Pulling down to correct level

Jim McKenney jimmckenney@starpower.net
Tue, 12 Jul 2005 18:46:35 PDT
Maybe we don't disagree as much as it seems on this issue.

In Paige's post, she mentioned several bulbs which, in my experience,
certainly do end up deeper year after year. But they are not pulling
themselves down. They are growing deeper year by year. I think there is a
difference to be observed here. 

The lilies which Paige mentioned do not pull themselves down. Their bulbs
are on a short rhizome which can grow downward yearly. That is not pulling
themselves down in my book. 

Many bulbs do grow downward. If you dig them at the right time of year, you
will see the growth emerging form the existing bulb and heading downward.
That is one thing, and yes, it happens all the time.

Part of the answer here may be related to the fact that the structure we
call a bulb is, in many taxa, of annual duration. The bulb that you dig in
the summer is not the one you planted in the fall. So in the cases of taxa
which have bulbs of annual duration, it makes no sense at all to speak of
the bulbs pulling themselves down. You may find bulbs deeper than the ones
you planted, but they are not the bulbs you planted!

But are mature bulbs ever pulled downward by their roots? I'm still not
convinced. What happens to the soil beneath the bulb? Does it squish out
sideways to make room for the bulb? You are asking me to believe that, on
the one had, the soil is moist enough to allow a broad object such as a bulb
to be pulled downwards by root contraction as the moist soil is displaced,
yet on the other hand, that that same soil is firm enough to allow the
contracting roots to keep a grip on the soil? Why don't the roots themselves
pull out? 

As Alberto said, it is against common sense. 

Of course, that does not mean that it does not happen. 

But I'm not yet convinced.

Jim McKenney
Montgomery County, Maryland, USA, USDA zone 7, where this would not be the
first time that common sense got me into trouble.  

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