By Johanna Silver, Sunset test garden coordinator
The most common question posed to me by visitors to the test garden is how much to water a vegetable garden.
The short answer: It depends.
I wish I could make this super simple for people, but the truth is that effective watering takes some exploration and experimentation. Here are some helpful hints:
Learn your soil composition
How often and how long you need to water depends largely on the makeup of your soil. There are three main compositions, and all have different capacities of water absorption and drainage:
1. Sandy soil - absorbs quickly, drains quickly
2. Clay soil - absorbs slowly, drains slowly
3. Loam - absorbs fairly quickly, drains fairly well (read: ideal)
You can improve any soil type by adding plenty of broken down organic matter. I've always loved that the solution on both ends of the spectrum is to add more compost.
Specific climate conditions impact a watering schedule
Hot weather and wind will make soil dry out faster than a calm, overcast day. When in doubt go outside and dig your finger into the soil. If it comes out dry it's probably time to water.
Not all vegetables are created equally
Most edibles need to be kept evenly moist during seed germination and early establishment, but crops have different needs as they mature. For example, leafy greens can turn bitter and go to seed if they don't get regular water, while established tomatoes thrive with deep, less frequent, deep waterings. Too much water will prevent tomatoes from developing. Consult the Western Garden Book or The Edible Garden Book for crop-by-crop instructions.
Drip irrigation is where it's at
Drip systems (or even a soaker hose) emit water more slowly than overhead watering, allowing for maximum absorption with minimum evaporation. It conserves water (saving you money), minimizes weed growth, and prevents disease on certain crops by keeping leaves dry. I also enjoy the puzzle of putting it together. Check out The Urban Farmer Store (and go to one of the three Bay Area locations to experience some serious drip-irrigation know-how).
Hand watering also works well in a small vegetable garden, particularly if you dig small basins around each plant and water directly over the root zone.
Mulch makes best use of waterings
Placing mulch on the bare soil around your plants increases water retention. Like drip, mulch also fights weeds. Careful though -- organic mulch (such as straw) decreases soil temperature, so don't apply to your garden until it's warm outside. Plastic mulch, on the other hand, heats soil.
1. An over-watered plant often resembles an under-watered plant. Be sure to get outside and dig around to determine what your garden needs.
2. Don't panic at the first sign of wilting. Many vegetables will wilt during the later hours of a hot, summer day and regain their strength at night. They should not, however, be wilting first thing in the morning. This is definitely a red flag that it's time to water.
3. Consistency is the trick of the trade. Figure out what method and schedule work in your garden and stick to it.