It's a wrap! Putting hydrangeas to bed for the winter.
Now that we've had a couple of frosts and had our first snow, it's time to put your hydrangeas to bed for the winter.
There can be no doubt, that although not always cold, Connecticut winters are unpredictable. There is usually a fair amount of freeze/thaw going on. That is – the ground freezes and warms up, then freezes again. We're also no strangers to sudden fluctuations in temperature. Some days are balmy in the forties, while others teeth chattering in the twenties. This temperature fluctuation can be especially hard on hydrangeas. All this fluctuation in temperature can really throw them for a loop. Just like everything else, who doesn't like a little extra love, especially in the winter? With a little extra attention, your hydrangeas can thrive through the winter and come back strong when the garden comes alive again come spring.
Take these few steps and give your hydrangeas a helping hand this winter, and they will reward you with a bounty of blooms next summer.
Keep Them Cozy
Temperatures in Connecticut can plummet well below zero. One of the most common questions we get is “Why won't my hydrangeas bloom?”. While their roots are hardy to the Connecticut growing zones 6a, 6b and in some cases zone 7, their buds can be affected by old man winter's harsh weather. Especially along the shore or in any windy areas, hydrangeas that bloom on old wood such as mophead/bigleaf (hydrangea macrophylla) benefit from wrapping. You can loosely wrap your hydrangeas in burlap and either tie it in a knot, or loosely “sew” it along the sides with some garden twine and a large needle. Essentially, you want to keep your hydrangeas protected from the wind. Wind damage is a very common cause of lack of bloom in these varieties. While some hydrangeas bloom on both new and old wood, it's a good idea to wrap the mophead/bigleaf varieties regardless of which type of wood they bloom on. By protecting them, you ensure a greater number of blooms the following season. Generally speaking, I like to leave the top open. Heavy, wet snow can crush the tops of them, and snow is an insulator. It's the wind you want to protect them from. Generally speaking, the hardier hydranges such as the paniculata and arborescens hydrangeas don't necessarily need the burlap protection, however, it can help prevent branch die-back in extreme cold or icy conditions. As most hydrangeas are wider at the top than at the base, it can sometimes be challenging to wrap them with burlap. You can always create a “frame” around them with bamboo so you have something to secure the burlap to. For smaller shrubs you can create a tepee shape to help with the heavy wet snow. Don't worry if all the leaves haven't yet fallen off your hydrangeas. What doesn't fall off over winter will fall off in the spring when the new leaves push out.
Although as I mentioned, all hydrangeas are root hardy in all of the Connecticut growing zones, mulch does help ad an extra element of protection. Hydrangeas need a lot of water (hence the beginning of their name “hydra”). When the ground is frozen, they can't absorb water. By adding an extra layer of mulch, you insulate the roots and also prevent the wind from causing the water in the ground to evaporate. This also helps keep the weeds down around them which compete for nutrients throughout the season. Decorative mulch is pretty, but for the winter, we recommend a good 3”-6” layer of leaves. It might not be pretty, but wrapped under burlap it doesn't matter. By the spring, most if the leaves will decompose and add organic matter to the soil, which is great for all plants. The freeze/thaw cycles can wreak havoc on plants and even pop them right out of the ground! They don't have the ability to put on and take off layers the way we do, so mulch keeps the soil around the roots a steady temperature which enables the hydrangeas to just be dormant rather than struggle with the fluctuation in temperatures. Early winter (now) is the best time to do this. If you mulch too early, that can cause rotting, disease, or a cozy warm spot for unwanted insects to winter over.
There is quite a bit of confusion when it comes to pruning hydrangeas. Sometimes hydrangeas can be too tall or too wide. Sometimes people just don't know how or when to prune them. I know some people that have had their hydrangeas cut back to the ground in the fall. This is a big no-no. Especially for the mophead, or pom pom hydrangeas. There is no doubt that pruning hydrangeas can increase their health and vigor, but not all hydrangeas can be pruned at the same time. Hydrangeas that bloom on old wood – such as the mophead hydrangeas, should only be pruned after they are finished blooming in the late summer or early fall. Others that bloom on new wood – such as the panicle hydrangeas, should be pruned in the late fall or late winter before they wake up in the spring. What about the newer varieties of hydrangeas such as the Endless Summer that bloom on both old and new wood? While these were developed to help with bud die-back over the winter and also to help take the mystery out of pruning, because they do have some blooms on old wood, it's best to treat all the mophead hydrangeas the same: as if they all bloom on old wood.