HortFACT - Proteaceae - Flower and Foliage Production
The demand for flowers and foliage from plants of the protea family for export has resulted in a significant increase in the number of properties producing this crop. Careful selection of planting material and correct management are essential to ensure a top quality product.
The international market for cut flowers and foliage is discerning and highly competitive. Growers should accordingly plan their plantings to achieve a high quality product to coincide with periods of demand. Varieties selected should be those with flowers and foliage that are acceptable to the end user and provide an economic return to the grower.
To determine the suitability of a species, variety, or clone for export, intending growers should consult leading growers and exporters who have experience with Proteaceae. Nurserymen can help with plant selection but will often be swayed by what they have available to sell. Some "crystal ball" gazing based on market feedback is also warranted, as the time lag from planting to full production is often more than three years. Because of this time lag, there is a requirement for alternative income sources in the first few years, and many growers do supplement their incomes with annual crops. It is important to realise that similar-looking varieties can often have very different handling and storage properties.
Proteaceae known to be currently trading successfully from New Zealand to international markets are listed below.
The selection is based on available information. Persons making selections for commercial plantings should base their final choice on whether that particular variety when grown in their locality will produce flowers or foliage that:
Protea cynaroides (King): Well known and established wherever proteas are sold. Stock planted should be of variants chosen for long stems, good flower form and colour, and appropriate flowering time.
Protea magnifica (Queen): Well established on all protea markets. Stock used should be of a variant known to produce well in the intended area. Does not grow well in all areas.
Protea neriifolia, P. compacta, P. eximia: Established on markets. Selected clones which are not susceptible to leaf blackening should be grown.
Leucospermum cordifolium: Select variants which have good colour (bright orange), stems 45 cm or longer, clean foliage (resistance to fungal attack), and an appropriate flowering time.
Leucospermum conocarpodendron: Bright yellow flowering species.
Leucadendron: Female forms are generally preferred, except for L. discolor and certain of its hybrids, which are male.
Single-head types are:
'Safari Sunset' (deep red, exceptional stem length) is still the preferred cultivar.
L. laureolum (yellow; selected forms).
L. salignum (yellow, pink or red).
Multi-head types are:
L. floridum
L. xanthoconus
L. discolor
All leucadendrons are regarded by the markets as foliage (greens) not flowers. Leucadendrons should have long straight stems - 45-60 cm or more.
Telopea speciosissima (NSW waratah): Telopea is a known flower on the European market and is becoming accepted elsewhere. It generally has a short flowering season (6 weeks in September - October).
Banksia: Where these can be grown successfully, limited production can be considered. Suitable species include B. menziesii, B. prionotes, B. speciosa, and B. burdettii.
Most forms of South African and Australian Proteaceae grown for cut flowers can be propagated vegetatively as well as by seed. While seed has been the traditional method, vegetative propagation is the only technique by which selected forms suitable to the trade can be maintained. Seed propagation is now only widely used to propagate banksias.
The soils in which proteaceous plants are found growing naturally are usually very acid and low in nutrients. The plants have evolved a complex root structure known as the "proteoid" root system to enable them to extract both nutrients and moisture under harsh conditions. Keeping these delicate, waxen, white rootlets alive and active is often the source of problems associated with successful cultivation of Proteaceae.
When soil tests are carried out it is necessary to look for low nutrient levels. High levels of both calcium and phosphorus can destroy the root system. As a result, although a plant may appear healthy, a period of stress, especially that caused by drought, may result in its collapse. Sometimes this has been unjustly blamed on Phytophthora, as some of the symptoms may be similar.
In the field it is wise to avoid the application of fertilisers completely. Research is being done on the nutrient requirements for proteaceous plants and although nutrients should be incorporated in soil-less container mixes, it is still considered risky in the open ground situation.
Practical experience has demonstrated that the following soil testing figures can be used as a working guide (based on MAF quick soil tests; QT values followed by ppm in soil):
A significant finding by South African researchers is that genetic variation within species may affect phosphorus tolerance. In problem soils, clones may be selected that exhibit sufficient tolerance to enable successful cultivation.
