Yellow Box Leaves

Wondered if any of you good people had some advice for me.

I noticed my three and four-year old box plants (grown from cuttings) have developed yellow top leaves in the past couple of weeks.

Over the winter I was sprinkling a row of wood ash about a foot from their stems which is still there. I guess that could be making the soil alkaline but I'm not sure if that can make the leaves turn yellow. Might dry out the soil perhaps? I must confess I haven't watered them at all this year as we've had a lot of rain this month and odd bits of frost till recently; we had snow on the first of the month. The soil isn't dry, but not overly moist either. I've been mulching them with bark chippings for two years now and now I'm wondering if the soil is leaching away from their roots to be replaced with wood bits which are dryer. It's difficult to tell where the mulch ends and the roots start now. Of course, there isn't a whole lot of room for anything above the box roots near the main stem as they start so close to the surface, as do the branches.

So, not sure if to water them a lot now or to dig away the wood bark chips and pack more soil around them first to hold water.

 

I'd wait and see how the new growth fairs.
I'd definitely not be watering plants that have been in for two years.
If you are in the UK?

Mulching will not remove soil from the roots.

 

There is a fungal disease that attacks box known as Cylindrocladium buxicola. Symptoms are that the leaves become yellow or yellow orange. There may even be brown black streaks or marks on the stalks.

I hope this is not the case with these, but if it is, the only cure is to dig them up, and burn them. It spreads rapidly, so if it is the case do it quickly.

 

Thank you for your kind responses (see below).

Her Indoors (who always keeps up with the temperatures) tells me we're still getting the odd touch of frost at night. So I shouldn't even water them yet.

I should say that one reason I got concerned is that one or two shorter plants (that would have been taken from my four-year-old sandy and sheltered cuttings bed and replanted in place two years ago) at the end of the row, appear to have died. That is, whitish-yellow and brown leaves and dried to a husk. You expect some to die, but.... Could have been slugs or ants from last year weakened them.

So could this be due to the varied weather we've been getting this month here: snow over the winter, sun, rain, then frost at night? And some wind too.

Do you think they could do with a closhe over them until the temperatures improve? I'll do it if it's a matter of life or death but closhes are a complete pain. I've got plastic sheet closhes with a frame I can stick over them but with the winds we sometimes get, I have to stake the sheeting down firmly. Getting the right amount of water to them is harder to judge because the top-surface dries out faster. And the closhes are much wider than the box bed so to stop the grass and weeds underneath running rampant and stealing the boxes' food and water I have to cover everywhere under the closhe except the box with black plastic or cardboard. Which kills the grass and gives the weeds a head-start in the summer.

I've got about thirty-five box in three rows in full sun. But also exposed to the winds. Ironic, if it's the winds doing the damage since my reason for planting them is to act as a wind-break for the terrace. I've nurtured them since they were 4'' tall. They're like my children. Except quieter. And slower.

Ah. A lot you say rings true. It is clay soil. And the bark mulch stops me seeing if the bed is waterlogged. I prepared the beds thoroughly with manure, straw, peat, soil, a bit of sand and compost to a 2 to 3 spit-depth, with some sieved soil around each cutting I planted. I thought I'd broken through what there was of a pan there. But it could have formed lower down since then as this was four years ago. Does trimming the yellow leaves help the rest of the plant? It's a shame of course as they grow so slowly so I could be cutting off half a year's growth.

OK - thanks. Though couldn't waterlogging? I can't tell what's around the roots anymore as the bark bits stop me being able to feel around there. But, yes, perhaps I should just wait for the new leaves to come.

Oooh er. I'll have a look.

A lot to think about.

 

Water logging could be the problem, especially if you keep worry about watering them and its still winter.
I've got box plants that I have grown from cuttings a few years ago, and once planted out I've never watered after the first summer, and even then only on the odd occasion.
My soil is pretty clayey, (not solid clay though), and I've not really done much in the way of preparation before planting.
Its a tough old plant in my opinion, but I am growing the species type rather than a cultivar.

There is some thing called "Box Blight" which I think @Sandy Ground is referring to, but never come across it myself so cant comment.

