Do you know how to water your garden correctly? Many gardeners put too much water on their gardens and too often. This can quickly lead to poor plant growth, damage from pests like slugs and snails, and diseases like powdery mildew and root rot. Our gardens do need water to replace the water they have lost through "Evapotranspiration". Evapotranspiration is a combination of evaporation, (the water lost from the soil) and transpiration (the water lost by the plants leaves). Sunlight, wind, humidity, temperature, plant and soil type all influence the rate of evapotranspiration (ET). For example, on a hot, sunny, dry and windy day, in a garden with sandy soil, more water will be lost through ET. Whereas, on an overcast, cool, humid day with a slight breeze and good soil with high organic content, less water will be lost to ET.
When a plant gets too much water, the symptoms can look like what you would assume to be a “thirsty” plant, but in fact it is the opposite. If your plant’s leaves turn yellow or brown, this can be a sign of too much water. When a plant does not have enough water, the first symptom is wilt, not yellowing or browning leaves. They will only start to turn yellow once the leaves have died off and dried out. Some plant leaves will naturally wilt a little bit during a hot, dry and sunny day. But don't worry, the leaves will firm up again when the weather cools down later in the day. There are many plants that have adapted to, and thrive in, dry conditions. Some of these varieties include: fuzzy, hairy, greyish, thin, needle-like, fragrant or succulent leaves to reduce transpiration, big tuber roots for storage and low, mounded shape to reduce their exposure to wind and to shade their roots. The more of these adaptations they have, the longer then can go with out water. Drought tolerant plants really do not like too much water and will quickly rot or die off if overwatered. So if you tend to not be on top of your watering, you should maybe try these plants.
All of this may seem too complicated or time consuming. We all have better things to do than to stand in the garden questioning the level and timing of a wilting leaf, calculating ET rates and assessing leaf adaptations. So how do you know when to water your garden? Use the Finger Test!
How the finger test works (..it’s time to get dirty!):
- Take your forefinger and push it into your garden soil, right up to your top knuckle.
- If you feel moisture in the soil surrounding your finger, no need to water - skip to #5. If the soil is dry right down to the tip of your finger, proceed to #3.
- Check the weather forecast. If rain is not forecasted for the next 24 hours, or you just don't trust the weatherman, you can add water your garden. Turn your soaker hose on or use a watering can filled with water from your rain barrel to water the soil at the base of the plants (not the plants themselves). Keep in mind that soaker hoses can add a lot of water in a short time, so make sure to monitor.
- If rain is forecasted and you do trust the weatherman, sit back and let Mother Nature do the watering for you.
When you do water, keep as much water off the leaves as possible. This creates the perfect conditions for disease like powdery mildew. Water during the morning to let the surface moisture dry off throughout the day and making it less friendly to slugs, snails and earwigs in the evening.
- Run your soaker hose under your mulch to further reduce your surface moisture. It can be kept there for the summer and removed in the fall.
- If you don’t have mulch on your gardens, add some. Just 2-3 inches of natural mulch will seriously extend the time between watering. It also reduces weeds and protects your plant roots.
- Amend your garden soil with organic material (i.e. compost) so it holds more moisture when it is dry, and to improve drainage when it is rainy.
- Group your plants according to water needs so you don't have to water your entire garden every time you water. Group water hungry plants in one area and drought tolerant ones in another.
By watering your garden correctly, you will see healthy and happy plants and less pests and disease.