Well since the boxes are going to run east-west, I would say that a spacing of 3' minimum should be fine. You'd want that much space between them to really get in there and work/harvest anyway, right?

In the early morning you could end up having a shadow 12' long it will go from east to west though. as the day goes on the shadow will get smaller and shift to a north to south oriantation. in the late afternoon it will shift back to an east to west oriantation but this time it will be on the east side of the trellis not the west side. at noon your shadow will probally only be a few inches long.

I think 3' path lengths sounds about right to keep from having a lot of shading but it won't stop al of it.
hope this helps.

The real question is what will be on the trellis and how high will it be? That is: it is easy enough to figure out the shadow pattern - and there will be a shadow - knowing these key pieces of information. You can then use the NOAA Solar Calculator to get the sun angles and then calculate the shadow length and duration. Else you can use SketchUp to do a better visual.

Dan

Thanks for the input guys! I think I managed to solve my layout problems. I'm going to devote one northern box entirely to tomatoes, trellising the rear row and staking the front in a staggered pattern. The other northern box will have beans and peas against the trellis. The boxes in front, that would have caused the issue with shade, I am going to use stakes or "mini-trellises" to plant my 4 cucumber squares -- I'll stagger them througout the 16 feet of box length. They don't get real tall, and spaced out the sun should get through well enough.

On the plus side, figuring out angles and shadow length was the first time I've used my high school trig knowledge in years!

Here is a link that might be useful: Garden blog

BTW Luke, I'm currently writing a series of articles and a journal paper on tree shadows and solar access easements.

Your question solidified my wondering whether I should do something about shadows on the ground as well, and am typing the outline for this article as we speak. One graphic will be a series of raised beds with trellises (trellisi?) in the front boxes...so thanks for asking the question!

BTW, a 48" wide trellis (using 42" remesh found at home improvement stores) will only shade for ~2 hours in any one spot. The kid is home sick today, but plan on doing this graphic PDQ and will post here if you wish and remind me.

Dan

Yeah, that would be cool Dan!

Here is a link that might be useful: Garden blog

The shadow length question came up a while ago in another post. It prompted me to look into it more, and ultimately break out the trigonometry that I never imagined using in real life.

Here is what I calculated. You are in NJ, so according to a web solar calculator (that Dan so nicely pointed out to me in the other post), on May 21, at 10am the sun's apparent elevation is at about 58 degrees, and at noon the apparent sun angle is about 70 degrees. For a six foot high trellis, that translates into shadow lengths moving from 3.75 feet at 10 am, to 2.18 feet at noon, back to 3.75 feet at 2 pm, all in standard time, not daylight savings time.

On June 21, the angles go to about 60 degrees at 10 and 2, and about 73 degrees at noon. That becomes 3.46 feet to 1.83 feet at noon.

So, roughly, if I figured everything right, a four foot pathway between boxes means no shadow coverage between the peak sun hours of 10 am and 2 pm from May to July. Practically, a two foot path should still be fine, since your trellis will not typically be full to the top early in the season. Even if the trellis was full to the top, the shadow direction changes during in the day so the south row of the second box should still get decent sun.

I've got commitments until afternoon, so I'll finish my initial and post later on today, and paully is correct - only the front part of the bed with a 3' path will be in shadow with a 6' trellis for ~ 1.5 hours, which people exploit to give a little cooling for, say, carrots or onions in front. That is to say, casting shadow on the raised bed in July is a good thing, as you don't want your soil at 85º & watering twice a day...

Dan

My head hurts just from reading this. God love you all who can do math, because I sure can't!

OK, so I tried to judge the latitude of Bruce's house near Rumsey for the solar angle ;o) .

The first is for Equinox at Solar Noon, you can see the shadow is about 9" into the bed, which is 18" high and 4x12, the aisles are 3' wide and the front trellis is 5' and the rear trellisi are 6':

So this one is at ~1000 on 9/12, the date at which the shadow from the 6' starts to touch the soil:

It appears at this latitude it looks like the 3' aisles and 18" height are optimal for full light and still close enough to shade the box sides to keep soil a bit cooler. I prefer my trellises at 6' (I'm 6'2") as most of my indet toms grow at least that high and my cukes get there too. Butternuts like to spread more than climb, so that ht. works best for me.

Dan

Heh. Going back to the beginning of this thread, I randomly said 3' spacing should be fine, with basically zero knowledge other than experience and intuition.
Yay me!

...but doesn't it feel good to have your intuition and experience confirmed by science?

It does! And I'm incredibly impressed by not only the science, but the rendering thereof, not to mention the time it took to actually 1) learn said science, and 2) create said rendering ;)

:o)

The 3' aisles are about the minimum for decent space for a wheelbarrow. Any narrower and it's too hard to operate, so maybe the good intuition is informed by experience as well.

At any rate, I'll be shopping around a trade mag paper for siting with shadows, so this rendering is pretty much going to accompany the manuscript, and the work was going to get done regardless, just sped up for this thread. I thank you folks for getting me into 4th gear.

Dan