1. Introduction
2. Location and Soils
3. Greenhouse
4. Preplant Preparation
5. Bed Layout and Plant Spacing
6. Cultivar Selection
7. Plant Sources
8. References
9. Further Reading
10. Acknowledgements

Introduction

Location and Soils

• If establishing a cut flower growing business, a land area of no less than 1 hectare should be considered. This will provide the business with sufficient flexibility for expansion and diversification.
• Proximity to markets, international airports, and availability of labour, should also be considered. Do not overlook factors such as water, power and Regional and Local Council regulations.
• A flat, well sheltered area is desirable. For carnations, any well drained loam is suitable. A generous addition of organic material is usually required and should be considered as an ongoing routine measure in preparation for planting. Peat is excellent to add as a organic matter, as is pulverised and decomposted pine bark and well rotted cow manure. But avoid composts and manures which may increase the soluble salt content of the soils. It is good practice to take soil samples for analysis prior to addition of organic matter. Wherever it is suspected soluble salts are excessive, flooding should be carried out prior to planting.

Greenhouse

To achieve the best production, greenhouses should provide maximum light interception. Side walls should be no less than 1.8 m and glazed to the foundation not more than 30 cm from the ground. Modern glass and aluminium structures are considered superior. The recent trend is for high-walled structures (4m), but some compromise between light transmission, heat retention and costs may be necessary. For example, a polyethylene greenhouse or tunnel is less optimal for light transmission and heat retention, but is much cheaper.

Carnations are best grown at an even temperature, as fluctuations accentuate calyx splitting. Accurate environmental control is required to maintain temperatures around 12°C (night) and 24°C (day).

Greenhouses must be designed with ventilation equivalent to at least 20% of the floor area. Where low-capital cost polyethylene structures are constructed, fans will be the only practical means of ventilation. Cooling pad/fan ventilation systems are not suitable in parts of NZ which have high summer humidities, e.g. Auckland and Northland.

In the top of large single span structures, large diameter fans could be installed to improve air movement, particularly during the winter months when vents are closed and heat accumulates at the top. For the latest information on greenhouse climate control, seek advice of a specialist.

Well-controlled hot water pipe heating is the most advanced heating system but is also the most expensive. Ducted air units are also considered appropriate for carnations, and the advantage is that they are rapidly able to respond to changes in temperature. They can also be used during the summer for additional ventilation. Remember, air movement is important in carnation crops.

Some suggest, that because of high energy costs, winter-night temperatures need not exceed 10°C. The choice of fuel will depend upon such factors as property size, initial capital costs, costs and availability of fuel, continuity of supply, price sensitivity, maintenance, depreciation allowances, and tax incentives. Should you consider carbon dioxide (CO₂) enrichment, you can choose a fuel that produces clean CO₂ (propane, butane, natural gas, kerosene, and other low-sulphur oils). Another consideration is that some fuels produce much more CO₂ than others, but not in a clean form (e.g. coal and waste oil), which is disadvantageous for the environment.

Heating is not widely practised in northern areas of NZ but may have economic benefits.

Provision for supplementary lighting should also be made.

Pre-plant Preparation

Prior to planting and between crops, the soil should be disinfected to reduce the carry over of soil-borne diseases. The greenhouse should be thoroughly washed down with formalin. There is a range of suitable chemical fumigants available. Contact a specialist to obtain the latest developments in this area. Also, growers could consider alternative, more environmental friendly options as well.

Methyl bromide should not be used for a carnation crop in any circumstances. It may cause severe damage. Where plants are grown in enclosed beds, steaming is preferable. Steam sterilisation will allow a quicker crop turn around but is often considered too expensive and impractical on a field scale in NZ.

An alternative to traditional growing of carnations is to use soil-less media. Overseas such techniques are widely practised, most usually where there is a particular soil problem. A range of media containers can be used from trays to planter bags, filled with growing media such as soil, peat, scoria, pumice or rock wool. Before trying soil-less media, seek advice from experienced carnation growers who use it.

