Hi, This year was the first year I tried growing Japanese Maples from seeds. I put lots of seeds in a tray outside over winter 2020/2021 and in April and May many seedlings started to come out (about 50), which I was really happy about! From about June onwards, I put all of them in a shady area to protect them from the sun and strong winds. This is what I know have (50) Many have grown at different rates. Some are quite tall and some are still very small. I've fully lost one to slugs/snails who ate the bark and killed the tree: and another one with its bark eaten and not dead yet My questions are related to their survival over winter What would you recommend to maximize their survival over winter? - Do they have to be protected from too much rain so that the roots don't rot? It rains a lot here in the UK - Shall I keep them from strong winds, but still left outside? - I guess I need to protect them from frost late in winter? - Shall I put them into 9cm in early spring? (allmost all are in 7cm pots) Thank you for your help Christophe
Hi, they look pretty good in the main, apart from the ones where the bark and cambium has been eaten. My 2 cents is leave them outside in a fairly sheltered area, such as next to the wall of a building. Has always worked for me in the past. As long as the pot and the potting medium is free draining enough you do not have to worry about winter rain (Your mix looks like it has plenty of perlite so should be good). If you have an unheated greenhouse, or even a shed or garage, by all means put them in there from December to February but they will need a little water to keep from drying out. The ones that have been eaten are goners for sure. Did you see the snails or slugs eating the bark...? Almost looks like the damage from vine weevil larvae - if they eat all the roots in the pot they are in and run out of food they will munch on the cambium/bark from the bottom up. Vine weevil grubs are by far the number one pest of Japanese maple seedlings. As for repotting, I don't like to mess with young seedlings in early spring. I prefer to wait till the leaves are fully expanded (around May) and do it then.
Personally I don't leave them wet, I find they really don't do well left out. Also they don't like sharp freezes much, some are probably still a bit tender. I leave mine inside in a frost free environment during the first year. I don't have a greenhouse, so this means an unheated room in an outbuilding. Those look nice, some are surprisingly big; did you fertilize? I've somehow ended up with a load of palm tree seedlings this year, they will go in a friend's greenhouse!
So far, almost all of the seedlings I got from 'Ryusen', 'Sango kaku', the plain species, etc. and that were in 6.5 cm pots survived the winter. It isn't as rainy here as in England (though...) but it's about the same climate. Dissected ones are more temperamental, but I think you shoukldn't worry too much. ..is what I do, and it seems to work for me. Another very sound piece of advice. What I do when I repot young seedlings, whenever the season: 1/ I wait until the soil is rather dry, the roots stick better to the particles. 2/ I repot in a slightly larger container. I cut the roots that are too long, and since I always put a layer of gravel or pozzolan at the bottom of the pot for the first year, I make a layer of new well-draining soil, and complete the sides with new soil too.
Thank you all for your replies, they are really informative @maf, I plan to make a small 2 or 3 tier shelving unit made from old wood pallets, and put something transparent at the top to prevent the seedlings from getting soaking wet all the time, and on the sides (but not all the time). Would they be prone to fungus if it’s not aerated enough? Otherwise, I’ll try get a small mini green house. I didn’t see them eating the bark, but I’ve often caught small snails going up the trunk and eating leaves. From May to July I had to check every day for aphids (not too many thankfully), then un July/August some small snails and slugs were going up the pots, on the bark, and eating some maple leaves. Since September it’s been better. I’ll have to check then for Vine weevil, as I can’t remember having seen any (nor larvae), but I’ll definitely keep looking. I guess they will be hibernating now, and would reappear next spring? @emery, thanks, I’ll will move them soon into a more sheltered area Yes, there is definitely a big difference in size between some of them, and some are quite tall (about 20cm I would say), and some really small (5cm). The tallest one is about 25cm tall. The seeds come from different trees, and the tallest ones weren’t necessarily those who came out first. I haven’t used any fertilizer. The mix I made was about 1/3 compost, 1/3 ericaceous bark/compost, 1/3 perlite. Thanks @AlainK for all the advice! I made the mistake - not following 1/ - with a small black pine tree I am growing from seed. I wanted to check its root system. The soil was wet. When I took it off, all the soil came off and only had the tree and its roots in my hand… Not what I wanted at all.
