HYDRANGEA - Popular ornamental plants

First discovered in Japan, the name hydrangea comes from the Greek “hydor,” meaning water, and “angos,” meaning jar or vessel. Common names are Hydrangea and Hortensia. Sometimes, this gorgeous flowering plant also known as Hydrangea arborscens, Mountain Hydrangea, Seven Barks, Smooth Hydrangea, Viburnum alnifolium, Viburnum americanum and Wild Hydrangea.

The Hydrangea group consists of shrubs and woody climbers, both hardy and tender. Most of the hydrangea are deciduous, which is the widely cultivated temperate species and just a few of the tender plants are evergreen. It is a genus of about 70 to 75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) as well as North and South America. By far the greatest species diversity is in eastern Asia, notably China, Japan, and Korea.

Most are shrubs 1 to 3 meters tall, but some are small trees, and others which is climbing type can reach up to 30 metres on trees. Through my readings, I find out that hydrangea is not only easy to grow but are also quite hardy and resistant to most pests and diseases, making it even easier to care for it. And with numerous varieties to choose from, you’re certain to find one that’s right for you. These beautiful bushes reward you each year a magnificent blooms that will surely brighten up overall looks of your garden.

The root and rhizome part(underground stem) are used to make medicine traditionally in some country to treat enlarged prostate, prostate and bladder infections, kidney stones, and hayfever. However, always bear in mind that hydrangeas are moderately toxic if it is eaten raw or being prepared using the wrong method, because all parts of the plant contains cyanogenic glycosides. Hydrangea paniculata is reportedly sometimes smoked as an intoxicant, despite the danger of illness and/or death due to the cyanide.

Mophead hydrangea flowers

Lacecap hydrangea flowers

Above are two pictures showing two types of flower formation in hydrangeas. Mophead flowers are large round flowerheads resembling pom-poms or, as the name implies, the head of a mop. In contrast, lacecap flowers bear round, flat flowerheads with a center core of subdued, fertile flowers surrounded by outer rings of showy, sterile flowers. The flowers of some rhododendrons can appear similar to those of some hydrangeas, but Rhododendron (including azalea) is in a different order.

Species in the related genus Schizophragma, also in Hydrangeaceae, are also often known as hydrangeas. Schizophragma hydrangeoides and Hydrangea petiolaris are both commonly known as climbing hydrangeas.

Growing Hydrangeas

Hydrangeas are popular ornamental plants, grown for their large flowerheads, with Hydrangea macrophylla being by far the most widely grown with over 600 named cultivars, many selected to have only large sterile flowers in the flowerheads. Although there are many types of hydrangeas, most can be grown in full sun or partial shade. Keep in mind, however, that many hydrangeas do not like extremely hot conditions, so try to locate them in an area where they can enjoy some afternoon shade. While they can be grown in a wide range of soils, hydrangeas typically prefer rich, moist soil that drains easily. Lots of organic matter will help here and as to feeding, don’t feed new planted hydrandea with chemical fertilizers unless it is well established (usually 1 to 2 months) and  after that use just a balanced fertilizer. Feed sparingly, as too much nitrogen stops flowering. However, amending the soil with just right amount of compost prior to planting is quite helpful for its growth. Hydrangea planting should be performed in spring once the threat of frost has passed (for cold climate region). Water thoroughly after planting. You can also add a layer of mulch following hydrangea planting for long-lasting moisture level. With good care and regular inspection for pest presence, you will be rewarded with abundant of beautiful eye-catching blooms all over your garden after a couple of months as the pictures below.

Hydrangea macrophylla being by far the most widely grown cultivars

Colour Changes of Hydrangea

Hydrangeas are fascinating plant to be owned. Unlike most other plants, the color of their flowers can change dramatically. However, in most species the flowers are white, but in some species (notably H. macrophylla), can be blue, red, pink, light purple, or dark purple. 

The people who have the most control over the color of their hydrangeas are those who grow them in containers. It is much easier to control or alter the pH of the soil in a container than it is in the ground. On the other hand, hydrangeas often change color on their own when they are planted or transplanted. They are adjusting to the new environment. It is not unusual to see several different colors on one shrub the next year after planting.

Generally as most people know, an acidic or low pH will induce 'blueness'; whereas, a higher or alkaline pH will induce 'pinkness or redness'. But recently, some research done in England seems to indicate that higher aluminum content also influences blueness more than pH levels.

Anyway, it is much easier actually to change a hydrangea from pink to blue than it is from blue to pink. Changing a hydrangea from pink to blue entails adding aluminum to the soil. Changing from blue to pink means subtracting aluminum from the soil or taking it out of reach of the hydrangea.

Limitations to hydrangea flower colour change:

1. WHITE HYDRANGEAS can NOT be changed to pink or blue by the grower. (Sometimes pink and red appear naturally on flowers as they age).
2. If you live in a hot climate, it is unlikely you will ever see a "true red" hydrangea. No matter how convincing those pictures in the catalogs are or how much lime is added to the soil, one can only achieve a very deep or dark pink, but not a true red.
3. One can rarely change the intensity of a color (how strong or pale the color is). The intensity develops for a number of reasons: the heredity of a particular hydrangea variety, weather conditions (hot or cold, humid or dry), health of the plant, and possibly other natural factors. Fertilizing hydrangeas once or twice a year may result in a little more saturated color simply because the health of the plant may be improved.
4. A few varieties of hydrangeas tend more toward the pink or the blue range of colors, but will not retain even this color if soil conditions are not right.

