How to Grow Hydrangeas

Hydrangeas are showy deciduous shrubs who's latin name comes from the Greek 'Hydor', meaning water and 'Aggeion', meaning vessel. This is a reference to a flower shaped liked a cup. It is also a reference to the fact that these plants love water! They do not want to be grown in dry places.

Types of Hydrangeas

Hydrangeas are a large group of plants that come in a variety of colours, flower shapes and species. The most common are:
 

Mophead Hydrangeas (Hydrangea macrophylla)

Mophead Hydrangeas are the most popular type. They produce large round or dome-shaped clusters of summer flowers in shades of blue, pink, purple, green or white.
 

Lacecap Hydrangeas (Hydrangea macrophylla, Hydrangea serrata, Hydrangea aspera)

Lacecap Hydrangeas are a little less popular, but just as showy as Mopheads. Flowers are flattened with a a central cluster surrounded by larger flowers on the edges. Climbing Hydrangeas also feature lacecap-type flowers
 

Mountain Hydrangeas (Hydrangea serrata)

Best grown in full to part shade, this species has summer blooming lacecap type flowers in shades of pink or blue. Fall colour is also attractive
 

Rough Leaf Hydrangeas (Hydrangea aspera)

These Hydrangeas have attractive peeling bark and leaves with a quilt-like texture. Summer blooming lacecap flowers are lavender blue in colour.
 

Oakleaf Hydrangeas (Hydrangea quercifolia)

As their common name implies, these Hydrangeas have oak-leaf shaped leaves. Flowers are pannicled or cone-like and usually white in colour. This plant also produces sensational fall foliage colour. They can be grown in part shade or sun
 

Pannicle Hydrangeas / PeeGee Hydrangeas (Hydrangea panniculata)

Pannicle Hydrangeas can be large or small and produce flowers that are usually white, creamy, light green or light pink in colour. Their flower shape is what makes them unique. Pannicles are best described as large cone-shaped clusters or flowers. They are also more sun tolerant than most other Hydrangeas. The most common variety is called the PeeGee Hydrangea.

Smooth Hydrangeas (Hydrangea arborescens)

Smooth Leaf Hydrangeas feature huge whit, green or pink flowers in summer on plants with smooth, green foliage. Unlike most Hydrangeas, they bloom on new wood so can be pruned virtually anytime of year. The best time is in late winter while the plant is dormant
 

Climbing Hydrangeas (Hydrangea anomala var petiolaris)

Climbing Hydrangeas are vines not shrubs. They attach to vertical objects as they grow and produce white-lacecap type flowers in summer. They are fast growing and prefer part-shade to shade
 

Planting Hydrangeas

Most Hydrangeas prefer shade to part shade and will not perform well in hot, dry environments. With that said, white flowering varieties, as well as Pannicle and Smooth Hydrangeas are actually quite sun tolerant. In all cases, try to keep the soil moist at all times. You can actually watch a hydrangea flag and wilt before your eyes if it is allowed to dry out. They are fairly tolerant of different soil types and soil pH's as long as the extremes are avoided. Like most other plants, dig a hole twice as wide and just as deep. Do a drainage test. Amend the hole with bonemeal if you don't mind pinkish flowers. Bonemeal makes soil less acidic! Place the plant into the hole and back fill with soil. Water it in well. A 2-3 inch layer of mulch will help preserve moisture and reduce soil temperature.

Fertilizing Hydrangeas

Like most flowering shrubs, apply a general purpose fertilizer in early Spring before new growth appears. A plant food with a higher middle number will encourage more flowering

Watering Hydrangeas

Hydrangeas need plenty of water! Water deeply and regularly. You may have to water more than once a day in the heat of the summer!

Pruning Hydrangeas

Most Mophead and Lacecap Hydrangeas bloom on old wood. The best time to prune is right after flowering. If you prune too late, or wait until Spring, you are actually cutting off the next seasons flowers! There are modern varieties of Hydrangeas that are re-blooming. The most common of which is the Endless Summer Series. These plants can be pruned anytime because they flower on old and new wood. In general, prune Hydrangeas right after flowering to remove spent flowers as well as dead, damaged and diseased wood.
 

Common Hydrangea Problems

Wilting Leaves

Hydrangeas need lots of water. If your plant is wilting in the hot afternoon sun, provide more shade and/or more water
 

No Flowers

Make sure you prune at the right time, otherwise you may be cutting off the next seasons flowers. Also ensure the fertilizer you are applying has a higher middle number (Phosphorus), to encourage blooming. Hydrangeas that get too much shade will also tend to flower less
 

Damaged, Distorted Foliage

Hydrangeas can be affected by common pests like Aphids, Slugs and Snails. Use a sharp jet of water to knock off Aphids, or apply an Insecticidal soap. Use bait near your plants to lure away slugs and snails. Hydrangeas can also be a light snack for Deer. Apply a deer repellant like Plant Skydd or Bobbex periodically
 

Changing Hydrangea Flower Colour

Blue and Pink forms of Hydrangea macrophylla will change flower colours based on the chemistry in the soil. Acidic soils will allow the plant to absorb any aluminum in the soil. This will change the flower colour to blue over time. Alkaline soils will modify the flower colour to pink over time. Use peat moss or acidifying agents to lower pH. One of the best commercial products for deep blue flowers is GardenPro Aluminum Sulfate. An application of Bonemeal or Lime can be used to increase pH for pink flowers