Most water gardeners will avoid trees near their ponds despite the fact that trees can offer one very important benefit to a pond in providing shade. Shade is important to your pond as it will help to reduce the temperature increasing significantly on sunny summer days and will also restrict sunlight reaching the pond. Direct sunlight is a significant contributor to algal growth. Preferably a pond should only receive direct sunlight for half of the day and remain in shade for the rest.
The objection of many water gardeners to trees is that they do have a number of downsides for water, which in many people’s opinion, far outweigh the benefits that shade can offer.
So what are the down sides of trees?
Some trees, such as laburnum are poisonous. Tree roots can cause problems with pond liners; in addition, particularly deep roots potentially affect the soil structure. However, the primary problem that trees cause is quite simply leaf-fall. All of the fallen leaves can be visually displeasing and a pain in the proverbial to clear. The real issue are the leaves that do not remain on the surface and cannot easily be cleared. These fallen leaves will effectively act as compost in the pond. Whilst the effects of this ‘compost’ will not be realised over the cold winter months immediately following the Autumn leaf fall, come spring, this will fuel algal and weed growth on a potentially troublesome scale.
Whether or not you are able to control the source of problem leaf fall, it is important that you tackle the symptoms and either cover the pond with netting or actively remove leaves from the pond with a rake, or similar, on a regular basis. If you are planning to create a pond within your garden and wish to incorporate trees into your garden design then smaller species such as silver birch or willow tend to be more suited to the pond environment.