This is a question I get asked a lot. A LOT! Here in Nashville we average approximately 50-52 inches of rain annually, using 52 inches a year makes the math easier – 1” per week. May is traditionally our wettest month with an average of 5.5”, followed by November with 4.3” and December with 4.2”. Most people don’t realize our driest month is October with 3.0” followed by August with 3.2” and September with 3.4”. All of these are averages based on a 30 year span. So how much should I water my vegetables?
When first planting annual vegetable seedlings often the plants will require daily watering. The reason for this is that the root system is very small and has not had the chance to spread out into the soil. Watering often and directly at the base of the plant will keep the plant healthy as the roots start to take hold, grow and support the plant. Water in this manner for approximately the first 1 – 2 weeks. After that increase the intervals between watering while watering more deeply (longer) than before. Eventually you want to get to the point where you are watering once every 4 – 5 days. Besides saving you time and money you will produce a healthier plant. Shallow and frequent watering prevents the roots from growing deep into the soil, consequently any period of drought, competition from weeds, or shallow tilling will adversely affect the plant.
So, as we naturally receive 1” of rain per week that is the amount of water that plants generally require here to perform well. With vegetables, since most of them have a high water content, I prefer they get at least 1” and preferably 1.5” of water per week. I use a garden hose, placed near the base of each plant, and do a quick calculation of how long I need to let the hose run and at approximately what rate; if I turn it on at a medium drip how long will it take to fill up a gallon jug? After doing this a few times you will get very good at estimating this. Also, keep a rain gauge handy and anytime you get rain in the garden subtract that amount from your watering schedule. It is extremely important to keep a regular watering schedule. While some plants do better drying out between waterings vegetables do not; they perform best with an equal and even watering. Excessive water can cause many of the fruits (technically the portion that we eat, not what we colloquially refer to as fruit) to expand so fast that they will split while too little water will result in misshapen and often hard fruits.
So, here in Nashville 1” – 1.5” of water per week will keep all your vegetables fruiting and healthy all summer long….as long as you keep the bugs away!