by Lizzie Bennett
Albedo: Albedo is the amount of reflectivity of an object. The amount of incoming electromagnetic radiation is compared to the amount of radiation reflected by the object.
Think about going out on a bright summers day in a black tee shirt and jeans…and then think about going out in a lighter coloured outfit.
You don’t just feel cooler in the lighter colours, you actually are cooler, and I’m talking temperature not style!
Vegetables need light and a certain amount of heat, but the high summer temperatures in places like California and Texas is often too much for tender plants. By changing the albedo rate your veggies will have a fighting chance. The higher the albedo the more heat is reflected from the object back into the air. This not only prevents scorching but reduces evaporation, keeping more moisture in the soil where your plants need it.
Whilst I’m talking about watering, surface watering in these conditions is a waste of water and often a waste of time. The water needs to be down by the roots, and there’s a couple of cheap and easy ways you can do this.
Putting a few holes in an old hose, filling it with grit and burying it a few inches under the soil delivers the water to where it’s needed without losing up to 70% of it to evaporation. The grit prevents the hose silting up.
Digging a hole about the size of a soda bottle and upending the bottle in it, a couple of holes in the lid, will also deliver water to the deeper levels of the soil.
Right, back to albedo, there are several ways to increase the albedo rate and take the heat off your plants:
- If you have a couple of small beds a simple sunshade, a sheet of lightly coloured fabric can be stung up to provide shade.
- Growing in raised beds with the sides painted white is will also reduce the heat that builds up in the soil behind the walls.
- For larger plots the easiest way is to change the colour of the soil surface. Light coloured stone or gravel is ideal and will prevent the delicate roots of plants from suffering heat stress and over-drying.
- Planting fast growing, light colored, drought resistant trees at reasonably regular intervals is also a good plan. The dappled shade they provide and their light coloured leaves reflect sunlight, lowering the temperature. Eucalyptus trees have evolved to deal with the Australian climate. If they are present in great numbers their high oil content can feed wildfires but they are commonly used for shading in Australia without issue.
- Many eucalyptus, such as gunnii, grow 3 feet a year, and there hundreds of others that grow just as fast, as well as a few dozen that grow even faster in the right conditions. It’s a hardwood which has been used for thousands of years by indigenous people for shields, weapons, furniture, medicinal purposes and firewood. The quality of the wood is such that in Western Australia some varieties are known as Swan River mahogany. They put down very,very deep roots and extract moisture far below the level that vegetables roots extend.
- Acer (Maple), Ash and to some extent Chinese Elm are all drought and heat tolerant and will provide shade for many years. The reason I prefer the eucalyptus is its speed of growth and the fact that its branches are wider spaced giving dappled rather than full shade, which suits a wide variety of food plants.
- Finally, just for your information eucalyptus gunnii survives well down to -12, I know this because mine did on many occasions when I lived in a colder climate.
Thinking outside the box sometimes provides relatively simple solutions to what feels like an overwhelming problem.
About the author:
Lizzie Bennett retired from her job as a senior operating department practitioner in the UK earlier this year. Her field was trauma and accident and emergency and she has served on major catastrophe teams around the UK. Lizzie publishes Underground Medic on the topic of preparedness.