I've also "destructed" four of 12 raised bed gardens for the sunflowers. These are made from (old) 2x6, and are 3x3 feet in size. Sunflowers were planted 6 inches in from each corner, which gives a 2 foot spacing between sunflowers. Pole beans (from some commercial packet of 3 different kinds of pole beans) were planted 1 inch from corners, or int he center (5 plantings per bed). Most of the sunflower locations did germinate, with some of these locations have 2 (and occassionally 3) plants per location, which were thinned out at some point by me.
The plantings were set up by putting 2 or 3 layers of newspaper on the ground (old pasture) and then setting the
wood raised bed on top. Or, that would be the description if there was no wind. We seldom have days of no wind. About 3 inches of peat moss were placed in the bed, and then about 1 inch of topsoil, and then some compost (sheep manure, commercial) on top.
During the growing season, I observed some weeds coming up. As many of the weeds I have no idea of the identity, it was hard to guess a source. The most common weed was grass. I have seen clover, vetch and wild
rose (my farm has tons of wild rose). And of
course, dandelion.
We have a lot of deer in the neighbourhood, and they wiped out two of my sunflower plantings early in the growing season. One sunflower in particular had the head and all the leaves removed by the deer. It later went on to activate new growth nodes, and was trying to recover. But it was so far behind, it never had a chance. Later in the season with a sunflower maybe twice as tall (at 3 feet), after a wind event knocked the head off, I cut all the leaves off. I was looking to see if this would kick start it into activating other growth nodes, and that didn't happen.
I pulled the sunflowers up by the stalk, and removed the "soil" that was embedded in the root ball. The largest sunflower pulled was in the 3-4 foot tall range, and the root mass was nearly 1/4 of the 3x3 planting. For all 4 of the planters investigated so far, I seen no evidence of sunflower
roots going through the newspaper bottom and into the clay soil underneath. In only a single circumstance, did I see evidence for a taproot. I don't know if the taproot penetrated the paper, but if it did it may have just been lying between the paper and the clay soil filled with fescue sod that was 40 years old. I seen no evidence of worms in any of the 4 planters. I suspect this might be drought related. If we would have had regular rain, maybe the newspaper would have rotted enough for worms to move. If there were worms in the clay under these planters.
People talk about nitrogen support for the corn and squash by the beans in Three Sisters plantings. Some have wondered how this comes to be. Some suggested it is the nitrogen in the roots, vine and pods. Well, the root mass of all of the bean plants pulled up so far is really underimpressive. I can't see how that is the powerful nitrogen source. And the vine and pod looks pretty meagre too. My guess is that the roots are sort of analagous to a series of ditches on slope, and a
bucket is used to lift water from the bottom of one ditch to the top of the adjacent ditch. And so, some water can be lost in the transfer. If that is how the roots function in pulling up water (and injecting nitrogen), maybe it is at each bucket lift station, that nitrogen is transferred to nearby plants?
I had planted daikon radish in some of these plantings mid summer (where there were sunflower failures), and I never seen a single one germinate. Not enough soil?
I did plant buckwheat in some locations where sunflower had failed, and buckwheat did germinate and grow. I would not characterise what grew as something which could outcompete a weed. I think the tallest buckwheat I got, was 6 inches at time of first frost. It did have little flowers on it.
In one planter (which the deer had gotten too early), in the process of digging up the "soil" (which is peat, and a bit of soil), I found a live
mouse in the "soil". And another. Eventually, I disposed of 5 "mice". Seemed to have a pointier nose than I was expecting, so maybe some relative of the mouse.
At this point, I have 4 finished blossoms cut at ground level, hanging in the garage upside down with paper bags over the blossoms. They were cut just before the first freeze and second freeze. Some of the sunflowers continue to live, and I currently have 2 plants with blossoms where about half the seed disk has been remodelled in the process of exposing male and female parts to lfowerets. I have a third freeze expected this weekend, so these plants will also get cut and hung upside down in the garage soon. I did see a couple of bumblebees on the one blossom today.