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Some people feel that hydrangeas are rather old-fashioned, having encountered them in their grandparents’ gardens, but think again! Hydrangeas are wonderfully generous plants, leafing out early in the year and suppressing weeds with their handsome leaves; they flower for months, usually from midsummer, often changing colour as they age. The leaves of these deciduous shrubs often colour well in autumn. The climbing varieties are self-clinging, so there is no need for supports. Macrophylla hydrangeas tolerate coastal exposure, too.
Hydrangea flowers are good for cutting, and also for drying for winter. The smaller ones are good in soil-based compost in large containers, which looks really wonderful if the same cultivar is planted in a row of identical pots, in a courtyard or formal garden.
There is one snag about hydrangeas, and the clue is in the name: they need a lot of water, unless your soil is reliably moist. They also dislike cold, dehydrating winds and frost pockets, and many dislike harsh midday or afternoon sun. Many macrophylla hydrangeas are blue in acid soil, pink in alkaline soil, and mauve in neutral soil; there are hydrangea blueing agents if blue is what you want, but these will not work on very alkaline soils. You can always grow smaller cultivars in a large container in soil-based, ericaceous compost (the one you use for camellias and rhododendrons); water with rain-water and use slow-release ericaceous fertiliser granules, and your blue hydrangeas will stay blue! There are also red cultivars, which change colour a little according to your soil, and white cultivars that don't change colour at all, although the latter usually turn pink as they age.
When you set the pros against the cons, hydrangeas are really good, easy shrubs with a lot of bang for your buck.
Hydrangea macrophylla is the one everybody knows, big, blowsy mop-heads with rounded flower-heads, or elegant, flatter lace-caps, with a ring of beautiful, infertile florets surrounding smaller, fertile flowers. They like a moist, humus-rich, well-drained soil, preferably acid to neutral, but will cope with a limy soil. Pink, purple or blue cultivars will change colour with the pH of your soil; red ones change a little, and white ones won’t, although they usually turn pink as they age. Older cultivars are usually about 5’/1.5m high and wide, sometimes much larger, but smaller cultivars, ideal for small gardens, are usually about 4’/1.2m high and wide. 5- and 4 footers can be grown in large containers.
There are too many cultivars to mention here, so check out the Hydrangea section on the website to choose the one that’s right for you.
Outstanding older cultivars include white mop-head ‘Mme Emile Mouillère’ AGM; white ‘Soeur Thérèse’, the connoisseur’s choice; red mop-head ‘Merveille Sanguine’, almost blackcurrant-coloured on acid soil; and reliable, clear blue (acid soils) or a good pink (limy soils) mop-head ‘Renate Steiniger’.
Some spectacular larger cultivars include the stunning blue (on acid soil) lace-cap ‘Mariesii Perfecta’, which extends to 6’6”/2m x 8’ (2.5m), and ‘Nikko Blue’ (blue on acid soil) 6’/1.8m x 8’/2.5m; both are lovely planted along a driveway in a large garden.
Smaller cultivars, at 4’/1.2m high and wide, include white lace-cap ‘Runaway Bride’, which flowers all the way along the stem; pretty lilac-blue (on acid soils) lace-cap ‘Blaumeise/Bluetit’ AGM, one of the well-known Teller series. Little ‘Masja’, a mop-head, deep pink to clear red on limy soil and a paler pink on acid soil, is only 3’/1m x 3’/1m, so ideal for a patio pot.
As with all hydrangeas, a good, organic mulch in spring will lock in soil moisture. Leave dead flowers on mop-heads to protect the young buds against frost; cut back to a pair of healthy buds in early spring. Lace-caps are hardier, and can be dead-headed to the second pair of leaves below the flower-head, so that the plant’s energy doesn't go into ripening seed. They won’t need pruning until established, then prune, if necessary, in mid-spring, occasionally taking out one or two of the oldest stems to the base to prevent the shrub becoming congested, and thinning out the centre a little, removing damaged and spindly growth. This pruning will encourage more floriferous growth.
Hydrangea arborescens ‘Annabelle’ AGM is naturally a fairly large, fast-growing shrub (10’/3m high and wide) with lead-green leaves and enormous, creamy-white heads, which emerge greenish-white, then age to lime-green and then beige – one of the best flower-heads to catch low winter light. The flower-heads can droop if the plant is over-fed; plant and mulch with leaf-mould rather than compost or manure to prevent this. It prefers a fertile, acid to neutral soil. It has quite an open habit, so regular pruning will keep the shrub dense and compact. Prune in mid-spring, removing most of last year’s growth to a pair of healthy buds.
Hydrangea paniculata, the paniculate hydrangea, is a large, very hardy, easy shrub, reaching 13’/4m x 8’/2.5, but there are much smaller cultivars. They have conical flowerheads, with showy sterile florets surrounding the smaller fertile flowers. It prefers partial shade but will tolerate full sun if the soil is reliably moist. ‘Grandiflora’ is full-sized, with creamy-white flowers deepening to soft pink. The fashionable cultivar ‘Limelight’ AGM (7’/2.1m high and wide) is a creamy, pistachio green, the flowers turning a rich pink as they go over – lovely in a shady border. For smaller gardens there is ‘Little Lime’ (4’-5’/1.2-1.5m high and wide) with rather blunt lime-green cones ageing to white and blush pink, freckled with deeper pink. ‘Diamant Rouge’, {5’/1.5m x 4’/1.2m) has flowers which emerge creamy-white, gradually turning pink and then raspberry-red. ‘Candlelight’ is a little larger, with upright flower-heads, which turn from creamy-white to pink from the bottom of the cone upwards. ‘Dharuma’ (4’/1.2m x 3’6”/1.15m has leaves that turn yellow in autumn, and creamy-white flowers that turn deep pink. ‘Vanilla Fraise’ (up to 8’/2.5m high and wide) opens clear white, turning a deep, rich pink. Paniculate hydrangeas should be pruned quite hard (remove 2/3 of the previous year’s growth) in mid-spring.
