I’m having my first case of “something is wrong and I have no idea what it is”. I have a very young Dawn Redwood I’ve been growing for future use. It’s been growing aggressively this spring; by volume, I think it’s doubled in size every month since May.
Around the time of the awful PNW heat wave, it got brown tips on some of the longer needles. I figured this was heat burn, and since the growing tips remained bright green I wasn’t too concerned. But over the past couple days the browning has been spreading. More needle tips have gone tan, and there’s a rusty brown color patching across some of the needles too.
The tree is an an air pot. Currently in regular potting soil. I’ve been fertilizing with high nitrogen granular fertilizer. I haven’t fertilized since I noticed the problem, but there’s some still in the pot. It’s 2 or 3 years old. I’ve been watering about once a day; less when it’s humid since it’s in potting soil. None of my other trees are behaving like this.
I’m consuming as much Dawn Redwood content and Fundamentals content as I have time for, but I’m still very new (first year doing bonsai!) and the problem is progressing faster than I can figure it out. I’d really appreciate any insights!
I agree with the sun/wind burn analysis on this very young tree. I also think there may be some root zone issues due to the combination of potting soil and an air pot. During the fast growth this spring it most likely sent roots into the outer portions of the soil. When it got hot and dry those roots were damaged as they sucked all of the moisture from that soil and the airpot allowed it to dry even faster. Now the tree is relying on the roots in the interior which may be too wet. I would protect from the hot sun and wind and watch the watering. You might even consider wrapping the sides of the airpot in something to slow evaporation.
I have 5 that are probably one year older that are doing well this year in the Spokane area. They were potted last year in plastic bulb pans with oversized drainage holes and a roughly 50/50 mix of bark and pumice. Last year they showed a little of this type of burn, but are doing very well this year now that they have a well established root system.
I agree with the other two Mirai members. I saw this on my dawn redwood in the heat of summer last year. I line in Orange County CA. It should bounce back, they are pretty resilient actually.
I’m in a completely different part of the country (Western PA), but I used to get this on my younger Dawn Redwoods all the time. For me, it was a combination of moving them out of direct sunlight and changing the water I was using. I think it was largely the sunlight, but it didn’t completely go away until I started watering with a softer water.
Hi Grace, I use airpots a lot and here’s my take on the problem. You haven’t filled in the cones on the top layer with soil. This is the water reservoir and the airpot will dry out quicker because of it. I would recommend using liquid fertiliser every fortnight rather than granular as it promotes faster growth, which is why we use airpots in the first place. You’ll find that it is the central roots that grow down first and once they reach the holes as the bottom, that’s when most of the lateral roots grow and once they strike through the cones they die off and promote finer roots further back.
When watering ensure it runs out of the bottom. Lift it up and look on the floor, you’ll see if you’ve got an even watering. With so many roots it’s easy to miss the central core beneath the trunk.as the water tends to run down the edge first. This is vital for rapid growth. Another tip is to feel how heavy it is when watered as this will give some indication when watering is required again. I never solely rely on the rain to water them as there is so much soil unless it is torrential it won’t reach the bottom and obviously kills those roots. I always feel the weight and then check the underneath of the pot to see if moist.
Normally if watered correctly they should easily last a day. Depending on the heat mine go two to three days on average before the next watering. My 9 ltr airpots usually take between 3 – 4 lts of water at each watering. I do mine in stints to allow it to soak the compost say 2 or 3 minutes between each stint until it makes a full wet circle under the pot.
I wouldn’t wrap anything round it as it simply becomes a large wet pot if you do. Far better to watch the watering.
Sorry for the late reply, but thank you for the info Keith! The air pots are a new experience for me (granted, all of this is a new experience for me, haha). I’ve been paying a little more attention to the watering and it seems to be doing alright. No new browning at least.
Just a little update: the tree recovered pretty well. I find that it gets a bit red after a few days in afternoon sun, but goes green if I put it back in dappled shade for a week or so. I think it’s just outgrowing its own sun tolerance. It’s about twice the size as my photos from a month ago. It is now my second biggest tree and poised to rapidly overtake its only competition: a coast redwood. These things are nuts. I’ll probably wire the first curves in early spring before its second round of explosive growth.
I generally repot the trees I have in airpots every year. This is because there are so many roots produced in the first year that there is very little growing room left. This in turn slows the tree down which you may not want. Plus watering becomes a real pain, hard to soak and used up far quicker. If you decided to repot into a bonsai pot the amount of roots needing pruning could be detrimental to the tree.
I also think that by giving the roots more room to grow each year really helps the tree grow faster and larger. During the autumn you’ll be amazed at how much fatter the trunk becomes.
I always am.
That’s good to hear. I was hoping to repot next spring in any case to get it into some more free draining soil (it’s just in miracle grow right now). I’m considering transferring it to an anderson flat to encourage more lateral, shallow root growth, but I suppose it will depend what I see when I open the air pot.
It outgrew every other tree in my collection. The sunburn is still there, but it’s buried so deep under green that it’s hard to even notice it. In fact it grew so enthusiastically that I fear I may have missed my window to put much motion into the trunk, haha. I might just have to accept some subtle bends from it.
The photo here represents about 6 months of growth. It absolutely blows my mind.
I planted 15 dawnredwood in my yard 33 yrs. ago. The ones that got alot of sun and moist soil grew unbelievably . some are 100ft.tall and 5ft dia. base. great furrowed trunks with nebari to die for. if i could figure out how to send pictures to forum off my email i’d like everyone to see them.
Wow! That is some growth. Have you lifted the airpot and looked underneath? You’ll be amazed at how packed the roots are. To keep momentum The best way to thicken it is to prune off the top third, wire up a new leader and repot. Depending on how thick you want the tree you could do that a couple of more times into the same airpot then it will need to be moved up a couple of sizes. That way the tree has maximum growing room next year. Maybe you could measure the diameter of the trunk at repotting and again before repotting.
Those all sound like great ideas. Most of my trees are pretty lanky, so I’m hoping to take full advantage of this tree’s rapid growth and develop it fairly thick. There’s a lot of well ramified branches at that 2/3rds mark that I could use as a new leader. And I have some nice sturdy XL net pots that I’m considering upgrading this either next year or the year after.
AKA pond basket or mesh pot. I’m not sure exactly how well they stand up in comparison to the air pots with the cones, but the idea of using them is similar, as they allow ample drainage and air prune the roots. They’re a little simpler, cheaper, and sturdier, but they don’t have the fancy cones.
These are the sizes I’m using right now and I’m thinking of upgrading the dawn to the monster 16 inch net pot at the back right.
