Pieris failing to thrive

[Stu]

My 4 yr.old Pieris, now in the largest of pots, is failing to thrive for the first time. Leaf reddening is weak, almost brown, and many new shoots are dying off at the tips. It is 22" high and a good round shape. I can see no evidence of pest or fungus. Your advice would be most welcome.

[gardening_guru]

Hello,

Some questions for you, to try and help me to establish what the problem is.

Is the plant being grown in ericaceous compost?

Is it watered with rainwater you have collected or mains tapwater?

Is the pot located in a sheltered spot, in semi-shade?

[Stu]

Hello

To answer your questions.

The tub is 80% ericaceous compost, set in semi shade, so receives rainwater, supplemented by mains water and ericaceous feed in summer.

The only odd thing I can see is a white deposit around the base of the pot which seems to come from the drained watering. I thought this might be to do with the feed, but other ericaceous pots don't have that.

Many thanks

Stu

[gardening_guru]

Hello Stu,

Do you know which cultivar your Pieris is? Reason being some are hardy to -15C but others are only hardy to -5C and we had colder temperatures than that in our last record breaking winter.

We have also had some late frosts recently, Pieris although hardy are susceptible to having their young leaf shoots damaged by late frosts. A piece of horticultural fleece over the top next spring when the young shoots are developing on cold nights will prevent any damage.

If flowering is finished this year give your Pieris a light prune, cutting off the damaged young shoots with a sharp, clean pair of secateurs. Healthy young shoots should consequently develop to replace the damaged ones.

Also I would not supplement with mains water, if you can buy and install a waterbutt to collect rainwater for all your ericaceous plants. Mains water usually has a pH well above 7 which is no good for ericaceous plants.
The white deposit on the base of your pots is probably limescale highlighting the alkalinity of the water.

Finally I'm sure you are but be very careful with feeding making sure you are not overdosing and I would feed a Pieris in spring, not summer, a few weeks before the flowers and new foliage are due.