Bulb Predators / Raised Beds
Rodger Whitlock (Mon, 27 Sep 2004 10:30:22 PDT)

On 23 Sep 04 at 11:03, Ann Marie wrote:

In my experience, a plunge bed's great advantage is the even
conditions it provides to the plants: both temperature and moisture
levels are kept very even, though of course changing with the
seasons. It is my belief that many plants detest the drastic changes
in soil temperature and moisture content that ordinary pot culture
entails, and do much better with more even conditions at the root.

I used ordinary sand as the plunge material; put the plants in *clay*
pots, not plastic; and had the plant pots directly in contact with
the plunge material. The bed of sand wicks up any excess moisture, so
overwatering is almost impossible, but at the same time acts as a
reservoir so the pots don't dry out at all easily.

Note that this has more than a passing resemblance to the "capillary
beds" one finds sometimes described in the horticultural literature.

Ann Marie's recommended method will control temperature variation,
but the use of gravel (not water retentive), plastic pots
(impermeable to moisture), and nested pots (breaking any capillary
contact between plant pot and plunge material) all work against
getting any useful control of the moisture level in the pots.

Some bulbs definitely do not like intense drying off. Iris
winogradowii has never grown as well for me as when it was in a large
terracotta pot plunged in sand, and watered with yesterday's cold tea
first thing every summer morning.

As for the "structure", make it strong and make sure the sides won't
bulge. The easiest way of doing this is to make sure the
"structure" isn't too big. The best I've had was an 8'x4' bed made of
railway ties stacked on the flat. Longer beds made with railway ties
would start to bulge in the middle of the sides sooner or later.

Also, you don't need much height: 12-18" is quite adequate for most
purposes.

As with raised beds, you do not need to excavate underneath or
install drainage. As long as the plunge material is in capillary
contact with the native soil, all is well.

--
Rodger Whitlock
Victoria, British Columbia, Canada
Maritime Zone 8, a cool Mediterranean climate

on beautiful Vancouver Island