Heirloom Tomato


Am growing an heirloom tomato on my balcony in mid town toronto. It faces East and gets the morning sun. Every morning there are droplets of water on the leaves. They do not come from water dripping from the balcony above me nor from any rain in the night. No evidence of this on any other plants on the balcony. Have success in growing tomatoes in that location in the past, but this is the first time have tried an Heirloom. What could be the cause of these morning droplets and what should I do about them.


Thank you for contacting the Toronto Master Gardeners.

It is the seeds that make an heirloom tomato an heirloom/ heritage tomato. The seeds are passed down from season to season, taken by the farmers from the tomato plants that produced the best fruit. This process allows farmers to select for certain desirable traits like juiciness, size, shape, or color. Heirloom tomatoes are also often open-pollinated, which means that they are pollinated naturally, by birds, insects, or wind. Basically heirloom tomatoes’ DNA  hasn’t been manipulated in the same way that the genetics of a lot of mass market tomatoes.

Heirloom tomatoes have two main different and distinct types of leaves – potato leaf and regular leaf. Plants with the regular leaves are what we all are use to seeing on tomato plants; multi-lobed, serrated and sometimes almost toothed branching off of the stem. Some varieties of heirlooms posses potato leaves. Potato leaved plants have broader, smoother single leaves branching off of the stem, missing the multiple lobes and serrations.

No matter what type of leaf you have all tomatoes exhibit the phenomenon called “guttation” which is Mother Nature’s way of allowing plants to relieve water pressure that can build up in their tissues under certain conditions. The water is exuded from a specialized structure called hydathodes located on the leafs’ margin.

According to the University of Missouri: “Under night time conditions of high humidity, cool air and warm soil, root pressure can move water to the leaves. Since the stomata are closed at night, transpiration can not remove water from the leaf as it does during the day. Hydathodes, located on leaf margins near the ends of tiny veins, exuded droplets of water to relieve the pressure.”

It is thought that guttation may help reduce the incidence of a non-infectious disorder called edema, in which tiny blisters appear on leaves during long periods of high humidity and excess soil moisture. Basically it is a built in pressure valve for plants. Plants never cease to amaze!