As a substitute for in-person programming, we’re offering a series of posts on starting a vegetable garden. This science-based information comes from the Seed to Supper program, developed by the Oregon Food Bank. During these difficult times, the Oregon Food Bank welcomes your donations.
OSU is also offering its vegetable gardening class online.
Even in the rainy Northwest, we get little rainfall during the peak growing season, so gardeners need to be prepared to water their vegetables. Many water too often and not deep enough. Watering should be deep and infrequent. In general, watering 2-3 times per week is enough.
Sandy, clay and loamy soil types accept water differently. Water moves through sandy soil about twice as fast as it moves through clay soil, so it takes longer to water clay soils to the depth your plants require. Loamy soil lies between these two extremes—it both retains water AND drains well, making it the best soil type for growing plants.
Not sure if you need to water? Use your hands to feel for moisture below the first inch or two of soil. It should feel moist, like a wrung-out sponge. If feels dry, it’s time to water.You can also spot-check your work by filling a jar or yogurt container with soil and placing it in your garden when you water. If the soil at the bottom of the container is still dry, you might need to water more deeply so that the water reaches the roots of your plants.
Remember that seedbeds and new transplants will need water daily until they are established. Use a gentle spray so you don’t wash them away. When you water, always aim for the roots of plants instead of the leaves. Try to water only where your plants are growing, and not the surrounding soil. This helps to prevent weeds from growing in between your plants.
You can water by hand with a hose or a watering can. Though this method takes time, it delivers water directly to roots, reducing waste. When you water by hand, do so GENTLY, like the rain. Use a gentle nozzle setting or angle your hose upward to avoid blasting the soil.
For leaf lettuce and other greens that are grown close together, it is okay to get water on the leaves. For all other crops, especially cucumbers and tomatoes, keep the leaves dry when you water.
Water until the soil remains “shiny” for 10 to 15 seconds after watering. Switch back and forth between sections as water soaks in. If your plants begin to wilt, you’ve waited too long to water.
Alternatives to hand watering include using a sprinkler or an irrigation system. Sprinklers and irrigation systems tend to waste water and encourage weeds by watering everywhere, not just the roots of the vegetables you’re growing. By wetting leaves that should remain dry, these methods also encourage fungal diseases to set in. Of mechanized options, drip irrigation is best because it delivers water directly to the roots of each plant. This online resource gives details on drip irrigation in a home garden.
Water at least 6 inches deep and then let the top inch or two of soil dry out completely before watering again. Shallow-rooted crops, like lettuce, onions and cabbage draw water from the top foot or less of soil. Deeper-rooted plants, like tomatoes, parsnips and winter squash, have root systems that allow them to draw water from the top 2 feet of soil.
Frequent, shallow watering makes plants develop roots close to the surface of the soil. Plants with shallow roots are vulnerable to stress. Overwatering also causes soil pores to fill up with water, leaving no oxygen for plant roots. In addition, too much water leaches away nutrients. Overwatering some plants, such as tomatoes, produces watery vegetables.
Remember that containers dry out faster than soil. Check the containers every day. When the soil is dry, add water until it runs out the bottom of the pot.
Next up: Protecting young plants