Snow would not hurt them, but colder temps. than usual, as you indicate, would. You're on the edge of their hardiness area.
How long have they been in the ground? If newly planted, shrubs typically need 3 years or more to settle in. No deadheading would not prevent bloom. You would only fertilize with acid if a soil test indicated too high alkaline PH. But, pictures indicate they were blooming well last spring, so I would wait it out. It helps to keep an eye on, and record low temperatures during the winter, for determination. Do you have leaf scorch on them?

I started this garden in the summer of 2005, and the pierises probably have been in the ground three to four years depending on when I got them (not all at once). The Mountain Fire was set back by the Siberian irises which were growing right in the middle of the shrub, so digging them out was necessary, but probably disruptive of the roots. I also moved some of the dwarf pierises last year.

The weather was odd last year - I remember it being very rainy last summer so I only had to water a few times. It's usually very dry here in the summer so the pierises may not have had a normal bud-set time, then they got hit by heavy wet snow with winds. The winter was really rough on some Ilex opacas and my big osmanthus lost a large branch. A new azalea planted last spring looks awful too (one of two).

No obvious leaf scorch that I can see. I just checked the weather history for Plymouth on Weather Underground, but that's recorded a few miles inland and I'm right by the bay with temperatures moderated by the water. I do monitor temperature daily but I haven't kept records (except on bird feeder watching days).

Thanks,
Claire

Another thought. How do pierises respond to crowding? The Mountain Fire certainly hated the irises.

That bed looks pretty sparse in early spring, but by late summer the Siberian irises, bearded irises and daylilies are rampant, there's chrysanthemums in there, and I let assorted groundcover wander around. Could that be just too much root crowding for the shrubs?

Claire

Claire,
since you moved them several times you already noticed how small their root systems are in comparison to the top growth.
Which means that competition with other plants is not a big deal for them, for as long as they got room and time to establish themselves.
I can't offer you a definite answer to your main questions, but could say only this: deadheading definitely helps.
I made an experiment last year and now clearly see results.
I have a row of 7 pierises (4 Scarlet O'Hara and 3 Brower's Beauty planted alternatively). Last year I decided NOT to deadhead BB and of course, they bloomed very poorly in comparison to SOH.
However, I do have some pierises in other places of the garden (all were deadheaded as were practical) and not all of them bloomed profusely this spring. Go figure :-)

The weather conditions in New England last summer and this winter probably account for the failure to bloom. Last summer's constant rain and gloom did two things. It encouraged vegetative growth at the expense of bud set. Too little sun discouraged the formation of flowers as well. The winter was exceptionally mild, but there were several occasions when we had extremely high winds. These certainly could have freeze-dried any buds that might have been set even though the actual temperature wasn't that low.

Dead heading is always a good idea. Allowing the zillions of seeds to ripen does discourage new bud formation. Failure to deadhead also leads to branch tip dieback in most varieties. You can see the buds for the next spring' bloom in the fall.

I thought about last summer's weather here too but the fact is that this spring has been breathtaking, with every flowering tree and shrub in full and fantastic bloom. The generally mild winter and all that rainwater last year have made an impressive show. So I think those pierises are not blooming for some other reason--maybe a setback from being transplanted?

George and mainegrower: I'm definitely going to deadhead from now on - in fact I've already done most of them (took off the remnants of 2009 bloom).

mainegrower: Winds are always a problem here by the bay and last year I lost my overgrown, but lovely rose arbor. My wisteria pseudostandard has been blown over several times which only makes it bloom better. My male Ilex opaca snapped off last winter and the two females were bent over by the wind and snow. The Ilex opacas are part of the windbreak for the pierises and their loss/bending may have contributed to wind hitting the pierises.

ginny: I can make excuses for each pieris individually, but unfortunately the same excuse doesn't work for all of them. I did transplant several of the dwarf pierises last year, but Mountain Fire and Karenoma have not been moved since they last bloomed.

Spring here by the bay is way behind inland areas. I'm still in middle daffodil and muscari season, with forsythia winding down but still blaring yellow. Early azaleas are just opening, and most rhododendrons are still in bud (if the squirrels didn't eat the buds). My wisteria is showing flower buds but not near opening.

George: I'm glad that crowding is not too big an issue - I hate to see bare mulch (hate more to weed it). I"ll just have to keep an eye on the Siberian irises which both spread out vigorously and seed all over the place. I still have place to move them to. For now.

I'm guessing that several things are operating here - mostly weather, deadheading and transplant shock. Each with a different level of effect on each pieris. The hardiest pieris seems to be Little Heath, now if it would just bloom better....

Thanks all,
Claire

Moving could be a factor. Also, how much sun do they actually get now, as compared to 2005, 2006,+ ? Less? They should get get eastern sun in the morning, shade in the afternoon for optimal bloom.

Paula: The sun exposure should be about the same as the last few years. Depending on the angle of the sun, the bed gets eastern sun in the morning and early afternoon, then filtered sun/part shade for the rest of the afternoon.

The sun exposure is determined by big pitch pines to the south, assorted big conifers to the west, and somewhat by a one story house to the east, but not very close. There's also a very big winterberry on the west side of the bed.

All of these factors have been about the same size for several years, so there isn't a case of sudden shade caused by an overgrown plant (not that I don't have many overgrown plants, they're just not in the way here).

Claire

Wendyb: I'm not sure, but there probably were few or no buds formed last fall. By late summer/early fall, pierises are simply under the radar for me. There are too many ornamental grasses, asters, goldenrods, mums, etc. to catch my attention. I don't think about pierises until late winter/early spring when they bloom. Or don't, like this year.

I started deadheading a week or so ago and I'm not sure how much of the residual material was past bloom from the previous year and how much was desiccated new buds. Most of it looked like seed pods.

