real problem if not used properly. The real power of these plants is their ability to reduce the nutrients available for algae such as blanketweed or greenwater. They do produce oxygen but at night they consume it in equal measure, so a balanced pond without a pump can have fatally low oxygen levels at the end of a warm summer night. As few of us are in the garden at dawn in the summer this is a common cause of fish death which can go completely undetected, as by the time a few hours of sunlight has shone on them, the oxygen levels have returned to normal, leaving a real mystery that normally gets blamed on disease or pests. Use oxygenators to control excess nutrients and add wildlife habitat but use a pump if your pond is home to a significant population of fish. When adding ‘bunched oxy’s’ to the pond, make sure that they’re placed in either shallow or clear water. A plant at the bottom of a pea-green pool won’t receive enough light to grow strongly and don’t forget to reward your hard-working plants with a container and some compost to get the best from the more choice varieties.
Floating plants are a mix of hardy species such as the native Frogbit (Hydrocharis morsus-ranae) and Water Soldier (Stratiotes aloides) combined with the tender plants best thought of as summer bedding for your pond – Water Hyacinth (Eichornia crassipes) and Water Lettuce (Pistia stratiotes). Natives will rise and fall depending on the season whereas the tender floaters will grow like crazy until killed by the frost, when they should be removed and placed on the compost heap. One plant worth a mention is Water Chestnut (Trapa natans), which shares its common name with a sedge used as an ingredient in oriental dishes. Both plants produce edible overwintering forms.
Now is a good time to divide and re-pot aquatic plants but avoid dividing iris until after they’ve flowered. Select your plants and choose a pond basket that they are unlikely to outgrow in a season, as vigorous plants will often grow through the sides of the container making further re-potting a harder task next year. Modern baskets are designed with very fine mesh sides that will hold soil, making the old technique of lining with hessian a thing of the past. Ensure that you only use specific compost formulated for aquatic plants, as other alternatives can lead to contamination with chemicals which can be harmful to fish or pond life, or an excess of nutrients which will fuel algae growth. Fill the planting container to within an inch or two of the top with compost, leaving a central well in which to place your plant. Without disturbing the roots too much, place your plant into the centre and back-fill with compost before topping the basket with a layer of gravel to prevent soil washing out or fishes digging in to the roots. If you have large goldfish or carp of any size, consider using a layer of pebbles. In the case of tall plants such as reeds and rushes, adding weight to the container will help to make them more stable and less likely to topple over.
In the constant fight to avoid algae plants can be useful allies, providing shade and absorbing many nutrients. Once all danger of frost has passed, add one or two of the tender floating plants to your pond to provide shade and balance. After all, Water Hyacinth is used in sewage treatment plants in tropical countries for very similar reasons. As these plants will grow and develop quickly you may notice that they lose their glossy green sheen and look rather anaemic and yellow. To keep these and oxygenators growing strongly, add an iron-rich liquid plant food to your pond to make sure that they keep fighting the blanket weed and green water algae that can thrive when essential elements such as iron are too low for plant growth.
If the weather returns to seasonal norms, we should see the start of spawning behaviour in ponds containing goldfish. As temperatures rise to 15c, male goldfish will develop a white ‘spawning rash’ on their cheeks and will drive the fuller-bodied females through the plants, leaving a cloud of fertilised eggs. Things can get a bit rough for the females if they are outnumbered by eager males and often if you have a preference for slender fishes with long fins, you can find yourself with some rather harassed females. To prevent this situation, consider buying some likely looking mature female fish to swell the numbers and if you select chunky individuals with shorter fins there is a great chance of them being females. As only males develop the spawning rash they should be easy to tell apart. Make sure that you have plenty of weed growth for egg-laying and if not, spawning mops or filter brushes can be pressed into service. As goldfish produce thousands of eggs, a healthy pond will often be home to generations of goldfish resulting form home breeding – more on the life history of goldfish next time!
Inside
As the sun shines and the smell of cut grass lures us away from our aquaria, it’s a good time to put in some extra effort with water changes and filter maintenance to see you through those inevitable moments when spare time is at a premium. Make sure that your external filter is nicely rinsed and free from large amounts of solid waste and check that your water change regime is kept up to date. A neglected tank is a lot of work to fix compared to the regularity of keeping a healthy tank looking good.
How well fed is your aquarium? Everyone knows that fish need feeding and indeed it’s one of the trickier areas of husbandry to get your head around but what about your plants? In the same way that a bare-root rose will fail to thrive in a bucket of gravel, aquatic plants become no more than a bunch of weed without trace elements and fertiliser. Even if you only buy a plants to give your goldfish something to nibble on, you’ll see a difference if you regularly add the right plant food to your tank. Previously we’ve discussed lighting and how bright lights give you the widest choice of plants but no matter how modest your lighting fixture, there is normally a species which will thrive. Look for slow-growing plants in low light, such as Crypts (Cryptocoryne sp.), Anubias or Java fern (Microsorium) which are undemanding and well worth the investment. Start with well-fed plants in a modest aquarium and who knows where that will lead – at the very least to a more natural looking environment for your fishes.
We know that keeping a marine tank can involve more algae control than a freshwater aquarium and now we’ve called in some reinforcements! Look out for the improved signage in your local marine-specialist store detailing the advantages of some of our ‘clean-up crew’. Snails, hermit crabs and a few more unusual creatures are now available to give a helping hand, or should that be claw?