Summer Care of Roses in the Flower Garden

New Zealand Journal of Agriculture, Volume 99, Issue 5, 16 November 1959, Page 488

Summer Care of Roses in the Flower Garden

FEW flowers repay the gardener more for regular attention throughout I the year than do roses. This article by J. P. Salinger, Horticultural Advisory Officer (Ornamentals), Department of Agriculture, Wellington, describes their routine care during the growing season.

APART from climbing roses of the rambler and wichuriana /A. types such as -Dorothy Perkins or Paul’s Scarlet Climber which normally flower once, all other roses will flower from late spring until late autumn or winter. Many gardeners obtain an abundance of blooms from their roses in the early part of the season, but after this first flush, growth and flowering are frequently disappointing. As each cluster of flowers is produced only on fresh new growth, the plants must continue to make new shoots and leaves during the whole of the summer to produce more flowers. To encourage this growth regular culture is necessary, the exact treatment to be given depending on the age and type of rose. These operations are described under two headings, the treatment for specific types of roses and the routine treatment for all roses.

Treatment of Specific Types of Roses

Newlv Planted Roses y . Roses planted the previous autumn and winter will be making new shoot growth; they will therefore require attention for the first year to see that a good root system is formed. Newly planted bush roses produce flowers in early summer at the same time as established plants, but it is unwise to let the plants flower at this time, as they will expend their energy in flowering instead of producing shoots and leaves. The best policy is to pinch off the first flower buds as soon as they are seen; the plants will then make better growth and may be allowed to flower , a little later, about December. They should be watered well, if the weather is dry in spring or early summer. If there has been heavy rain, the soil may have been washed away from the base of the plants. The soil should then be replaced or soil added if the bed has sunk, exposing the stem below the bud union. The young shoots of climbing roses should be regularly tied in gently to the supports. 6 J c.x-J Established Hants Established plants should be growing- strongly and will require regular examination. In windy areas it is advisable to stake these plants not only to prevent the whole plant rocking in the wind but also to prevent young shoots being blown off or damaged by

rubbing against the thorns. One short strong bamboo cane or green-painted me | a i stake inserted near the centre of the bush will be suc i e nt. The base o f the plant can be tied to this near ground level and the young shoots lightly looped to the stake at varying heights. The stake will not p e seen, but will provide sufficient support and ties of soft brown string are inconspicuous. Ties on standard roses should also be examined, . Climbing and Rambler Roses Climbing and rambler roses flower initially on short young shoots produced on o i der wood. At the same time strong young canes grow from the base of the plant or from the main branches. These young canes should be gently placed and tied in an upright position to one side of the plant. If left too long without tying, they may break off or grow unsuitably. , . , . As rambler and wichuuana ros s have only one crop of flowers each year, they can be piuned immed 5 aft D\ flowering. Where there are .sufficient replacement shoots on rambler roses all the older wood may be removed . wic U riana roses do not usua ßy produce enough young shoots, SQ a propor ti on o f the healthier older shoots should be retained, Weeping standard roses are usually rambler varieties and so should be pruned like ramblers after flowering.

Routine Work with All Roses

Watering and Mulching In an established rose bed the topsoil is normally full of roots, and to ensure adequate growth throughout the season it is necessary to apply water in all the drier areas during summer. Watering should commence as soon as the top 2 in. .of soil becomes dry and a large amount should be applied at every watering. Care should be taken not to flood the beds, but to apply the water in fine droplets. This can be done by watering through a hose with a fine nozzle or with a perforated plastic hose, ensuring that- a minimum of water falls on the foliage, as damp foliage is conducive to the spread of black spot disease. Frequent light applications of water are of no benefit to the plants, as the water will not penetrate to the deeper layers of the soil and the plants will tend to produce roots close to the surface and so be more susceptible to drought. Watering can be reduced by mulching the beds with organic matter and this is essential if there are local water restrictions or the ground is sloping. Suitable mulching materials are well rotted deep litter poultry manure or other decomposed animal manures, rotted compost, spent hops, or a mixture of sawdust and grass mowings. Freshly decomposing animal manure or green plant refuse are not satisfactory, as they can damage the plants when decomposing; fresh sawdust, even when mixed with nitrogenous fertiliser, is not satisfactory, as it dries out in hot weather and is very difficult to wet again. All mulching material ' should be well broken up before use, so that it can be easily spread on the bed with a shovel or fork without damaging the plants. The soil should be really moist before the mulch is applied, and in drier areas it can be spread over the bed by early. December. Where mulching is not done the soil should be hoed frequently to maintain a surface layer of loose soil. Under this condition it is essential to hoe after each watering. Manuring Most rose growers give a dressing of a mixed fertiliser in late winter. This should be sufficient to maintain growth until mid summer, but additional dressings at this time will probably be required. Unless a mulch composed of animal manure has been used, roses will benefit from the application of fertilisers high in nitrogen and phosphate in mid summer, while later in the year mainly phosphates and potash will be required. The mid summer mixture could be 2 parts of dried blood and

