Grey Leaved Plants, Dry Soil and Water are synonymous with dry climates. The grey leaves on plants are covered in small upright hairs that trap moisture next to the leaf thereby reducing the amount of water the leaf loses. A leaf will evaporate water from its surface as it gets swept by any breeze, which sucks the water away from the leaf. By having a ‘forest of hairs’ a physical barrier retains water next to the leaf surface.
Grey leaved plants are generally found in very dry places, like a desert, so they need to trap any available water as there is no indication when the next lot of water will arrive. When Bob was a Jackeroo in Far Western Queensland, west of Quilpie, he experienced only 6 inches (150 mm) in 6 years with sometimes half an inch (12mm), then nothing for another 2 months. In this climate, all the native plants were grey leaved, including many in people’s gardens, as experience had taught the owners that grey leaved plants survive dry conditions.
Dry Soil Repels Water
I often tell people that very dry sand or soil repels water. If you put a drop of water onto dry sand at the back of the beach, the water will just sit there. BUT if the sand is even slightly moist, the water will immediately go down into the sand.
Exactly the same situation occurs with your garden soil or potted soil that has dried out. The dry soil will repel the water. In a pot of dry soil, the potting mix will shrink away from the side of the pot so when water is applied the water comes straight out the bottom BUT the potting mix is still dry.
If you have super dry soil you can help to re-wet it by applying a wetting agent. In most cases you can use a small amount of washing up liquid mixed in with the water to wet the potting mix or soil in your garden. This will break down the water surface tension letting the soil or potting mix take in some water
For those people with a Compot, the contents of the Pot will be moist, including the surrounding soil as moisture is constantly leaching out (assuming you are continuing to feed your Pot). So you will not have super dry soil to try and re-wet. However if you pot dries out and the surrounding soil dries out you will get hydrophobic conditions between the walls of your Compot and the soil .
The same remedy is used to re-wet the soil by putting some dishwashing liquid in the water with ALL your waste. The dishwashing liquid breaks the surface tension of the dry soil allowing the liquid and nutrients to leach into the surrounding soil.
Of courses it is far better to avoid super dry soil by continuing to water your garden, prevent evaporation with a mulch or suitable cover and or top up your Compot with water and waste. This will keep the surrounding soil moist, especially if you are collecting all your waste water with your kitchen scraps.
Covering your soil
Cover your soil with straw, hay, leaves, mulch, grass clippings (I lover shredded bamboo mulch) or whatever to help retain moisture and plant grey leaved plants that don’t require much watering such as Lavender, Salvia argentea (Silver Sage), Echeveris, or Kalanchoe Beharensis
Today’s Did You Know…?
It is a lot better to have water applied to soil or pots with a regular light watering application. When conditions become dry, and we then get rain, it usually comes in a heavy downpour all at once. If the soil is dry the water simply runs off the dry soil taking a lot of topsoil with it while very little will actually penetrate below the surface soil.
The same applies when you are watering pots or garden soil. It is better to apply the water gently so that it penetrates below the surface. If watering at long intervals then water a lot all at once. With water penetrating deep into the soil the plant roots will go deeper to seek out the water rather than staying in the topsoil where the soil dries out faster. This way you will obtain a greater benefit from your watering, use less water in total and lower your water bills. A Win Win situation.