Surviving Drought:

Storing water

Many plants manage to survive droughts by storing water. These plants are called succulents because they have many cells in their roots, stems or leaves that can store water.

When it does rain, these cells absorb a lot of water and store it in tiny sacs inside the cells called vacuoles. The plants swell up and become plump. Once the rains are over, the plant can continue using the water it has stored in its cells.

Most succulents have shallow roots. When it rains, they can quickly absorb water from the upper layers of the soil before it evaporates. During droughts when water is scarce, many animals get their water from eating plants. Most succulents contain chemicals that make them either poisonous or distasteful to stop thirsty animals eating them. 

Succulent leaves

• Plants like the Sour Fig (Carpobrotus edulis) and vygies (Lampranthus filicaulis) store water in their leaves.

• If you squash a Sour Fig leaf, the sap that drips out is the water the plant has stored.

• Unlike most leaves that have only two sides, the Sour Fig leaf has three sides. This triangular shape helps it to swell and shrink as it absorbs and loses water during the year.

• To prevent thirsty animals eating its leaves during the summer, the sap of the Sour Fig contains chemicals that make it very bitter.

Succulent stems

• The Medusa's Head (Euphorbia caput-medusae marlothiana) is an example of a Euphorbia or Melkbos plant. It stores water in its stem.

• Euphorbias store water in the form of a sticky, milky sap called latex. This milk is poisonous and can burn. Do not taste it or get it on your skin or in your eyes. The latex prevents animals from eating the plant to get its moisture. Strangely, the Steenbok is able to eat this shrub that would poison other animals!

• The stem of the Medusa’s Head has a bumpy surface that allows it to swell and shrink as it absorbs and loses water during the year.

• In addition to storing water, most Euphorbias have very few leaves. This also helps them to lose less water.

• Look for the plants mentioned in this section on the poster and key.
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