1 part of superphosphate applied at 2 oz a bush or 6 oz a climber, and the later dressing of 1 part of dried blood, 3 parts of superphosphate, and 1 part of sulphate of potash at the same rates. Fertilisers should be applied only when the soil is moist and should be watered in after application. Alternatively soluble foliar fertilisers may be added to a spray mixture and applied at monthly intervals. Disbudding If individual flowers of hybrid tea roses are required for exhibiting or for cutting, all the small buds except the centre bud should be regularly removed when the stems are still soft. They can then be easily broken off close to the leaflets at their base, and the wound will soon heal over completely; the main bud will continue to grow with a long straight stem. It is not usually necessary to disbud a few vigorous varieties such as Queen Elizabeth, as each bloom is carried on a reasonably long stem. Cluster-flowered types such as floribundas, polyanthas, and hybrid tea

roses with single flowers are not disbudded. Flower Gathering To prolong the flowering period it is essential, to prevent the plants producing seed heads (hips). Flowers not gathered for use in the house should be regularly removed as soon as they are past their best. During the early part of the season all flowers should be cut with fairly long stems, as this acts as a type of summer pruning. The stem should be cut with secateurs rather than scissors just above a plump bud in the angle of a fully formed leaf; these have five or more leaflets. Later in the season when growth is less vigorous, flowers can be cut with shorter stems and if seed heads have already formed, these should be removed as one group, being cut back to a bud on the main shoot. The simplest way to gather flowers is to hold the stem beneath the flower with one hand and cut the stem correctly lower down the shoot. The flower stem can then be drawn away from the plant without damage from the thorns on other shoots. Flowers for the house are usually cut when the first two petals are un-

furling. The best time to gather them is in the evening, as they can then be placed in water overnight. After cutting, the stems should be laid flat in a shallow basket with the heads in rows. They should then be taken indoors, the lower leaves and thorns should be removed, and they should be placed upright in a deep container of water. The next day before they are arranged J in. of the base of the stem should be cut off and any additional leaves and thorns removed. If the flower is cut in the heat of the day, it may be necessary to trim the base of the stem under water. If a quantity of flowers are required for a special occasion, they may be stored in a cool dark basement or in a domestic refrigerator, preferably in an empty vegetable compartment. To keep them in good condition in the refrigerator they should be taken from the water, any surplus water shaken off, and then placed in a plastic bag lightly closed at the neck. No additional water is needed in the bag and the flowers should definitely not be sprayed with water before they are placed in the bag. Alternatively shorter - stemmed flowers may be kept on the shelves of the refrigerator with the base of the stem in a shallow container of water. When the flowers are removed from the refrigerator the stems should be trimmed again. These flowers will open quickly when placed in an arrangement in the house. It is often an advantage when gathering cut flowers to have an additional container as well as the flower basket so that blooms past their best can be removed at the same time. Roses for Showing Most gardeners growing roses like to exhibit their best flowers in shows. The specialist will grow varieties for exhibition, but frequently these are not the most satisfactory for garden display. Exhibition roses are usually fullpetalled large flowers which hold their shape well, while other roses, sometimes called decorative roses, are smaller, open more quickly, and usually have a somewhat flatter centre. Roses for showing should have a good circular outline, plenty of petals, and a well formed centre. The colour should be bright and pure and the whole stem should be strong but not coarse, with clean, healthy foliage. The flowers should be cut when the outer petals are just unfurling the evening before the show and placed in deep water in a cool, dark place. When the exhibit is being set up the base of the stem should be cut again and the outer petals gently brushed open but not folded back to appear artificial. Preferably some foliage should be left on the st-em; normally two leaves are sufficient.

With floribunda and similar clusterflowered roses the whole truss is picked and exhibited. The first flowers should not have passed their best; it is better to have a spray with the first flowers in perfect condition and the later flowers in bud. Gardeners wishing to plant more roses can make their initial selection at a rose show, but it is advisable to confirm with the exhibitors that the varieties selected will do well in the district. A visit to a rose nursery a little later in the season will enable the gardener to see the varieties growing and to check on their habit and general growth. Summer Pruning and Wafershoots During the whole of the season all dead shoots, stubs, or dying tips of the branches should be regualrly cut off and burnt. Regular cutting of flowers will act as a summer pruning of the healthy shoots.

