Hydrangea, Christmas Rose, Krismisrose, Florist Hydrangea, Mophead, Lacecap - Hydrangea macrophylla hybrids

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Hydrangea Teller 'Lady Oshie' Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea Teller 'Lady Oshie' Picture courtesy Leonora Enking Visit her flickr photostreamCondensed Version:

Hydrangea remains a firm favourite with gardeners around the world and is grown for its luxuriant foliage and abundance of huge ball-shaped or lace-capped flowers, from November through to late summer.  Innumerable hybrids have been bred for the market from about 20 wild species and newer hybrids include red varieties. Many of these hybrids will bloom from spring to autumn, and many keep their colour no matter the pH of the soil. Cultivars vary in size from 90cm to 2m tall with an equal spread; older specimens can take 6 to 10 years to reach full maturity, but once mature can exceed 3m.

Hydrangea macrophylla occurs in two forms – the hortensias or ‘mophead’ hydrangeas, and the ‘lacecap’ hydrangea. Mopheads form large pom-pom shaped balls of flowers, while lacecaps are round and flat.  Blossoms can be white, or shades of pink, blue, or purple, depending on a pH-dependent mobilization and uptake of aluminium from the soil into the plants. Acid soils with a pH of less than 5.5 produce blue flowers, and soils with a pH greater than this produce pink flowers. White flowers are not affected by pH, although sometimes one will find that nature has added splashes of pink into the white flowers.

Hydrangea macrophylla Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea macrophylla Picture courtesy Leonora Enking Visit her flickr photostreamBecause of their lovely round form, large dark-green leaves and spectacular flowers, hydrangeas make wonderful background plants for the mixed shrub border. They grow well in shady woodland gardens where they receive mottled shade; blending beautifully with other shade loving plants like azaleas, magnolias and gardenias. They also look spectacular planted near still dams or ponds where the water will reflect the blooms, providing double the impact. Hydrangeas look especially good planted with light coloured flowers and even tall growing perennials and annuals. Flowering is especially prolific in December, making hydrangeas a favourite Christmas cut flower. They also grow beautifully in large pots as long as they are watered regularly.Hydrangeas can be planted in almost all of South Africa’s growing regions but do best in temperate regions with good summer rainfall; they are not suited to humid, or very hot and dry regions.  Because they originate in coastal regions, they are quite happy in coastal gardens, provided they are given some protection from strong winds. The plants are hardy to frost, but the buds can be damaged by severe winter weather and freezing winds. In very cold regions, site the plant in a sheltered part of the garden, mulch the roots well, and cover in winter. Although hydrangeas are shade lovers they do require some sunlight to flower well, and perform best in dappled shade, or morning or late afternoon sun; excessive midday heat will cause the plants to wilt.

Hydrangeas will adapt to most garden soils, but prefer a very fertile, loose, moist soil which drains well. They are not very drought tolerant, and should be watered deeply and regularly during dry or hot summer periods; reduce watering considerably during the winter months. To enhance the colour of your blooms and to promote flowering, feed regularly until the plants have finished blooming. Excellent commercial feeders are available at your local garden centre to enhance or change the colour of your blooms.

Hydrangea 'Renate Steinige' Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea 'Renate Steinige' Picture courtesy Leonora Enking Visit her flickr photostreamFull Version:

Description, History & Interesting Facts:

Hydrangea macrophylla is a deciduous species of Hydrangea which comes from the coastal regions of the Japanese islands, especially the south coast of Honshu. This hydrangea remains a firm favourite with gardeners around the world and is grown for its luxuriant foliage and abundance of huge ball-shaped or lace-capped flowers, from November through to late summer.  Innumerable hybrids have been bred for the market from about 20 wild species and newer hybrids will bloom from spring to autumn, and many will keep their colour no matter the pH of the soil.

Hydrangea macrophylla occurs in two forms – the hortensias or ‘mophead’ hydrangeas, and the ‘lacecap’ hydrangea. Mopheads form large pom-pom shaped balls of flowers, while lacecaps are round and flat.  Blossoms can be white, or shades of pink, blue, or purple, depending on a pH-dependent mobilization and uptake of aluminium from the soil into the plants. Acid soils with a pH of less than 5.5 produce blue flowers, and soils with a pH greater than this produce pink flowers. White flowers are not affected by pH, although sometimes one will find that nature has added splashes of pink into the white flowers. If you are aiming for a strong blue colour, avoid planting hydrangeas close to a concrete wall or foundation as concrete can leach lime into the soil, making it difficult to obtain a true blue colour.

