How Much Water Does Your Vegetable Garden Need?
Water is the most essential resource plants need to survive, but gauging how much water your vegetable plants need can be difficult as there's really no specific number that fits all gardens in all areas. Weather conditions, natural climate, micro-climates, and the category and variety of plant all act as variables to water needs. A few tips can help give you a basic framework for developing an individual water schedule for your garden.
How Much Water?
Before approaching a water schedule, keep in mind that both too little water and too much water can stress your vegetable plants, causing both a reduction in growth and overall harvest. Stressed plants also invite disease and pest damage into your garden. The benchmark for most gardens is 1/2" of water twice per week for those with sandy soil and 1" of water for those with clay soils once per week. Those with sandy soil may need to increase watering depending on how much sand is present, as water may move too quickly through the soil, leaching nutrients with it.
The temptation is always there to go out and water every day, but that typically results in shallow watering. It's much better to focus on deep, infrequent watering for optimum plant health.
Gardeners aren't perfect, and even the most experienced gardeners can have trouble gauging water needs. Luckily, keeping your watering schedule consistent can help offset these effects, as the plant is able to adapt to the level of moisture in the soil. Even then, watering schedules need to be slightly altered to account for sudden weeks of drought conditions or heavy rains. Climate is also important to keep in mind, as wetter climates like Seattle will need to adjust for natural rainfall, while dryer climates like Phoenix may need to increase watering during hot summer months.
If you grow in pots, you will most likely need to water your vegetable plants daily as there's not as much soil mass to hold onto water over longer periods of time. The greater surface area exposed to the sun on the sides of the pot also cause water to evaporate faster from the soil.
Use a Water Timer
Water timers used to be expensive, but increasingly more manufacturers are coming out with more affordable models with just as many features as higher end water timers. A water timer not only saves water, a great feature for those in areas with watering rules and restrictions, but it also makes successful gardening easier. Simply hook up to your water line like you would a hose, set what days and times you want your garden watered, and run your hose or irrigation line off the nozzle. Your garden will automatically be watered without even thinking about it. A multiple zone system like the one below is also helpful, as you can divide your garden into zones based off each plant's water needs, creating a different schedule for each zone. Many models also have rain delays, allowing you to pause the watering schedule when rain is in the forecast, or manually turn on the system extra days during higher temperature weeks.
Add Organic Matter
Whether you have clay or sandy soil, adding more organic matter to the soil can help your watering schedule. Add high quality compost to break up clay soil or bulk sandy soil to improve their water holding capabilities. As you add more organic matter each year, you not only improve the soil's ability to hold water, but you improve the health and life of the soil, resulting in vegetables with higher nutritional value and more disease and pest resistance.
Don't Water the Leaves
Contrary to popular belief, watering from above does not automatically mean that you'll burn the leaves or end up with powdery mildew. However, it does increase the risks of these issues (less so with leaf burn as there is continuing discussion on whether or not watering your plant leaves actually causes the majority of leaf burn issues). Whenever possible, water at the ground level. If you must water from above, consider laying down a layer of mulch near the base of the plant or use weed block to prevent soil from splashing up onto the leaves. Soaker hoses are a great way to keep water where the plants need it without wasting water or hitting the leaves. Opt for flat soaker hoses if you need to weave in and out of plants or through raised beds as they tend to be easier to manipulate and bend.
Look For Signs
It's important to not only rely on a watering schedule, but use common sense as well. Look for signs that your plant is not receiving enough water, such as wilting or drying of the leaves. Leaves wilt as their internal water stores decrease or external heat increases as a protective mechanism to decrease the surface area sunlight can hit. However, some plants with large leaves, especially squash, may do this even if their water levels are okay, especially in warmer climates. You'll know they're probably fine if they bounce back later in the evening or early in the morning.
If You're Unsure, Dig
Don't gauge how much water your plants need by how dry the top soil looks. Dig two to three inches into the soil, and if below that level it's still dry, your plants probably need more water.