Japanese Black Pine from seed

Hi Jonas. I have several Japanese Black Pines that I planted from seed. This batch will be 4 years old in spring (September). I’m in Cape Town, South Africa. After the first year I planted them in pond baskets, then the following year, I placed the pond baskets in to colanders. Free draining soil used throughout. I’m concerned as most of the needles are yellowish instead of dark green (old and new needles). I have been fertilising spring to fall, holding back in winter. Some do not drain well when watered though. Should I repot these by just removing a little off the top, sides and bottom or would I need to do a more severe repot to really improve percolation?
Secondly, would you advise to leave the long leaders or at this stage, or cut back to a new lower leader, and hopefully generate back budding on the lower part of the trunks, which will better thicken the base?
I really appreciate your blog posts, they’re very inspiring!
Best regards, Mark

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Hi Jonas, or anyone out there that would like to comment… any advice would be appreciated.

Hello, the pines look like you have got a good start on them. The bark is very well developed for four years, rather amazing, i would have guessed closer to seven years.
The yellowing is likely from overwatering, the soil may be remaining too wet. Pines like dry feet.
I typically begin some cut back of sacrifice branches or leaders at this stage to encourage more back budding lower down on the trunk. It is also wise to remove excess needles that are shading the areas you would like to see new buds develop. I would like to stress that it is important to maintain a strong apical leader/ or a strong sacrifice branch to continue thickening the trunk and keep enough foliage for the trees to remain vigorous. Here is a picture of one of my five year old pines for a comparison.! The picture shows the lower branchingIMG_1124|669x500

Thanks for your advice Frank, much appreciated! We’re in winter now with quite a bit of rain. I’m going to battle to keep them dry but will do my best.

One way to help keep them properly draining is to prop one side of the pot up with a stick so it sits on a bit of a tilt. Removing the top 1/2 or 3/4 inch of old soil and replacing with new soil can improve drainage as well. The top layer tends to compact more quickly than deeper down in the pot. Another trick if the drainage is impeded is to just poke some holes in the soil with a chopstick to open up the drainage.

I’d try digging down to the center of the rootball to see if the soil is too wet or too dry. Frank’s right that overwatering pines is a common source of yellowing. My trouble with pines in colanders is that the akadama can break down and the water doesn’t percolate through when I water - it runs around the core of the rootball and drains out the sides instead leaving the core to get really dry. I find this problem is the worst in trees in double colanders as a long time can pass before the soil at the base of the trunk is replaced with this approach.

Poking around can also reveal if there are other root problems or root aphids/adelgids. I’ve seen similar discoloration in my trees which usually means something’s off in the roots.

Sorry, btw, for the delay in responding!

Thanks Jonas! I’ll wait till spring and repot, and possibly remove the inner colanders. I’m sure this will set the tree back regarding thickening a bit, but the health of the trees are more important.