Over or under watering, or something else?

Hello All, my first posting here but by no means a first time gardener

My circumstances dictate that all my plants need to be in pots, troughs, or some sort of container. About 12 months ago I planted a Betula jacquemontii in a large 50x50x50 cm trough using a compost supposedly designed for trees and shrubs.

The tree has not particularly grown much this year (thought it may be establishing) but now some leaves are starting to turn yellow and others look a little flaccid. My initial thought was overwatering, so I reduced this with no real improvement.

I bought a moisture tester today and upon inserting the probe into the compost it indicated dry! So I’m at a loss as to what might be the problem. There are no classic signs of under watering, brown, crispy leaves etc. It wasn’t an inexpensive purchase so I’d really like to save the tree. Any thoughts or advice please Thanks in advance.

 

If it says its dry, then it might be dry, try extra watering.

 

I think 50 x 50 x 50 is rather small for a birch tree so, if you can, give it a much larger pot but first of all, stand it in a saucer and give it a good 10 litres of water and let it soak up any that seeps out. Leave it 3 days and repeat. When you see water coming out of the bottom you'll then be able to guage how much your tree needs. In hot weather you'll need to water more.

In the ground, your jaquemontii would get to 12m tall and 8 to 10 metres wide and will need 30 to 30 gallons of water a month. With restricted roots and food supply in pot yours will clearly not get that big but it is very difficult to over water a birch. They survive having their roots in winter floods in their natural home.

 

Flaccid, yellowing foliage would always tend to suggest underwatering @The Enquiring Gardener .
If it was short of water last summer, it'll have struggled to establish, especially in a container. If it was in a sunny and/or windy site, it's also much harder as soil dries out much quicker, and then it's hard to get rehydrated. You'd need to follow the advice given re putting it in a saucer or similar.
Personally, for containers, I wouldn't even trust the mixes that are supposedly suited for trees and shrubs. I'd just use soil, with some grit or fine gravel to ensure openness for drainage. Maybe some well rotted manure mixed in, or leaf mould.

If you're in a drier area to start with, it all gets magnified. In cooler, damper locations, it's much easier for container plants, but even then, anything 'woody' ie shrubs, trees and hedging, needs attention until properly established, even in the ground.

 

I'm in the process of making several multistem birch and they are in pots at the moment. The one thing I have done is kept them in shade because it helps stop them drying out as quickly. In my experience yellowing leaves and dropped leaves at this time of year is because the birch is thirsty. The dryer the summer, the less leaves they have by the autumn because they are conserving water, the yellowing is because they are drawing the energy back before they shed the leaves.

 

Thanks all, for your replies. On reflection, and considering the above comments, it does look like under watering. I would agree with @fairygirl , that perhaps I should have used proper soil and not some so called ‘specialist tree and shrub compost’, as it does seem to dry out very quickly. Will alter my watering regime.

 

You can always top up the existing soil mix with a better one @The Enquiring Gardener . Levels in containers tend to drop over time anyway, especially if there's compost in them, so you should be able to add something extra each year.
You may also need to consider having a larger container for it. That would make it easier to give it enough heft to thrive. I'd look at building something specifically for it, rather than trying to get pots etc. If you're handy with tools, you can do a timber or sleeper 'box'. Alternatively, get someone to do similar but with block or brick.