London plane seeding pattern / rhythm?

[Low Altitude]

I live in an urban area in hardiness band/zone 7b, where the London plane Platanus acerifolia is common. Because I'm an idiot, I thought it might be fun to try growing a couple from seed. I've had some success in previous years growing thornless honeylocust Gleditsia triacanthos and elm Ulmus americana from the seeds that litter the sidewalks hereabouts at the right time of year – hey, they'd only wash down the drains.

So a bit of research indicated that London plane grows seeds that are pretty hard to miss: compound spherical pods that can be over an inch in diameter. Here's a photo from the Wikipedia.

And on the trees:

But: I've been keeping my eyes open for close to two years now, two falls/autumns and two springs, and I've barely seen seed pods on the trees and none at all cast and lying around. So now I'm wondering: might they seed not annually, but every few years, not necessarily a discrete regular interval? And might the seeding event be 'triggered' not just by elapsed time since the last seeding, but by conducive combinations of environmental factors – complete guesswork on my part, but something like maybe there needing to be protracted cold over winter, followed by a warm spring. Or a cool spring. Maybe it likes it wetter or dryer for certain (extended?) periods?

Does anyone even know whether they are 'supposed' to seed in the spring or fall? Some other time?

Any ideas, anyone?

 

[Sheal]

I've done a little reading on the internet Low Altitude and it would seem the tree produces seed every year, so I can't explain why you haven't found any. It also mentioned that seed isn't always viable and if it germinates often produces weak plants. Below is a web site you might find of interest and it seems it's easier to propagate cuttings.

London Planetree Grow & Care Guide

A popular, durable and attractive shade and street tree, London planetree (Platanus acerifolia hybrida) is very tolerant of adverse conditions and road salt. London planetree has interestingly shaped leaves and beautiful white and brown mottled bark

www.rayagarden.com

 

[Oliver Buckle]

Two possibilities occur to me,firstly they are pretty long lived, up to 400 years, so are they mature trees? They are big 75-100 feet tall when they are mature. The other possibility is that because they are a hybrid of an American and an Oriental tree (They just met in London) they might not be super fertile, I note propagation references cite hardwood cuttings, of course that may be to keep them true to type, but it might also be easier.

 

[Low Altitude]

Oh, that's good thinking. As to maturity, there are young and old, but yes, the ones I'm thinking of are surely in the 75-100 foot range. Saplings they ain't. I hadn't considered 'hybrid sterility', but yes, I wonder if that's a factor.

I would love to try cuttings, but they aren't my trees to cut. I don't feel guilty about seeds that would otherwise be washed away...

Thanks, Oliver – that makes a lot of sense and helps. I'll keep looking at the trees.

 

[Low Altitude]

I've done a little reading on the internet Low Altitude and it would seem the tree produces seed every year, so I can't explain why you haven't found any. It also mentioned that seed isn't always viable and if it germinates often produces weak plants. Below is a web site you might find of interest and it seems it's easier to propagate cuttings.

London Planetree Grow & Care Guide

A popular, durable and attractive shade and street tree, London planetree (Platanus acerifolia hybrida) is very tolerant of adverse conditions and road salt. London planetree has interestingly shaped leaves and beautiful white and brown mottled bark

www.rayagarden.com

Sheal,

Thank you – that's a useful web page and one that inspires confidence. I see that the writer supports Oliver's suspicion that there might be a hybrid problem with the seeds – both production and viability. Makes sense. Oh well – much better to know than to keep wondering. Thank you both!

 

[Sheal]

I read all the way through the web page too. There's always something to learn. Yes, it does seem there's a hybrid problem so will you continue to look for seeds, or abandon the idea?

 

[Low Altitude]

Ha! Good question! Maybe because I'm an idiot (and got lucky with the elms and the honey locusts, the seeds garnered from these same sidewalks) and because keeping my eyes open is fairly effortless, I'll keep looking – and if one day I actually end up with seeds in my hand, it'd be criminal not to give them a try


Oliver's idea of trying cuttings is much more sensible, but I can't really go taking cuttings from public trees – if everyone did it, the trees'd be ravaged, at least within 'human height' of the ground... but you make me think: once in a blue moon around here, we have a storm powerful enough to down a few branches. Next time it happens, maybe I will take a tour around the neighborhood before the cleanup crews arrive, and see what I can pick up.

 

[Sheal]

I'm sure you'll come across the seeds. Have you any local parks or woodland where you might find some? Cuttings may also be available to you there.

 

[Low Altitude]

I'm sure you'll come across the seeds. Have you any local parks or woodland where you might find some? Cuttings may also be available to you there.

Sheal, it's so funny. There are scores of these London plane trees in my neighborhood and in the park nearby. This year I've been diligent looking: people must think I'm daft, standing looking up at a tree for minutes on end as i try to catch sight of a seed pod. Nary a one, I promise. Weird. Unless they seed autumn not spring.

