Hydrangeas are a pretty addition to any garden. Find out how to treat them right and which variety is best suited to your outdoor oasis.
Hydrangeas have a common need for moist soil in spring, when they make most of their new growth. Most adapt well to partial shade, so they make fine plants to work into boundary plantings.
- The best flowers are produced from buds that grew the previous season, so it’s wise to locate hydrangeas where they will receive shelter from cold winter winds.
- In cold climates, the south side of the house is often the best place to grow colourful bigleaf hydrangeas, which have been favourites in gardens for over a century.
1. Watch out for tree roots
Although hydrangeas like partial shade, they suffer when forced to compete with tree roots that rob the soil of moisture.
- Plant them where their roots can enjoy moist soil, and provide a mulch to help keep the soil from drying out too quickly.
2. Try them in threes
- If you have the space, plant three hydrangeas together; they look spectacular when massed.
In smaller yards, a single plant makes a great specimen. Try growing daylilies on the sunny sides of your hydrangeas.
3. Don’t deadhead
The dried flower heads are not only beautiful, adding interest to the winter garden, but also useful: they help protect tender emerging buds from frost damage.
- Leave them on until early spring, then prune them back to just above a bud. Use spent heads for mulch or in the compost pile.
4. When to prune
Prune hydrangeas in late winter or early spring, cutting out damaged limbs and very old branches.
- Don’t remove live wood that grew the previous season unless the plant needs serious shaping, because this is the wood that will produce the best blooms.
- After plants leaf out, trim off any bare branches, which were probably damaged by cold winter weather.
5. What bloom colour means
The colour of a bigleaf hydrangea’s blossoms reveals the chemistry of your soil. Blue flowers indicate acid soil (below pH 7), while pink indicates alkalinity (above pH 7).
- To make a blue hydrangea bluer, acidify your soil with aluminum sulfate, iron sulfate or soil sulfur.
- To make it change to pink, add lime to the soil to raise alkalinity.
- Be patient, nudging the pH in the direction you want gradually, over a period of one to two years, because adding too much sulfur or lime at once can damage the plant’s roots.
You’ll want to research varieties to decide which ones will best suit your garden. To get started, read about these five varieties.
1. Smooth hydrangea
Smooth hydrangea is native to eastern North America.
- The wide, mounding plants adapt to full sun or partial shade and grow one to 1.5 metres high and wide.
- “Annabelle” produces huge, creamy white flower clusters in early summer.
2. Bigleaf hydrangea
Bigleaf hydrangea is sometimes called French hydrangea, although it’s native to Japan.
- This popular shrub grows about 1.2 metres high and wide and produces large blue or pink flower clusters in early summer.
- Lacecap varieties bloom for a longer period and produce smaller flower clusters.
- The ‘Endless Summer’ variety blooms on both old and new wood.
3. Peegee hydrangea
Peegee hydrangea is native to China and Japan, and is the biggest of the free-standing types, growing five to six metres high and three to five metres wide.
- Elongated white flower panicles appear in late summer and persist until winter.
- Older plants often thin out at the bottom and resemble small trees.
4. Oakleaf hydrangea
Oakleaf hydrangea is native to the southeastern United States.
- It grows one to two metres high and wide, and its large, lobed leaves often turn rich burgundy red in the fall.
- Elongated cream flower panicles appear in early summer and persist through winter.
- This hydrangea thrives in rich, acid soil and partial shade.
5. Climbing hydrangea
Climbing hydrangea originated in China and Japan. Climbing hydrangea can climb to 18 metres, and the stems cling to walls or other supports with sticky roots.
- Airy white flower clusters appear in early summer.
- This beauty requires extremely sturdy support; it’s a great plant to grow up a failing tree.