A good trellis is.........
• Sturdy/Won't blow over
• Easy to assemble/take apart
• Doesn't make holes in the roof; holes = leaks
The key thing is to use the weight of the SIP (about 40 lbs for the 2-bucket design) to anchor something that you fasten poles to. Angled braces keep them from tipping over.
I've spent the last three Friday mornings building a simple set of trellises for about 100 2-bucket SIPs on the rooftop of the Pacific Garden Mission.
After setting a post at either end--and at each of the corners--of what viewed from above looks like a giant question mark, we used a variation of the Florida Weave to support the tomatoes, squash and cucumbers.
Each post, nothing more that a scavenged piece of 2"x4", was attached at the bottom to a 4 foot long piece of salvaged 2x10 deck joist. 1x4 angled braces were placed to prevent the post from tipping over. To keep it all in place, 2 or 3 planted SIPs were set on each 2x10 plank.
I put a few of the extra photos of the PGM Rooftop garden in my Picasa account:
|Pacific Garden Mission Rooftop SIP Garden|
My rooftop garden has an overbuilt, industrial strength trellis, made of electrical pipe and 2x4's. I was worried about a tall plant catching the wind and blowing the entire thing off the edge of my roof. Now I think all that piping is overkill. Also, I could have eliminated all the "A" frames next to all the SIPs in the middle of the grid.
If I were starting from scratch, I'd make something like what I did at PGM. It's so much easier--cheaper too--and works almost as well. A downside to the Florida Weave is that you need to add a horizontal run of twine every 8-10 inches, following the plant up as it grows. Also it's only good for one season. What I did on my roof is more permanent and works year after year.
Art (Mr. H2) had another idea, one that worked well with all their 2-bucket SIPs.
He used several of the green metal grids he bought years ago at an industrial auction. If you did the same, here's your chance to put them to work.
For more good trellis ideas, check out this Fine Gardening article.
Good luck making your own!
[Updated 6.8.09 - In the comments, Russ added this useful link, "Tomato Staking Techniques Evaluation", put together by the Master Gardeners of Santa Clara (CA) County.]