Constructing an Automated Propagation Mist BenchI can’t imagine conducting my greenhouse operations without a propagation bench. I use it for so many things including, stem cuttings, leaf cuttings, acclimating tropicals, starting seeds of all kinds, etc… I thought that I’d write up a description of what I built so that others here could replicate it or modify something similar for their particular growing situation.
The whole idea behind a mist bench is to create an environment suitable for rooting cuttings, ie. ~100% relative humidity and heat around the rooting zone.
Step 1: Build a tableYou want to have a table with side walls and drainage. It should also be water resistant as much as possible. I simply used an old greenhouse bench with painted lumber as my frame. I added some extra bracing, because this table will be holding a lot of weight when full of wet sand. I also raised the legs of one end about 3 inches to slant the entire table. I cut up some aluminum bleacher seats to use as the bottom of the table (bleacher seats also work great for any greenhouse bench). I cut the bleacher seat into sections the width of my table and screwed them adjacent to one another. I left a gap of 2 or 3 inches in the lower end of the table for drainage.
Step 2: Layer the table interior with plastic on top of weed barrierI used black pool liner plastic in the bottom of my table, overlapping the side walls. Again, I left a gap in the lower end to allow drainage. I put the plastic in over a solid sheet of woven weed barrier. This keeps sand from washing out the drainage gap. I didn’t secure the plastic in any way, as the sand will hold it firmly in place.
Step 3: Add sand, and heating cable I put in my first 2-3 inch layer of sand. You will want to use coarse sand. Fine sand or playground sand will be more susceptible to nasty algae growth. On top of the sand, I coiled heating cable, being careful not to overlap the cable anywhere.
Step 4: Add hardware cloth and the final layer of sandOn top of the heating cable, I laid hardware cloth. Then I added the last few inches of coarse sand over the top. Now the bench is full.
Step 5: Wire up timers and thermostat(ATTN: have an electrician do this if your unfamiliar with wiring) You’ll need to wire up two timers for your mist system, and one thermostat for your heating cable. You’ll want a 24 hour timer, and a 10 minute cycle timer. This allows you to set your system to go off at night, when it’s not necessary, and then to turn the misters on every 10 minutes. There’s a fair amount of flexibility with these timers, and you can adjust them according to your plants needs. The thermostat will allow you to control the temperature of the sand or soil (depending on where you put your sensor).
Step 6: Install solenoid valve and pvc mister system.You can simply use pvc fittings to design your mister system. You need to connect to a water source that is continually on. Install the solenoid valve inline and wire it to your timers. I use mist emitters with a 0.043” nozzle size. Once you have that done, you’re good to go. I usually set mine for misters to come on every 10 minutes for 7 seconds with it turning off at night.
MaintenanceI replace the top layer of sand every six months or so due to algae buildup. You can use algaecide or bleach/water solution to lengthen that period, but I try to avoid that because I always have plants on the bench. Alternatively, drying the bench out every month or so, also works. Also, the timers seem to have about a 2-3 yr life span. It’s best to have a spare of each one laying around…
Of course... this type of system can be scaled to whatever size and dimensions that fit your particular growing space.
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Topic: Constructing a propagation bench (Read 9080 times)