Some great advice above..I dont have a greenhouse either..Last year I bought a clear plastic 3foot x 2foot x 2foot storage containers, drilled holes in the bottom for drainage filled it with 15” of sharp sand and buried my small pots with seedlings.so the sand was at the top of each pot.I’d leave the plastic lid on loosely for a week or so then leave it off for a bit..during hard frosts I leave the lid on. My logic is that the sand bed will stop the small pots freezing solid during hard frosts. I didn’t loose any seedlings last winter..although it was mild here..just an idea
The other issue leaving them out..with no protection is that I find birds sometimes pick them out the pots thinking they are a tasty treat..leaving them close by on the ground..they seem to do this with my succulents too ..has anyone else experienced this?
When the weather is dry, blackbirds grate the soil when the pots are watered, looking for eartworms and various insects, especially when there's moss on the soil. Though there isn't much to eat if you only get one, they taste very good as far as I can remember. Haven't had any since I was a kid... ;-)
I don't recommend having maple seedlings up above the ground on wooden shelves in freezing weather. When the air gets really cold the ground acts as a heatsink and stops the pots from freezing as hard as they would if up in the air. @dicky5ash 's idea of a bed of sharp sand in a plastic box is a much better idea, (a traditional cold frame would work also) and I would do something similar if I wasn't happy with just leaving them on the slabs near the house. BTW I have overwintered Acer pentaphylum seedlings this way and they are much less hardy than Japanese maples.
How to check if it is vine weevil larvae or slugs and snails that ate your seedlings - de-pot the dead ones and spread the soil out on a flat surface. If the small roots are all gone and the woodiest roots have been stripped of root cambium (same as the above ground part) then it was vine weevil grubs. If the roots are looking healthy it was the slugs/snails. If it was vine weevils you may even find the grubs if you are inclined to examine the depotted soil; they are white grubs similar to a maggot in appearance about 1cm in length. I don't think the adults overwinter but the larvae do. I believe they continue eating through the winter, not sure what temperature they stop, and can often be found as grubs in spring which have obviously overwintered feasting on maple roots. I don't like vine weevils, they are bastards.
And more: Blackbirds first and all birds needs to dampen their beak all during hot and dry days. Insects or not, it is necessary for them to humidify their beak so that it does not deteriorate; a beak that is too dry, the horn breaks or splits. They grate the soil, grating is a reflex, that is vital for them.
Same here I live right next to a small park and grey squirrels have taken occupation over only the last couple of years..I’ve got 4 oak tree seedlings that I’ve removed from my pots this year..am growing them on and will plant them :) No chipmunks..I don’t even know what they look like..am intrigued!
they are cute little creatures. but man, they can cause some problems. my cat died in 2019, then they took over.
I've got the same issue here :) Regularly I see a squirrel in the garden, holes in pots. This year we had four oak trees that have grown from acorns left by squirrels. We don't even have oak trees nearby! I try to keep them alive (the oak trees seedlings).
Thanks for describing this! I've checked yesterday and the fine roots seem (lots of them) fine and I haven't seen grubs. Also, the stripped bark is only outside the soil, the bark is fine below it. However when looking closely in the pot, I saw these two little beasties. What are they?
Mice will eat bark on young plants also, I lost a couple of grafts to that this year. One time I lost about 50 A. davidii seedlings to hungry mice. Re: inside or out, the questions to ask are how wet it is, and how often the temps hover near freezing. A tiny pseudomonas infection that even a 2 year graft will laugh off will kill a young seedling. Coldframes are good, they do get quite humid though. And warm if in the sun. @LoverOfMaples get another cat!! Although they cause their own damage! -E
New kittens are so cool. Even if they do break a lot of branches learning to climb (this time in A. negundo 'Sensation'). We've had Tasha for a couple of months, she's already showing mousing talent. Our big cat Miko even catches moles sometimes.
No idea but may be something related to aphids - in any case too small to cause any harm except if they occur in large numbers. Not vine weevils. Good point made above regarding rodents stripping lower bark.