Irrigation could be needed in situations where the proteoid root system does not develop (e.g. owing to high nutrients) or on light soils subject to summer drought (e.g. coastal sands).
Only a few species will tolerate gale-force winds as most have comparatively shallow root systems, and if these are disturbed through wind movement the resultant root damage may allow pathogens to enter the plant. This type of damage due to wind is more serious than foliage burning, which is not often a problem.
In exposed wind-prone situations shelter belts which create a "filter" effect are recommended, as opposed to dense heavy shelter. Fairly wide-spaced trees such as Casuarina are preferred.
Planting Leucadendron 'Safari Sunset' as close as 60 cm apart in an effort to achieve longer stems is not recommended. Cramming can result in premature losses through root competition and disease.
Penetration of sprays is more difficult in densely planted rows. In summary, some air space between bushes is regarded as desirable to give longer life to the bushes and fewer maintenance problems.
Where annual weeds and grasses are a problem, spray a 0.6-1 m strip with a desiccant herbicide. Problem perennial weeds such as couch, paspalum, and similar should be sprayed with a suitable non-residual herbicide. If the weed problem is widespread, the entire block should be sprayed off.
The strips where the shrubs are to be planted should ideally be rotary-hoed. This enables the roots to spread out quickly into the surrounding soil. When planting out into rotary-hoed ground, the bushes should be planted slightly deeper than appears necessary to allow for the soil to sink and compact. Digging holes in straight pasture often slows the growth of the plant, because the roots have to penetrate the harder surrounding ground.
This system also provides a straight line for planting. The height of the first wire will differ according to the size of the bush being planted, but is usually about 15 cm from the ground. A second wire is installed as the bushes grow and is normally about half-way up the posts. As the bushes grow and the second wire is utilised, the PVC clips may need to be removed from the first wire to prevent ring-barking.
Leucadendrons need to be well cut back at the end of the flowering season to encourage plentiful new clean growth. On vigorous hybrids such as 'Safari Sunset', it may also be desirable to thin some shoots to encourage longer stems.
Waratahs need to be pruned well down after flowering to encourage vigorous new flowering stems that can be picked easily.
Proteas only need to be shaped, with straggly branches eliminated and unpicked flowers cut back to the point just above the new season's growth.
Leucospermums and banksias need little pruning.
Although weeds can be controlled by mulching, caution should be exercised in the choice of material.
Porous "weed matting" materials are now the norm for weed control, with the width used and method of laying dependent on crop and site.
Wide black polyethylene mulches can reduce aeration and may have long-term detrimental effects.
Sawdust and straw mulches tend to take nitrogen from the soil during their decomposition process, which could be a disadvantage. Such mulches also tend to cause types of collar rot - particularly if sawdust builds up around the plant in windy situations. Pathogens may also be harboured in such mulches.
Herbicides
The use of herbicides is the most common form of weed control. Post-emergence herbicides can be used for emerged weeds, and several residual herbicides show promise for longer term weed control.
Your local nurseryman, MAF horticultural advisory officer, or representatives of spray companies should be contacted for the best advice.
It is important to minimise any contact between the spray and the crop by the use of low pressure sprays and anti-drift guards.
Hand hoeing and "dust mulches"
This method is still widely used. As many proteaceous plants have roots near the surface it is very important that hoeing is shallow.
Mowing inter-row strips
Mowing is the most common method of inter-row grass control. Avoid clippings being thrown into foliage or around the trunks of plants. They can cause blemishes on the foliage and collar rot around the trunks.
In more intensive plantings, where it is not possible to manoeuvre machinery between rows, either hand-hoeing or chemical weed control is normally used.
In their native habitat Proteaceae are subject to a wide range of pests and diseases.
The plants grown in NZ are in general less subject to attack by diseases and pests than many others. However, commercial cut flower production, particularly for export, requires a clean healthy blemish-free product, therefore plants should be protected from pests and diseases.
