There’s a saying that we can live four weeks without food, four days without water, and four minutes without air. Today I’d like to talk about water, or the lack of it, and how it affects plants.
My friend Peggy Dyson and I were sharing a cup of coffee at her house the other day when the topic of weather came up. Peggy, who arrived in Kodiak in the 1950’s, knows a few things about weather. For many years, she broadcasted the marine weather to mariners from her shore-based, single sideband radio using the call sign, WBH-29.
I asked her if she remembers a hot and dry summer like this one. Peggy sipped her coffee and gazed at the laminated nautical chart of Kodiak Island that covers her kitchen counter.
“I think it was August of 1972,” she began. “The canneries were processing shrimp and salmon, but they were running out of water. Of course, the reservoir didn’t have the same capacity as we do now.
“The crab boats cleaned out their tanks and headed over to Long Island. The City of Kodiak helped rig up a hose to a lake. The boats filled up with water and came back to town. They went back and forth.”
Plants, like seafood processors, depend on water for basic operations.
HOW DOES WATER MOVE THROUGH PLANTS?
Unlike animals, plants lack a pump like the heart to move fluids in their vascular system. Instead, water is passively driven by pressure and chemicals gradients. Did you get all that?
Let me put it another way. Simply put, water moves toward areas that contain less water. Many gardeners know what happens when they sprinkle salt on a slug. The slug shrivels up and dies as the water in its body moves outside toward the salt because the outside of the slug (with the salt) has less water than the inside of the slug. And so the water flows or diffuses toward areas of less water.
This passive diffusion works in plants, too. Most soil contains lots of water, which flows or diffuses into roots. In the root zone there are sugars, amino acids, and lots of other dissolved substances, which means that the water content is relatively lower compared to the soil.
Leaves have even less water because then have even more dissolved sugar. And this is how water moves through plants without the addition of energy, such as a pump, or a heart: Water moves from the roots, through the stems (like giant straws), and into the leaves. The final pull comes from the atmosphere, where water concentrations can be quite low, especially when it’s sunny and yes, windy.
Just like what Kodiak has experienced most of the summer.
Water is pulled through the stomata, those tiny pores in the leaf surface, into the atmosphere, dragging chains of water molecules behind. This is called transpiration. Minerals, nutrients, and other dissolved substances all hitch a ride on the Transpiration Express.
When the weather is hot and dry, water loss from the leaves works to lower the leaf temperature which keeps the photosynthetic machinery in a healthy state.
HOW TO CARE FOR PLANTS IN TIMES OF DROUGHT
There, I said it. The “D” word. Drought. Has anyone talked about conserving water yet?
Many folks are wondering if ‘dry and warm’ is the new normal. It certainly is in many parts of the country. But that doesn’t mean you have to throw your hands up in defeat this summer. Here are a few tips to help your garden and lawn survive:
• First and foremost, your best defense against too little or too much water is to use compost and mulch. That goes for your lawn, too. Organic materials encourage deep root growth while lawns treated with chemical fertilizers (or nothing) develop dangerously shallow roots. They suffer through survive extreme conditions, be it cold snaps or hot spells.
• Let your lawn get shaggy. Mow at the highest setting, at least 3 or 4 inches. Most lawns are a blend of annual and perennial plants. And mowing your lawn too short can mean it will be unable to recover once the rain and cooler temps return. Keeping the lawn high helps retain moisture and photosynthesis.
• Water your lawn once a week rather than every day. Give it a good soak then let it sit.
• For annuals and perennials, watering strategies are a tad different. For example, spring-flowering shrubs like lilacs and rhododendrons are building next year’s blooms. They need water to do it, so don’t short-change them. If possible, water whole areas rather than single plants. Dry soil wicks moisture away. Remember, water moves toward areas that contain less water.
• Place straw or other materials around vegetables such as potatoes, broccoli and kale to prevent moisture loss.
• Move begonias, nasturtiums that prefer mottled light and cooler conditions into shade or partial shade; at least until this heat wave passes.
As for the future, I turned to Peggy. “Well, we might be paying for all this heat with an early winter.”
Back in 1972 however, they made it through the summer. It just goes to show that it takes a village to get through tough times.
I hope you enjoy your week. If you have a garden question, pop me an email to: firstname.lastname@example.org.