If a rose is healthy, it will produce 5 strong young growths from the base 5 or the lower part of the older shoots; ; these are known as watershoots and t if growing in the right direction, they j will form the future framework of the plant. ' As they grow extremely quickly, the 1 watershoots in all windy areas should J be lightly looped to a stake as they ' grow; once they have flowered they ! will become thicker and firmer. i ! Watershoots produce clusters of ’ flowers at the top only, usually a central truss with two side trusses beneath it. These shoots should not be pruned hard, as they are soft and full of sap. Pruning consists merely L of cutting out the centre truss after , flowering and later trimming back the S side trusses to a well formed bud. . This will induce buds lower down the ; stem-to grow out, and harder pruning is carried out in winter.

Overseas, where roses are budded on to a different stock from the one used in New Zealand, growths known as suckers arise from the original rootstock. This seldom occurs here, where the multiflora rootstock is used, but if suckers do grow from this stock, they can be'easily recognised, as the leaves are small, crinkly, and pale green, quite unlike the usual- rose foliage. Suckers should be traced to their point of origin and cut away completely. Autumn Flowering ' Though roses will flower during the whole of summer and autumn, there is a recent trend in warmer areas to modify cultural methods to reduce flowering in the heat of summer and encourage flowering in autumn, especially if an autumn rose show has been arranged. These methods involve watering, feeding, and summer trimming. A period of partial dormancy is induced by reducing watering or omitting it during the latter half of January. In early February the rose beds should be thoroughly watered. During this period all flowers should be gathered with very short stems. After watering, a dressing of fertiliser containing nitrogen and phosphate should be applied and the plants trimmed. The exact date on which the roses are trimmed will determine the peak of autumn flowering. Local rose growers who practise this method will be able to give the exact date for the district. This will normally be during the first or second weeks of February. Summer trimming is a simple method of pruning in which all mature shoots are cut .as though gathering flowers with a long stem. The shoot is cut back to a plump bud which has developed in the angle of a complete leaf. ' Small shoots and watershoots are not cut back. If the weather is dry, watering should be continued. Pest and Disease Control Unfortunately roses ’ are susceptible to attack by a number of pests and diseases and the best results will be achieved only by regularly spraying or dusting to prevent infection or obtain immediate control. District experience will indicate the best spray programme to adopt. When pests and diseases occur control will be ensured only by identifying the trouble, applying the correct therapeutant promptly and adequately, and by continuing to apply these materials over a period. During the summer the materials can be applied by spraying or dusting, and many rose growers make regular applications every 10 days to a fortnight irrespective of the troubles likely to be present.

The following is a good generalpurpose spray: Captan 50 . per cent wettable powder - - 1 oz Colloidal sulphur 70 to 75 per cent wettable powder 3 oz Malathion 25 per cent wettable powder - - 3 oz Household detergent - | teaspoon Water - - - 4 gallons . A general-purpose dust can be made from: ■■ Flowers of sulphur 5 parts by volume Thiram or captan 50 per cent - -2 parts by volume Lindane 1 per cent dust - - - 3 parts by volume Full details of rose pests and diseases and their identification and control are given in Department of Agriculture Bulletin No. 359, “Roses in the Home Garden”. Local offices of the Horticulture Division of the Department provide leaflets on this subject appropriate to the area.

Work for December

Routine garden tasks should be attended to early this month if the display is to be at its best during the Christmas and holiday period.

Lawns Lawns set the tone in a garden and regular mowing will help maintain a fine, even turf. If mowing is spasmodic, the fine grasses do not receive enough light and the turf will open up and become uneven with tufty growth. The quarterly lawn dressing of 1 oz per sq. yd. of a mixture of 1 part of superphosphate to 3 parts of sulphate of ammonia -could now be applied, preferably while the dew is on the ground. Trimming of lawn edges with a sharp spade is sometimes necessary if they have become very ragged. A tight string or wire line should be used to ensure a . straight cut. The cut itself should slope away from the lawn at an angle of 45 degrees to give stability to the edge. Weed Control Topdressing usually controls lawn weeds, but if many weeds are present, a spray of MCPA could be applied before topdressing.

