Stoep Harvest part 7: Intelligent Watering

So far in the Stoep Harvest series we have covered how to plan your organic vegetable garden, increase your soil health, plant your crops and make compost. We have also discussed the benefits of mulching and how to weed and prune in the small-scale vegetable garden. After a few months without an article, it’s time to begin the series again. In a prelude to next month’s article on what to plant in winter, this article looks at some intelligent tips for watering.

In the Western Cape and other Mediterranean climates we experience hot, incredibly dry and often very windy weather conditions. The hot dry wind rapidly removes moisture from the ground. These are not easy conditions to grow vegetables in. With the strong winds, my sweetcorn and mealies have been growing in ‘italics’! If you are based in the rest of South Africa, it is now your wet season and these suggestions will come in use as your dry winter approaches.

As we all know, life is dependent on water. Our body mass is made of 60% water (our lungs are as high as 90% water!). For fruit and vegetables, it is also an incredibly high proportion:

• Apples are 84% water
• Broccoli 91%
• Cabbage 93%
• Grapes 81%
• Lettuce 96%
• Strawberries 92%
• Tomatoes 94%

Even a hard potato is 79% water. This means that vegetables and fruit are predominantly water, indicating how critically important it is that they receive sufficient water.

Many people ask me how much water should be given to their plants. It is a difficult question to answer as it depends on a number of factors. Firstly, the age of the plants needs to be considered. Younger plants, as with humans, require more care and attention. Seeds and young seedlings grow best when the ground is permanently moist, so a regular showering of water works well. Older plants are harder and can cope with less frequent watering.

Secondly, the type of soil has a significant bearing on watering. Sandy soil quickly absorbs the water and therefore feeds the roots immediately. If you have sandy soil, it is best to water for shorter periods, more frequently. Clay soil absorbs water slowly and should therefore be watered slowly and less frequently. If you are fortunate enough to have loam soil, then your situation would fall in between these two extremes.

Another question I am asked is what the best time to water is. My personal preference is to water first thing in the morning, however, I believe there is no right or wrong for this issue. Watering in the morning before the heat of the day minimises water loss to evaporation. The water will seep into the soil so that the plants have access to water as the day gets hotter.

Watering late afternoon and early evening also avoids evaporation and I often do this on hot days to replenish the plants. However, a caution is that some plants will suffer if they are wet and the night air is cold. This can cause rot and disease, particularly with the tomato and pumpkin families.

Water Saving Tips

My first water saving tip is always to emphasise the need for mulch. I covered this in The Stoep Harvest Part Five: Mulching, back in October. By using mulch on exposed soil, evaporation can be decreased by approximately 40%. This simple solution essentially halves your water bill!

Another water saving tip is to design your garden intelligently. The small round ‘rose’ hosepipe spray covers a circular area around 4-5m diameter. A clever garden design, therefore, is to build a circular vegetable garden that will be covered by the spray. The rose spray should be placed in the middle of the circle where it can water every area instantly. Drought tolerant and indigenous plants can be placed around the edges of the garden to fill any odd corners.

Carrying on with intelligent design, it helps to save water by planting taller summer crops on the north of the garden, which provide shelter to weaker smaller plants. A good example of this is to plant tomatoes, mealies, and sunflowers on the north. In the mottled shadow, plant lettuce, rocket, spinach and other plants that do not like too much hot sun. You can also plant butternuts and pumpkins on the shadier side - they will fill the gaps amongst the taller plants and their big leaves act as natural mulch.

Lastly, if you have a fitted irrigation system, drippers or small sprays are more economical than big sprays. Particularly in windy areas, the bigger sprays lose a huge amount of water. On our smallholding we have recently replaced our single large spray with numerous smaller sprays.

In conclusion, watering your garden correctly is of great importance. Start by designing your garden intelligently and make use of natural solutions such as mulch. Adjust your watering according to the season, to your soil and the age of your plants. And always observe how your garden responds to the watering and make any necessary adjustments. It is a process of learning and adapting to the ways of your garden.

February Planting Table

• Western and Southern Cape: beetroot, broccoli, cabbage, carrot, cauliflower, lettuce, potato, radish, swiss chard.
• Inland: beetroot, broccoli, cabbage, carrot, cauliflower, leek, lettuce, parsnip, potato, radish, swiss chard, turnip.
• Coastal KZN: beans, beetroot, broccoli, cabbage, carrot, cauliflower, cucumber, eggplant, lettuce, onion, pepper, radish, swiss chard, tomato, turnip.

By Sam Adams

Sam runs Living Green, an organic food gardening company in Cape Town.