Matt’s Tips on Watering Your Garden – Part III
July 13, 2012
Hello fellow Gardeners, summer is officially here. And with summer, we have hot sunny days aplenty. Generally most of our plants are loving this right now. Your peas may have seen better days, but your tomatoes, peppers and zucchini are just starting to hit their stride. Let’s talk about watering for a minute. How often should I water? How long do I need to water for when I do water. Can I use tap water? Do some plants need more water than others?
You thought this was going to be a simple answer? All of the variables above are going to affect how much water your soil will hold, and how fast your soil will lose that water. The answer to how often I should water is dependant on a few factors. Namely, how hot and dry it is out, how big is the plant in the soil, what type of soil is it, do I have mulch on the soil. What if your soil is sandy? Well then it’s going to hold a lot less water within its structure. And a heavy clay soil will do the opposite. You will have to water more often in sandy soils, and less often in heavier clay type soils. Adding compost to your soil regularly (yearly) will add extra organic material into the soil which will help it hold onto more moisture, allowing for longer time between watering.
A big water hog like pumpkin or watermelon plant is going to suck the soil dry very quickly. They have huge leaves which transpire a lot of water daily. They also have a shallow root system, they don’t go down real deep for the water so for plants like squash and melons, you are going to have to water more frequently. Now on the opposite end of the spectrum we have an onion. The onion has very little leaf surface and roots that easily reach 3 ft into the soil, they transpire quite a bit less moisture and thus, if well mulched will have to be watered sparingly.
I try to plant my garden so that plants with similar water needs are in the same beds. This makes watering a bit easier. I have all my melons and squash and cucumbers in one bed. They all receive water 2-3 times per week. Usually every other day or every third day, but as much as every morning on days which are supposed to be really hot (85 or above). My Tomatoes, all in tomato-only beds, with their massive foliage but similarly impressive roots (4 ft deep or more) get watered about every 5-7 days. Again, if it’s going to be really hot, I am likely to give them a little watering in the morning, this will just help them protect themselves against the extra heat. Plants cool off just like humans do. They will open their stomata fully to allow for maximum transpiration; the evaporating water uses up heat as energy and leaves the surface of the leaf cooler. The harder the plant has to work for the water, the better the chance you are going to see heavy wilting.
The rest of my garden beds will get water on a 3-4 day rotation, when I do water, I water slowly and deeply. Most of these root systems will develop down to at least 3 Ft deep. You have to make sure you let the water get down that deep or the roots will stay more in the higher zones where they are more likely to encounter water. Watering every day is a huge mistake. You are essentially encouraging your plants to make the most roots possible in the top 12 inches or so of soil. In order to keep them healthy, you will have to make sure that top 12 inches never dries out; a pretty tough task in the middle of august. When watering, try to water for at least an hour, more if you can. Just keep going through the beds that you are watering, start at one end and water lightly all the way to the last plants that are getting water that day. Then go back to the beginning and water again, then again, and again, for a full hour. If you have a large garden, two hours may be needed. Remember, you are not going to be out there every day, so this extra water is going to have to get down deep so the plant has enough to make it safely to the next watering.
How about that tap water? Can I Use it? Well, in a perfect world, I would avoid using it. It has had its PH increased to Alkaline, probably around 8.0 so it won’t eat at the plumbing, and it has chlorine and probably fluoride in it. One good thing is that we have somewhat acidic soil here in the NE, so the alkaline nature of our tap water isn’t going to hurt too much. Don’t water azaleas or blueberries with it though. They love acid environments and tap water can throw them off bad. If you can collect rain water, that is the best option, but overall Tap water is OK to use. If you have to water your acid loving plants, use a watering can and add 1/2 cup of white vinegar per gallon of tap water to make the PH more suitable to your plants.
When you water correctly you will end up with plants that are deep rooted, drought resistant, with a couple added secret benefits. One of those is less fertilization. When your plants roots are digging down deep, they are taking up a lot more soil volume. That opens them up to access much more of the residual nutrients held within that soil. If your roots are only in the top 12 inches, they will use the nutrients up in that “zone” and need fertilizing more often to be as healthy as they can be. When they occupy 3-4 ft, they will have more overall nutrients and thus, you will need to fertilize less. Another great advantage is that deep roots will help prevent fruit from splitting or cracking after a rain storm. If most of the roots are shallow, when a heavy rain storm comes and soaks the top 12 inches of soil to saturation, the roots are going to be taking up a lot of water all at once. If you have fruit ripening on the plants at that time (especially melons and tomatoes) the fruit will swell and split because of so much water. Also if they don’t split, they will be watered down in flavor. When the roots are down 4 ft, and the top 12 inches are saturated, only approx 25% of the roots are going to be gobbling up that water, the fruit will be much more resistant to cracking or splitting and they will be less watered down, making their flavor more concentrated.
So, while you obviously can’t just sit back and watch your garden grow, you can certainly enjoy the ‘fruits’ of your labor.