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Gardening: Hydrangea growing tips
Hydrangeas are an elegant and dramatic option for the garden, providing endless vibrancy and unique colour variation in your space.
With their clusters of large, colourful blossoms and playful names like mop head and lace cap, hydrangeas are easy to fall for. They come in numerous varieties, including spring or fall blooming, ever-blooming, climbing, shrub-forming and potted.
Your first introduction to them was probably when you gave or received one for Mother’s Day. A consummate display flower, its huge balls of pink, white or blue blossoms can grace dining room tables or windows for weeks.
Native to Japan, these are Hydrangea macrophylla, otherwise called big leaf, French or florist’s hydrangea. You can plant these hydrangeas outside but they will only bloom if there is an early spring and a late fall, giving enough frost-free days for the plants to develop flowers. Lace cap cultivars (H. macrophylla var. normalis) have the same growing characteristics as macrophylla but have an inner ring of small, fertile flowers surrounded by an outer ring of large, showy blooms.
The newest macrophylla available are the ever-blooming variety, including the brands “Forever and ever” and “Endless summer.” While blooming and re-blooming on new wood each year sounds great, you must plant these hydrangeas in a protected area and cover them during the winter (even though they will die back completely). Even with such protection, they still may not have enough time to bloom more than once in our growing zones. You can force more blooming by keeping the plants moist (not wet) and feeding them with fast-acting fertilizer every week, starting as soon as they show green in the spring.
Blue heaven. Hydrangeas have the remarkable ability to change the colour of their blooms. Blue tones require a pH of 5.5 and lower. You can get that by adding aluminum sulphate to the soil and organic matter, such as peat moss.
For pink blooms, add lime to raise the pH. If your soil is between pH 5.5 and 6.5, you will have purple or a mixture of blue and pink flowers on the same plant.
Panicle hydrangea (H. paniculata) is the most cold-tolerant member of the family and grows easily in the Atlantic region in zones 5 and up.
Staples in older landscapes, these plants form a woody shrub or small tree three to five metres tall. Large creamy-white flowers in 15- to 45-centimetre panicles, similar to lilacs, appear in mid-summer. The flowers turn pink as they mature, and by September, they cover the shrub in a rosy glow. You can prune Grandiflora (‘Pee Gee’) into a tree form and grow it as a specimen plant.
Oak leaf hydrangea (H. quercifolia) is one of two hydrangea species native to North America. With its large, pointed cones of white flowers that age to dusty rose and its attractive dark-green leaves, it will complement shady areas of your landscape. It can grow up to two metres as a woody shrub and has orange-to-burgundy fall colour.
Smooth hydrangea (H. arborescens) is the second North American native and includes the popular brand “Annabelle.” These plants bear spectacular large rounded flower heads in late summer in either sun or shade and can be dramatic in mass plantings. At the peak of flowering, the blooms are a pure white (the latest variety now comes in pink) and as they age, they develop a pale green colour. Without pruning, these plants can grow quite large. For a fuller shrub with fewer but larger flowers, try cutting it back to about 30 centimetres in April.
The flowers turn pink as they mature, and by September, they cover the shrub in a rosy glow.
While not as common as the previous four species, climbing hydrangea (H. anomala subsp. petiolaris) is a great vine option. While initially slow growing, the plant can cover up to 25-metre structures. White, lace cap blossoms bloom in early to mid-summer, though plants may be slow to flower (some take up to three years). Choose your location wisely as their rust-coloured stems leave a stubborn residue on surfaces. Consider letting them climb up a tree or cascade over a rock or hill.
All hydrangea varieties grow best in evenly moist, well-drained soil. Most will benefit from some shade, especially during afternoon heat. Big leaf, oak leaf, climbing and smooth hydrangeas usually perform well on the north side of a house or along the edge of a wooded area. Panicle hydrangea tolerates more sun than other species.
Deep shade and incorrect pruning will reduce flowering. Since big leaf and oak leaf hydrangeas flower on the previous year’s growth, fall or
winter pruning will remove new buds. Panicle, smooth and ever-blooming hydrangeas flower on each year’s growth, so early summer pruning will reduce flowering for that year.
But the most common culprit of flowering problems for H. macrophylla cultivars is weather conditions. Early fall freezes that occur before the plant is dormant, extreme winter temperatures and late spring freezes can all damage tender new growth.
The ability to change blossom colour adds to the appeal of Hydrangea macrophylla. Rich blue hues are particularly sought after in Atlantic Canadian gardens. Aluminum in the soil produces the blue pigment but the plant cannot access it if the soil is too alkaline (if the soil pH is high).
For blue flowers, you will need a pH of 5.5 and lower. Try adding aluminum sulphate to the soil, plus lots of organic matter, such as peat moss and pine bark. Keep in mind that some hydrangeas never produce blue flowers, including panicle, oak leaf, smooth and climbing varieties. For pink flowers, add lime to raise the pH. If your soil is between pH 5.5 and 6.5, you will have purple or a mixture of blue and pink flowers on the same plant.
Whether in the ground, in a pot or dried in an arrangement, hydrangeas of any colour and shape are a beautiful addition to your garden and your home.
Drying hydrangeas
Hydrangeas are some of the easiest blossoms to dry. Their large flower heads are striking when left natural or when spray-painted in gold or other colours. Panicle hydrangeas are the easiest to dry. Wait until they have taken on their pinkish hue in the fall and cut them the length you desire. Pop them in an empty vase and you’re done. They will look lovely tucked into your holiday greenery.
Other hydrangeas are trickier to dry successfully as you must cut them at particular times—ideally, just when the tiny flowers in the centre of the larger flower (called the sepals) begin to open. This is usually in late summer. Cut the flower stems at least 30 centimetres long for ease of handling. Remove all leaves below the bloom and place stems in a vase with water that covers more than half their length. Let sit until the flowers use up the water or it evaporates. The flowers should be dry and ready to use in arrangements.
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