How do I protect the roots and adjust watering levels in a non-draining indoor pot?

Question

The long, winding backstory: We have a rubber tree which has been in the same pot for ages. It has been moved twice, and in our new home we're still trying to find it a spot it likes. Recently, when we went to water it, we noticed standing water on top of the soil. It's been very droopy lately with leaves falling off. Thinking it's getting over-watered, we move it to get a bit more indirect sun and hold off watering for a while. Not much changes (maybe a bit more drooping). I start worrying about mildew and root rot, and as we're discussing what to do about it we realize it's been in the same pot/soil for probably over a decade. So I re-pot it in fresh soil and clean out it's pot. It's been about a week; and the rubber tree is starting (very slowly) to improve. Some wilted leaves are still falling off, but a few fresh green ones are starting to open. Now I'm worried about how to keep it happy.

Now that I have fresh soil in a nice large pot, I have the issue of keeping the water fresh. My past experience of plants is either in proper ground, or pots which can drain excess water. I understand I've just shocked this poor rubbery tree quite a bit, and I don't want to add more stress. But I feel there's a fine line between under-watering and over-watering when one leads to drought and the other to rot. We thought maybe a watering spike would help keep things even (as the water would be released about root level), then thought maybe that was a bad idea when the entire bottle emptied in about 18 hours. Now we figure there's a lake in the bottom of the pot, and we might be headed back where we started.

Rubber trees are very, very slow growing; and I'm not sure how quickly they take up water. Then again, maybe they like a bit of stagnant water in their pots. I've heard they very much like pots, at any rate.

My questions: In a sealed pot, how can I measure the water needs of my plant, and how can I make adjustments? Is there something I can do to protect the roots, or prevent water trapped in the bottom of the pot from causing health problems?

Answer 1

The fact that your rubber plant has survived so long in a non-draining pot is a credit to your watering skills; in my experience, very few indoor plants will tolerate a non-draining environment very long, however careful one is to avoid over-watering. In addition to causing root-rot as you pointed out, standing water at the bottom of the pot will sooner or later lead to a build-up of harmful salts which will poison the plant. Even if your watering is so finely judged that there is rarely any standing water in the pot, the plant will still suffer from the build-up of toxins in its root- ball, which would normally be washed away whenever the plant is watered.

Unless there is a compelling reason to keep the plant in a sealed pot, I would move it into a pot with drainage holes as soon as possible and hand-water. If you have to keep it in its present pot, I would use a peat-based compost which will absorb any excess water better than a soil-based one and also dry out more quickly.

If you are bent on keeping the sealed pot (perhaps for aesthetic reasons), you might be able to transfer the plant to a slightly smaller pot with good drainage, as Mike Perry has suggested, and place it inside the sealed one which would then serve as a pot-holder.

Answer 2

If you like the pot that it's in, then the optimal solution is to drill a decent sized hole or two in the bottom of the pot and place it on a secondary tray to collect the excess water.

Did you notice any rot when you transferred it into new soil? It is suggested that you cut out any diseased or rotting roots before replanting, as the rotting could continue even in the new soil.

It could also be possible that the plant is root bound due to an excess of roots. During a time when the plant is dormant you can trim excess roots so that new roots and feeder roots have space to grow. Hardened roots will absorb less water and nutrients.

My last suggestion is to fill about 1/8 of the bottom of the container with smashed pieces of tile or pottery so that any excess water can fill that space and the plants root system won't be sitting in excess water.

Answer 3

I often add some gardening or aquarium charcoal to the bottom of sealed pots to freshen the soil. I also use a water meter (large hardware stores sell them). I push the rod of the meter more than 1/2 way down into the soil and don't water unless the meter indicates that the soil is dry.