Advice - Japanese Buxus

[d23]

Hi there,

I'm from Australia and looking for some advice to understand what the colors of the the Japanese Buxus leaves mean as they change.


Some history to the images:


- I have the buxus in full sun, next to fence above the pool tiles

- Pots are fibre glass, black, have bitumen lining and drainage holes, off the ground, plenty of soil - used Jeffries veggies and garden soil

- Had them for about 2 years now so not fully mature yet

- I did use Jeffries Forever Black Mulch, for last 2 years, but have since realised its taking nitrogen from the soil etc and have last week replaced with an organic Recover mulch instead that provides nitrogen/potassium etc

- I've used fertiliser on the leaves and soil in spring - Powerfeed and others such as Plant Doctors seaweed with humic and fulvic acid, Activ8mate and Qauntum H. Use liquid iron but not a huge amount.

- I'm trying to understand the soil moisture levels better - at the top it seems dry, half down OK, deeper it looks wet - when digging down the soil itself seems dry but is warm/moist - would this be because the pots are black and the area is hot from the tiles and fence vs actually being moist - i.e. a false positive - I'm wary of overwatering but could I be underwatering especially in recent hot weeks


My question: Last summer I saw the same process, where the leaves start to brown like the photos and then turn to a yellow crisp eventually some of the leaves dying - what nutrients (if any) am I missing that's not keeping the leaves green and healthy? Or is this normal for this aged of buxus to go through?

Thanks so much

 

[Marck]

Greetings, welcome to the Forums.

It is interesting that your Japanese Boxwood (Buxus microphylla) show a color change in Summer. I am more used to seeing Boxwood leaves turn shades of Yellow, orange, or olive in Winter due to cold weather. I enjoy that color shift as under-appreciated foliage color.

Perhaps the orange color on your Boxwood is due to watering irregularities and/or heat stress. I don't think it is due to a nutrient deficiency, especially as you have now given the plants fertilizer. I don't use water meters, as I prefer to directly observe the soil and plants. As you see, they tend to give odd readings that require direct confirmation or rebuttal anyway.

Boxwood want Full sun, regular water, good drainage, near-neutral soil pH, and moderate fertilizing.
Overall, your boxwood plants lo0k healthy, but I understand that you are concerned with the changes you are seeing.

When watering water completely so that water comes out the drainage holes. After two years, the boxwood roots should reach to the bottom of the container. I don't understand the phrase, "soil itself seems dry but is warm/moist". Does the soil seem to be repelling water? That sometimes happens with peat-based soil that is let to go too dry.

 

[d23]

Greetings, welcome to the Forums.

It is interesting that your Japanese Boxwood (Buxus microphylla) show a color change in Summer. I am more used to seeing Boxwood leaves turn shades of Yellow, orange, or olive in Winter due to cold weather. I enjoy that color shift as under-appreciated foliage color.

Perhaps the orange color on your Boxwood is due to watering irregularities and/or heat stress. I don't think it is due to a nutrient deficiency, especially as you have now given the plants fertilizer. I don't use water meters, as I prefer to directly observe the soil and plants. As you see, they tend to give odd readings that require direct confirmation or rebuttal anyway.

Boxwood want Full sun, regular water, good drainage, near-neutral soil pH, and moderate fertilizing.
Overall, your boxwood plants lo0k healthy, but I understand that you are concerned with the changes you are seeing.

When watering water completely so that water comes out the drainage holes. After two years, the boxwood roots should reach to the bottom of the container. I don't understand the phrase, "soil itself seems dry but is warm/moist". Does the soil seem to be repelling water? That sometimes happens with peat-based soil that is let to go too dry.

Hi Marck,

Thanks for the welcome, most appreciated and your feedback. I've done a bit more of a review today.

On a few of the hedges, the brown has turned some leaves now to a crisper dead yellow per these photos.

I used a electrical pipe to take a sample all the way to the bottom. Generally the pipe needed some force to push through (thinking this is dry) but found the bottom inch - 1.5 inches to be moist with the soil lumping a little in the bottom of the pipe but dry further up.

I assume the bottom is the 'perched water table' and not a drainage issue.

We've had a week of approximately 90F with high of 100F so it's been hot for them so thinking similar it may be a lack of watering issue. We've got a cooler week ahead, would you suggest with a deeper watering in this situation maybe 3 times over the next week?

Thanks again

 

[Marck]

Don't go by a strict schedule of three times a week. Keep observing soil moisture and drainage. If it is hot and the soil is draining well you might need to water that often, but it sounds like the soil does not wet or drain evenly, which might be the cause of the problem.
If the drainage is fine, perhaps the plants did get to dry during the recent heat, but things you describe sound like there could be drainage issues. For example, a 'perched water table' is a hydrological term that usually isn't applied to a container's drainage, but if a container did have one it would be a drainage problem.

You might want to try unpotting one of those boxwoods and seeing how they've grown. After two years you should see a fine network of white roots all the way to the bottom of the container. if it doesn't look like that, something is going wrong.

 

[Oliver Buckle]

I am guessing my box is sempervarums, it is a variegated one my father got a cutting of years ago, and I have supplied loads of them to friends and gardeners over the years. It is slow growing, so tends to get left alone for long periods, and i have known cuttings to survive for a couple of years before they root. This can mean it will dry out in summer sometimes, too dry and it is fatal, but if the bottom of the pot stays just moist it will get much yellower, but survive. then the yellow effect seems to persist, even in new growth.