Meanwhile, though, today i overcame my scruples about mutilating park trees: there's a particular plane i like in the park. I walked by it today and there were sprigs growing out from around its base. Now, I've been looking at this tree for fifteen years and i can say with certainty that in a couple of days, or a week or a month, someone from the Parks Dept is going to come around with a scythe or a strimmer and 'neaten things up', i.e. cut down/off all the sprigs and throw them away. So I saved them some time, detached a couple of the sprigs and brought them home. As you'll see from the photo below, one is about a foot long and the other is about eighteen inches. For now, I've put them in an inch of water in a jam jar.

If you were making cuttings, where would you cut? How many cuttings from the two twigs? I can guess, but I've often been wrong before...

 

[Oliver Buckle]

Cuttings are usually taken in Autumn when the tree is dormant, about a ten inch cutting , similar to a rambling rose cutting, but it is always worth a try.
This is not based on any specific knowledge of planes, but I would take a piece cut just below a leaf node and with probably two leaves on it. I would make a potting mixture with plenty of sharp sand and a bit of seaweed based, non hormonal rooting powder mixed in it, then dip the end of the cutting in water , then a hormone based rooting powder before planting. I would probably cut the leaves in half to reduce water loss.
I can't remember the details, but cutting below a leaf node does something hormonally which makes root production more likely.
It might be worth standing one in water with a bit of rooting hormone added to it. Another thing to try is to go back and see if you can cut an inch or two below ground level; basically try ringing the changes and see if one of them works.
Reading further I discovered that if you do find seeds you should soak them for forty eight hours before drying and planting, and that individual trees vary with the success rate of cuttings.

 

[Low Altitude]

Cuttings are usually taken in Autumn when the tree is dormant, about a ten inch cutting , similar to a rambling rose cutting, but it is always worth a try.
This is not based on any specific knowledge of planes, but I would take a piece cut just below a leaf node and with probably two leaves on it. I would make a potting mixture with plenty of sharp sand and a bit of seaweed based, non hormonal rooting powder mixed in it, then dip the end of the cutting in water , then a hormone based rooting powder before planting. I would probably cut the leaves in half to reduce water loss.
I can't remember the details, but cutting below a leaf node does something hormonally which makes root production more likely.
It might be worth standing one in water with a bit of rooting hormone added to it. Another thing to try is to go back and see if you can cut an inch or two below ground level; basically try ringing the changes and see if one of them works.
Reading further I discovered that if you do find seeds you should soak them for forty eight hours before drying and planting, and that individual trees vary with the success rate of cuttings.

Oliver, Thank you for the time you took to look that up. Here's what I think I'll do with the two stalks I got yesterday. Diagram speaks quicker and clearer than words:

That'll give me five cuttings. The three 'down-stem' will each have two leaves; the terminal ones more, but smaller ones. I'll trim most of the leaves, certainly the bigger ones, to reduce the 'transpiration load' as you suggest. I'll put one of the 'terminals' and two of the others in soil – again, thanks for the composition tips, which were news – and the other two in water as a 'control experiment' / backup.

Overnight, although kept planted in water, there is noticeable wilting in the smaller twig, less so in the big one. I'd better get on with it...

 

[Sheal]

Meanwhile, though, today i overcame my scruples about mutilating park trees:

Think of it as helping nature by producing more trees. I hope you're successful in getting them to root.

 

[Low Altitude]

Sheal,

A long-overdue update and report on this attempt:

I put three cuttings in soil and two in water. The three in soil died promptly. The two in water struck! They were slow, but after about a week, the first 'nubs' appeared, the nubs became roots, and after another couple of weeks they were looking great. I only have a photo of the 'nubs' stage:

Then I killed them. Utterly stupid: I thought they might be able to use some fertilizer. What i gave them was much too concentrated: I saw what was happening and washed them off and put them back in plain water, but it was too late. They died immediately.

I was so upset. Stupid! And after all that thought and work! Something I've been trying to do for years, It came right – with your help! – and i messed it up.

Well. It will be spring again soon. I'll look for more sprigs from the tree and try again – and when I do, I'll use your water technique – which worked perfectly, thanks again – and not over -fertilize the poor little things this time and kill them.

Happy New Year!

 

[Oliver Buckle]

Look on it as a learning experience, and they were small enough the tree won't have suffered for their loss, any high wind could do that.

Have a happy and successful New Year yourself.

 

[cpp gardener]

I think you haven’t found any seeds because it’s not a London Planetree. I think what you have cuttings of is a White Mulberry. Plane trees have lots of indumentum, fuzz all over the leaves and especially on the bottom, which yours do not have. Did they leak white sap when you cut them? The bark on Platanus flakes off in pieces an inch or two squarish as well, so check the trunk, too.