There is a very simple rule when it comes to watering container garden plants.
Always water so that at least 15-20 per cent of the water poured in the top comes out the bottom.
Having done this, do not water again until the surface of the soil is just dry to the touch.
Until your finger comes away dry from touching the soil, the plant does not require watering.
This system of watering ensures that the entire soil ball is wet so tender young roots do not go begging for moisture. If the soil ball is wet right to the bottom of the pot, the roots too will grow to the bottom of the pot. Deeply rooted plants are invariably healthier and better able to resist stress than are the more shallowly rooted ones. A thorough watering also ensures that all excess fertilizer salts are always being moved to the bottom and right out of the pot so as not to damage the tender young feeder roots.
“Another reason why plants kept in rooms are generally unhealthy, is, that they are watered in a very irregular manner.”
Ladies Companion to the Flower Garden
When Your Container Goes Bone Dry Because You Forgot To Water
Should the artificial soil mix dry right out, it will pull away from the sides of the pot as it shrinks. This will allow the water to run quickly and easily down between the pot wall and the soil ball. This, of course, isn’t doing any good to the plant in the process.
The remedy with these types of shrinking soils is to sit the pot in a tub or pail of water for at least an hour to allow the soil ball to absorb all the water it can handle and expand again.
If the container is too large to move into a tub, then very slow and often-repeated waterings will accomplish the same thing. I have often had to trickle water over some of the larger containers three or four times, with a half-hour between waterings, to convince them to rehydrate and soak up moisture.
“A great many ladies kill their plants by extreme kindness; that is, they keep on feeding them until the plants get too much water, when the roots rot and the plants die.”
The Window Flower Garden
The secret to this container watering, whether it be inside or outside potted plants, is to learn restraint.
If you touch the soil and your finger comes away damp, then do not add more water. Too much water will kill a plant almost as fast as will too little. If your finger comes away dry – then and only then do you water.
Mr. Heinrich did not mean to be particularly sexist when he refers to the ladies killing their plants by “extreme kindness”. The fact is that at the time of writing, maintaining the container gardens was very much a proper ladies form of gardening.
Women, at least those who would purchase and read a book on container gardening, did not work out in the fields. They gardened on a more refined scale in a container garden.