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Dundee Fact Sheets

Hydrangea                                              Print This Sheet


       Growing Beautiful Hydrangeas in
                          USDA Zone 4

In recent years growers have introduced many new hydrangea cultivars for northern gardeners to enjoy. Here are some hydrangea guidelines for achieving the greatest success:



All hydrangeas need rich, well-drained soil so it’s very important to prepare the planting area. Dig a hole about the size of a bushel basket and mix an equal amount of peat moss and compost into the soil you’ve removed. Now plant the hydrangea bush, at the same depth as the container it came in. Water very well and then add a natural shredded wood mulch at a depth of three inches.



Every spring, after the hydrangea has leafed out, work some 10-10-10 fertilizer into the soil around it. Endless Summer hydrangea also requires about a cup of soil sulfur applied around the plant in order to bloom blue. Put an inch or two of a peat moss and compost mix all around the plant. This is top dressing. Now water well, and renew the shredded wood mulch.



Hydrangea aborescens, such as old fashioned Annabelle, blooms on new wood; that is, on this season’s growth. Annabelle benefit from being taken down to the ground in early spring, before the plants break dormancy and start growing. This assures the largest and most plentiful blooms.

Hydrangea paniculata such as PeeGee, Limelight, Quick Fire, and many others that bloom later in summer and on new wood should never be pruned in summer, since this is when they are forming flowers. These are large shrubs, needing a lot of space, and cannot be made smaller by pruning. Once they are well established, they benefit from having one-third of the oldest, coarsest wood removed at ground level every year in early spring to promote plentiful, large blooms.

The Endless Summer Hydrangeas, Hydrangea macrophylla, bloom on both old and new wood. In late spring to early summer, when the plant has leafed out, prune any dead wood down to the ground. Very established plants will benefit from having one-third of the oldest wood removed down to the ground just like the paniculatas.

Tree hydrangeas are Hydrangea paniculata. They are prone to sucker growth at the base of the trunk that should be removed as it appears through the growing season. Branches can be shortened in early spring back to two or three growth nodes, or bumps, on each branch. The bumps, or nodes, will become shoots with the blooms on them as the season progresses, so do not remove this growth in the summer or the bloom will be lost.



As flower heads turn brown, they can be removed. Some people prefer to leave the brown flowers on the plant for interest in the winter landscape. Others like to harvest the dry heads in fall for use in flower arrangements and with spruce tips and other greenery in winter pots.



“Hydro” means water, thus all hydrangeas require large amounts of water for the strength and good health that leads to large and plentiful blooms. Water for several hours, on a slow drip, several times a week, for the deep rooting required for excellent hardiness.


By Barbara Whipple


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