Lynne Forbragd, UM Extension Master Gardener in Anoka County, August, 2014
If you are considering adding hydrangeas to your landscape, this is a great time of year to see them in full bloom. From mid-July through the end of August, hydrangea flowers transform from bright white or cream to shades of pink, blue, burgundy and lime green. Almost in every neighborhood, you will see them as showy shrubs or trimmed into tree form in front yards, public gardens and commercial properties.
Before buying a hydrangea, it is good to understand the different varieties that are available for us in Anoka County, which is Zone 4 on the USDA plant hardiness zone map.
Hydrangea aborescens Annabelle is the most popular and easy to grow hydrangea. The flower heads can grow to 10” in diameter which provide impact in a landscape from a long distance. This variety prefers morning sun and partial shade in the afternoon but can be planted in full sun. Due to its large leaves, it is important to keep watered to prevent wilting in the afternoon sun. Once the flowers turn lime green, they can be cut and used in dry flower arrangements.
Hydrangea Paniculata is very cold hardyThe flowers form a cone shape starting out white and become a dusty pink as they age through the season. This variety must be in full sun to produce flowers. Limelight is a very popular lime green paniculata. As the season progresses, the blooms will take on shades of pink and burgundy for a multi-colored effect. Pink Diamond is another paniculata. Its large flowers will turn a deep burgundy by season end.
Hydrangea macrophylla (Mopheads) are very showy with bell shaped flowers and bloom in pink and blue colors. Endless Summer is mophead that produces both pink and blue flowers on the same shrub. Not all mophead varieties are hardy in Zone 4 and it is important to check this when purchasing these shrubs.
Hydrangea macrophylla normalis (Lacecaps) are more informal in shape than other hydrangeas. They have small flowers that bloom on the perimeter of the flower head and are typically smaller. They tolerate more shade and can be planted with other shrubs as a background in a border.
All the above hydrangeas, with the exception of Mopheads, bloom on new wood each year so you do not need to worry about winter temperatures. The size can be controlled by pruning early in the spring or late winter before they leaf out and you can see their shape. Do not cut them back too severely as you need the main stems to become woody and strong enough to support the large flowers. The blooms will be at the end of the new growth which can be up to two feet in length.
Newer selections such as Quick Fire, Pinky Winky, Strawberry Vanilla, Bombshell, Twist and Shout and many other varieties have been introduced which can bring more color into your landscape. By knowing the varieties of hydrangeas and their growing characteristics, you can select a variety that will work in your garden.