Watering Tomatoes

So things are really going well now, and the season is underway. My transplants are 2 feet tall already—the photo here shows the Marvel Stripe heirloom. Blossoms have begun to emerge, and I've started feeding them. You know, I just love this part :)

I'm watering every morning, with about 1/2 inch of water for each plant. When you're new to tomato gardening, you hear over and over to water consistently and never water from the top, but at least for me, it seemed like no one really explained what the big deal was. Well, here it is ...

Tomatoes need consistent water to prevent a condition called blossom end rot (BER). BER is a cultural problem with tomatoes and peppers. It causes the fruit to develop dark, rotten spots on the blossom ends, eventually leading to collapse of that fruit. It's a heartbreaker.

BER is caused by a calcium deficiency in the developing fruit. This is why calcium is such a big deal for tomatoes, why people use dolomite and bone meal and why tomato fertilizers always include plenty of calcium. As young tomatoes develop, they use calcium sort of like young humans do: to build structure. According to horticulturists at the University of Georgia, about 90 percent of the calcium the mature tomato will contain is already present in the fruit by the time it's the size of your thumbnail.

Now here's the tricky part: your tomatoes can suffer BER even with plenty of calcium in the soil. Heck, they can suffer BER even with plenty of calcium in the plant itself. This is because of the way calcium moves through the plant. It's absorbed from the root zone in water, then moved through the leaves and finally into the fruit. However, if the plant is under water stress, water is directed to the leaves because they transpire faster than fruit, meaning that water evaporates more quickly from leaves than fruit. The plant is just trying to protect itself, but as the water transpires through leaf tissue, it leaves behind the precious calcium. Meanwhile, the poor fruit isn't getting any water or calcium.

The worst part is that this tends to happen when your tomatoes are young and still developing. Even a temporary disruption in regular watering of young tomatoes can set the stage for BER later on in the season. So, make sure you're absolutely consistent with the water. To some degree, self-watering containers prevent this automatically (assuming you're keeping the reservoir filled).

As for watering from above, it's pretty simple. This encourages fungal diseases, wilts and blights. So for safety sake, don't soak your plants down. Water at the ground level.

Up Next: Training Tomato Vines ...