Generous applications of organic matter should be made to maintain soil structure. A soil analysis is essential for determining base dressing and possible lime requirements; a pH between 6.0 - 6.5 seems to be most suitable for this crop. Sufficient phosphate should be available to last the full period of the crop. Potash should be brought to the desired level and nitrogen may be required to start the plants off and keep them growing until supplementary feeding commences. Base dressings should be applied several weeks before planting and cultivated into the top soil. Your fertiliser supplier will have useful advice on what product meets your requirements.

Make request for soil testing sufficiently early so that planting will not be delayed, particularly if high soluble salts are suspected and flooding may be required.

Bed Layout and Plant Spacing

Although the orientation of the greenhouse seems to matter little, more balanced development of the crop occurs when the beds are placed north-south. If the beds run east-west the crop tends to crowd the northern (sunny) side. Layout will in each instance depend on overall width of the greenhouse and greenhouse design, but it is unwise to plant up against the glass. There should always be a path on the outside. Beds should run lengthways in the house. A maximum length of 35 m should however be considered and beds should not exceed 1.2 m in width.

Paths should be no less than 50 cm wide, and 60 cm is more desirable. Regardless of bed layout, it is unlikely that more than 65% of the greenhouse can be fully planted. Curbing of the beds is not considered necessary, as this only complicates management. Carnations need support while growing to ensure erect stems and ease of harvest. Usually three to four nets are needed and position is dependent on stage of growth, they should be moved higher as the plants grow.

Carnations are normally regarded as a two year crop, where a plant spacing of 15 cm x 20 cm is most appropriate. This equals approximately 30 plants per nett square metre, and has proved the best balance between plant costs, flower quality and production. A planting density of 24 plants per nett square metre is recommended for GIPSY carnations.

Cultivar Selection

The selection of colours and cultivars to ensure good returns is determined by market requirements. The market is mainly driven by customer preferences and fashion has a clear influence on the colour preference. Trends have an influence on the demand for certain flowers, e.g. old-fashioned looking flowers or low pesticide use flowers.

In the case of export, the colour mix and type of carnation chosen will depend on the requirements of the market to which the flowers will be sent. It pays to have ongoing contact with your chosen exporter.

It is not possible to give a up-to-date list of cultivars presently being grown in New Zealand as this is subject to regular change and what stocks the suppliers hold or can obtain.

Considerable differences in production and flower quality do exist between cultivars and between the different districts. When selecting colours, the advice of your exporter and experienced growers should be sought. Consideration should also be given to factors such as disease resistance or susceptibility to Fusarium, particularly in warmer districts.

Plant Sources

Propagators should be given at least 2 months notice to ensure supply. Consult each for their conditions of supply and prices. You can also ask experienced carnation growers who their suppliers are.

Some growers prefer to produce their own cuttings. If you are a good propagator this saves money. However, the scheduling of planting of your crop is critical and good quality cuttings are worth the investment. Please also be aware whether a cultivar is protected under Plant Variety Rights.

References

Forsyth and Maynard (1969): The sensitivity of ornamental plants to insecticides and acaracides. Commonwealth Agricultural Bureau.

Holly and Baker (1963): Carnation Production. Wm C. Brown Co Inc. Subuque, Iowa.

Langhans ed. (1961): Carnations - a manual of the culture, insects and diseases and economics of carnations.

Larsen ed. (1980): Introduction to Floriculture. Academic Press Inc.

See also:
Carnations - Harvesting and Post Harvest Practices for Commercial Production

Further reading

• Read national and international floricultural magazines.
• Browse the Internet for the latest information.
• Contact a technical library such as a Crown Research Institute library.

Acknowledgements

P. J. Batt (former Horticultural Advisory Officer, MAF, Christchurch) for preparation of the original AgLink, and Theo van Lier (van Lier Nurseries, Henderson) for editing of the revision.

Prepared for HortNET - June 1998