Planted this hydrangea 4 years ago. second year had pretty good blooms. Did light pruning in spring of 3rd year & had very few blooms. This year did not prune it at all & it had only a few small flowers. I thought this plant blooms on old & new wood, but am confused as to what to do with it now....think I'll do nothing & see what happens next year. Appreciate any info or suggestions. It has grown quite large & foliage looks healthy.....gets more than half day morning sun.
bigleaf hydrangea, lacecap "shamrock"
Hello, Alegria316. Shamrock blooms only old wood so your pruning is off a little. I suggest that , next year, you prune it after blooming but before the start of July in order to make sure that next year's blooms are not cut. It should be a nice looking and compact shrub although it may get large in places where the growing season is long (like here for example).
I was wondering, how large is it now and when does it bloom for you? It is advertised as a late bloomer (June) and 3.5 to 5' HxW at maturity (i.e., 10 years). It is also advertised as winter hardy to Zone 5. I assume it is not troublesome because not too many people have posted about it and it is sold in many places.
Other suggestions:
Hydrangeas are not heavy feeders so do not overfertilize. Provide them with a single application of fertilizer in June and that should last all year. You can also apply weak fertilizers like liquid seaweed, liquid fish or coffee grounds but stop all fertilizers by the start of July to make sure no new growth gets zapped by early frosts (although Shamrock is advertised as being as being slightly more frost hardy.... whatever that probably means! Ha!). Late fertilizer applications can also cause the plant to stay in growth mode so early frosts can kill the flower buds because the shrub does not harden off for winter in early Fall.
Aim for constant soil moisture... as best as one can do of course. Flower buds are the first thing that hydrangeas will abort when they lack water; blooms and leaves are next. Reduce watering in the Fall but watch out for dry winters. If the winter is dry then water it every 1-2 weeks provided the ground has not frozen. Replanish your mulch in order to maintain about 3-4" up to drip line; now would be a good time to check and add more if needed.
You did not indicate your zone but I assume you are about a Zone 6 so you should not need to winter protect it. If your soil is deficient on phosphate, that may result in less blooms. Amending the soil may help but you need to either do a soil test or get a soil test kit from nurseries in order to see if this is really needed.
Does that help you?
Luis