Top tips for looking after your water garden

Following a few simple guidelines can simplify pond care and help prevent problems.

• Do not use chemical fertilizers or pesticides, as these can be detrimental to pond life and water quality.

• Stretch netting over ponds in the autumn to catch falling tree leaves (spread these among bog garden plants) and prevent them from sinking and fouling the water.

• Clear dying plant material from the pond, but do not cut down dead marginal stems until spring as they protect dormant roots and supply wildlife cover.

• Remove tender pond plants in autumn for overwintering in a bowl of water indoors or somewhere frost–free.

• Mulch bog gardens and beds of marginals with garden compost every spring to control weeds and supply slow–release nutrients.

Green water

Ponds often turn green in late spring as increasing warmth and sunlight fuel the rapid growth of aquatic algae, which feed on the dissolved minerals that often arrive in water draining from the surrounding soil or in tap water used to top up levels.

You can reduce the problem by including plenty of submerged oxygenating plants, shading part of the surface from sunlight with floating foliage, and stocking the pond with snails and freshwater mussels, which feed on algae and filter the water.

More filamentous algae can develop into green mats of ‘blanket weed’. Do not treat this with chemicals; it is easily dredged out with a lawn rake or twisted on to a rough stick for adding to the compost heap, or you can sink barley straw pads in the water as a natural form of discouragement.

Top tips for preventing green water:

• Clean, service and store pumps over winter, and replace with a pond heater where fish need ice-free conditions.

• Vigorous plants in baskets will need dividing and replanting every three to four years to rejuvenate them and prevent them from spreading beyond their confines.

• Thin floating plants if they cover more than two-thirds of the surface, and fish out blanket weed and other algae before they can take over.

Feeding plants

Established deep–water and marginal plants may need feeding when growth resumes in spring because nutrients easily leach from the soil or compost into the pond. Feed them cautiously to avoid enriching the water further and stimulating algal growth.

Use a slow–release fertilizer applied direct to individual plants, and where possible choose one that is seaweed–based. Do not over–apply, and never feed floaters and submerged plants.

This is an extract from 'Water in the garden' by Andi Clevely.