Cape Cod is famous for it’s seaside cottages with white picket fences and beautiful blue Hydrangeas. It is more difficult to grow Hydrangeas further away from water, as cold winter temperatures can damage the buds which are set in the fall. Cold temperatures do not kill the plant, but will destroy the buds. Hence the most common problem with Hydrangeas in this zone is the lack of flowering. To preserve the buds through the winter, cage the plant with chicken wire. Fill the cage with mulch, leaves, or pine needles. This will insulate the plant and allow the buds to open in the spring. Hydrangeas are probably best around the edges of your property as the winter landscape can be marred by the presence of leaf filled cages.

Proper pruning is also very important.  Hydrangeas set their buds in the late summer.   Fall or spring pruning will remove flower buds which will reduce or eliminate flowering. Pruning should be done just after the blossoms have gone by and as a cleanup the following spring to remove damaged tips or older canes whose buds have difficulty opening. Once you’re getting abundant flowers, work on getting that great blue color.

Varieties of the common greenhouse Hydrangea or French Hydrangea (Hydrangea Macrofylla) can be pink, blue, or any variant of the two depending on how much aluminum is present in the plant tissue. Aluminum is soluble in acidic soils with a pH of 5.5 or below. For pink Hydrangeas, reduce the aluminum concentration by adding lime soil so that the pH is between 6.8 and 7.0. To produce blue Hydrangeas, reduce the pH, and make sure that plenty of aluminum is available. Amending the soil with aluminum sulfate will take care of both issues in one fell swoop.

Dry aluminum sulfate and pH test kits can be purchased at a good nursery or garden outlet. Aluminum sulfate should be used in the spring at a rate of 1 lb. for each square yard of soil. It may be necessary to repeat the application for a few seasons to get the desired results. Aluminum sulfate can also be mixed with the soil medium upon planting. Thoroughly mix 1/2 lb. of aluminum sulfate per bushel of soil for best results. You’ll almost be able to hear the surf breaking as you swing in your hammock surrounded by beautiful blue Hydrangeas at your metrowest summer retreat.

Written By: Terence Boots
Massachusetts Certified Arborist
Owner: Emerald Acres Inc.