Water garden calendar, April

The wildlife pool at the beginning of April seems very quiet. N.B. The net has been removed.

The pond in April is beginning to come alive. Here in the Webbs of Wychbold Japanese garden, many plants are fully into their spring glory by the end of the month.

Machinery and Sods Law walk hand in hand through the history of our tormented lives, and pond pumps, filters and U/V clarifiers are that sort of machinery. Waterfalls and fountains can be included as accessories to pond pumps. If you didnt put your pool or pond to bed at the end of the year by cleaning and checking the submersible pump, the filter and the U/V then youve only got yourself to blame when you switch it on and it doesnt work! So if you didnt do it then, and even if you did and you seemed to have escaped the hand of fate for this year, still give it a thorough check out.

Check the trip switch on the outside electrics first. Then have a look at the pump.

Spring clean the pump. This is the old style sump pump.

This Hozelock Titan pump has been dismantled to check the impellor. Note that the outer casing has an adjustable grill for the inlet of water to the pump specifically for the protection of wildlife.

Take it apart and give it good clean. If it is one of those cylindrical sump-pump type pumps with the open grill round the bottom and youve been running it for a short while, you will probably find it gunged up with tadpoles. Not a pretty sight. (You might want to devise a sort of prefilter with a strip of open mesh foam or a couple of those washing up spongs split open and tied round the pump intake grill).

Work your way to the U/V and change the bulb. From thence to the filtration unit and see what delights have been nestling in that throughout the winter. The very least it will need is a back-flush. If you havent got this facility i.e. a bottom drain at the back of the filter box in a gravity filter or a modern pressure filter, you will have to get all the filter medium out and give it a quick wash through, with rain water or pond water. I have a leaky bucket that is almost like a colander that I rinse the filter medium in.

If the filter has been working fairly non-stop through the winter you will be surprised at how dirty it is. This was because the biological activity in the filter would have slowed to virtually nothing at low temperatures, but the filter would still be working effectively mechanically. This would mean a build up of sludge without it being digested.

If you have a stream or waterfall, check this for leaf litter and silt build up. There is often a dry spell in April, which is a great time for spotting leaks and overspill in the surrounding soil. People with preformed waterfall units will need to check that their units are still well supported underneath as they very often get undermined in heavy rain. If the stream or waterfall has been constructed on made up ground, before the undergrowth around the stream build up, check around the inlet to make sure there is no overspill or consolidation that has caused the back of the waterfall to drop down.

Apart from maintenance (or lack of it) problems, the main thing is the blanket weed, spirogyra, cotton weed whatever. It is the candyfloss type of algae that gets a start on the rest of the plant life in the pool and just loves that bright sunlight. It also loves water with a high pH. So if you reduce that with proprietary chemicals, although I have a client experimenting with vinegar, you will find that any other treatments are a lot more effective. Most aquatic suppliers have some remedy. Barley straw is effective for certain periods as long as the water is very well oxygenated and the straw is changed at regular intervals of not more than 10weeks. Certain of my colleagues tell me that Barley straw actually pollutes the water in order to clear it and that there are compounds on the market that remove nutritional elements that blanket weed in particular thrive on. Phosphates are the main culprits and many of these come from run off from the surrounding soil. Once again these remedies wont work in situations where the pH is above 8.5. When the product comes at well over 30 a tub for one seasons treatment, you dont want to be effectively pouring money down the drain just because your pool has got hard water. They also will not work if you are regularly topping up the pool because of a leak. Not only are you adding more pollutants, nutrients into the pool for the algae to consume, the chlorine in the water is damaging the microflora (bacteria in the pool) and thus undermining the whole balance of the environment.

Plants of the month.

On the margins

The Marsh Marigolds (Caltha palustris and all the species and varieties) are still at it. Brilliant.

The Water Forget-me-not (Myosotis palustris) is also making waves of blue around the pond.

Also there is the Golden Club (Oronitium aquaticum)

In the deep water

The old South African ingredient for a Malayan style stew, the Water Hawthorn, Aponogeton distachyos, is flowering its socks off. This is an amazing plant that comes up from unlimited stygian depths to perform at the most ludicrous times of the year. It still thinks its down in the Cape, nestled in the Fynbos looking up at Table Mountain.

Happy in the margins or the bog garden the American skunk cabbage, Lysichiton amaericanus, here at the fabulous Merriments garden in Kent.

Thinking of bogs, the American Skunk Cabbage is up. Lysichiton Americanum, it looks almost too alien for our water gardens. Its big spathe of a flower is like a starters flag in a motor race and a timely reminder that things have got into gear and now were cruising!

Seasonal Tips

If you are contemplating a major clean out, this is one of the best times to do it, although personally Id have done it before the tadpole explosion. If you do it, rescue as much wildlife as possible and leave any debris draining away on the side over night so that beasties can make their way back into the pool. Also treat any fresh tap water with pool conditioner.

Even though the plants will be coming into new growth. There is still time to divide and replant if you want. You can also feed with a slow release pellet in each basket.

Pool lights can come back out now.

Check the water quality. Many serious fish keepers will do a partial water change of up to one third in order to dilute any build up of salts and chemicals they may have been adding.

As the water temperature gets nearer to 10C (50 F) you can start feed the fish their normal food. A bit of live daphne would be a special treat or chopped worms, yummy!