JBP - Watering

[JamDonut29]

I recently bought a JBP in a nursery pot and haven’t changed the soil, which seems to be a mix of organic and inorganic material. It’s summer here, and I keep the JBP in full sun, except on days over 30°C, when I use a 30% shade cloth.

Lately, I’ve noticed yellowing tips on the needles in the apex. I water when the top 2 inches of soil are dry, as commonly advised, but I’ve read that yellowing tips can indicate over watering.

Using a moisture meter, I found the lower part of the pot is still wet while the topsoil is dry. Could I be over watering by relying on the topsoil to decide when to water? Should I instead use the moisture meter to guide my watering?

Thanks for your help.

 

[Brian Van Fleet]

Could be underwatering. Most of the active roots circle the walls of pots and will get hot and dry first in summer time, causing some stress. When you water, drench the tree several times in a row over the course of a couple minutes to ensure the root ball is saturated. Feel free to post photos of the tree for more accurate guidance.

Welcome to the site.

 

[Shibui]

It is definitely possible to overwater if just observing the surface to decide when to water. We often advise using a wood chopstick or skewer as a cheap moisture meter but if you have a genuine meter that works that's good too.
It is also possible to underwater - and that's way more common in summer. Conifers typically do not show signs of stress for days or weeks after the event so the yellow tips could be from a dry day a week or more ago. Often we've forgotten about missing watering that day by the time the symptoms show up.
Just watering the top of the pot may not properly water a dry pot. Most of the initial water runs around the soil and out the bottom giving the false impression we've done a good job. Meanwhile the centre of the pot is still dry. On subsequent hot days the roots get even drier until there's a problem. See recommendation above to water thoroughly several times to get the soil fully hydrated after a dry day.

There can also be other causes of yellowing needles on pines.

It’s summer here, and I keep the JBP in full sun, except on days over 30°C, when I use a 30% shade cloth.

It should not be necessary to put pines under shade. Mine live year round in full sun with occasional max temps above 40C.

It’s summer here

Which means you are somewhere in the Southern hemisphere. That still doesn't give us much of an idea of your climate - tropical, temperate, mountain, coast, etc , etc. Bonsai culture and timing can be quite season specific so it would be great if you can narrow down the location a bit further. Best to add your location to your profile so it shows up every time you post and saves you from having to type it each time.

Photos are also great way to convey information. Often we can see things in a photo you have not even thought of yet.

 

[JamDonut29]

Could be underwatering. Most of the active roots circle the walls of pots and will get hot and dry first in summer time, causing some stress. When you water, drench the tree several times in a row over the course of a couple minutes to ensure the root ball is saturated. Feel free to post photos of the tree for more accurate guidance.

Welcome to the site.

Thanks for the insight! That makes a lot of sense, especially with the summer heat. I'll try soaking the root ball more thoroughly and see if that helps.

 

[JamDonut29]

It is definitely possible to overwater if just observing the surface to decide when to water. We often advise using a wood chopstick or skewer as a cheap moisture meter but if you have a genuine meter that works that's good too.
It is also possible to underwater - and that's way more common in summer. Conifers typically do not show signs of stress for days or weeks after the event so the yellow tips could be from a dry day a week or more ago. Often we've forgotten about missing watering that day by the time the symptoms show up.
Just watering the top of the pot may not properly water a dry pot. Most of the initial water runs around the soil and out the bottom giving the false impression we've done a good job. Meanwhile the centre of the pot is still dry. On subsequent hot days the roots get even drier until there's a problem. See recommendation above to water thoroughly several times to get the soil fully hydrated after a dry day.

There can also be other causes of yellowing needles on pines.


It should not be necessary to put pines under shade. Mine live year round in full sun with occasional max temps above 40C.


Which means you are somewhere in the Southern hemisphere. That still doesn't give us much of an idea of your climate - tropical, temperate, mountain, coast, etc , etc. Bonsai culture and timing can be quite season specific so it would be great if you can narrow down the location a bit further. Best to add your location to your profile so it shows up every time you post and saves you from having to type it each time.

Photos are also great way to convey information. Often we can see things in a photo you have not even thought of yet.

Thank you, Shibui, for your insightful answer. My watering process is based on what I've read—that pines prefer to be almost dry before watering—so I use a moisture meter to determine when it's time. When I do water, I thoroughly drench the pine until water drips from the bottom of the nursery pot like a tap. After a few minutes, I water again to ensure the root ball is fully saturated.

I'm wondering if my mistake is relying too much on the moisture meter. If the topsoil is dry but the deeper layers are still moist, I usually wait until the meter indicates that the soil is almost dry before watering. Could this be causing an issue?

I've updated my location and attached photos as well—hopefully, they provide more context. Thanks again for your help!

 

[Shibui]

From the extra info I'd say it got a bit dry one day - possibly a week or so back. That little bit of browning at the tips is not unexpected. I have plenty of JBP that look like that this time of year so would not be unduly worried.
Some people have reported that moisture meters are not as accurate as expected so maybe that's the problem.
It is also possible that moving it to shade on warm days has stopped the needles from adjusting to full sun and it got a bit of sunburn.

Summers in Adelaide are dry. I think it would be difficult to overwater pines in summer in Adelaide. I don't think a bit more water will hurt your pine at this time of year.
You can usually slide the root ball out of the pot and check how well you have watered or how dry the soil is before watering. Will also allow you to check the roots. If you see white furry stuff and/or white root tips everything is OK.

 

[JamDonut29]

From the extra info I'd say it got a bit dry one day - possibly a week or so back. That little bit of browning at the tips is not unexpected.

That makes sense as about a week ago the temperature was about 40°C. I did try to monitor it and water it more, but it may have been insufficient.

I have plenty of JBP that look like that this time of year so would not be unduly worried.
Some people have reported that moisture meters are not as accurate as expected so maybe that's the problem.

Thanks for your reassurance. I'll try and monitor the soil using the chopstick method and I'll see how that changes how I water my JBP.

It is also possible that moving it to shade on warm days has stopped the needles from adjusting to full sun and it got a bit of sunburn.

The temperature the next few days will be above 30°C, so I'll test out not using the shade cloth and see how the JBP will adapt.

And again, thank you for your suggestions Shibui and hopefully I'll see an improvement in the health of my JBP.

 

[WNC Bonsai]

In my experience are on the thirsty side of pines and like a bit more water. I usually water mine once a day.