HYDRANGEAS

New Zealand Journal of Agriculture, Volume 74, Issue 1, 15 January 1947, Page 109

HYDRANGEAS

Hydrangeas must be given pride of place among flowering shrubs in all except the coldest districts of New Zealand. There are few other garden shrubs which will flower for so long each year, make such a bright display, flower as such young bushes, succeed in such diverse situations, or have so few diseases and pests. Hydrangeas are easy to grow, but some points often overlooked are mentioned in this article by J. P. Hudson, Horticulturist, Wellington.

T JYDRANGEAS have been cultivated for centuries in Japan and China, and 'improved garden forms are said to have been introduced to Kew, England, from Japan in 1790, long before the natural wild species was discovered, through a Dutch firm which was permitted to maintain a trading firm at Nagasaki.

■ The plant has since earned great popularity both as a pot plant for indoor decoration and as a garden shrub in districts which are not subject to severe frosts in winter. It has found great favour in New Zealand; especially in the coastal regions, where it grows with the greatest luxuriance; Unfortunately many gardeners have planted the common white varieties, which have rather a funereal look. Many of the newer varieties are far brighter and more desirable, providing welcome and unusual colour displays for long periods each year. Soil and Situation. One of the main reasons why hydrangeas have become so popular is that they can 'be grown in a very wide' range of soils and situations, though they do better in some than in others. A rich, well-drained, loamy soil which does not dry out produces the largest bushes and finest blooms. A constant supply of moisture at. the roots is necessary if growth is to continue unchecked through. the season. Hydrangeas. growing i in light, . sandy soil . suffer in dry weather unless special attention is given to watering and mulching. On the other hand, soils which lie very wet in winter are not suitable, as the roots are injured if the soil is waterlogged for any length of time. s '

■ The hydrangea is hardier than is commonly supposed, and will grow outside in all but the coldest places in the Dominion. Hard frosts may cause the shoots to die back, leading to loss of the buds which should have flowered in the following season, but it is unusual for bushes ,to be killed outright by frost unless the ground freezes hard. The hydrangea is accommodating in its choice of situation, growing in full sun or heavy shade, but it probably comes nearest perfection in partial shade. It will also stand wind better than many . broad-leaved deciduous shrubs, but does best where it is sheltered to some extent from bitterly ' cold winds in winter and. hot, searing winds in summer. Hydrangeas will do quite well in shaded corners, between houses, and in other closed-in places where little else will grow, though the best flowers are not usually produced in such situations; That is chiefly because' corners overshadowed by buildings often receive much less than their full allotment of rainfall, and are apt to dry ' out completely in summer. Timely soaking with water and liquid manure will do much to help plants growing in odd corners and passages. Fertilisers and Mulch Each bush should be given an annual spring topdressing of 2 or 3 handfuls of blood and bone, scattered on the surface round the plant to cover a circle •of soil about the same diameter as the bush. The surface of the soil should then be lightly pricked over with a fork, taking care not to injure the roots, many of which lie near the surface. .

In the early summer the surface of the soil around the bushes should be mulched with a layer of well-rotted animal manure, compost, or leaves to conserve the moisture in the earth and prevent the. sun’s rays from beating directly on the surface of the soil. The mulch also reduces the risk of the soil cracking, which may lead to the roots being seriously injured. In high summer an occasional topdressing of complete fertiliser thoroughly watered in, or generous applications of liquid manure, will help to keep the bushes growing strongly and ensure healthy new shoots as well as a long succession of flowers during the season. Liquid manure can be made by half filling a sack with animal manure and suspending it in a tub of water. The liquid, which soon becomes dark brown, should be diluted with water to the colour of tea before it is watered on to the soil around the plants. Rainfall and Watering Rainfall is not evenly distributed on the soil of a shrubbery. The arrangement of the leaves is such that rain drips from leaf to leaf and often tends to fall more on one spot than another. A high proportion of the rain may be diverted to one area while other places remain, relatively dry, even after heavy rain. Moreover, the total rainfall absorbed by the soil in a shrubbery is less than in open ground, as much of the rain, especially when it falls in showers, remains on the leaves and branches to dry off when the weather clears without reaching the ground at all. These points should be borne in mind where hydrangeas are growing in the shelter . of hedges and near

houses, as it may often be found that the soil under the bushes is bone dry though it may be quite moist in other parts of the garden. The condition of the soil near the bushes should occasionally be investigated with a trowel to see whether it is quite moist to a depth of 9 or lOin. If not, a thorough soaking with water will put new life into the plants.

