How tall to trellis beans? Does it matter?

I’m planning to extend my trellis in the off-season, and I’m unsure about how high to make it.

My existing trellis is a simple wooden frame about 7’ tall strung with twine. Early this season, a couple of my plants were overachieving and I decided to give them an extra 5’ in the form of two lashed on sticks “to see how high they’d grow.” Soon enough I had a half dozen vines at the top of those, reaching an extra foot above that and looking for more! Either the wind breaking them or just the natural course of things had them settle with what they had.

That leaves me with a number of questions moving forward. How high would they grow? Does the extra height contribute to extra yield or only extra difficulty in harvesting? Should I build (potentially much) higher for next year‘s editions?

Personally, difficulty harvesting is my concern. I've got some scarlet runner beans and they're inside a frame which has allowed me to encourage them to go sideways once they reached the top of their tripod. I've seen elsewhere growing beans on hoops and harvesting from underneath, but when I tried it, my hooped fencing wasn't strong enough. If it were me and I had some way to build an arbor so they travel across above my head, that would appeal to me! I'd get a good crop, but my short painting ladder would be enough to reach them.

If I were to get more beans total, I’d probably prefer making something taller; the out-of-reach beans might just not get eaten as snap beans.  I’ve also got some ideas about how I might design something very tall but maybe able to swing down for harvest (I got the idea because my lashings loosened and I was able to swing the whole thing down without the beans seeming to care.)

If they would set the same number of beans, just more densely in 7’-8’, then that would just be easier.

On my property, taller things get more sun, so frequently they produce more at the top. But having to set up my 10 ft orchard later entertains the risk of collateral damage!

Some pole bean varieties state how tall they expect to grow. It's been my experience that they can indeed grow much taller. It's also been my experience that what ever type of support system you choose to use, it should be very strong and sturdy. One year I had 2 rows of beans on an A-frame type of trellis, just pvc and string. It did quite well right up until it didn't.  A little too much breeze and it went right over on top of the tomatoes. Another year I used a section of "wrought iron" style fencing "threaded" onto rebar shoved into the ground. That did much better.

I really like the idea of a full on arbor. Then I think about the need to cycle crops around when using the age-old method of single-crop beds. Suddenly I'm seeing the need for multiple arbors in this scenario.

Well, good luck in what ever you choose.

If it ends up too tall to harvest easily, can you just use those high beans as a dry end of season harvest?

Use those for dry beans and next years seeds?

Question - my beans have already flowered and been picked from low on the plant. Will they flower a second time low down, or does future harvest depend on the individual vines growing longer and setting more flowers? If so allowing them to grow taller seems to indicate higher yield.

I agree with everyone else. The answer to your question is, "How high can you reach?"

Michael Cox wrote:

Will they flower a second time low down, or does future harvest depend on the individual vines growing longer and setting more flowers?

That's a *really* good question. I do know that Scarlet Runner beans bloom on side-shoots and I've gotten the impression they get better production up higher, but it may be that those bean flowers get more pollinator attention? My reality is that if beans vines run out of support, they just topple sideways and keep growing.

I have grown a variety of bush beans which is noticeably "determinate" - it does one bunch of flowering and it's done. If it does put out more flowers, they're usually weak.

I can share my observations of these plants.  To be clear these are common beans (most of them started their stay here as "Rattlesnake" beans, but there have also been "Taos Brown" as well) and not runner beans or another species, but I am intending to grow runners and teparies next year.

An individual flower stem will grow a couple of flowers at a time, and will grow more if you pick its beans (I can't find any cases on my plants where there are either flowers or tiny beans on the same flower stem as a mature bean).  Additionally, when the terminal bud gets damaged (I think this happens with the buffeting of the wind, but it could also be a natural mechanism the plant employs when it can't find anything more to grow up) some of them will back bud, and those shoots are producing both flowers and beans.  That said, the leaf density there gets really high and it might be crowding out itself.

I suspect but can't confirm that the taller plants will produce more beans.  I think my tallest plants are blooming top to bottom (though it is really hard to disentangle which vines are which!)  It's also possible that the back-budding individuals will also produce a large lode (they're working on it now!)

To address some of the other comments:

Cindy Haskin wrote: I really like the idea of a full on arbor.

I do too!  My yard, however, runs east-west and the photo in the first post is the northern edge of the yard, so this whole area gets tons of sun, and a tall trellis in the back is "free" space for me.  If I build something like an arbor here it would shade the other plants I grow in this bed.  However, there are other places where I could build such a thing (I have space in the front where something like that could look good).  Incidentally, despite this trellis looking quite flimsy, it's held up three years of beans and peas (and one very viney tomato plant).

Michael Cox wrote:If it ends up too tall to harvest easily, can you just use those high beans as a dry end of season harvest?

Certainly!  In fact, it makes the balance of how to decide whether to keep harvesting or let the beans dry down much easier (the high ones stay).  I really think that the solution to harvesting in this case is simply to make the extensions able to swing down and lock in place.  Designing such a thing would be a fun, over-engineered project for the winter months.

Here are a couple pictures that illustrate the above:

I don't know the answer but I will say that my pea plant is 12 feet high and I was kinda thinking it would peter out.  Now thanks to this thread I'm wondering if there's any way I can coax those last 4 feet to follow the horizontal beam instead.

What are you sharing out or providing shade for if you go taller? My reasoning for not going taller would be so I could harvest in a reasonable manner, but it sounds like you're unconcerned about harvesting those skyscrapers ;).. In which case, if harvesting isn't a decisive factor, than the issue of shade production might be. And it could work either way, as argument for going really tall, or for staying shorter, depending on what else you are growing.

I find that beans and peas will just continue to grow until the weather no longer permits. At least here in my 5b Canadian garden.

I train my beans and peas  up on strings or nets attached to solid wooden frames.

Most of my beans are trellised up on vertical string along the back of my extra-big patio planter box with a big pergola top. It's about 3m high, and over 5m long. It has solid wooden frame and a pergola top, which I also string up. Once the beans have reached the height, I give them a little starter twirl on the horizontal strings, and they proceed to wind themselves across. When they run out of space and loop over the edge of the pergola I just nudge them sideways across themselves.

It results in a shade canopy as well as a VERY important privacy screen against my neighbours raised deck that sits along the other side of the fence. It also means the beans are super easy to reach up and pick, and they are safer from grabby squirrel paws and greedy little birds.

Sionainn Cailís wrote:I train my beans and peas  up on strings or nets attached to solid wooden frames.

Lovely!