As a general guide the following spray programme for disease and pest control is suggested:
benomyl ('Benlate'), plus permethrin and pirimiphos-methyl ('Attack'), plus cyhexatin ('Plictran'). Take care with the use of benomyl as there is a tendency for resistance to develop.
Alternate with:
chlorothalonil ('Bravo'), plus acephate ('Orthene').
A protective type of fungicide such as 'Mancozeb' and a variety of potent fungicides can be used whenever fungal problems occur. This practice can be more economic as some of the potent fungicides are too costly to be used on a regular basis.
Applications can be made at monthly intervals after harvesting has been completed, reducing to 10-14 day intervals during periods of active growth, and to 7-10 day intervals approaching harvest.
These are not the only chemicals that may be used and alternatives are available.
There is no assurance that flowers and foliage treated with chemicals in the above programme will be acceptable to all countries to which they may be exported.
Frequent inspections should be made to check for the presence of pests and diseases. With experience, the interval between sprays and the types of sprays used may be varied to suit individual situations. However, once damage occurs it cannot be reversed and can adversely affect the profitability of the crop.
It is important to pick at the right stage of development to ensure that blooms travel well and have a good vase life on arrival.
Harvesting should be completed in cool conditions if possible, either early in the morning or late in the afternoon when carbohydrate reserves in the leaves could be expected to be at their highest (see later).
Maturity at harvest determines both vase life and product quality. Less mature flowers have a longer vase life, as long as they are not picked too immature. They may also place a heavier demand on the carbohydrate reserves of the leaves in blackening-susceptible cultivars (see later).
If flowers can be picked as the first florets are splitting, this will reduce the problem of nectar being released into the package and spoiling the product.
Leucadendron
Most of the popular picking varieties are female forms, and the main criterion is to pick when the bracts (the terminal leaves which surround the central seed-bearing cone) are at their most colourful and yet remain firm.
Male flowers must be harvested when the crop is showing good colour, but before the pollen is shed. Experience will help identify these stages.
Leucospermum and Banksia
Leucospermums and banksias should be picked just as the first styles begin to unfold. This results in less damage in transit, more stems per carton, and maximum vase life at the other end.
Protea
Proteas should be picked just as the flower begins to open. If the bud is too tight when picked it will not usually open. Flowers that are too far open have a shorter vase life and are bulkier to pack.
Telopea (waratah)
Generally telopeas should be picked just as the first styles start to open. Stem length is no problem as stems are generally very long.
Stem length
Maximum stem length is needed for export. Leucadendrons, leucospermums, and banksias can be picked almost as far down into the bush as possible without affecting future growth. Protea stems generally should not be cut below the previous season's growth as they do not generate much new wood from old growth. P. cynaroides is an exception and benefits from being cut hard.
Bunching and tying
Most larger-flowered varieties are not bunched. Slimmer-stemmed leucadendrons are usually bunched into 5s or 10s, but this depends on market requirements.
The newly cut flowers should be placed in tap water (room temperature) and transferred to a cool room (approximately 4°C) for 3-5 hours or overnight. Good quality water should be used for holding the stems. If the water supply is high in salts then rain water should be used.
Tests with floral preservatives have given inconsistent results and holding in water appears to be the most satisfactory treatment at this stage. However 50 ppm chlorine (e.g. 1 teaspoon of Janola in 5 litres of water) is a useful precaution against bacterial growth.
Dependent on the market destination flowers may need to be treated with Floragas (disinfestation treatment) before or after packaging.
Flowers should be packed to restrict moisture loss. Waxed paper lining the carton or flower sleeves can be used. Exact packaging requirements need to be discussed with individual exporters, as often their requirements differ.
The packed flowers should be recooled using forced air cooling and kept cool throughout the transport period. It should be emphasised that cooling and refrigeration during transit are very important for immature flowers to enable them to open. Some exporters require icepacks to be used within the cartons to maintain cool temperatures during transit.
Leucadendron
The flowers of the red leucadendrons (cultivars 'Safari Sunset' and 'Red Gem') do not bruise as easily as the other Proteaceae and are long-lived in the vase. They can be stored at 0 - 2°C for 2 - 3 months, though vaselife decreases with increased length of storage.
