At my house, my general rule for irrigation and choosing plants is: if it gives me food, i’ll water it. Otherwise, tough luck. However, it always seems like an extra awesome bonus when there is a plant that will give me food AND I don’t have to water it.
My landscape may look a little ratty by the end of summer, and sometimes I do break down and give a struggling plant some help, but overall the thought of having an entire landscape that requires regular supplemental water just doesn’t seem right to me in our Western summer-dry climate.
I do make an exception for food. Plants need water to grow, and fresh summer vegetables need to be growing during our driest time of year – otherwise we wouldn’t call the fresh summer vegetables. Despite this general rule of thumb, knowing which plants don’t absolutely need water can help with your garden planning and can give you a unique sense of accomplishment, knowing that you are farming in tune with the rhythms of our local climate.
Your success with dry farming is going to depend on a number of factors, some within your control and some not. Planting on the early side of the appropriate season allows the plant roots to go deeper by the time the top of the soil starts drying out. Increasing plant spacing reduces competition for water. Mulching helps hold moisture in the soil. Soils with higher clay content hold moisture longer. Natural weather variations from one year to another lead to milder or more extreme conditions for your plants.
Tomatoes – I first heard about dry farming tomatoes from a farmer in Berkeley, Ca, who told me that he grew all his tomatoes that way. I have since grown tomatoes this way in Portland for many years in a row, and until the last two years it was always successful. Tomatoes have more flavor when they don’t have too much water in them, and as plants adapted to hot and arid climates they are very good at sucking the tiniest bit of water out of the soil. I have seen volunteer tomatoes thriving in the most inhospitable places
Black eyed peas – These tasty legumes originate from Africa, and are well adapted to dry climates. As an experiment one year I grew an irrigated and an un-irrigated plot to compare the results. The irrigated plot grew bigger and greener plants, and the seed pods matured later. The dry plot had smaller plants that set seed earlier. Overall, yield from the two plots was similar, meaning that the irrigation led to more leaves but not to more beans.
Quinoa – this Andean grain does well in Northwest climates and once it gets a few inches tall is quite drought tolerant. In one garden plot I planted it and did not water it past the seedling stage – and it grew beautifully. Another year I planted it in a sandier bit of ground, and although it was much more tolerant of drought than some of the other plants around it, it still did wilt and appreciate a bit of supplemental water towards the end of the season
Depending on what time of year you plant, what your soil is like, and what the overall weather pattern for the year is, here are some other crops that I have had luck with:
- Winter squash – There are multiple species of winter squash, and they are not equally drought tolerant. I have had great luck with Cucurbita maxima selections such as Kabocha and Hubbard, but very poor luck with Butternut (Cucurbita moschata.)
- Chard – As a leafy green, chard does not look drought tolerant. However, volunteer seed-grown chard that is left in a neglected corner of the garden will often produce the biggest and juiciest leaves without any apparent help or irrigation. Their huge fleshy roots (they are actually the same plant as beets) no doubt helps them store water.
- Potatoes – If planted early in the spring, potatoes will be finishing out their life cycle just as the soil is drying out in early to mid summer.
- Garlic – The life cycle of garlic is perfectly timed to a no-irrigation garden. Plant it in the fall, during the month of October. It develops roots over the winter, and in the spring sends up green leaves. It starts to develop bulbs just at the end of the rainy season, in late May, and then should be allowed to dry out in June as the bulbs mature. By the time they are ready to harvest and pull, you can dry them in the sun – voila! (Word of warning, garlic doesn’t love being scaled, so better to dry it in the shade on a sunny day.)