Are Your Houseplants Dying of Thirst?

visit me with a large houseplant she purchased last summer. It was dropping most of its leaves, and the margins of the remaining leaves were turning brown.
    After questioning her on how she was caring for the plant — watering practices, fertilizer and quantity used, proximity to windows and room temperatures — I invited her to the farm. Soon after I hung up, I saw the car coming down the farm lane. Her husband was driving while she sat in the back seat with a schefflera between her legs. The things you see when you don’t have a camera.
    The plant was in terrible condition. It was also apparent that she had spent a considerable amount of money for it.
    After examining the stems and leaves and not seeing any symptoms of insect problems, I felt the rooting medium, which was moist. However, the minute I lifted the plant, I recognized the symptoms as drought-related. It was growing in a five-gallon pot, and I shocked her when I turned the plant upside down and slid the root ball from its container. The lower two-thirds of the root ball was bone-dry; the only visible live roots were in the upper third of the root ball. I took the plant into my greenhouse and plunged it, pot and all, in a barrel of water. I allowed the root ball to remain submerged until water appeared on its surface. She appeared shocked but said nothing.
    The lesson of this encounter?
    Always irrigate houseplants thoroughly. This means adding enough water that an excess drains out from the bottom of the pot. That is what saucers are for.
    However, the rooting medium can become so dry that the root ball shrinks and water runs between the wall of the pot and the root ball. Suspect this if the plant seems to weigh too little for its size. When this occurs, simply dunk the pot in water and allow the water to completely saturate the root ball.
    I often recommend that houseplants be dunked at least each month.
    I do not recommend sub-irrigating plants because that results in salts accumulating on the surface of the growing media. If you are in the habit of sub-irrigating plants, water heavily from the surface at least monthly to flush the fertilizer salts back where they belong.

More on Beating Back Bamboo

Q:    I re-read your bamboo advice article in Bay Weekly: cut in the spring and spray foliage in the fall.
    What do you prescribe for the young shoots that are popping up in spring?

–Kevon Watson, via email

A:    Let them grow, and spray again in mid- to late-October. Sometimes it takes two years to obtain 100 percent control.
    How late in the fall did you spray, and did you make two applications 10 to 14 days apart last fall?
    The later you spray in the fall, the better the control. In one of our studies, I delayed spraying until after the first frost and we had excellent results.

Ask Dr. Gouin your questions at [email protected] All questions will appear in Bay Weekly. Please include your name and address.