In large shrubberies weed control is often a problem. It has been found experimentally that if the area is cleared of weeds now and sprayed immediately, good control of weed seedlings can be obtained for up to six months. Monuron (formerly called CMU) at 1 oz to 150 sq. yd. dissolved in water can be sprayed over the area. Care should be taken not to spray the foliage of shrubs. On paths a mixture with water of 1 part of amitrol and 5 parts of dalapon at 1 oz to 30 sq. yd. will control a wide range of flat weeds and grasses. It can be applied at this time. Silver Leaf Fungus Flowering plums, cherries, peaches, and apricots, and roses, escallonia, japonica, lilac, rhododendrons, poplar, ash, and silver birch are all susceptible to attack by this fungus through wounded tissue. The symptoms are silvering of the foliage and debility of the plants. New growths should be examined now for this silvering, as especially later in the season it can be confused with damage by thrips or red spiders which suck the sap from the leaves and thus cause silvering. If new growth is silver when it develops, the plant is most probably harbouring the fungus. This is the best time to cut out and burn infected branches and dead wood, as spores are not usually produced at this time. All wood which has stained cells inside should be cut out. If the whole plant is infected, it should be removed entirely and burnt. Plantings The more tender bedding plants such as zinnias, salvias, and cannas and the more hardy bedding plants can still be planted up. It is useful to have a few extra plants of nemesia, phlox, and calendula for filling in gaps as they occur throughout the season. Autumn crocuses and other autumnflowering bulbs can now be planted up "to give interest when the mass of summer annuals is finished. Freesia seed treated as mentioned in last month’s notes can now be sown in boxes or in flowering positions. Anemones planted now will be useful for picking during late winter. Sowings Useful plants which can be grown from seed sown thinly at this time include cinerarias, pentstemons, Brompton stocks, Iceland poppies, pansies, Russell lupins, and anchusa. A little extra organic matter could be added to the seed sowing mixture recommended in the August issue to prevent drying out. The boxes could be placed, for germination, in a shaded position, but not under the eaves of

houses or under trees where large rain splashes can do damage. Lily of the Valley Beds of lily of the valley which have become overcrowded and have thus not flowered so profusely could be lifted and divided now. This plant prefers partial shade and soil which is rich in organic matter to help keep the roots moist and cool in hot weather. The soil should be well worked up before planting and a balanced garden fertiliser should be applied at 6 oz per sq. yd. This could be mixed in during the final forking. The young pips should be set 4 in. apart, with the tips just below soil level. If the original bed is not crowded, it could be topdressed with compost and a balanced fertiliser used at 3 oz per sq. yd. Perennial Plants In very dry weather paeonies should be kept well watered. An application of bone meal and careful watering will build strong blossom buds for next season’s flowering. Violas and pansies should be cut back hard now to remove the exhausted flowering shoots. New growths will soon appear and will be improved by a side dressing of balanced fertiliser mixture at 1| oz per yard of row. This will help to bring them quickly back into flowering. The bearded iris should be lifted and divided after flowering. If rhizomes are damaged or diseased, they should be cut back into healthy tissue and the end could be dusted with flowers of sulphur. The rhizomes should be nestled into the top of the soil so that the roots are well anchored but with the rhizome above ground level. Feeding Plants Most plants will benefit from side dressings of a balanced fertiliser, especially if their roots are in a poor soil or lack organic matter. In good soils a balanced fertiliser dressing given at planting or in early spring will generally be sufficient. Soluble fertilisers are available, but it is more economical to apply a good balanced dressing early in the season and only follow up if necessary with side dressings during the growing season. A balanced fertiliser can be made by mixing: 3 parts of blood and bone 2 parts of superphosphate 1 part of sulphate of potash Plants from Cuttings During the next three months a wide range of plants can be propagated from soft and half-ripe cuttings. So wide is the range that it is usually worth

while to try any desired plant by taking a cutting, of this season’s growth. Alyssum, aubrietia, fuchsias, sweet williams, arabis, violas, pansies, and geraniums will all root readily from soft cuttings, which should be kept under humid conditions until they root. Methods of preventing moisture from the leaves include covering with a preserving jar, placing in a closed frame or glass-covered box, dr the use of polythene plastic. The plastic, allows air to pass through but does

not allow the passage of moisture. If cuttings are placed in a pot of sand and the whole pot is enclosed in a closed polythene bag, the cuttings can breathe, but the moisture does not escape while they are rooting. Fuchsias, hydrangeas, coleus, and many shrubby plants can be propagated in this way and many perennials root easily without this extra care. The taking of cacti and succulent cuttings should be concluded this month.