Hydrangea 'Leuctfeuer'Hydrangea 'Leuctfeuer'Cultivars vary in size from 90cm to 2m tall with an equal spread; older specimens can take 6 to 10 years to reach full maturity, but once mature can exceed 3m. Hybrids include red varieties and the unusual ‘Lady in Red’ - a white lacecap hydrangea with flowers that mature to a deep red colour toward the end of summer; ‘Sweet Dreams’ is a soft pink lacecap with a generous amount of flowers per bush; and ‘Nikko Blue’ is an easy-to-grow mophead hydrangea, which produces bright blue flowers in acidic soil and lilac to light pink flowers in alkaline soil.

Newer varieties are bred to be compact and don’t occupy as much space, so they are great for smaller gardens and pot culture. 'Endless Summer' is a popular new selection which produces pink or blue flowers on the current year's growth as well as on old wood. It will often produce a full set of blooms twice each summer; and in warm areas can bloom for up to six months. Look out for Endless Summer ‘Blue’, Endless Summer ‘Pink’. ‘Blushing Bride’ has the same re-blooming qualities as its parent, ‘Endless Summer’ and produces radiant pure white, semi-double flowers that mature to a sweet pink blush. The plant produces strong sturdy branches making it a perfect flower for cutting and its full yet compact growth habit makes it an ideal plant for decorative containers, as well as in the garden.

Other hydrangea species include: Hydrangea serrata (mountain hydrangea) which is closely related to H. macrophylla, but it is smaller and finer than its popular cousin, and hardier. Hydrangea paniculata (panicle hydrangea) is the most hardy to cold temperatures and also the giant of the hydrangea genus, growing +-3m tall with an equal spread; varieties change in colour throughout the flowering season. Hydrangea arborescens bears small white to green coloured flowers; and the stem of this variety tends to peel off in layers leaving various different shades of bark on the stem; the most popular variety of H. arborescens is ‘Annabelle’. Hydrangea quercifolia (oak leaf hydrangea) grows best in inland gardens in South Africa; bearing pretty white flowers in the summer, followed by beautiful foliage in autumn. Read more about it here.
 
Hydrangea 'Rose Swirl'Hydrangea 'Rose Swirl'In the Garden:

Because of their lovely round form, large dark-green leaves and spectacular flowers, hydrangeas make wonderful background plants for the mixed shrub border. They grow well in shady woodland gardens where they receive mottled shade; blending beautifully with other shade loving plants like azaleas, magnolias and gardenias. They look spectacular planted near still dams or ponds where the water will reflect the blooms, providing double the impact. They also look especially good planted with light coloured flowers and even tall growing perennials and annuals. Flowering is especially prolific in December, making hydrangeas a favourite Christmas cut flower. They also grow beautifully in large pots as long as they are watered regularly.

Hydrangeas are fantastic cut flowers, and dry well; but need to be picked when they are fully open. The woody stems cannot absorb water well, so remove the bark completely up to about 5cm from the bottom, before placing the stems in a bucket deep enough to cover the entire length of the stems with water; leave in a cool place overnight before arranging.

Cultivation:

Hydrangeas can be planted in almost all of South Africa’s growing regions but do best in temperate regions with good summer rainfall; they are not suited to humid, or very hot and dry regions.  Because they originate in coastal regions, they are quite happy in coastal gardens, provided they are given some protection from strong winds. The plants are hardy to frost, but the buds can be damaged by severe winter weather and freezing winds. In very cold regions, site the plant in a sheltered part of the garden, mulch the roots well, and cover in winter.

Hydrangea 'Lacecap' Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea 'Lacecap' Picture courtesy Leonora Enking Visit her flickr photostreamAlthough hydrangeas are shade lovers they do require some sunlight to flower well, and perform best in dappled shade, or morning or late afternoon sun; excessive midday heat will cause the plants to wilt. If you have a hydrangea that used to bloom well but now flowers only sparsely, evaluate whether the growth of nearby trees or shrubs have reduced the amount of light that reaches the plant. If so, you may want to consider moving the hydrangea to a sunnier location, or pruning the offender to let in more sunlight. Hydrangeas will adapt to most garden soils, but prefer a very fertile, loose, moist soil which drains well. They will adapt to well-prepared clay, clay loam, loam, loamy sand, sandy clay, sandy clay loam, and sandy loam soils. They are not very drought tolerant, and should be watered deeply and regularly during dry or hot summer periods; reduce watering considerably during the winter months.