Summer Pruning /

Few flowering shrubs will withstand neglect as well as hydrangeas, which will flower regularly and z . profusely without being pruned at all, which is not surprising as pruning, in any case, is an unnatural operation. Under this system, or lack of system, however, the: bushes become larger, the flower stalks shorter and more bent, and the bush more leggy. At the other extreme, bushes are sometimes slaughtered annually as though they were bush roses, yet somehow recover and flower, though unduly late in the season.

The most desirable type of hydrangea is a neat, well-clothed bush, covered throughout the summer and autumn with large trusses of flowers borne ‘on strong, straight stems suitable, for cutting. This habit is the result of careful and intelligent pruning.

Each hydrangea branch bears a series of leaves arranged in opposite pairs. One bud is produced where each leaf joins the stem (axillary buds), and an additional bud develops

at the tip of each shoot (terminal buds). The buds are of two kinds, flower buds and wood buds. The flower buds are larger and rounder than wood buds, although this distinction is not always clear, as there is a considerable gradation of size. The bud at the tip of each branch is usually a flower bud, as is one or more of the buds produced in the leaf axils nearest the tip of each branch. The remainder of the buds placed lower on the stem are all wood buds.

When the buds grow in spring, each flower bud develops into a short leafy shoot at the end of which is a truss of flowers. The wood buds develop into leafy shoots which normally grow into long branches .which do not flower that season, but on which the next year’s flower buds develop in the autumn.

Thus any pruning done in the winter will inevitably reduce the following season’s flowers, as the tip flower bud will, in every case, be removed when a shoot is cut off, and the axillary flower buds will also be removed if more than a few inches is cut off the end of any shoot. The best treatment where pruning is necessary is therefore to cut back the bushes in the summer to allow time after pruning for flower buds to develop on the shoots which remain.

Immediately the main batch of

flowers is over, in late summer, each bush should be carefully examined. First, any weakly shoots should be cut out altogether. Next, if there are plenty of strong new shoots several feet long coming away from the base of the bush or the main branches, all the shoots which have flowered should be cut out altogether, preferably to the base of the bush or to the lowest strong new shoot. If, on the'' other hand, there are few new shoots, some or all of those which have flowered should be retained, but each should be shortened by removing the flower head and three or four leaves. The new shoots should not be thinned or shortened unless they are unusually numerous. Old bushes which have been neglected are not so easy to prune because any treatment is bound to reduce the show of blossom in the first year after pruning. The best plan is to cut the branches hard back in the middle of summer, sacrificing some of the current blooms, but allowing time for new shoots to grow and form flower buds which will produce blooms next year.

Other Pruning Systems

A system sometimes practised is to prune in winter by cutting every shoot back to leave the lowest two flower

buds on each. This preserves the shape of the bushes, but the loss of the terminal flower buds is a disadvantage, because the terminal and upper axillary flower buds usually produce the best trusses of flowers.

Another system which has its advocates in New Zealand, and has much to commend it, is to summer prune all new shoots by nipping out their centres when each is 6 to 12in. long. That ensures that the short new growths do .not need to be pruned in winter and all the best flower buds, which develop toward the ends of the shortened shoots, are thus retained. Where necessary, growths which have flowered are cut right out in late summer when the flowers have faded, or are shortened back to the lowest new side shoot.

