Green County MGA

Green County Master Gardeners Association, Wisconsin

Hydrangeas

The hydrangea is a plant with a name of Greek origin that means water cup.  It thrives in moist soil, and in light of all our recent rains, this proves to be a banner year for hydrangeas.

There are approximately 23 species of hydrangeas.  This article will focus on the two hydrangeas that are native to the United States.

H.arborescens or smooth hydrangea is native to eastern United States and as far west as Iowa and Louisiana.  The most popular cultivar in this group is Annabelle.  This is a very easy plant to establish.  Its large white ball-like blooms can grow to 12 inches in diameter.  Annabelle is cold hardy to zone 4 and tolerates very harsh winters.  As it blooms on new wood each year, this hydrangea is an easy one to prune.  All stems should be cut back to approximately 10 inches.  This should be done in very early spring.

Annabelle blooms best when given ample morning sunshine and some afternoon shade, but it will also bloom quite well in dappled shade.  It likes rich soil, with a yearly application of compost.  A 10-10-10 fertilizer can also be applied in late May.

This plant blooms in mid summer and can reach a height of 3-5 feet with a width of 4-6 feet.  The only challenge in growing an Annabelle is trying to keep it upright.  A heavy rain will bring the entire shrub to the ground due to the weight of the blooms.  The blossoms on this plant will dry on the plant and if not removed they can provide some fall and winter interest to your landscape.

Hydrangea quercifolia, or oakleaf hydrangea, is native to southeastern United States where it is found growing in moist woodlands.  This hydrangea can tolerate more sun and heat than other hydrangeas and actually does quite well in drier soil once it is established.  It is very important to select a site that drains well.  The oakleaf hydrangea will develop root rot if allowed to sit in soggy soil for even a short time.

There are two forms of oakleaf hydrangea, such as the zone 5 single blossom cultivar Snow Queen and double blossom cultivar Snowflake.  An advantage to the double blossom is a slightly longer bloom period, but both forms are gorgeous.

Oakleaf hydrangeas will grow to a height of 6-8 feet.  They are the only hydrangea to develop a fall colored foliage.  Select a site that will receive significant early day sunshine with some afternoon shade.  This is best for flowering as well as fall foliage color.  The creamy white flowers grow 4-12 inches in length with the panicles turning a rose pink color as they age.  This plant also has an exfoliating bark which adds to the winter landscape.

It is undoubtedly the large flower heads of the hydrangea that make this plant a popular choice for many gardeners.

Until next time … happy gardening.

Nina Binkley, U.W. Extension Master Gardener Volunteer