Air Pruning

Jane McGary via pbs pbs@lists.pacificbulbsociety.net
Sun, 05 Nov 2023 10:09:45 PST
I thought "root pruning" pots were the ones growers use around here when 
field-growing woody plants. They have quite a large mesh on all sides, 
and they are plunged in the soil of the field. Their advantage is that 
the plants can be dug and lifted quickly by chopping off the outside 
roots while the pot retains the ball of very cohesive soil. They do 
prevent the circling root growth that causes such difficulty when trying 
to transplant something that has been allowed to stay in a regular 
plastic pot for too long. Growers who use band pots, the ones with 
crossbars on the bottom, either use a soil mix that is quite cohesive, 
or they put a square of something like window screen inside the bands. I 
don't like fussing with the screens, and when I use plastic pots for 
non-bulbous plants or bulb seedlings, I choose the kinds with 8 drain 
holes instead of 3. My summer-dormant bulbs are almost all in terracotta 
pots plunged in sand; a few are in plastic mesh aquatic containers, also 
plunged, which are good for big plants that make a lot of annual root 
growth, notably dryland irises. Mark Akimoff has found that the mesh 
pots can be used without plunging as long as they're closely grouped.

There is a detailed discussion of soils and "drainage" (more 
appropriately, aeration and moisture retention) in a book I edited for 
NARGS some years ago, "Rock Garden Design and Construction." It's 
applicable to bulbs as well as alpines.

Jane McGary, Portland, Oregon, USA

On 11/5/2023 6:36 AM, Tim Eck via pbs wrote:
> I would guess root pruning pots are similar to the drying action of terra
> cotta pots but not vitrified or glazed pots.  Also, it might not be as big
> an issue in dryer regions but eastern USA can be problematic for drainage
> all year round.
>
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