 

There are three diseases ( for lack of a better word) that affect box. They are:

Cylindrocladium buxicola and Volutella buxi whichj are fungal dieases, and Diaphania perspectalis which is a grub that primarily attacks box. If any of these are known as Box Blight, I haven't a clue.

I'm going off memory now, and if I'm wrong I hope someone will correct me. From what I've been told, the fungal diseases were first known in the UK around 1990. In this part of the world, they are a major problem. Its traditional for graves to have box edging, and the fungus has totally destroyed this in some areas. I'll try to find a photo and post a "before" shot of how it used to look in local graveyards.

 

just what I know in the UK.
https://www.rhs.org.uk/advice/profile?pid=96

 

The RHS refer to Volutella buxi here...

https://www.rhs.org.uk/advice/profile?pid=851

..and the grub here...

https://www.rhs.org.uk/science/pdf/plant-health/salisbury-korycinska-halstead-2012-box-moth

 

Happy Easter. You've got a good memory. Yes, it's clay. Things grow well in it though, as long as I dig deep and mix it up with something when I plant.

Perhaps it's the waterlogging in the autumn that does it - but I didn't think there was any last year. I just wondered why it should have the yellow leaves now, in the late Winter. It's interesting you leave your box alone. Perhaps I should do the same. But I got worried when some of the smaller plants shrivelled and died. I thought they needed water.

My box with yellow bits.

Oh. I'll investigate.
Box blight.
http://www.zen-garden.org/wp/2010/08/buxus-disease-box-blight-problem-with-box-topiary/

Oh dear. This looks exactly like some of my less robust box last year. It's caused by a combination of the two fungii you quote. Some leaves turn yellow, then suddenly the whole stem has shrivelled and the white-cream coloured leaves fall off.

Oh. So if it's that, not happy news then. The only warning apparently is spots on the leaves: black on top or pink underneath. And it's caused by airborne spores that like damp, less ventilated plants and shade.

The only thing you can do apparently is to clear away and cut off the dead material (as Sandy Ground mentioned) because the spores can hibernate on it. And not water the foliage and ventilate the plant. And hope for a dry summer to kill them off.

Of course, when leaves were shrivelling late last Summer and Autumn, I thought they weren't getting enough water! Which is all wrong. If it's that. So less watering then. Perhaps no watering. Which is what most of you wrote.

I wonder if the yellow leaves I see now are the blight or that's the effect of frost and that will sort themselves out once the temperatures rise. Let's hope.

I wouldn't have known all this unless I posted it on here so thanks so far.

How do you ventilate box?

 

Could be. The yellowish leaves are the same size as the rest. But in previous years the new leaves were a nice healthy light green, not this sickly yellow. Still, I can't see spots on them so perhaps it's down to just some temporary nutritional deficiency or stress. Or waterlogging from the thaw.

OK - let's hope it's just some metabolism thing that will sort itself out. And I should leave it be.

Seems the blight was a completely separate thing that needs spotting and cutting out quick.

You know where you are with clay. Can't understand my neighbours who moan about it.

The cane is just temporary to make the end of the bed stand out a little more so the children don't step on the plants.

Incidentally I grew these from cuttings - following the advice you read everywhere to make them 4-9 inches long and plant them in sandy soil. Nuts. Nuts. Takes years for them to grow and while they're small they're more vulnerable. I put egg shells around them to stop the slugs, kept the weeds back; tended them. But that blight caught a couple of small ones and within a few days they were just husks.

But the biggest and most vigorous plant I have, that one in the first photo, started life as the original branch that I cut off the box bush. I was taking cuttings from this branch and keeping it in a bucket of water in a cold room for a year, with a clear plastic bag over the top. I didn't cut off any more leaves. Roots grew in the water. After a year I added sandy soil to the water to thicken up the roots, stuck the bucket outside for a few days in the summer to acclimatise and then planted it out. So seems to me, it's best to start with the largest box cuttings you can get. Madness to start with small cuttings.

 

So, were my new season's yellow leaves water-logging or fungal box blight? Over the past few days.....

....they've changed.

Here's one plant that died last year. I thought, from lack of water.




But more likely, from too much water. See those black spots?


The books say blight.



Have I got any more?