Granted, it has been a heck of a summer in the Northeast (zone 6) with a lot of rain and very few hot days. This is my second season with 4 Hydrangea 'Hornli', which are dwarfs. One put out 3 blooms, another put out 1 bloom, and the others none. I have heard that hydrangeas might not bloom if they're planted too deeply. How can I tell now (with full foliage) or next spring (before shoots have emerged), if any are planted too deeply? Secondly, how and when should I "raise" them? Lastly, here in the Northeast, is it preferable to plant hydrangeas in full sun rather than part shade?
Hydrangeas planted too deeply
Please post photos of where the stems meet the earth. Did you feel you were planting them too deeply? Generally we put plants in so they're level with the surrounding soil and not into a deeper hole.
I certainly wouldn't prune them at all and maybe you'll have more blooms next year.
I'd go with dappled shade.
Planting too deep could cause problems with crown rot or things along those lines and an unhealthy plant that's got a fungal infection is unlikely to bloom well. So in that sense planting too deep could affect blooming, but I'd be more worried about the overall health of the plant if that's the case.
As far as the blooms--a couple things could be going on. The first possibility is that they're still young--shrubs will sometimes follow the "first year they sleep, second year they creep, third year they leap" rule so I'd wait and see how they do next year. The other possibility is that you may need to protect them for best results--I know in zone 6a it's generally best to protect them if you want to guarantee blooms and by the time you get to zone 7 they're generally fine without protection, but since you're in between you may find that some winters they'll do better if you protect them so that the buds don't freeze off if you get a late cold snap, etc. So if you still aren't seeing good blooming next year that may be something you want to consider.
Hornli's european heritage (Switzerland) should allow it to grow well in your zone but post pictures showing how deeply they are planted. I generally try to plant shrubbery less than one inch above the surrounding soil because settling can make them sink afterwards.
Hornli is a nice shrub that blooms on old wood, which means it is now producing the flower buds for Spring 2010. The exact time when flower bud production starts varies; it starts in July here and probably happens in August or September in NY. So, if you were to prune these plants now, you would be cutting off the Spring 2010 flowers. Have you pruned them before in the last two years? If so, do you remember on what month?
For me, the best time to prune Hornli would be after it has bloomed but before the month of July. In NY, I would prune it after blooming but before the start of August.
Next year's buds could also be killed if you tend to over-fertilize or if you fertilize late in the growing season. These two things can keep the plants in growth mode at times when they should be getting dormant in preparation for winter and early Fall frosts.
Fertilize them with 1/2 cup of manure, compost or cottonseed meal in June only (that is all they need for the whole year by the way). You can also add weak fertilizers like coffee grounds, liquid fish and liquid seaweed. But stop all fertilizers by July. That way, when early frosts come in the Fall, the plants will be ready and you will not loose flower buds because the plant was in growth mode.
Luis
Sorry for the delay in responding. The plants are in good health. I don't recall how deeply I planted them. Planting at surface level is not obvious to a beginning gardener so I may have planted them 1"-2" deep. I've attached a photo of where the stems meet the earth for a plant, which produced no blooms.
The only pruning I've done would have been in April-May this year. I believe I pruned a tiny amount of the old wood, which hadn't generated new growth and didn't give me reason to believe it would.
I don't recall when I last fertilized them in 2008, but it could have been in August or even September. I don't believe I fertilized them after July this year.
I didn't cover them last winter. I learned too late that there's an absence of covering/insulating products on the market. I gave up my frustrated search and threw caution to the wind (pun intended)!
I read today in a planting guide where mulch should not touch the plants. What are the consequences of letting mulch touch the plants? Once again, this is not obvious to a beginning gardener.
Thanks for your insight.
I know many people are against the mulch touching the stems but I've never had a problem doing it. Your mulch looks light in weight and I doubt that's the problem nor does it appear to be the depth of planting. Give it next summer (no pruning in the meantime) and please let us know how it's blooming for you.
I lived in 6B for 28 years and never covered any hydrangea and they all did very well for me.
The reason they say not to pile mulch up around the plant is because it can hold moisture around the base and that can cause rot, so you're supposed to leave a few inches of space between the base/trunk and where the mulch starts. Some plants are more susceptible to that sort of problems than others though. I try to be careful about it, but my dog runs around the yard and kicks mulch everywhere and it inevitably winds up piled around something and I haven't had any trouble either (at least not yet!)
Since pirl said that they'll do fine without protection in 6b, I suspect the reason they haven't bloomed much is just that the plants are young and they're doing the sleep-creep-leap thing that I mentioned earlier. I've had tons of shrubs (including hydrangeas) that haven't put on much of a show in year 2 but usually by year three they do start to get going.