Cuttings Root Easily

Hydrangeas root readily from cuttings, which can be taken in the winter or, more usually, in the summer. Hardwood cuttings are taken in winter, 6 to Bin. long, trimmed off below a leaf, and inserted firmly 3in. deep in soil. Soft-wood cuttings, which give better results, are made by taking off pieces with 2 or 3 pairs of leaves on each from the ends of new, non-flowering shoots in January, February, or March. Each cutting should be shortened to about 4in. by cutting it off cleanly just below a pair of leaves. The bottom pair of leaves should then be cut off close to the stem, and about half the leaf blade cut off each of the remaining leaves. It is important that the cuts be made cleanly, using a sharp knife or razor blade.

The cuttings should be inserted about lin. deep in sandy, open soil in a cold frame, making sure that each cutting is firm, though pressure applied to the soil by the fingers should not be sufficient to bruise the soft stems. Water lightly with a watering can fitted with a rose, cover the cuttings with a single sheet of newspaper, and close the frame. Keep the cuttings moist by damping plants and soil regularly for a few days to prevent them from flagging, but as soon as they root the paper should be removed and the frame opened to give more air. When the cuttings are seen to be making new growth they should be removed from the frame and planted in a nursery bed until the autumn, when they can be planted out into their permanent places or left for another season to make better bushes before being planted.

Colour Manipulation

The colour of hydrangea flowers depends on a combination of factors, including the “true” colour of the variety concerned and the nature of the soil.

Unlike most plants, hydrangeas of a particular variety can vary violently in flower colour with the chemical composition of the soil in which the plant is grown. In soils which contain soluble aluminium compounds the petals of many hydrangea varieties are bright blue, but the same varieties have pink flowers when grown on soils containing abundant lime. Soluble iron salts cause some varieties to assume an unnatural dark green colour. The best way of ensuring a good blue colour in varieties which are capable of turning blue is to dissolve alum or aluminium sulphate in water at the rate of 1 teaspoonful or 3oz. respectively to the gallon, allow the solution, to stand for 12 hours, and then water the plants thoroughly, with it. Iron sulphate, often recommended instead of alum or aluminium sulphate, is not as satisfactory for producing blue colours, but can produce mauve tones in some varieties, though it may also cause the flowers to assume an unpleasant greenish colour. In some soils the liquid application may not be sufficient to ensure a good blue colour; the soil itself may absorb the aluminium before the hydrangea roots can take it up. In such cases a dressing of up to 101 b. of aluminium sulphate scattered round each bush as a topdressing in winter should ensure the desired colour. The use of such a heavy dressing in the growing season is not safe, because it might cause the leaves to turn yellow and even to fall prematurely. To ensure good pink colours the soil should be dressed very liberally with lime before the bushes are planted and should be given an annual topdressing of lime at the rate of 4oz. to the square yard. ' The natural white varieties will not take on any other colour, but remain white whatever treatment they may be given. Choice of Varieties With so many brightly-coloured, showy types of hydrangeas available, it is a pity to give garden space to the old, colourless white type, which adds nothing to the cheerfulness of the garden. Among the many good varieties available the following can be recommended:— Parcival: The best of the rich, bloodred flowers with heavily-frilled petals. Deutschland: Rosy-red, blues well. Blue Prince: Rosy-red, but goes bright blue when treated. Holstein: Deep blue when treated. Carmen: Brilliant red dwarf. Marechai Foch: Rose-pink, blues well. Sensation: Deep mauve, huge cupshaped flower. Niedersachsen: Large mauve-pink flowers. Peer Gynt: Rich rose-red, with very large trusses of flowers.

Culture as Pot Plants Hydrangeas make first-class pot plants which are easy to grow and i very showy. The usual method of growing them in this way is to strike cuttings individually in 3in. pots, and later pot them on to flower the next year. Ensure that the soil in the pots is well drained by putting a piece of broken plant pot, convex side down, over the hole in the bottom of the pot. Cover this with a few smaller pieces of pot, and place a thin pad of moss or leaves over these to prevent soil from working down among the drainage and choking up the hole in the pot. Fill the pots with a turfy compost to which plenty of decayed leaves or chopped moss has been added, press the soil down gently, and insert one cutting in the soil in each pot. The cuttings should consist of the ends of new shoots taken, as described earlier, when the first flowers are beginning to fade. The pots should be stood in a frame or a shaded place in the garden, watered carefully, and then covered with a sheet of newspaper to maintain a moist atmosphere around the cuttings and prevent them from wilting unduly. Damp the cuttings and pots every day if the weather is dry, and continue to give protection with the newspaper until the cuttings have rooted, as shown by the fresh green appearance of the leaves in the centres of the shoots.

