Shrubs In Tubs - Part 2 - Building The Tubs
When we realized that we could NOT fill the trough with growing medium (too heavy) then the idea of "Shrubs in Tubs" came into focus.
The big issues relate to insulation of the root ball and the isolation of the plant from sun / shade heat/ cold cycles, be they diurnal or seasonal.
We developed two tubs. One was based on traditional circular landscapers tubs. The second was a rectangular planter, on legs.
The circular tub consists of a 20 gallon tub set inside an 25 gallon tub, with the intervening space filled with insulation.
A circular disk of insulation goes on the bottom.
The walls are insulated with rectangular pieces of 1.5" EPS rigid expanded polystyrene (cut from a sheet). The staves of EPS were about 2" wide and 18" long. They sit in between the tubs like barrel staves. The space in between the rigid EPS was then foamed with a regular can of insulating foam sealant - $12 at Home Depot. It took about two cans of foam per tub set. Had I spent more time customizing my barrel staves of EPS I might have saved a couple of $$ on canned foam.
Here is a pictures to save me a thousand words.
The only caveats are that sometimes the expanding foam can push the inner tub out of the outer tub. So stand inside it as you foam, and while the foam sets a bit (stops expanding). Secondly, foam should extrude out of all holes in the tubs. These need to be trimmed and caulked.
Drainage. You need to provide some drainage. I drilled two holes out horizontally at the base of the inner tub and inserted 1.5" PVC pipe about 6 in long. The diameter is not crucial - its just what I found lying around the neighbouring building site. Just provide a reliable conduit. Then caulk it into place both inside and out. Another picture.
This one not only shows the drains but also the caulking of various holes in the original tub.
Coaming. You need to provide some form of coaming around the top of your assembly to keep the rain off the insulation. Trim all the surplus foam and tub handle off. The coaming itself is an expandable down spout extension, cut half longitudinally. You drap it around the top of your tubs concave side down, and with a good overlap. Then having drilled holes at 2" spacing around the top of the tubs (through both tubs and the intermediate foam, you use a palstic tie (or a pair of them) wrap to tie the wrap down onto the top of the tubs.
A circular disk of insulation goes on the bottom.
The walls are insulated with rectangular pieces of 1.5" EPS rigid expanded polystyrene (cut from a sheet). The staves of EPS were about 2" wide and 18" long. They sit in between the tubs like barrel staves. The space in between the rigid EPS was then foamed with a regular can of insulating foam sealant - $12 at Home Depot. It took about two cans of foam per tub set. Had I spent more time customizing my barrel staves of EPS I might have saved a couple of $$ on canned foam.
Here is a pictures to save me a thousand words.
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| 20 gal tub foamed inside a 25 gal tub |
The only caveats are that sometimes the expanding foam can push the inner tub out of the outer tub. So stand inside it as you foam, and while the foam sets a bit (stops expanding). Secondly, foam should extrude out of all holes in the tubs. These need to be trimmed and caulked.
Drainage. You need to provide some drainage. I drilled two holes out horizontally at the base of the inner tub and inserted 1.5" PVC pipe about 6 in long. The diameter is not crucial - its just what I found lying around the neighbouring building site. Just provide a reliable conduit. Then caulk it into place both inside and out. Another picture.
This one not only shows the drains but also the caulking of various holes in the original tub.
Coaming. You need to provide some form of coaming around the top of your assembly to keep the rain off the insulation. Trim all the surplus foam and tub handle off. The coaming itself is an expandable down spout extension, cut half longitudinally. You drap it around the top of your tubs concave side down, and with a good overlap. Then having drilled holes at 2" spacing around the top of the tubs (through both tubs and the intermediate foam, you use a palstic tie (or a pair of them) wrap to tie the wrap down onto the top of the tubs.
Here is the finished version with the coaming cinched down into place.
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| In the end I made five tubs in tubs. |
These are now ready for hoisting up to the trough and filling.
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