To enhance the colour of your blooms and to promote flowering, feed regularly until the plants have finished blooming. Excellent commercial feeders are available at your local garden centre to enhance or change the colour of your blooms. Generally gardeners find it easier to allow their plants to bloom according to their soils pH, and then to enhance that colour; rather than attempting to force a blue hydrangea to flower pink, or vice-versa.

To enhance the colour of pink blooms, dust the soil around the plants with agricultural or dolomitic lime every 2 to 4 weeks from spring onwards, and water it in well. Mulch the roots with compost in spring and autumn and feed with a fertiliser with high phosphorus content like 2:3:2; phosphorus helps to prevent the plant from taking up aluminium.

To enhance the colour of blue blooms work some aluminium sulphate into the soil around the roots in autumn; and apply 25g of aluminium sulphate dissolved in 5 litres of water at two-weekly intervals from early spring onwards. Mulch the roots in spring and autumn with acid compost. Use a fertiliser that is low in phosphorus and high in potassium like 8:1:6; and avoid bone meal and super phosphates. Add organic matter such as rich compost, grass clippings, coffee grounds and fruit and vegetable peelings; all these help to lower the PH of the soil.

Hydrangea 'Lacecap' Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea 'Lacecap' Picture courtesy Leonora Enking Visit her flickr photostreamIt’s not uncommon for hydrangeas to produce lush foliage, but few or no flowers. This is often a result of over-feeding with a high nitrogen fertiliser, as nitrogen stimulates leaf growth at the expense of flowers.

The main cause of hydrangeas not blooming is incorrect pruning, or pruning at the wrong time. Until your hydrangea reaches maturity it is not necessary to prune the bud bearing stems at all; but it is necessary to selectively prune out all the dead and weaker stems completely at ground level. Many South Africans prefer to prune twice a year – once very lightly after flowering and another harder pruning in June, July or August. This method is quite acceptable, but because Hydrangeas set new buds soon after blooming, the ideal time to prune is as soon as the flowers have faded; usually at the end of January or February. Prune the bud bearing stems by about 1/3, to just above a new bud; hydrangea plants generally flower on the older stems, and the mistake gardeners often make is to prune the older stems too hard.   

Another common reason for lack of flowering can be due to unfavourable weather conditions like early autumn freezes before the plant is totally dormant, or when warm temperatures in late winter and early spring break the plants dormancy;  but is immediately followed by early spring freezes. The severity of the damage caused by these freezes depends on how many of the buds have broken dormancy; if a substantial portion of the buds on a stem were actively growing, the whole branch may die.

Hydrangea arborescens 'Grandiflora' Picture courtesy Leonora Enking Visit her flickr photostreamHydrangea arborescens 'Grandiflora' Picture courtesy Leonora Enking Visit her flickr photostreamPropagation:

Propagation is easy from softwood tip cuttings taken in summer, or from cuttings of un-flowered shoots taken in early autumn. Layering is also simple; bend some of the younger branches to the ground and remove the leaves where the branch touches the ground. Cover the stem with soil and place a brick on top. Within one season the branch should have formed roots and can be cut away from the mother plant and transplanted.

Pests & Diseases:

Hydrangeas are prone to rust, powdery mildew; leaf spot, slugs, aphid, red spider mites; and chlorosis (yellow leaves).

Toxicity:

Hydrangeas are moderately toxic if eaten by humans, dogs, cats and horses, with all parts of the plant containing cyanogenic glycosides. Cyanide intoxication is rare and usually only produces more of a gastrointestinal disturbance. If ingested, stomach pain, nausea, vomiting, sweating, gastroenteritis, vomiting and diarrhoea which may be bloody can occur. If you suspect that a child or animal has ingested hydrangea it is advisable to consult your doctor or vet immediately.

Additional Info

  • Common Name: Hydrangea, Christmas Rose, Krismisrose, Florist Hydrangea, Mophead, Lacecap
  • Latin Name: Hydrangea macrophylla hybrids