When the cuttings are well rooted and growing; strongly the pots should be put out where they get plenty of sunlight, though it is an advantage if they are ’ stood under a tree which shades them from the full glare of the midday sun. At this stage the plants need watering frequently, except in wet weather, and the soil should never be allowed to dry out. It is worth while to sink the pots in ashes or soil up to their rims, which makes it easier to keep the soil moist. When the roots of the young plants are filling the soil in the pots (which can be seen by carefully knocking a plant out of its pot and inspecting the ball of soil), pot them on into sin. pots, again using a turfy compost. Damp the foliage once or twice a day for the next few days, but do not water until it is really necessary. Toward autumn the pots should be stood out in the full sun to make sure the plants are thoroughly ripened before the winter. In winter, when the leaves are seen to discolour (or fall off in colder districts), it is an advantage to put the plants inside a light shed or under a hedge to avoid the. pots being soaked by rain. Though hydrangeas should not be allowed to dry out completely in the winter, it is necessary to keep the soil in the pots only very slightly moist.

When the buds start to grow in the spring the pots should again be put out into a sunny position, watered, and, as strong growth develops, fed with liquid manure. At the beginning of the season many gardeners add a teaspoonful of blood and bone to each pot, scratching it into the soil; to prevent it from going mouldy on the surface. That dressing obviates the need for using r . liquid manure until the flower buds can be seen in the developing shoot. If particular colour- effects are desired, the colouring treatments detailed earlier may be applied to pot plants, starting when the flower buds can first be seen. Half a teaspoonful of alum to a pot, applied to the surface every 2 .or 3 weeks and watered in, should ensure a good . blue tone. - When the pot plants have flowered the flower heads should be cut off and the plants repotted into larger sizes. But for use as decorative plants in the house it is, probably better to bring on a fresh batch of cuttings each year, as these flower as plants of a size convenient for use in the average house. Few Diseases or Pests i The hydrangea is remarkably free from diseases and pests in New Zealandin .fact, no diseases of hydrangeas are recorded at all, and the only

pest recorded is the apple mealy bug, which attacks many fruit' and ornamental bushes and trees. Mealy bugs can cause considerable damage by

sucking the sap, but cause an added nuisance by secreting a sweet, sticky juice (honey-dew), on which black moulds develop, causing unsightly black blotches on the foliage. Mealy bugs can :be controlled by spraying the trees with nicotine sulphate (2oz. of soap, dissolved in a little hot water and added, with 1 fluid oz. of nicotine sulphate, to. 4 gallons" of water)/ or by the use of summer spraying oil diluted to a strength of 1 part in 100 of water. HOLIDAY BOOK WHAT A pleasant afternoon I have spent, thanks to “Lincoln”, of Dannevirke'. My small nephew usually spends -his holidays on the farm with me and, being a city , child, the beach and the animals are a constant delight to ..him. He .. loves to help feed the calves and see the cows being milked. Later on, perhaps, the novelty of -these things will wear off, but Tim’s “Holiday Book,” which I have begun this afternoon, will ■ keep these memories close, I hope. I have a full set of snapshots of him feeding the pet lamb, sailing his small boat, and even one of him with his very first -fish sprat! I wonder what his thoughts will ■be in, say, 20 years’ time, when he opens his “Holiday Book” and sees those photos and paragraphs I have pasted in for him. Perhaps, like the rest of us,' he will think, “Those good old happy, carefree days.” Thank you, “Lincoln.” "

-“Ellen May,” Kaipara.

[There is much confusion about the nomenclature of the common garden hydrangea which should be known as Hydrangea macrophylla Thunk, but is .usually listed as H. Tiortensis Smith, H. hortensia Sieb. or H. ovuloides C. Koch.]