It is that time of the year again, spring, and your water plants need to be divided or re-potted and fertilized. For the water garden it is best to keep plants in submerged containers. Planted in the bottom soil, most aquatics would either take over the pond or get choked out by more aggressive species. Container planting allows plants to be easily moved and confines invasive species. This month's topic is how to pot up aquatic plants. There are several types of aquatic pots available. Keep in mind the most important goal is to confine the soil. Because spilled soil will dirty your pool and give nutrients to the algae. The mesh type containers are called "laundry baskets". These containers are available in square or round styles. They have to be lined with untreated burlap. This has to be done to keep in the soil and eventually the roots will find their way into the pond. This makes them unattractive to me. I personally prefer containers without holes. For the water gardener who keeps a "clean" pond, few nutrients are available to the wandering roots of an aquatic plant outside the container. Consider that if a pond is free enough of excess nutrients to prevent the growth of green water algae, how many nutrients can be present for higher plant forms? Most aquatic plants such as water lilies or marginal plants grow from water saturated soil from which they get their food. They need to be fertilized with special pond fertilizer tabs. These are available in aquatic shops or some hardware stores. Water lilies need to be fertilized once a month for best performance. As it is not practical to pull the plants out of the pond to fertilize them once a month, it is best done with a long-term fertilizer. All lilies from my nursery will have this kind of fertilizer stick. These sticks are not available here in the area; they need to be ordered from one of the catalogs you find on my website. Standard terrestrial pots can also be used, as long as the drainage holes are closed off and the container is wider than high. One gallon nursery containers are not practical because they are higher than wide, which makes them top heavy. Using black or dark green containers lessens their visibility. The most commonly recommended soil for planting aquatics is "heavy garden loam". This term can mean different things in various parts of the country. Here our heavy clay mixed with play sand is just right. Do not use builder's sand it is usually dirty and needs to be washed. Do not ever use potting mix. It is too light and full of nutrients. Being light, it can float out of the pot and having nutrients it will feed the algae and cloud the water, never add compost for the same reason. There are aquatic soils available, they are very expensive and I don't like to work with them. To pot up, fill some soil in the container and place your fertilizer tab, add some more soil and place your plant, fill the container with soil about 2 inches from the top, than add a layer of sand and a layer of pea gravel to finish it off. Gravel is available at Dreezdens, Buffalo Soldiers Trail, for $ 2 a 5 gallon bucket. The gavel will hold the soil in place and also functions as biological filter because it gives the nitrifying bacteria a place to hold on to. By the way the gravel needs to be washed well before using it. If you have Koi fish in your pond it might be good to have a layer of bigger stones on the pot to prevent up rooting, the bigger the fish the bigger the rocks. Water lilies should be placed on the bottom of the pond, no deeper than 3 ft. Marginals do better with no more than one to two inches over their crowns. Water plants need to be divided and the soil replaced at least once a year, keep in mind water plants are heavy grower and most of them are invasive. |
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