As soon as the Marsh Marigolds in the pond start to poke their sunny little heads out of the water, we get customers coming in to our Water Plant Nursery eager to get their ponds up and running. However, before we can get to all the fun stuff of replanting, we do need to do some of the less exciting maintenance jobs that involve getting the pond ready for the new season.
Spring Cleaning a pond most definitely does not mean emptying out all the water and giving it all a good scrub with bleach. An established pond is filled with microscopic life that is part of the eco system that keeps your pond balanced and healthy. Maintaining the colonies of bacteria that do so much beneficial work once the weather starts to warm up is the best thing you can do for your pond. Start by cleaning up all the dead leaves in and around the pond and remove the sludge from the pond bottom. If left, the organic matter at the bottom of the pond will start to decompose and become a food source for algae blooms once the water starts to warm up. Renting a pond vacuum for a day to remove this can save you a lot of hard labor. A 25% water change is a good idea to dilute any build up of salts in the pond, treating chlorinated tap water with a conditioner as you add it. Also, don’t be tempted to scrub off the green coat that forms on the sides of the pond. This is actually a beneficial algae that is packed with beneficial bacteria. Check the pond perimeter for rocks that may have become dislodged or liner that may have may have slipped out of place.
Turn on your pump, and check for frost damaged lines or cracks in the pump housing. Mark the water level and monitor for a few days to ensure that you have no hidden leaks. Rinse filter pads by swishing them in a bucket of pond water; again, spraying them off with tap water that’s chlorinated will kill all those little beneficial bacteria that are growing there.
Once all the grunt work is done, the fun stuff is rediscovering all the water plants that have over-wintered in the pond. Check pots for signs of growth and determine which need to be divided. Plants that still have growing room in the pots can simply be fertilized with an aquatic pond tab and placed back in the pond. Spring is an excellent time to divide and fertilize the summer blooming marginals and grasses. Plants that are pot bound will, like any perennial, benefit hugely from a good ‘chop and repot’ and as pond plants are nearly all vigorous growers they will usually fill their container in one season. A good stomp on the pot will usually dislodge them, but sometimes you just have to sacrifice the pot by slitting it with your pruners. Although not all pond plants have the same growth pattern, a good rule of thumb is to take the outside growth around the perimeter of the pot and discard the rest putting no more than 1/4 to 1/3 of the old plant in the new pot. I like to divide the really early blooming marginals like Marsh Marigold and Irises in the fall to prevent disturbing the flower buds the following spring. Still, if you didn’t get around to it then, there is nothing as forgiving as a water plant, you could chop them up mid-summer and they would still bounce back.
Of all the pond plants, lilies benefit the most from a little care and food. Although it can be hard work hauling out an overgrown lily for repotting that hasn’t seen the light of day for a few years, your efforts will be rewarded with much more frequent and larger blooms. Water lily rhizomes typically grow along the surface of the soil so wide shallow pots work well. Here at the nursery we use large hanging baskets to pot them up in. The shape works well and the hook is great for pulling up the plants to fertilize them during the season. If the hook protrudes above the water level it can be tucked out of sight by hooking it under the rim of the pot. When repotting up an old overgrown lily, much of rhizome can be discarded. Use only the new healthy outer tips, cutting these off with a sharp knife and potting them up with the cut side close to the edge of the pot. This will give the rhizome the most room to grow along the top of the soil. Add a long acting fertilizer spike and top with an inch or so of small gravel or sand. Fertilizing is really the key to achieving multiple summer blooms as well as moving them up to the top 3 feet of the pond. The water is warmer at the surface as well as the light will penetrate to the lilies earlier. If need be stand them on an upturned pot.
Although it’s satisfying to over-winter your hardy pond plants, don’t be too disappointed if the occasional one doesn’t make it. This gives you the opportunity to try something different. There are always so many new and exciting plants that become available.