Kim Wilde answers your gardening questions.
Is it OK to put water used for washing dishes on to plants?
Garden plants can actually flourish on washing-up water (grey water), as they respond to the phosphates in it. Use it in different parts of the garden every few days, to allow dilution by rainfall or fresh water irrigation. Avoid contact between grey water and plants, watering only the soil. Also, avoid using on acid-loving plants. The quality of grey water depends on what you put in it, so use biodegradable cleaning products such as Ecover.
I would like to plant a group of silver birches, if I can be confident that they won't dominate the garden. I was very taken with the examples in front of Tate Modern.
The trees outside Tate Modern are Betula costata and B. albosinensis. Their 'coppiced' appearance is achieved by taking out the main leader stem and allowing the smaller shoots to develop into a multi-stem tree. This takes a long time. More common is when three single-stem trees are grown as a cluster, developing into the same root ball. B. utilis var. jacquemontii is usually used. This has dazzling white, peeling bark, and can take a long time to reach its maximum height of 10m. Growing a group of any trees close together will affect their eventual size, because all compete for the same light, nutrients and water. Betula thrive singly or 2-3m apart in groups of up to five. They tolerate a wide range of soils and conditions, although B. costata requires fairly sheltered conditions.
I have grown tulips in pots. How should I store the bulbs for next year?
Leave bulbs for at least six weeks after they flower and let the foliage die down; it helps build up the bulb for next year's display. Select only the best bulbs and clean off any soil, as well as removing old foliage and dried roots. Once the bulbs are clean, dry them in the sun and dust with a fungicide from the garden centre. Dry bulbs can be stored in a paper bag or cardboard box: label it and keep in a cool, airy place, such as the garage. Check once in a while and remove any that are rotting.