Beginner Gardening: Good Growing Practices - an Overview for Beginners, 1 by tapla

tapla wrote:
MYTH - with a small qualifier. Here is something I wrote a while back that hopefully dispells the myth and explains why it's parrotted and perpetuated so widely:

I would like to talk a little about, and hopefully dispel the myth that certain plants 'like' or 'prefer' to be grown tight (under root-bound conditions). Maybe we can also understand that no plant will 'do well' when it's pot-bound if you are using a plant with plenty of room for its roots to run as your standard of judgment. If plants did better growing under root-bound conditions, Mother Nature would have arranged for in situ (where they naturally occur) plants to grow with their roots in tight little cones or cubes, yet we never see that occur. While it's true that we may be sometimes be able to use the STRESS of our plants being root-bound to bend plants to our will and achieve OUR goals, the fact is that this serves US well, and not the plant.

Let's examine what 'growth' is. Growth is simply a measure of the increase in a plant's biomass, how much bigger it has become (the weight of the sum of its parts), and is the actual measure of how 'well' a plant is doing. We know that tight roots restrict growth, reduce the amount of branch/stem extension, and reduce the potential for an increase in mass, so even if we THINK plants are doing well because we use the stress of tight roots to get them to bloom or grow in a particular habit that we like, the truth is tight roots are stressful, and plants would rather have plenty of room for their roots so they could grow as mother nature intended. No one is more aware of the negative influence tight roots has on growth than the bonsai practitioner who uses that tool extensively to bind down the plant's growth habits so the will of the grower, not the plant, prevails. Using tight roots as a tool to achieve an end is all about the grower's wants, and not the plant's.

Interestingly, many mistake the fact that a plant seems to be extending and growing leaves for actual growth, but if the plant is robbing nutrients from other parts and then shedding them in order to support new leaves or branch extension, it may not be increasing in mass, and therefore not growing ..... only robbing Peter to pay Paul.

If we chase the 'root-bound issue' a little further, we can see the reasons that it is suggested that particular plants might like root-bound conditions. Tight roots alters the plant's growth habits, and the stress of tight roots can cause other physiological responses, like bloom induction. Again, this is happening because of stress, and is the plant's unhappy response. Bright flowers make the grower happy, but the plant's perspective may be entirely different.

Where I was really heading when I started to write this is: There is a relationship between plant mass (size), the physical characteristics of the soil, and the size of the container. In many cases, when we are advised that plant X prefers to be grown tight, we are being told that this plant won't tolerate wet feet for extended periods. Someone somewhere assumed that we would be growing this plant in an out-of-the-bag, water retentive soil, and "a big pot of that soil stays wet for a long time, so we better tell these people to grow this plant in a tiny pot so the plant can use the water in the soil quicker; then, air will return to the soil faster and roots won't rot."

If you place a plant in a gallon size pot of water-retentive soil, it might use the water fairly quickly, at least quickly enough to prevent root rot; but if you put the same plant in 5 gallons of water-retentive soil, the plant will take 5 times as long to use the water and for air to return to the soil, making it much more probable that root rot issues will arise. So lets tell 'em to grow these plants tight to save them (the growers) from themselves ......... because we KNOW they're all going to be using a soggy soil.

The key here, is the soil. If you choose a very porous soil that drains well and supports no (or very little) perched water (perched water is that water in the saturated layer of soil at the bottom of the pot), you can grow a very small plant in a very large pot and make the plant MUCH happier than if you were growing it tight. You still have the option of choosing those plants you prefer to stress intentionally (with tight roots) to get them to grow as YOU please; but for the others, which comprise the highest %, it makes much better sense to change to a soil that allows you to give the plant what it wants (room for roots to run) than to stress the plant (with tight roots) so it won't die (from root rot due to an excessively soggy soil). That's a little like keeping your dog in a sleeping bag 24-7 to ensure he doesn't get cold.

Al