Roses and Carnations

Roses and Carnations

The rose as a flower crop

While commercial rose growing is on the decline in Britain it is becoming increasingly popular in amateur and exhibition circles, including floral art. Suitable varieties for forcing can be obtained from specialist rose firms. They tend now to be treated as a short-term crop, the bushes being forced to produce up to five flushes per year, and replaced after two or three years according to their performance.

The amateur gardener, however, may merely concern himself with a few bushes in 23-25cm (9-10in) pots to provide blooms in advance of those grown outside, and for a longer period into the autumn (the Royal National Rose Society has a recommended list).

Ideally roses thrive best in light airy conditions in a well-ventilated greenhouse with a minimum temperature of 10-12.8°C (50-55°F). The soil, of good texture and porosity, should have a pH of 6.5 (too far above this can lead to deficiency problems) and a phosphate/potash index of 3-4. Much use is now made of complete traceelement-containing fertilizers such as Vitax Q4 at 204g/m2 (6oz per sq yd) in addition to farmyard manure at 50kg/8m2 (1cwt per 6/10 sq yd). Good drainage is essential, which means thorough cultivation if borders are to be used, and the free use of crocks in pots.

Roses and Carnations Roses are grown commercially ‘on the flat’ in borders (4-5ft) wide, planting distances being 25-30cm (10-12in) each way. The situation regarding stocks for roses is a changing one and best taken up with specialist suppliers. The best time for planting is early spring or autumn. Planting should be firm, and the same is true with potting.

Growth should be commenced slowly in January/February with 7.2°C (45°F), rising gradually over 14-21 days to 12.8°C (55°F). Higher temperatures will obviously prevail during the summer months, but excessively high temperatures should be avoided by free use of ventilators. Regular watering, preferably by low level irrigation systems, or on a small scale by hose (with a fine rose) is essential, avoiding either saturation or excessive dryness.

Budded roses when planted should be pruned back to 10-13cm (4-5in) from ground level and main shoots pinched when they develop to encourage lower growth when approximately at the 5-fivers stage (5 leaflets). There should ideally be some selection and thinning of shoots and a degree of disbudding is necessary with hybrid teas.

Following each flush of growth a straight form of nitrogen should be given — Nitro-Chalk, Nitram or urea fromaldehyde, at normal application rates and watered in. Pest and disease control is particularly important, using sulphur if necessary for mildew on a continuous basis.

Potted roses can be rested by plunging in ashes out of doors in mid-autumn, being pruned and brought into the greenhouse in late winter/early spring for the production of early blooms. Liquid feeding should be given. Roses should be pruned lightly between flushes.


The culture of carnations

The carnation, like any other crop, reacts unfavourably to mono-cultural practices, diseases becoming established in border soils which are virtually impossible to eradicate. Border culture should only be considered, therefore, where the soil is ‘new’; subsequently isolated beds of one form or another are necessary, and in amateur spheres this includes pot culture.

Raised beds can be constructed of pre-cast concrete, sheet or corrugated plastic; ground or surface beds are best prepared on a concrete base with wood sides and ends; and for small-scale culture sunken beds can be constructed cheaply by using polythene sides and base, providing outleats for surplus moisture by drainage tiles or slits in the base. Some form of sterilization will be necessary for all beds. Growbags can be used on a short term basis.

Carnations on a long-term basis require support, this being best provided by the use of strong metal supports at the ends of the bed, using wires, cross battens and coarse string or alternatively meeting. For pot culture, support is provided by canes and string.