It's interesting that your new growth on Little Heath is brown - mine is reddish pink. This photo was taken this morning:

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Also interesting, a few years ago my Mountain Fire put out new brown growth which was a disappointment. It was red again the next year. I'm not sure, but the other pierises may also been brownish, but Mountain Fire was the most obvious. Maybe a nutrient issue with my compost?

I don't have Silver Flame, but maybe I should. Oh great, something else to squeeze into the garden somewhere.

Claire

Claire, Your Little Heath new color looks like my Silver Flame, so maybe you don't need to get yet another!!! Maybe its a sun thing. My Silver Flame gets better sun than my Little Heaths. I see yours is near a colorful berberis so I suspect there is maybe more sun than mine.

Here's a pic of my Little Heaths brownish:

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Here's last year's Silver Flame (its 2nd year here)

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Here's one of my charming fall Cavatines who won't be ignored:

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Looking through my pictures I saw one pic of April Cavatine's dessicated buds, but I think that was the only time that happened. They might be getting tougher as they get older. (me too - LOL)

Wendyb: Good! I won't buy a Silver Flame since I have three Little Heaths and they don't seem to know they're dwarf. Maybe I should call them Middle Heaths, not Little Heaths.

Your brownish foliage is the same color I got a few years ago. I don't remember the spring weather that year so it could have been a sun issue.

I'm always a little embarrassed showing photos with the berberis in it. I bought it way back when I didn't know better, but it's so healthy and gorgeous when it blooms that I won't get rid of it. A few days ago I did notice what may be a purple seedling in another area - no green ones.

I probably would have noticed if my Cavatines had those flower buds, although it amazes me what I can overlook when I really try.

Claire

Hi Claire, I'd love to see an update of how your shrubs are doing this year and if you did anything different. Did you have a lot of snow cover like we did last winter?

I think your conditions may be a little better than mine. I have clay soil and even though my pieris faces East, it has a tree directly to the south of it and to the west of it that only allows for less than 2 hours of direct sun a day. It has a lot of root competition from a neighboring maple and my soil is between 6.4 and 7, so not all that acid. I did add Hollytone this year. I have 'Dorothy Wycoff'. I lost 'Scarlett OHara' because I moved it a little too late in the spring last year. One of my few transplant failures.

I think the 'Dorothy Wycoff' is in it's third year and hasn't been moved since the initial planting. It was a small plant and it is still a small plant. I will have to go take a look at it soon, I haven't been paying attention for the past month. Is this the right time to deadhead it?

Update, Spring 2011

All is well in the pieris patch this year! Last year I deadheaded leftover blooms from 2009 and I gave all the pierises plentiful compost. I may also have added some Plantone, I'm not sure. I got a little giddy with Plantone.

I moved a few of the dwarf pierises to give them some more room and I pruned reverting branches from two of the three Little Heaths.

P. Mountain Fire on April 9, 2011
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The Cavatine and maybe a Prelude also bloomed but I don't have a good photo.

Little Heath is becoming a real joy. Of the three, I left one alone, moved a second one with light pruning of reversions, and heavily pruned a third. The one I left alone bloomed heavily. The second one that was moved also bloomed heavily, just later, and the one I heavily pruned didn't bloom at all.

This is the Little Heath I left alone, on May 4, 2011 with new red foliage appearing with blossoms remaining. There's a piece of Cavatine (I think) showing on the left.
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The red or pink foliage was like a second bloom this spring. This is some of the pierises on May 18, 2011 with a Euonymus Silver King and a big old Ilex verticillata as backdrop. I think that's Cavatine and maybe a Prelude on the lower right still blooming. The overall bloom time was really extended well over a month.
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There was much more snow cover than usual last winter (usually we get minimal cover) so that may have helped. In any case, the problem seems to have been transient, or maybe I now know a better way of maintaining the plants

Claire.

Pieris japonica, 'Valley Valentine' in my garden April 3rd.

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Mike

Gorgeous, Mike! but snow in Seattle?

Claire

Claire, we get snow in Seattle. Not much, and it usually doesn't last long. I'm in the foothills southeast of Seattle and get more snow because I'm higher and further from the salt water.
As a side note, we're further north than Maine.
Mike

Thanks for the update, Claire and glad to see your Pieris are doing better. I had all that snow cover and it doesn't seem to have helped my 'Dorothy Wycoff' I have a bag of Planttone and Hollytone and plan on adding some of that. I did put compost down in the fall. Maybe just waiting another year and adding fertilizer and keeping it watered correctly will bring a better spring next year for it.

I really like that 'Little Heath' Going to have to look for one.

Mine did not bloom this year either. We had a huge blizzard in January which broke off a third of the bush.

Or maybe it is the partial sun location?

Are these flower buds? Isnt too late in the year for blooms? Overnight Temps are in the 50s already.

Yes, those are flower buds. Pieris set buds in late summer and early fall and hold them through the winter. These should bloom at the appropriate time in spring. I think the presence of the flower buds through the "off season" adds another dimension to the appeal of these plants. The pink flowered ones can be especially striking with their colorful buds in place all winter!!

Pieris are workhorses in many gardens here, in much the same fashion as their cousins rhododendrons and azaleas.

Oh thanks for explaining. I wonder if the snow and late frosts we had earlier killed my buds from last year.

Late hard freezes in the eastern part of the country prevented many flowering shrubs, pieris and rhododendron included, from blooming last spring. A great disappointment since the mild El Niño winter temperatures seemed to promise lots of spring bloom.

Wow. I've not read all the responses in this thread, but we had some devastating late frosts last spring and that zapped many of my pieris (and a number of orchard crops as well). Perhaps yours too.