Problems with new japanese maple

Carl Williams
August 13, 2019

Bought a small "Autumn Moon" maple last year. Planted it late spring. South San Francisco, moderate climate, but we got a lot of wind right after I planted it. It got a lot of leaf burn (I think) and seemed to go dormant early. Came back a little late this year. We had a lot of unusual late spring rain. The tree had a lot of die back on top (see full shot on bottom of page), and it looks like I'm going to have to cut back the remaining branch to the left. Where should I trim it to. Is this tree worth saving?

Comments (6)

  • gardengal48 (PNW Z8/9)

    I wouldn't prune anything yet. Adverse conditions can cause a loss of foliage but there is the potential for it to releaf. If there are no new buds forming on that branch in late fall, then it is likely dead and you can safely cut it off.

    Is this in full sun? I would consider that a less than ideal situation for this maple as it is prone to leaf scorch, as are most JM's with very light colored or gold foliage. Even though my garden has nowhere that is full sun, I moved mine to a much shadier location as it was showing signs of sun stress. It now only gets sun until about noon then dappled shade for the rest of the day.

    If under a guarantee, I'd consider replacing. And re-siting. Or select a variety that will hold up better to lots of sun.

    Carl Williams thanked gardengal48 (PNW Z8/9)
  • Carl Williams

    Unfortunately, I specifically picked the "autumn moon", because the attached nursery information claimed it could handle direct Sun (Southern exposure). As I mentioned, I'm in a very moderate climate, near San Francisco. If it can't handle the sun here, I doubt it can handle it anywhere!

  • Mike McGarvey

    Have you ever watered it?

  • gardengal48 (PNW Z8/9)

    Whle some JM's can take full sun very well (depending on location), virtually every source you can find will recommend partial shade over full sun for any JM. They are by nature woodland understory trees. Those with very pale foliage are less adaptable to full sun than those with a deeper green or even red leaves. This is a blurb from Mendocino Maples, a major grower of JM's in your area: "Keep in mind when you place your tree into the landscape that morning sun and afternoon shade will suit most maples best. Wind and hot sun can wipe a small tree out in no time, regardless of the cultivar. Leaves will show signs of stress with burning on the tips. Sometimes the roots will become sun baked and the stress will show up in the leaves as if there has been too much sun or wind. Maples are thin-barked and can be sun scalded during the first year or two after transplanting. This injury can set the trees growth back considerably. Most maple species are naturally under story plants, but as gardeners we have forced them into the open landscape."

    My location is pretty far north and summer sun is not very intense here. And it is rarely hot.....anything over 85F is a heat wave!! But still, 'Autumn Moon' will experience leaf scorch or early color change if exposed to excessive sun. A southern exposure is tough siting for any JM!

    Carl Williams thanked gardengal48 (PNW Z8/9)
  • Carl Williams

    I was afraid that might be the answer. There is a small JM up the street with the same exposure that seems to be doing well, but it's the dark variety. As a neophyte gardner, the contradictions I get from different nursery staff and especially nursery literature is very frustrating.

    Which brings up Mike's point about watering. Yes...I've paid strict attention to watering. However depending who I talked to last, sometimes I think I'm overwatering. I talked to two guys from the same nursery (a real nursery, not Home Depot). One guy says "stick your finger down into the soil. If it's cold and moist, you don't need to water". Another guy (who I've actually seen doing Bonsai cuttings) went off on a 5 minute spiel about how the soil may be dry at the surface, but the roots may have moisture available below, and should be encouraged to go down for it. My only guess is that the first guy was thinking (appropriately) about a newly planted tree, while the second guy was thinking of an established one. Yet a third guy thought that the die off was probably do to the late spring rain we received, and I think "Am I killing this poor thing with kindness?". So, I leave the nursery shaking my head, more confused then when I arrived.

    I've always wanted a JM but thought the exposure and my skill level probably forbade it. I think I should have stuck with that wisdom!

  • gardengal48 (PNW Z8/9)

    A slow, deep soaking a couple of times a week - if that - should be fine. And by slow, I mean leaving the hose on at a slow trickle and letting the water soak well down past the root ball. As long as your soil drains well, spring rains should not be an issue and I doubt had any rains pretty good here in spring as well :-) But good drainage is key - JM's will not tolerate soggy soil conditions.

    If you want to replant in that location, I'd consider something like Fireglow. Most red leaved JM's will tolerate a lot of sun and FG in my climate does very well in full sun. And it will look stunning backlit by the southern really lives up to its name!!

    Carl Williams thanked gardengal48 (PNW Z8/9)

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