I have an Acer buergerianum cultivar that displays an unusual behaviour. The cultivar name is 'Nokoribo' which, if you do a Web search, you will find it only at Esveld's website. In fact it is there where I bought it this summer. It is supposed to have red growing tips and 1.5-2m height after 10 years. The maple was installed in the ground in light shade. The unusual behaviour is that the plant has kept its leaves unchanged up to today, not a single leaf has turned yellow (or red). The pictures below were taken late today. It's as if I had an evergreen Buergerrianum ;o)) It is true that we have had a warm Fall in Western Europe but all other decidious trees have already lost their leaves a month ago. In addition, in this area (zone 8), it has been fairly cold for the last two weeks with highs in the 30's and lows in the low 20's with frost each night. I do not understand this behaviour, anybody has a hint? Gomero
Japanese Maples (Timber Press) says of trident maple "The fall color appears late in the season, with the leaves often not falling until late November or early December." If this cultivar originates in a warmer part of the species' range it may have more persistent leaves than some others originating elsewhere. One thing I do notice in your middle picture is that you appear to have vigorous, large-leaved shoots exploding out of a small, compact growth with small leaves. If this is supposed to be a diminutive, bonsai-suitable selection those may be reversions or perhaps even rootstock sprouts, needing to be pruning off/out.
My two other trident maples have shed their leaves about a month ago. As pointed out above this cultivar originated and was raised in Holland which is a colder zone 8 than mine. I guess my question is, what could make a plant keep photosynthesizing in spite of all external clues telling it should stop doing so?..... overfertilization? Gomero
Hi Gomero, As it happens, I also bought Nokoribo from Esveld late this summer. :) I was waiting to put in into the ground until the leaves dropped. Which certainly it was in no hurry to do. The plant seemed to want to keep growing vigorously, even in the small original pot, I noticed it continued drinking a great deal even after everything else I got in Holland this summer had gone dormant, so (no need to tell you I'm sure) make sure it got enough water while the leaves last. Finally near the beginning of the month the leaves turned a very pretty light orange-yellow, and I put Nokiribo in ground. One of the tempests of the subsequent days knocked the leaves off. Given the vigour of the plant I'm guessing it will make a pretty large shrub. I don't believe you've got any sort of reversion to be pruned, yours is behaving just like mine, given the warmer situation it lives in. Sometimes the sizes on the Esveld site or labels are just educated guesses about a plant brought from Japan without much information; this may be the case here. In any case I'll be surprised if it doesn't make better than 2m, and quickly too, unless things really slow down next year. Best for the hols, -E
I have noticed that it is common for plants forced into growth or exhibiting vigorous growth late in the season not to respond to external temperature cues for dormancy. This can be the case with summer grafted maples that push their leaves late in the summer, near fall. The new leaves on these plants can tolerate an incredible amount and duration of cold (but not a persistent hard freeze). The leaves will stay on the plant, seemingly unchanged before suddenly turning and falling or being frozen. I suspect the growth state of the plant makes it incapeable of atering its course of growth to poperly respond to fall given that it has been inappropriately forced to grow when it was not ideal. Plants I bring in from nurseries late in the summer almost always hold their leaves 2 weeks or more longer than the plants already here. Not only do they hold their leaves longer, but fall color is delayed as well. The only constant is that most all of these plants are under the influence of a good deal of nitrogen in most cases or are in states of persistent and forced growth. The less vigor on a new plant, the soon it likely exhibits fall color. Same deal as when we have drought stressed maples or otherwise stressed maples prematurely turn fall color or turn earlier. With the vigor on your plant, I would think it was simply not ready and tolerable or slightly above normal temps made it easy for the plant to sustain itself without immediately responding to fall. I bet after you have it a year or two it will fall right in line with all your other maples.
You said the specimen originated with Esveld, you did not say the cultivar was from Holland. And even if it was selected in Holland, if the sport or seedling from which the selection was made was of a warm-climate ecotype, form or race it would probably still have the same tendencies as the original plants in the wild. The genetics of the plant are not affected by what climate the supplier is in.
Hi Gomero, Just in passing, I looked up your maple in Masayoshi Yano's book, and he mentions in his description, that the leaf fall is extremely late, and that it holds onto it's leaves for a long time, so it is a possibility that the change in environment, has encouraged it to hold on a little longer than usual. It is certainly a handsome Maple, maybe you will let us know when it finally releases it's leaves. Ashizuru............
Thanks to all for the comments. Galt, I do not graft so I have not been confronted to the behaviour you describe of some summer grafted maples. Ashizuru, I agree but one thing is 'late fall' and another is 'no fall' ;o)) After 10 days of very cold weather the leaves look to me now pretty frozen but still hold well horizontally, amazing. I expect them to drop anytime now. Merry Christmas and Happy New Year to all Forum readers. Gomero
If you have Maples of the World, you might want to look for a mention of evergreen vars or ssp of trident maple, or introgression/intermediate forms between it and related species. Three other Section Pentaphylla, Series Trifida maple species (AA. coriaceifolium, oblongum and paxii) are evergreen.