Bulbs Iris bulbs should be dipped or dusted with lindane before storing to prevent a carry-over of aphids which spread the iris mosaic, virus. Bulbs from iris which have been attacked by rust fungus should be lifted and stored

until planting time under dry conditions. The rust spores which spread the disease have only a short life under dry . conditions and a clean crop can eventuate from such bulbs. It is important, however, not to replant into the same ground, as the rust spores, may still be alive on pieces of plant leaves left from the previous season. Tulip bulbs should be lifted annually in warmer climates, but under cool, conditions and deep planting need only be lifted every two to three years. Narcissi bulbs should be treated with, aldrin when lifted to prevent damagefrom bulb flies. Pest Control The caterpillar of kowhai moth,, leafroller caterpillar, looper caterpillar,, cherry slug, and any other pests which eat large holes in leaves can be controlled with sprays of arsenate of lead,, malathion, or lindane. Mealy bugs on fuchsias, cottony cushion scale on hydrangeas, scales or roses and shrubs, and thrips on a widerange of plants from roses to rhododendrons can be controlled with sprays: of summer oil or malathion emulsion. On roses, however, emulsion forms of' therapeutants should be used at thelowest recommended strengths. Red spider mites make many plants; including cantua, violets, and carnations look very sickly in dry conditions. They suck the sap from theplants and cover themselves with a. fine webbing underneath the leaf.. Keeping conditions moist and spraying, with malathion will prevent a build-up-of the pest. Where insect populations in the soil, are high aldrin or nicotine sulphateplus soft soap should be watered intothe soil round the plants. General All autumn-flowering chrysanthemums should be stopped again in the? early part of this month. Flowering brooms, kerria, philadelphus (mock orange blossom), and', similarly flowering shrubs could bepruned immediately after flowering. Layering of plants could be done now. Aerial layering with polythene plastic and sphagnum moss is a method worth trying. Compost heaps should be in constant use now, but large amounts of lawn clippngs should be broken up with other materials to prevent them becoming soggy; Sawdust is suitable. If flies are - troublesome, the heap, should be covered with soil or sawdust and dusted with DDT. Carnations can be cut back after: flowering and cuttings of dianthus. (pinks) can now be rooted. Roses will benefit from an organicmulch as well as regular spraying. Wallflower plants can now be lined!, out to develop for setting out inautumn. . 1

BY

ROSALIE A. CAMPION,

Horticultural Instructor, Department of Agriculture, j Wellington

the CjfaM house

Some shading will be necessary in most glasshouses to prevent burning and help keep the temperatures between 60 and 75 degrees F. A suitable mixture for spraying on to the glass is 2 lb of hydrated lime, 3 tablespoons of household detergent, and 2| gallons of water. Free circulation of air is important, as many fungous diseases thrive in high humidity and stagnant air. Plants should not be allowed to dry out and individual pots should be checked daily for moisture content. Dry pots will have a hollow ring when tapped. Quickly growing plants such as cinerarias, begonias, and coleus should be potted on into larger pots as soon as the roots show through the sides of the soil ball. A potting mixture suitable for most, plants is made using 7 parts of good loam, 3 parts of leaf mould, compost, etc., and 2 parts of sharp sand plus 4 oz of the balanced fertiliser (see page 495) and 3 oz of lime per bushel (apple case) of mixture. This is the mixture used for pricking out seedlings; for pot plants the amount of balanced fertiliser can be increased up to three times this amount. Poinsettias can now be cut back hard for winter flowering. Cuttings of young shoots can be rooted in a closed frame. The base of the cuttings, which exudes a milky substance, could be dipped in charcoal before it is inserted in sand to root. Pelargoniums which have finished flowering should now be stood outside in a sunny place to ripen the wood for taking cuttings later. Begonias will need constant care now if they are to give a worth-while display. The secondary side flower buds should be removed to allow the central flower to develop properly. Faded flowers and seed pods should be removed and liquid feeding is desirable. Chrysanthemums for flowering in pots should be given their final potting this month and should be nipped back once more. Thrips are sometimes a problem on chrysanthemums, carnations, and orchids. DDT sprays or smokes could be used for control. Aphids are a problem on many plants and fumigation with lindane or malathion aerosols at 5 seconds per 500 cu. ft. of house, or sprays of lindane, malathion, or nicotine sulphate, could be used. Red spider on carnations, vines, and orchids is another problem. Two azobenzene smokes at a 10-day interval or sprays of malathion at 7-day intervals should give control.