Below are the pictures showing the three main colour of hydrangea flowers:

 

More Info about Hydrangea

Hydrangea is indigenous to the United States where it grows from New York to Florida and then west to Iowa and Oklahoma. Several varieties of hydrangea are cultivated around the world to adorn gardens with their splendor, such as Hydrangea hortensis. This variety is native to North America, although it is widely found in gardens in China and Japan for its aesthetic beauty.

As for hydrangea care, water really is an important factor for it to grow lush . They enjoy deep watering at least once a week, especially in dry weather. Hydrangeas also benefit from an occasional boost of fertilizer once or twice a year in spring or summer. Hydrangeas can also be transplanted easily, but this should only be done during dormancy in fall or winter. Be sure to dig up the entire rootball and replant immediately. Since flowers are produced on new growth, you should prune hydrangeas once their blooming has ceased.

Many hydrangea plants require a lot of space in order to grow and spread out. Planting hydrangea away from trees and other shrubs will be a good idea. More than that, hydrangea is actually a type of shrub that will last a lifetime if proper care and attention is given from the beginning. They are relatively easy to grow and have several different uses in the garden. Whether used as a focus point or border, the hydrangea plant will add life and color to a garden throughout the growing season.

Failure to flower: frost and late pruning
Hydrangeas fail to flower for several reasons. Most common would be frost damage, followed very closely by late pruning. Too much shade or nitrogen are other likely culprits, but lets look at siting our plant and pruning as our best controls. If your hydrangea is not flowering look at your growing practices and where you have it planted and make appropriate changes.
Partial shade means more than four (more like six) hours of sunlight. Finding a more sheltered spot may help. But I suspect that the reason 9 times out of ten is pruning practices.

Example of lush growing hydrangea that are not producing flowers.

Pruning

Incorrect pruning is the biggest downfall of hydrangeas. Too much pruning and the macrophyllas won’t bloom, too little and the paniculatas will spoil the looks of your lovely garden. Some flowerheads best pruned on an annual basis when the new leaf buds begin to appear. As for the old flowers and dead stem, it must be prune as well to promote the growth and improve its appearance. If you not doing regular pruning, the bush will become very 'leggy', growing upwards until the weight of the stems is greater than their strength, at which point the stems will sag down to the ground and possibly break. Other species only flower on 'old wood'. Thus new wood resulting from pruning will not produce flowers until the following season.

The vine and big leaf types should be pruned immediately after flowering or not at all! Cut back to a good pair of buds, the last pair if you want to dwarf the plant back some. The panicle hydrangeas should be pruned in winter or very early spring and pruned HARD. Selecting 5 to 10 canes will produce the huge panicles most people are looking for. Besides, at 15 feet, Pee Gee(other common name) needs reigning in. Cut it back to that last pair or two of buds. You’ll be glad you did in 10 years.

Cutting stem just above the pair of new buds

Pruning that is done close to hydrangea's base

Pests and Disease

Hydrangeas are susceptible to leaf spots, blights, wilts and powdery mildew. Insect pests on hydrangea include aphids, leaf tiers, rose chafers, oyster scale and red spider mites. These pests are uncommon and if seen may be a sign of another problem causing plant stress. Powdery mildew is common on some varieties, but is rarely life threatening(easily controlled with benomyl, oil or lime sulfur). As always, gardeners should make choices based on varietal resistance, and desired traits. A little research goes a long way in making the best selection for your garden. Generally the biggest problems with this plant are siting and culture, so find a sheltered, partly shaded spot, water regularly, and soon your summer and fall will be filled with hydrangeas.

 Cercospora leaf spot on upper leaf surface of Endless Summer big leaf hyrdrangea. (Hydrangea macrophylla 'Bailmer')

 Unidentified fungal infection spreading throughout hydrangea leaf.

While Powdery Mildew will not usually kill a plant, it does distort growth, reduce flowering, discolor foliage and impact vigor. Not desirable for garden or nursery.

 Another hydrangea leaves showing more severe powdery mildew symptoms.

 Mealy bugs ( Pseudococcidae ) sitting under the leaf of hydrangea. Any plant with enough mealybugs feeding off it will induce leaf drop, killing the plant.

Medicinal Uses of Hydrangea

Hydrangea macrophylla is one of the Asian origin species and is used medicinally. The name hydrangea comes from the Greek word meaning water vessel, very appropriate due to its action on our water processing organs. Therefore, the Cherokee Indians used hydrangea for treatment of kidney and bladder stones illness and introduced it to the early settlers. It became very popular with the eclectic American herbalists of the 19th century.

The root is the part of the Hydrangea plant that is used internally for medicinal purposes, and fresh root can be dug in the fall and used as a syrup with honey and sugar, or simply steeped in water and drunk as a tea. The root becomes quite hard and difficult to work with once harvested, so cut into pieces and dry for long-term use.

Externally, Hydrangea bark can be peeled and used as a compress or ointment for treatment of bruises, burns, sprains, and sore muscles.

Hydrangea flower arrangement in a glass vase

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