Hydrangea quercifolia, the oak-leaf hydrangea, also has conical flowers, and beautiful leaves, rather like an oak-leaf in shape, which colour well in autumn. It flowers best in full sun, but the beautiful leaves are larger in partial shade. It has a rather spreading habit. ‘Harmony’ (5’/1.5m x 8’/ 2.5m) has double white flowers in dense cones. ‘Snow Queen’ AGM (6’/1.8m high and wide) has conical heads of single, pure white flowers, which turn pink as they age. ‘Burgundy’ (6’6”/2m x 8’/2.5m) has the best autumn colour, purple and wine-red, and creamy-white flowers ageing to pink, really beautiful against the autumn foliage. Paniculate hydrangeas need minimal pruning; remove any dead or overlong stems in early spring.
Hydrangea serrata has pretty, flat lace-cap flowers and good autumn colour. ‘Bluebird’ is a compact form, just 4’/1.2m high and wide. It has deep blue fertile florets, surrounded by lilac-blue infertile florets (on acid soil) and can be grown in ericaceous compost in a pot if you want the blue colour and have alkaline to neutral soil. Prune in mid-spring if necessary, in the same way as Hydrangea macrophylla.
Hydrangea aspera ‘Anthony Bullivant’ AGM is an excellent small cultivar (5’/1.5m high and wide) of the otherwise large species, with flat lace-cap flowers, showy pink to mauve florets surrounding tiny purplish-pink fertile florets. Best grown in afternoon shade or in the shade of trees, in cool, humus-rich, moist but well-drained soil. It needs minimal pruning; just remove any dead or overlong stems in early spring.
Hydrangea involucrata ‘Yokudanka’ (5’/1.5m high and wide) has domed, lace-cap flowers with creamy-pink double sterile florets and small pale primrose fertile florets. It dislikes hot, dry sites and full sun. Leave the dead-heads over winter. It needs minimal pruning in mid-spring to remove the dead-heads and shape the bush.
Hydrangea anomala subsp. petiolaris AGM is a climbing hydrangea, self-clinging, so needing no support, and ideal for a north wall. It can be slow to take off, but once it gets going, it romps away, climbing to 50’/15m, and about 16’/5m across, although it can be pruned back to prevent it getting into gutters and under the slates. It has beautiful white lace-cap flowers 8”/20cm across in midsummer, the leaves turn yellow in autumn, and it has attractive, peeling, rust-coloured bark. It loves a moist, humus-rich, well-drained soil and shade or partial shade (it copes perfectly well with sun, but the flowers don't last as long).
If you prefer pink flowers, try the cultivar ‘Crûg Coral’, which opens dusky red, turning coral-pink, then pink-flushed cream. ‘Miranda’ has creamy-yellow variegated leaves, and ‘Silver Lining’ has beautiful grey-green leaves with cream variegation; both are good for lighting up a shady wall.
If your wall space is restricted, the variety cordifolia ‘Brookside Little Leaf’ is smaller, reaching 16’/5m x 10’/3m in 5-10 years, and has (as you would imagine) smaller leaves.
Hydrangea seemannii is a smaller species, reaching 33’/10m x 10’/3m, and also happy on a north wall. It won't tolerate more than a few degrees of frost, so is only suitable for milder areas. It’s an evergreen, with a long summer period of pretty, rather domed. greenish-white lace-cap flowers. It must be kept well watered while (slowly) establishing, but will then romp away.
Climbing hydrangeas are low-maintenance plants, and should be pruned immediately after flowering – all that’s needed is to prune out branches growing away from the wall (and stop them getting under the slates). They flower on the previous year’s growth, like all hydrangeas, and drastic pruning will reduce flowering, so give them a spacious site.
The best time to plant hydrangeas is spring or autumn, when there is more rain to help them settle in, but don't leave your hydrangea in its pot; plant it out at once, unless conditions are freezing or very dry; if they are, you may need to pot your hydrangea on into a pot just one size larger.
Hydrangeas prefer light or partial shade, but will tolerate full sun where the soil is reliably moist – they love a fertile, humus-rich, clay soil. They can be damaged by cold, drying winds and late frosts, so avoid frost pockets and windy sites, although the macrophylla cultivars famously tolerate coastal exposure.
Before planting, dig in well-rotted compost or manure to the whole area (not just the planting hole) as this will help the soil to retain moisture and drain well. Use a bucketful per square yard/metre. Make the planting hole as deep as the root ball and three times wider, to encourage the roots to spread out. Water the hydrangea well before planting, and plant so that the level of the compost in the pot is the same as the soil level. Back-fill, firm in well, then water thoroughly, then mulch with bulky organic matter (keeping the mulch away from the stem/s). Water well until the plant settles in.
Prune, when necessary, with gloves, as the foliage may aggravate skin allergies. If there has been frost damage, prune to a pair of healthy buds, and remove any stems that are touching the ground. Otherwise, prune as suggested for each species and its cultivars.
Mulch your hydrangeas with well-rotted compost or manure each spring when the soil is moist, to enhance water retention, but keep the mulch away from the stems.