Growing media and nutrition

Carnations make large demands on nutrients and soils should be adjusted following soil analysis as follows:

pH 6.5 at planting time;

Nitrogen High (50-150 ppm mg/litre nitrate), a difficult figure to adjust

Phosphorus and potash Index 3-5

Magnesium Index 4

Soluble salt Index 2-3

Such nutrient levels are met by using John Innes No 2 potting compost or equivalent soilless mixes. When the existing soil is being used, and subsequent to adjustment of the pH following analysis, a normal base application is 33-136g/m2 (1-4oz sq yd) super-phosphates 68-204g/m2 (2-4oz sq yd) magnesium sulphate, and between 18136g/m2 (2-4oz sq yd) hoof and horn according to the time of year and soil analysis. The higher nitrogen dressing is given at times of the year when water requirement is low in winter or early spring and liquid feeding is therefore not practical. Compound base fertilizers can be used at rates of up to 271-305g/m2 (8-9oz per sq yd) there being virtue in selecting one with a trace element content. Applications should be reduced if analysis merits it. Hydroponic systems have much application in carnation culture especially aggregate culture.



The commercial practice in the UK and Europe generally is to buy in high-quality tested cuttings from specialist raisers. There are some excellent sources of supply open to the amateur grower, and arrangements can sometimes be made to obtain small quantities of cuttings from specialist nurseries. Research has shown that cuttings taken from flowering plants seldom show the same vigour as cuttings taken from stock plants used solely for the purpose.

Dip cuttings in hormone rooting powder or soak overnight in a diluted solution (alpha napthalene acetic acid formulations give best results). Insert in porous rooting medium (pH 7 being desirable;  at a density of 60-84m2 (50-70 per sq ft), which is fully 2.5cm (tin) apart each way. Give good light and bottom heat, either by soil warming cables, under-bench or mini-bore pipes, in the region of 21.2-22.2°C (70-72°F) for ten days after cutting insertion, when thereafter temperatures are reduced to 16.7-18.3°C (62-65°F) as a weaning measure. Rooting should take place in 18-21 days. Smaller scale propagation can readily be carried out in seed boxes with plastic domes, and mist benches, if available, are also helpful, especially from early spring to early autumn. No more watering should be carried out than is needed to prevent wilting, since too much watering encourages fungal diseases. There is no advantage in leaving the cuttings after rooting, as this merely results in a greater check when planted or potted.


Programme of production

Carnations can be planted at any time of the year and will start flowering according to the light intensity, heat level and other factors. The following are the advantages of planting in different months:

Mid-winter planting

Cuttings rooted in good light areas will, if left unstopped, produce the first flush of flowers by mid-/ late spring, and the first lateral flowers in early summer. Stopping the plants by nipping out the centre stem will delay flowering by 2-3 weeks.

Mid/late spring

Cuttings planted in mid/ late spring and stopped once will flower in late summer/early autumn. A second stop will enable the plant to give greater continuity of flowers into late autumn.

Early summer

Most gardeners will find that summer plantings suit them best, stopping the plants to take the first flowers in winter, after which there tends to be a shortage of flowers until about mid- to late summer the second year.

Autumn planting

The worst time, as the young plants will have difficulty in developing in the diminishing light and may fall prey to fungal disorders if environmental control is not of a very high order. The first blooms will not appear until the following spring.

Growers and professional gardeners will obviously need to study planting times from an economic angle.

Plant spacing

Average planting distances are 20 x 20cm (8 x 8in) in a square planting system. Closer planting up to 13 x 10cm (5 x 4in) gives an earlier yield but generally increases disease potential. For pot growing, three plants per 23cm (9in) pot is average.


Water requirements

Plants are set out in relatively damp soil or media and should merely be watered in and thereafter watered according to their needs, which will vary enormously according to whether plants are in raised, sunken, or ground beds, or in pots. In commercial spheres water requirements are related to the readings taken from evaporimeters and determined in the UK by Ministry of Agriculture centres. These, and tensiometers, can be used on a small scale with some success.


Stopping and disbudding

Stopping refers to the removal of the terminal growth to encourage lateral bud development; it also delays flowering. The single stop is the removal of the first small pair of leaves, the plant being bent over until it snaps off cleanly. Raising the night temperature to 15.6°C (60°F) for 2-3 weeks after stopping, and more frequent damping, encourages lateral growth development. In general, from a single stop about five buds will be produced.

A stop and a half relates to a supplementary stopping of some of the subsequent laterals. Commercially this is done to delay flower production over a poor price period. It can also be done for flower show timing. Where no stopping is carried out the plant is allowed to form its terminal buds and flower early, a practice which may well suit the amateur. It is used as a means of avoiding glut periods. Spray blooms are now popular.

