B. Rosie Lerner
Consumer Horticulturist


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Question and Answer

Plants absorb water better through soil than leaves

tomato foliage
Tomato leaves

Photo credit: Rosie Lerner

Q. Can tomato plants absorb water through their leaves on humid days? Also on cool and hot days, how often do you need to water with our heavy clay soil? C.W., Crown Point, Ind.

A. While plants can absorb water through their leaves, it is not a very efficient way for plants to take up water. If water condenses on the leaf during high humidity, such as fog, then plants can take in some of that surface water. The bulk of water uptake by most plants is via the roots. That said, high humidity does decrease the rate at which water is lost from the plant, and so will decrease the uptake of water from the soil.

As for how often to water, it is complicated! How often will depend on many factors including the type of plant, stage of plant development, air and soil temperature, relative humidity, soil moisture status, as well as soil structure. In general, plants will need less frequent watering during cool and/or humid conditions than during hot/dry conditions.

Q. We will be receiving a couple of small dormant seedlings in the fall. Do the roots continue to grow through the winter months? C.W., Crown Point, Ind.

A. The minimum temperature for root growth will depend on the species of plant. Although you don't mention what type of seedlings, for most plants that are winter hardy in our area, roots will continue to grow as long as soil temperature is above about 40 F. But the rate of growth will slow considerably as the soil temperature approaches the minimum threshold.


Writer: B. Rosie Lerner
Editor: Cindie Gosnell,