KC Gardens

Hydrangeas are gorgeous, but here’s why they don’t thrive in the Kansas City area

A Mophead Hydrangea bloom
A Mophead Hydrangea bloom Kansas State University Research and Extension

If I had a nickel for every time I was asked about this plant … well, you know the saying.

Hydrangea macrophylla, also known as bigleaf hydrangea, mophead hydrangea or Endless Summer hydrangea, is a popular plant. But due to its fussy nature, people have difficulties growing it here, which leads them to ask me for help.

Plant profile

Hydrangea macrophylla is prized for its large, showy flowers in shades of pink or blue, depending on the variety and soil pH. The plant reaches three to four feet but often remains shorter.

At least a half day of sun, preferably morning, and protections from the extreme afternoon heat produces the best flowers.

Hydra means water, so this plant requires evenly moist, well-drained soil to survive. A dry location or poor, clay soil will doom the plant. The large leaves will wilt on a warm, sunny day even with ample moisture.

Bigleaf hydrangea blooms are gorgeous. The majority of the varieties on the market today are remontant, or reblooming, flowering in spring and fall.

Flower timing

To use another old saying, the proof is in the pudding when it comes to its ability to rebloom.

The best flower buds appear on old wood. Buds are set in late summer and flower the next spring.

Unfortunately, these buds often don’t survive our winter. Extreme cold or wide swings in the weather can kill the buds and stems, resulting in small or no flowers. This has happened in the last couple of years.

Based on the early cold spell, it will most likely happen again this spring.

New growth in the summer produces the fall blooms. Remember, this plant struggles in a hot, dry summer.

Another issue is the plant doesn’t start to flower until late September or October. Last fall, the buds were about the size of tennis balls before a freeze killed the blooms.

Pruning is key

Knowing when and how to prune this plant can affect flowering. Since the plant blooms best on old wood, do not prune in the spring. Wait for new growth to emerge, only trimming the dead growth. The developing buds could be your flowers.

The best flower bud is usually the terminal or tip bud, which is also most likely damaged in winter. Removing the deadwood is typically the only pruning needed. If necessary, a few nips could be made late spring to help shape the plant.

Yes, I know a few will disagree!

Every time I write about this plant’s fussy nature I receive emails with photos, letters and phone calls telling me I don’t know to “fertilize.” For those who have great success with this plant, I bow down to you. You have the right conditions for success, but most of us will struggle.

Why did I choose to write about this plant in the dead of winter? Hydrangea macrophylla is a popular florist gift plant for Valentine’s Day, Easter and Mother’s Day. The stores are brimming with these beautiful plants. These are greenhouse varieties that are less winter-hardy.

This plant is probably best discarded after blooming. They may survive in the garden, but continuous blooming is unlikely.

Yelp! I just set myself up for more emails.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org.

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