Strategic watering for various garden plants

By Rennie Phillips

I belong to a group on Facebook devoted to growing tomatoes. It doesn't matter what kind or color, as long as it's a tomato. Recently one of the growers on the site wrote in about how each of his tomatoes had a dark spot on the bottom of each tomato, and the tomato would end up being ruined. He said he consistently watered his tomatoes and also watered them deep. His tomatoes probably have blossom-end rot.

As I was responding to his post, I thought about how all of us have been told to water deep, that watering shallow will cause shallow root systems. And it's true.

If you water deep or water slow and allow the water to soak in deep, it will cause the roots to go down deep.

When you are watering most trees or bushes, this is very true. You want an oak to send its roots down deep. It's the same with cyprus or ash or any other long-living tree.

Deep-rooted trees aren't dependent on inconsistent rainfall. A deep-rooted tree is dependent on an underground water supply.

But this is not true, in my opinion, for blueberries. Blueberries have a very fine root system that spreads out like a mesh blanket, but they seem to be very shallow. Some of my blueberry bushes' roots aren't over 3 or 4 inches deep.

To water deep would seem futile for blueberries. What they need is a consistent watering that will soak down at least half a foot. Consistency is most important. One problem with overwatering is it washes the goodies out of the soil around the roots.

The way you water and the amount of watering is dependent on the crop or plant. Corn is one I would think you want to root deep. I'm not a corn expert, so this is just my opinion. Water them deep, but not often.

Other plants, like daikon radishes or carrots or those plants that send down a main root deep into the ground, need to be watered deep. The key is to water thoroughly, but not real often.

One other key is to change the amount of watering according to the age of the plant. Water more often and more shallow when young and small. Increase the amount of water and the time between waterings as the plant matures.

Let's take radishes, for instance. If you can water enough to get the water down 3 inches or so, it's sufficient. There is no need to water deep. But the key to a shallow root system is watering often. They will have shallow roots, which tend to dry quickly, so water often, but you don't need to drown them every watering.

Tomatoes have a shallow root system. I've pulled hundreds of tomato plants in the fall and almost without exception the main root isn't over 4 to 6 inches deep. The key on watering tomatoes is don't overwater when you first put them out. Watch the plants or the ground. If the ground appears dry or the plants have that "just starting to wilt" look, water them. Don't drown them when they are little. Overwatering will leach the calcium and other nutrients from around the roots and will cause blossom-end rot. Add nutrients as you water. Later, when they are putting on or growing tomatoes, water almost daily up to a half gallon to a gallon of water per plant. Use a dripper system.

If you always have run a sprinkler on your garden, do some research on switching to a dripper system. Most garden centers or even some of the big-box stores will have drippers. I order mine from DripWorks out in California and from Morgan County Seeds here in Missouri. Right now I use two systems. One runs at normal water pressure, which is 60 or 65 pounds of pressure. The other system has a pressure reducer on the lines, so the pressure in them is around 10 pounds of pressure. I'd recommend the low pressure lines.

My drip lines have an emitter every 4 inches and they put out half a gallon per hour. I can then record the time the system is on and know how much water goes on each plant. My tomatoes are about 18 inches apart, so in that 18 inches I have approximately four emitters. If I run the system for one hour, I have put two gallons around that plant. When my tomatoes are mature and putting on fruit, the one hour is about right. I water every other day or so. Some of the water will evaporate, so each plant isn't getting the full two gallons.

Cucumbers are not a deep-rooting plant. I run the dripper line along my cucumber plants and run it for about an hour or an hour and a half. I vary this when we receive rainfall. I also have a way to inject fertilizer into the water line so plants receive fertilizer on a regular basis. Zucchini tend to root deeper than tomatoes, so I water them a little more and not as often as tomatoes. Potatoes are a different critter. If we get some rainfall, it might be sufficient. I haven't watered my potatoes this year. They have done well with just rainfall.

Water thoroughly, but don't overwater. Water according to the size and age of the plant. Base the amount of water on specific plants and don't just water them all the same.

Until next time.