Water-wise Food Gardening for Fall & Winter
Before you decide the what and where in your fall/winter garden, we recommend determining if there is extra water available beyond your basic household needs of cooking, bathing, etc. that is appropriate for use with edible crops. This would include rain collection systems, as well as captured tap water or well water (not to be confused with “gray water”). Captured water is uncontaminated water that does not enter the drain, such as a bowl of water used to rinse fruits and vegetables or buckets used to capture water while the shower warms up. Remember that collected roof water may have contaminants and should not be used for watering food crops where the stems and leaves are consumed.
Gray water is untreated wastewater that has not been contaminated by toilet discharge. This can include waste water from your washing machine. Gray water is an option for irrigating your ornamentals but it should absolutely not be used to water root vegetables or any vegetables whose plant parts come into contact with the soil. This is due to the potential that human pathogens might be present. In addition, gray water is only suitable for ornamentals if the household products being used do not add salt, boron or chlorine bleach to the soil. County water agencies do indicate that gray water is safe to be used for fruit tree irrigation.
It’s planting time! We recommend the following key takeaways for successful fall/winter crops that use less water:
1. Compost, compost, compost! Add organic matter to the soil. If soil is sandy, it will allow the soil to hold more water. Organic matter will also help open up soil, allowing roots to go deeper and find more water at lower depths if there is any. Higher soil nutrition helps plants produce better yields with the same amount of water. Avoid adding excessive amounts of nitrogen, as this encourages lush leafy growth that requires more water to sustain.
2. Mulch, mulch, mulch! Three inches of mulch on top of the soil keeps soil cool, conserves moisture, and reduces weeds. You can choose from straw, fallen leaves, hulls, shredded bark, grass clippings, and newspaper. Be aware that the larger the material size, the deeper the layer that you need to provide. (Avoid plastic sheeting: it deprives the soil of much-needed oxygen.) Keep the mulch two inches away from the base of the plant in order to avoid rot. When hand-watering, pull back mulch so that the water goes directly into the soil.
3. Use a drip system. Learn about individual plant moisture needs and plant/ group like-needs together on the same valve. Base this largely on the root systems of the plants. Monitor obsessively from the start so that any adjustments needed for specific plants can be made right away (including moving plants around at an early stage). If using in-line emitters in one-fourth inch tubing that use one-half gallon per hour per emitter and there is a length of ten feet with emitters spaced every foot, five gallons of water an hour is used on that section of tubing. Add up all the drip lines to determine total water used. Install a timer. Install shut-off valves at the beginning of drip lines in order to turn them off when an area is fallow or when blessed rain occurs. Irrigate only as long as it takes to moisten the active root zone. It is best to water in the early morning so that the soil stays evenly moist. Don’t forget the drip system once it’s set up, even if it’s working perfectly. They do require some light maintenance regularly. Another important benefit to drip irrigation is it largely avoids the fungus problems brought on by damp leaves from overhead watering.
4. Be selective. While prudent crop selection matters more during the summer season for drought years, the same practices of selection are wise for winter crops. Grow only the amount and types of vegetables that the household will consume. This is not the time to experiment with cool new products that won’t be tried and true for your household’s consumption. In other words, don’t grow vegetables you know your household won’t eat! This may seem obvious but space and resources are precious. To get the most out of the water you apply, grow high-yielding vegetables that do not need consistent moisture if there are unexpected hot spells during the season. Perennial herbs generally thrive in our winter climate (i.e. sage, rosemary, thyme, oregano, marjoram and mint are true ‘workhorses’). And consider the water needs according to plant growth timing. For example, peas need water most during pod filling. And if possible, select varieties that are described as “widely-adapted” or drought-tolerant, as well as those varieties that have a shorter maturity time.
5. Increase plant spacing. If you have room, increase the plant spacing in your garden. Spaced plants are not competing as much for water in the soil, especially in containers and above-ground beds. (Very deep, open soil planting allows vegetables to be closer together because the roots have more room to grow deeper and find water if present.)
6. Eliminate weeds. Weeds compete for water. Be aggressive in removing them from planted areas. If the garden is mulched well (see #2), weeds should pull out quite easily.
7. Use shade and windbreaks. Heat-sensitive vegetables (most winter crops) can benefit from being planted where they receive some afternoon shade. You can plant them (i.e. lettuces, with very shallow roots that would not compete with deeper roots for water) underneath or behind taller plants. In addition, windbreaks will keep your garden’s plants from drying out too much in areas with a lot of wind (often our coastal areas).
8. Determine wisely when it is time to water again. Use a soil moisture meter. Or squeeze the soil in your hand: if it sticks together, it is still moist; if it is crumbly and falls apart, it’s time to water. Adjust any drip irrigation to fit the timely needs as the season progresses.
-- UC Master Gardeners Charlene McKowen and Barbara Davidge, adapted from “Food Gardening with Less Water”/ February 2014, SCMG (dePeyster, Wrightson, Cary).