plunge beds

That depends on how strong you want it to be and also on how you intend to grow the bulbs, ie. in pots or in compost in the bed. I think I have a set of pictures of how I built my indoor (under glass that is) Rock gardens. If needed I will find them and post in a Blog for you.

We have two plunge beds in different greenhouses, one is at floor level and the other at bench height.
The one on the ground was easiest as I simply dug out a pit about six inches deep along the side and lined it with weed suppressant membrane. I then surrounded it with a frame of four inch boards, above the pit, and filled this with concreting/coarse sand.
The one at bench height was more difficult. I got a blacksmith to weld me up a frame of tubular steel to my specificationand and stood this against one wall of the lean-to greenhouse. My intention was to use two foot square paving slabs as the base of the plunge but when I lifted the first one up the whole frame began to s-w-a-y! Oh dear, re-think. I then bought some thick marine ply for this purpose and mounted a box made from two widths of six inch treated timber on this. As this is a lean-to greenhouse against the wall of the wooden shed I was able to construct some stays to anchor the plunge against the shed wall to keep it rigid. Not entirely satisfactory but it has stood for about ten years now without any problems. In retrospect, I should have paid more attention to supporting stays on the frame and a couple of extra legs in the middle of it.
I do believe that you can purchase ready made plunge beds but they are quite expensive and not nearly as much fun. Good luch with the project, Steve.

I love that word PLUNGE. When I was a little girl my mum used to take me swimming to Warrington baths. This was a combined laundering and personal cleanliness place in this then grim and dirty northern town. One of the first to be built ooop north. There was a double door with LADIES an one glass panel and PLUNGE on the other. We used to giggle as we approached for our PLUNGE. So happy PLUNGING Steveg. Anyone else have a recall of this sort of word that might have a gardening connection

No, but we used to go to Warrington Baths every Saturday morning, the ones just near to the old town Hall, remember the wonderful gates to that place.
Actually Widnes had Plunge baths too, built by ICI for their workers but open to the Public.

So ... is a plunge bed bascially a flower bed between one higher and one lower restriction, either with rock or stone or something? Almost like a flower bed edging to a higher level? I do not recommend typing 'plunge' into google - I am still laughing at the results ... isn't the english language great!!

A plunge bed is a large trough full of sand and the plants are grown in clay pots 'plunged' into the sand. The idea is that it is used for plants that resent overhead watering. You just keep the sand moist and this seeps into the pots. It also makes an excellent display showcase for other plants that you might grow in pots.

Wonderful - thank you Bulbaholic - great idea maybe for changing displays through the season, as things die down? I am thinking of pelargoniums and such which prefer water at the base and not on their leaves.

They are often used for changing displays in the Alpine House at botanic gardens, Akvg. At Edinburgh RBG they have two plunge beds. One is planted permanently with cushion plants that need a lot of tlc but the other is changed on a weekly basis to display alpines in flower.

I think you might have a good wheeze there AVKQ47(secret agent?)If I didn't have my left ankle/leg in plaster I'd have gone out and PLUNGED some geraniums/fuchsias by now and then fleeced them over protected by shrubs. All very frustrating.

Secret agent? I wish ... sorry about your ankle/leg. Get 'plunging' in the spring. Merry Christmas!