Decay in storage can be a problem. Stems to be stored should not have any foliage stripped from them, and fungicides such as 'Benlate', 'Rovral', and 'Ronilan', which are active against Botrytis spp., should be used as a pre-storage dip.
Other types of leucadendrons do not store as well as 'Safari Sunset' and 'Red Gem' and should therefore be cooled rapidly after harvest and handled quickly.
Holding in water during cooling and rapid transport to markets is necessary for most leucadendron material.
Leucospermum
Maturity of leucospermum flowers at harvest determines their vase life. Over-mature flowers are generally shorter lived, but immature flowers do not open well in the vase.
The flower heads are easily broken from the stems, and problems can occur in packing with interlocking of styles from adjacent flowers. This results in damage when the flowers are unpacked, and some method of keeping the heads separate in the pack would be worthwhile, e.g. head sleeves.
Crushing of the styles and release of nectar are problems with more mature flowers.
Protea
Protea flowers harvested as loose buds open satisfactorily but tend to have poorer colour than more mature flowers.
Holding in water and rapid cooling of flowers are beneficial postharvest treatments.
Storage of Protea foliage is often hampered by "postharvest leaf blackening". A few days after harvest, leaves on the flower stem become limp, and within a week develop large deep brown to black areas, especially in the tip regions and around the leaf edges, making the flower stems unsaleable.
The extent of the disorder appears to vary widely between species (particularly affecting P. neriifolia and P. eximia), individual clones within species, the time of year (higher during summer), maturity of the inflorescences (higher in immature stems), weather conditions at harvest, and the time of day that the stems are harvested (lower when stems are harvested in the late afternoon). It can also occur rapidly during shipping when flowers are packed dry in shipping cartons. Methyl bromide fumigation can accelerate leaf blackening in some species.
Water stress was originally thought to be the trigger of leaf blackening. However, more recent evidence has suggested that the depletion of leaf carbohydrate is the more likely cause. The respiration rate of Protea inflorescences is very high. In the field this demand is met by ongoing carbon assimilation via photosynthesis from the surrounding leaves. Once harvested, the stems are shipped in darkness and then placed under light conditions too low for active photosynthesis. Because of the high respiratory demand, leaf starch is rapidly hydrolysed to sucrose, which is then rapidly transported out of the leaf to the inflorescence. Because of this depletion, the leaf looks to other glucose sources for its energy demand, such as the phenolic glycosides. An enzyme hydrolyses phenolic glycosides to release glucose and toxic phenolics. The highly reactive phenolics can then be oxidised non-enzymatically by free oxygen in the cells, leading to leaf blackening. Blackening is partially retarded by inhibitors of that enzyme such as Zn2+ and Cu2+ ions, and ethanol (1 minute dip in 30 - 50% ethanol). However, none of these treatments is completely effective. Maintenance of coolstorage conditions will keep respiration low and help delay onset of blackening.
Supplying 0.5-1% sucrose in the vase solution can retard blackening but the effect is small and unreliable. Continuous treatment with higher concentrations of sucrose tends to aggravate leaf blackening. The efficiency of sucrose supplementation depends on when the stems are given the treatments. Stems packed and shipped immediately and not supplied with added sucrose will lose up to 70% of their leaf starch reserves within the first 24 hours. If leaf blackening has already been initiated by this decline, then application of sucrose at a later stage will not have much effect. Therefore, sucrose needs to be supplied as soon after harvest as possible.
CA storage of Protea stems can retard the onset of blackening, but once the stems are removed to air, the leaves blacken within 3-6 hours.
Telopea (waratah):
Waratah flowers should be cooled promptly to less than 4°C. If held at this temperature during transportation waratahs will have a longer vase life and will continue to open in the vase. Warm conditions tend to reduce the ability of the flowers to open.
| Note: |
| Trade names appearing in this publication have been used solely for easy identification of the chemicals and not as an endorsement of any individual product. |
Prepared for HortNET - June 1998