Thirsty Trees

Rian and Cian soak the garden.

February was Singapore's driest month since 1869 and the drought looks set to continue. Our trees and other plants are visibly suffering. Wilting leaves are a common sight and the main playground is carpeted with fallen brown leaves every morning. Our landscape gardening staff, led by Andy Tan, have been busy watering plants around the College buildings, but they are overstretched. For the past couple of weeks the Middle School “40 Trees for 40 Years” group and the cross-grade Campus Gardening group have stepped in to help.

Tobias keeps the jungle green.

So what effect does a long dry spell have on trees? Wilted foliage, yellowing leaves and leaf drop are some of the obvious symptoms, but there are other, less visible effects. One of these is the closing of tiny openings on the underside of the leaves. Known as stomata, these openings allow the tree to release water vapour in a process called transpiration, but during a drought the stomata shut down to conserve moisture. If this happens for an extended period, transpiration ceases altogether and then photosynthesis cannot occur. This, of course, means that the tree stops growing.

Kylie is a role model
with her sunhat.

In temperate regions (not in southeast Asia) the annual growth of trees produces a ring. During a drought, this ring is very narrow. Consequently, scientists (dendrochronologists, if you want to learn a new word and impress your friends) can examine the growth rings of old trees and learn about rainfall patterns decades, or even hundreds of years, ago. 

The “40 Trees” and Campus Gardening groups have focussed their watering efforts on the gardens bordering the Main Playground and the Herb Garden beside the Infant School. They have learned that a light sprinkling is not adequate - mature trees need slow, deep watering weekly. Ideally, the younger trees planted out by the Rainforest Nursery GC should receive more frequent watering, but many of these are far from taps. If the drought persists, a rescue operation may become necessary.