I would tend to agree that the root growth is largely a factor of what
they are growing in. We try to keep an eye on what our competitors
do and several local growers use growing mixes that are very different
from each other. Among these guys, if you show me a bare root plant,
I can often tell you who grew it by looking at the root systems.
Mobjack's plants have an incredible root system, long, thick roots that
fill the pot, even in smaller plants. The mix they use is the coarsest
I have ever seen, chunky bark and small gravel. You have to water
it about every 10 minutes.
Growers that use more peat than we do often have thiner, fiberous roots
and a much more compact root system. Ours are somewhere in between.
I think it's obvious that the plants grow whatever roots they need to obtain
water, just as they do in the ground. Why bother growing long roots
if the soil is always wet?
The other thing I notice is that I don't think having a huge root system
means that you necessarily have a bigger or better plant. Huge root
systems are not the objective unless they are needed.
Bill Meyer wrote:
I'm not sure why hostas produce such different root systems between pots
and ground, but they clearly do. Take a large potted plant with a huge
root system and plant it in the ground and the following year the plant
may be bigger, but the root system is clearly much smaller. I have a retail
nursery near me who does pretty much the opposite of what most commercial
growers do as far as their mix goes. They use a very rich, fine mixture
with a lot of mushroom soil (old manure) in it. They really don't lose
too many through the winter, as might be expected, and they've been doing
this for years. Growth is really very good and rot only a problem with
certain varieties, particularly 'Aristocrat' and 'Great Expectations".
The actual growth rate is not much slower than the airy, chunky mixes favored
by Southern growers. These lightweight mixes tend to show the most root
growth, while the rich heavy mix favored by these people shows root growth
that is only about half that.
There does seem to be a tie-in between root growth and the density and
richness of the soil. Producing the highest root-growth possible may not
make for the best plant, if the plant is intended to be placed in the ground
that season, though. Plants grown in very light mixes often don't adapt
well to the transition.
It may not be only the physical structure that causes the difference in
the root systems. One possibility is that it may be tied to trace elements
not found in potting mixes or the most commonly used fertilizers. Has anyone
tried using trace element supplements on their potted plants? If so, has
it made a difference?