Best Plants for Northern Gardens: Day 28 — Hydrangea

limelight hydrangea

Limelight hydrangeas are a form of paniculata hydrangea shaped like a tree.

By midsummer, many of the flowering shrubs in the northern garden have finished their show. The lilacs, azaleas, spirea and fruit shrubs have mostly settled down for the season. This is when hydrangeas shine, adding brightness and big puffs of bloom to gardens. Those blooms later turn brown, but they continue to add beauty to the garden as an architectural element in winter.

There are four popular hydrangea types: lacecaps and mopheads (Hydrangea macrophylla); oak leaf (H. quercifolia); Annabelle (H. arborescens); and PeeGee (H. paniculata). Technically, all four types can be grown in northern climates, but the easiest ones to get to thrive here are the arborescens and paniculata types.
‘Annabelle’ is an old-fashioned hydrangea and will get 5 feet tall and wide in the right place in a northern garden. It makes a lovely hedge and is a reliable bloomer as far north as USDA Zone 3. In the last couple of years, a pink Annabelle, called Bella Anna™ has been introduced. The blooms are magenta-pink in color and it blooms on both old and new wood.
Endless summer hydrangea blooms

Endless Summer hydrangeas bloom blue in the right situation.

Among the lacecap or mophead hydrangeas, the best known in our area are those in the Endless Summer series. Some of these hydrangeas have blue flowers and are said to bloom all season long. Some gardeners have had difficulty getting blue blooms (or blooms at all) but in the right setting they are stunning. For example, we know of one gardener who grows them in a well-drained but  frequently watered site in a part-shade area that was the former home to a large pine tree. (Those are her blooms in the vase at right.) The gardener speculates that the slightly acid soil, the moisture and just enough sun lead to an endless number of blue blooms.
For size and ease of care, you cannot beat paniculata (or PeeGee) hydrangeas. They make great fences or hedges, they love sun and they can be pruned. That’s good because they grow 8 to 10 feet tall and wide. These are the base plant for all tree-form hydrangeas, especially the lovely Limelight series of hydrangeas.
In terms of care, hydrangeas like a dash of fertilizer in spring, but don’t over-fertilize them or you will get all leaves and no blooms. Sufficient water and enough sun will help them grow. When in doubt, read the plant tag thoroughly to understand the needs of your plant.  There are dozens of varieties of hydrangea, so ask your local nursery for advice about which ones will thrive in your yard.