Plunge beds

[ArnoldT]

I have seen plunge beds in many of the images posted here.  Some look like pure sand and other look like a collection of whatever was left lying around.

Any suggestions about about fill used for a plunge bed.

Thanks,

[angie]

Arnold I am glad you asked this question I also would like to get some advice too.
Dont like to hijack your topic but I was also wandering what depth the plunge beds should be.

Angie 

[Maggi Young]

Some of our plunge beds look a bit scruffy, because for the Erythroniums we are growing in them we have been covering over (those sand plunges that have the bulbs in pond baskets plunged up to the rim) the beds with  a  mulch of composted shredded hedge  trimmings. This helps to  keep down the growth of mosses and liverworts and aslo helps keep a moist atmosphere around these bulbs, which would really prefer a woodland situation.Whether for inside a glass house, in a frame or outside, any plunge bed should be as deep as possible. ...and sand is without doubt the best medium for such a bed.
In our glass houses the plunge benches are really too shallow but we are constrained by the need to have a double layer so we cannot have the very deep (at least fifteen inches/ approx 38cms) plunge benches, which old style alpine houses used to have, usually made of brick and  providing a great place for plants in pots to live!

 Outside,  whether in the open or in a  frame then, again, the more depth the better- this will keep a steadier temperature and moisture level around the pots .
It is best if the sand can be in contact with the ground below since this will greatly aid in drawing moisture evenly through the sand.

 Hope this is some help.... it works for us!

[angie]

Sand for the plunge beds in the greenhouse, I have read in some old posts that you can't use builders sand, I was just going to get some sand from our local quarry .
Also if I heat the greenhouse do you need to put warming cables under the sand.

Angie

[Maggi Young]

Builders' sand is fine , Angela. You want a coarse sand anyway, the very fine stuff tends to get "caked" too much.

Warming cables are a good idea..... Ian has 'em. They hardly ever go on, they're on a thermostsat just to be able to protect the bulb pots from being frozen right through in the worst of the cold weather. In a mild winter they may never run at all but it is good to know you have the option to either protect from frost or even raise the temperature a bit higher for some plants or when propagating.
I think there's a thread here somewhere for warming cables.... I'll go have a look......

[LucS]

Some of our plunge beds look a bit scruffy, because for the Erythroniums we are growing in them we have been covering over (those sand plunges that have the bulbs in pond baskets plunged up to the rim) the beds with  a  mulch of composted shredded hedge  trimmings. This helps to  keep down the growth of mosses and liverworts and aslo helps keep a moist atmosphere around these bulbs, which would really prefer a woodland situation.Whether for inside a glass house, in a frame or outside, any plunge bed should be as deep as possible. ...and sand is without doubt the best medium for such a bed.
In our glass houses the plunge benches are really too shallow but we are constrained by the need to have a double layer so we cannot have the very deep (at least fifteen inches/ approx 38cms) plunge benches, which old style alpine houses used to have, usually made of brick and  providing a great place for plants in pots to live!

 Outside,  whether in the open or in a  frame then, again, the more depth the better- this will keep a steadier temperature and moisture level around the pots .
It is best if the sand can be in contact with the ground below since this will greatly aid in drawing moisture evenly through the sand.

 Hope this is some help.... it works for us!

To illustrate what Maggi means, this is how I constructed my glasshouses.
All the clay-pots are plunged in a yellow sand that is able to hold the moisture for some time and that stays firm enough when a pot is lifted.

[Maggi Young]

Well, Luc, I have to say that your glasshouses are a treat to see.... so neat and tidy.... very impressive 

I haven't found the thread that I mentioned.... must have been imagining things  ... there are odd mentions but here is a link to a good post
 by Gerd K. about an experiment he made...........

http://www.srgc.org.uk/smf/index.php?topic=2496.msg59350#msg59350 


For anyone wondering what our system is:  The cables are below the pots, set to come on when the temperature at about an inch or so below the sand plunge surface goes down to minus 1 degree C and the heat goes off again when the temperature is raised to around plus 1 degree C.
I had a look in Len Rhind's Bulb Log Index ( what would we do without that man?)
http://www.srgc.org.uk/bulblog/index.pdf  and found this.....

http://www.srgc.org.uk/bulblog/log2004/270104/log.html


 I am worried to post that because the contrast between our glasshouse and Luc S' one is more than extreme!! 

[ArnoldT]

Wow. Luc I'm envious now.

I don't think soil cables would work here as well.  Our lows can get down to 10F at times. 

Builders sand may contain some salt.  I used Play Sand which is washed and sterilized for use in childrens play boxes.

Must be careful with the overall weight on greenhouse benching. Wet sand can be heavy.

[Mick McLoughlin]

Maggi,
There is this thread about thermostats on cables?#
http://www.srgc.org.uk/smf/index.php?topic=1098.msg25509#msg25509

[Maggi Young]

Well done, Mick..... I thought there was something else to be found!

Arnold, of course you are right, for greenhouse staging with sand benches the whole construction  needs to be VERY strong and solid.

[annew]

My plunges are mostly about 25cm deep, and contain 'sharp sand' from our local dealer (just ordered some more today cost £24 per bulk bag -about a ton-plus vat). Get a look at it first if you can and hopefully get stuff which is not too dusty.

[angie]

I think I need a new greenhouse and start right at the beginning again.

Luc I can only say one word and it's WOW , can I move into your greenhouse.

Now I will have to find where to buy, heated cables, plunge beds and everything else I need, can anyone pm with any information please.

Away to have a long look again at Luc,s amazing greenhouse , mine is such a muddle

Angie

[gote]

Builders sand may contain some salt.  I used Play Sand which is washed and sterilized for use in childrens play boxes.

If by salt you mean sodium chloride (table salt) builder's sand should be free from it since it causes problems with frost resistance and corrosion of steel. Why do you think there is salt in it?
Cceers
Göte

[LucS]

I've never used heating cables. My benches are 70cm deep because they stand on the concrete greenhouse floor. That volume of sand gives enough heat-capacity to prevend the pots from freezing
through. In a hard winter, I give some overhead protection with fleeze or air-bubbles plastic.

About the cleanliness. I think this is necessary if you want to control deseases.

[Gerry Webster]

I grow all my bulbs in clay pots  in plunge beds - they are only brought under 'glass' (i.e., plastic) when in flower. My plunge beds are 60cm deep. The bottom 30cm of most of them is filled with builders rubble - in one case with wine bottles (empty) -  & the top 30cm with coarse, sharp sand sometimes  known as concreting sand, quite different to the soft, yellow builders sand. This holds water reasonably well for a short time.  I don't think it matters what bulky material one puts in the bottom of a plunge & I recall Bob Wallis recounting how their plunges were filled up with old lawnmowers, defunct TV sets & similar rubbish - veritable time capsules.