Irrigating your Backyard Vineyard

As I begin to write this it’s raining. It is an overcast gray November day in northern California. Since northern California, the Sierra foothills, is where my backyard vineyard is, most of what I am about to say applies to this area. When considering irrigation for your backyard vineyard there are several things to be addressed. Things like; how much water should you give the vines, how frequent should the watering be, how does rainfall impact the irrigation plans, what does water do for the vines, what does it do for the grapes? Understand that what I am going to share with you applies to vines that are 4 years old or more. You will need to treat younger vines differently.


Typical average rainfall where I live (Auburn, CA) is about 30 inches per year. For the average backyard vineyard, that is all the water needed. Does that mean you don’t need to water in addition to the rainfall? Well, yes it is pretty much just that. If the owners of home vineyards have a common fault, it is over watering. Each vine needs roughly 100 gallons of water each year. Here is how the math works out. I have 100 vines in an area of approximately 5000 Sq. Ft. or 720,000 Sq. Inches. The formula is: Area in Sq. In. X rainfall in inches = cubic inches. Cubic inches / 231 (cubic inches per gallon) = gallons. So… 720,000 X 30 = 21,600,000 / 231 = 93,506 gallons for the entire 5000 Sq. Ft. If we then divide the 93,506 by the 100 vines we get 935. THAT IS 935 GALLONS OF WATER PER VINE! If each vine only needs about 100 gallons to survive, why do we ever need to irrigate? If you don’t want to do the math you can go to: http://www.virtualsecrets.com/annual-rainfall-water-calculator.html and use their calculator.


Let’s try to pin this down a bit. Obviously, each vine will not benefit equally from all rainfall, let’s just look at an area around each vine that is equal to 5 feet by 5 feet. We will assume this is the area from which each vine will benefit from rainwater. So that is 25 sq. ft. per vine. Since we know at 30 inches of rainfall annually each foot will get 18.6 gallons of rainwater. That is then 465 gallons per vine. If the annual rainfall were to fall substantially below the average, we would still be in pretty good shape, water wise.

So, why do we water at all? Well, some people don’t, and often have very favorable results as far as the crop is concerned. I do irrigate some. Let me explain. The first thing to be recognized is that watering is for the vines, not for the fruit. Let me say that again because it’s very important. Watering is for the vines, not for the fruit. If fact, watering with fruit on the vines can at times be detrimental to the fruit. Should you irrigate heavily after veraison it can pump the berries full of water lessening their quality and possibly splitting the berries.

Because Auburn is so hot in the summer, I do irrigate to be sure the vines have enough water. When irrigating, you must "deep water" and only do it infrequently. Watering small amounts and frequently will cause the root system to stay a lot closer to the surface that you want it. Roots need to be trained to reach very deep for water.

I water once when the temperature has reached 100 degrees and stayed at 100 degrees or more for three days. I put 20 gallons centered between the vines over a 10-hour period. I look to do this again just prior to veraison. Then NO MORE water until after harvest. Within just a few days after harvest you need to again give the vines a good drink of water. I use the same method I described above. Now my vines will get no more water until Mother Nature takes over in the late fall or winter.

You need to consider and make small adjustments for any slopes you may have and your type of soil (absorbency). Stay somewhere close to this watering routine and schedule and you should be very pleased with the quality of your harvest, and resultant wine