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Hydrangeas

April 4, 2013

Hydrangeas

One of the most frequent asked questions that we encounter at the Mustard Seed Market are “When do I prune my hydrangea?” and “Why isn’t my hydrangea flowering?”. These questions can be answered by finding out what type of hydrangea you have and how it blooms. The five types of Hydrangeas we typically sell are all zone hardy for our area (zone 5-6), require part shade to full sun depending on variety and fall mainly into two pruning categories.

  • Hydrangea paniculata ( “panicle” hydrangeas) are commonly found in our High Country. The large cone-shaped flowers start off white and gradually turn pinkish-red as they age. These famous shrubs love the sun, and are the only hydrangeas capable of becoming tree form. They grow and form flower buds on current season growth. ‘Limelight’, ‘PeeGee’, ‘Tardiva’, ‘Pinky Winky’, and ‘Vanilla Strawberry’ are some of the many varieties available.
  • The large leaf “French” Hydrangea, or macrophylla are the wonderful old fashioned ones we remember from grandma’s house. They are commonly called mopheads or lacecaps and are either pink or blue in color, with color being determined by the acidity of the soil. The greater the acid levels the more blue flowers you’ll get! These guys can handle some shade. Morning sun is perfect in a hot spot. They form their flower buds on previous years growth.
  • Hydrangea ‘arborescens’ is native to Eastern US. These shrub- like hydrangeas often act like perennials, dying back each fall only to return in spring. They boast huge 10” blooms earlier in the summer than the panicle types. The most common is called “annabelle”.
  • ‘Oakleaf’ Hydrangea is another stellar native shrub. The gorgeous oak-shaped leaves and cinnamon colored stems produce large creamy white blooms in mid summer. The ‘Oakleaf’ prefers afternoon shade. The organic structure and excellent fall color give the Oakleaf Hydrangea multi seasonal appeal. 
  • The climbing Hydrangea anomala petiolaris is one of the best of the ornamental vines and useful because it will grow and flower even in a northern exposure. This is a large heavy vine that requires a very sturdy support. Reddish brown, peeling bark is attractive in the winter. It is slow to get started growing, often taking a few years before any considerable size is noticed. The classic white spring flowers are beautiful against the shiny green leaves. No need to prune except to maintain size.

The best time to prune hydrangea is after they flower and before they set buds for next year. On some species, such as Hydrangea paniculata and arborescens, you can prune very heavily and it won’t affect next year’s bloom because they bloom on new growth. To enjoy the winter beauty of snow on the dried flower heads, we recommend a heavy pruning in spring, cutting back to about 18”-24”. Anytime in April is ideal in our zone. Often I don’t get to this task till May without any problems!

For most Hydrangea macrophylla and Oakleaf quecifolia, if you prune in early spring or late fall, you will cut off the bloom buds for next year’s flowers. Many of these varieties bloom on old wood and set their after they bloom (think August). Thus “cleaning up the flower bed in fall” cuts off next year’s flowers! It is best to wait till late Spring/early Summer, when the new growth starts to appear on the brown stems, to cautiously trim off any dead tips only….but you must wait till all the new growth starts! There are more improved types of macrophylla hydrangea such as’ Endless Summer’,’ Penny Mac’ or ‘Mini Penny’ on the market that bloom on both old and new wood, resulting in long bloom seasons and not stressing the gardener if a late freeze damages the flower buds.

If you are having problems getting your hydrangea to bloom, make sure you are pruning at the proper time according to species. If it still doesn’t bloom, the problem could be related to the soil, not enough sun or planted in a too exposed spot. In some of the older macrophylla varieties like Nikko Blue, the flower buds can freeze too severely in the winter to come through in the spring and bloom consistently. Severe die back ensues and you end up cutting back all the flower buds and just having a green plant. You can try moving your plant to a sheltered location or wrapping it in burlap for extra protection.

Planting your Hydrangea in well drained soil amended with compost and organic soil amendments and regular watering (especially the first full season) to ensure your success!

Let the Mustard Seed Market help you choose a beautiful and proper Hydrangea for your garden!

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