Disbudding of stems down to the one terminal bud (except sprays) is necessary weekly in summer and every two to three weeks in winter.


Seasonal feeding

Supplementary feeding is usually necessary soon after planting carnations, this either being applied dry and flushed into the soil or growing media, or applied in liquid form through an irrigation system or a rose on the end of a hosepipe. The dry feed generally used is 3 parts by weight of dried blood (or 2 parts sulphate of ammonia) and 1 part sulphate of potash applied at 68g/m2 (2oz per sq yd) at 12-14 day intervals. Very considerable research has been carried out in the whole sphere of carnation nutrition at the HRI (Horticultural Research International), Littlehampton in Sussex and elsewhere, and generally speaking equal parts of nitrogen and potash (K2O) throughout give the best results. A range of nutrients are very important, it being especially important to avoid too high concentrations which can quickly result in salt build-up.

Gardeners using pots may also find it inadvisable to feed too lavishly and there is much to be said for erring on the side of safety, since feeding can always be increased but it is not so easy to remove excess nutrients to repair damage caused.



Accepted regimes now appear to be a night temperature of 10°C (50°F) raised to 12.2°C (54°F) from early spring to mid-autumn and a positive day temperature of 15.6°C (60°F) with ventilation coming into operation at not more than 21.1°C (70°F), although it is doubtful if such precision is possible or necessary in small greenhouses.



Research findings indicate that periods of long days or continuous lighting hasten the inducement of flower buds. Lighting is applied from dusk to dawn using tungsten filament lamps, with 150 watt bulbs at (3.6-4.5m) (12-15ft) centres, 1.5m (5ft) higher than the growing point of the plant, for 14 days in summer up to 45 days in winter.

Young shoots remain vegetative until they have formed 5-7 pairs of expanding leaves, after which in forming another 5-6 pairs of leaves a flower bud develops. This means that from mid-spring onwards in the U.K. And countries of similar latitude, plants have 12-14 pairs of leaves to the flower bud, but if the shoot reaches 5-7 pairs of leaves when days are short (ie. from early autumn onwards) it will grow up to 22 pairs of leaves before flowering in the spring. Dusk to dawn lighting will induce all the plants in the 5-7 pairs of leaves category to produce flower buds despite the short days. The whole technique of lighting carnations is still the subject of considerable research, but the general implications are quite clear.


Carbon dioxide enrichment

This is still not a precise technique, but research workers claim that an improvement in the quality of cut flowers is achieved by two-or three-fold carbon dioxide enrichment, especially during the winter period.



There is a countless number of varieties demanding constant reappraisal, but in re- cent years many new varieties have been developed and to keep up to date, consult specialist suppliers. Spray varieties and Pinks (grown as sprays) are now becoming popular as a greenhouse crop and are generally easier to manage and more productive.


Foliage and flower crops from seed under glass

A number of perennials and annuals are grown in greenhouses for cut flower production, decorative purposes and floral art. Culture is usually straightforward and involves sowing seed and pricking off.

Culture of many foliage and flowering plants from seed is becoming more popular in plastic structures or greenhouses, especially with flower arrangement enthusiasts, to provide material on a regular basis, free of weather damage. It is essential to provide free and full ventilation to avoid soft, floppy growth, coupled with regular pest and disease control.

Popular subjects are :

Alstroemeria from seed or division, annual chrysanthemums, Clarkia, dahlia from seed or tubers, Dianthus from seed, everlasting flowers and foliage such as Acrolinium, Ammobium, Craspedia, Helichrysum, Rhodanthe, Statice, Xeranthemum — all from seed sown in early spring — Gerbera from seed, Gypsophila from seed or root cuttings (perennial type), stocks, sweet peas, sweet William (all from seeds) and Pyrethrum (seeds or division).


14. April 2011 by Dave Pinkney
Categories: Roses | Tags: , | Comments Off on Roses and Carnations


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