Okay, I'm going to say something important now. Usually I try to say interesting things, or funny things; I try to be informative, but, if you're a gardener, this is a big thing. If you were in front of me, I'd put my hands on your shoulders and look into your eyes to get your attention. Because I'm going to suggest something that goes againt the common opinion. It's that sort of statement that we usually react to by nodding in agreement while we inwardly shake our heads in disbelief, waiting for a chance to get away, or at least change the subject. This is going to sound like one of those wild ideas, but it isn't. And I'm not the only person who believes this.
Pretend I'm shaking your shoulders and looking into your eyes and telling you that this is important. "It's not better to grow plants on to 'get some size' before you plant them out into the garden". "Smaller is better in transplanting".Plants were designed, excuse me, evolved to survive in less than ideal hydrological conditions. Most of them, almost all, can deal with a good bit of drought so long as their root system and their top growth are in correct proportion. Plants know, oops anthropomorphizing again, plants as biological systems evolved to deal with being dry. It was the main thrust of their evolution for a long long time. Faced with drought, they go through a whole sequence of steps before they die, all designed to leave them in a condition from which the inevitable eventual rainfall can resurrect them. The first thing they do is close their stomates to decrease transpiration. Somewhere down the line they sacrifice leaves, easy for deciduous plants, more involved for evergreens, but not tragic or fatal. Farther down the line they begin to sacrifice significant parts of themselves: twigs, even branches. Still, they are set up to maintain that life force, that ability to revive when water finally appears. We don't need to let them go through all, or any of the stages but it's comforting to know that they aren't as delicately close to death as we often think.
I remember distinctly, hearing Dr. Baker say in Plant Propagation at the University of Maryland in 1977, that, "plants are totipotent". That means they can reconstitute themselves entirely from one single cell. Now I don't like to drive my plants down to their last cell, but again, isn't it nice to know that they don't go down easily; they fight to live. If they start out healthy with roots and shoots in good proportion, it takes a lot to kill them.
We can make them fragile, unstable, and we do. When we grow plants on in pots we pretty nearly always end up with a top that's too big for the root system in the pot to maintain.....unless we supply more water than the plant ought to reasonably expect. Then we create these upside-down monsters that are completely dependent. And we plant them in the garden and they're still dependent. If we're lucky, the root system eventually catches up with the top and everything's cool, but wouldn't it have been easier to have planted it out the first year after it germinated? When the root and ths shot were in harmony. The second year of a plant when it typically goes into about a 1 gallon pot is when the top first begins to outgrow the root. It only gets worse the more a plant is bumped up, and the inevitable "weaning process" becomes longer and more complicated.
With the passage of time, it gets even better, or worse. Any given plant, like any given person, is a product of its genetic heritage combined with it's life history. It's not heredity versus environment, it's both. If we want to populate our gardens with ideal plants, and I hope we do, we want to start from a seed, or maybe a cutting, and transition it smoothly to maturity. That doesn't happen when we turn them into unnaturally dependents and then try to work backwards, weaning them away from an unnatural watering regimen.What we need to do is plant them small and pay close attention to them for their first year or so. I water only when a particular plant needs it. I know this flies in the face of tradition gardening practice, but I've grown plants this way for over 25 years and my plants match up favorably plant for plant with their counterparts in other gardens.