Water is a precious resource locally and globally. As part of our commitment to sustainability we carry out as little irrigation as possible. Watering is principally limited to any new plantings of annuals, herbs and trees whilst they establish. Occasionally, during prolonged dry periods, we may water some of the ornamental lawns to improve their ability to tolerate visitor pressure and large events.
We also select plants that are more able to grow in our dry climate and do not require extra watering to grow. However, at the end of a dry summer some plants may look limp and drop their leaves early. This is a natural response to dry conditions and the plants suffer no long-term harm.
In fact by limiting watering we encourage the plants to develop a deep and extensive root system drawing on water supplies deep in the soil. This ensures we grow tougher plants more able to tolerate drought. Our Dry Garden is a great example of water-wise planting.
We have invested in large rainwater tanks which collect from the glasshouse roofs and surrounding buildings. This provides our main source of water for the glasshouses. If we do need to draw on additional water this is obtained under licence from boreholes in the Garden, avoiding the need to use purified mains water.
It is our general policy not to use fertilisers in the Botanic Garden. Most of our plants growing outside receive sufficient from the soil and natural rainfall. The addition of fertiliser encourages soft, sappy growth which is vulnerable to pests, diseases and drought and leads to the excess leaching away into local water sources. We use fertiliser only when plantings have exhausted the soil or to help the establishment of new trees.
We carry out a programme of lawn care in some areas where the grass receives the greatest pressure from visitors. Fertiliser is needed to help lawn recovery and improves the lawn's ability to survive wear and tear.