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Growing waratahs commercially

Ross Worrall, Senior Research Horticulturist, NSW Agriculture, Div. of Plant Industries, Gosford

Aspect  Bract burn  Fertiliser  Irrigation  Planting  Pruning  Postharvest  Seed  Soil  Vegetative  Yields & Price  

Waratah postage stampThe New South Wales Waratah (Telopea speciosissima) is the State's floral emblem. The crimson inflorescence which is formed from numerous individual flowers and surrounded by large bracts, is sought after both as a garden specimen and a cut flower.

The plant occurs naturally in the Central and South Coast districts and the Blue Mountains region of New South Wales on poor, deep sandy soils (over 1.5m) derived from sandstone.


Yields & Price

Yields from commercial planting can be high, with 20,000-50,000 blooms per ha annually produced after 5 years in high density plantings. However, these yields are often not realised. High yields will depend on the use of selected clonal material, optimum environmental conditions (such as soil and climate) and good cultural practices.

Prices for blooms can vary greatly, depending on quality and time of flowering. Returns in 1992 ranged from about $0.50 to $4.50 with an average mid-season return on the Sydney flower market of $3.50. Prices in other Australian centres were generally lower. Highest prices are generally received earlier in the season for high quality blooms.

Production and marketing costs should be taken into account when calculating potential net returns. After establishment, a planting can be expected to remain productive for 30 to 40 years However, because of the number of failures that have occurred, waratahs must be considered a high risk crop. In most instances these failures can be attributed to inadequate soil aeration (good aeration and drainage is critical for waratahs) or inadequate attention to their culture.

 

Seed

Waratah seed germinates readily, providing it is fresh (under 6 months old). If refrigerated at 5C, however, it will remain viable for at least 2 years. Seed is harvested from about April in the warmer areas, and from about June the cooler areas. Collect pods when they begin to turn brown and allow them to open in a well-ventilated area. Sow the seeds thinly (1.5 cm between seeds) onto trays filled with a coarse, well drained sterile medium such as perlite. Cover the seeds with about 5 mm of medium. Drench the trays with a general purpose fungicide. Transplant the seedlings either at emergence (2.5 to 4 weeks) or wait until at least 6-8 leaves have expanded as the young seedlings are easily damaged. Transplant them into 5 cm tubes. A suitable medium for the tubes is a mixture of one-third peat and two thirds coarse sand or perlite, sterilised and adjusted to a pH of 5.5 with dolomite. Fertilise the seedlings weekly with a solution containing 0.2 g/L of a general purpose soluble fertiliser such as Aquasol or Thrive. Don't over-fertilise. When seedlings are about 150 mm high they can be transplanted into the field after hardening off. However, losses will be a lot less if the seedlings are grown in larger containers (1 litre, 125 mm. or above). A suitable medium for larger pots is 33% (low P) composted hardwood sawdust. 33% aged pine bark fines and 33% coarse sand adjusted to a pH of about 5.5. Add 0.5 kg of IBDU and 4 kg (low P) of 4-5 month Nutricote (or 8-9 month Osmocote) per cubic metre.

This fertiliser treatment should be sufficient to last them until they are transplanted into the field.

They are normally ready to transplant 6 months after potting up and preferably in spring or autumn.

Avoid over-watering of pots as this favours development of damping off diseases such as Pythium, Phytopthora and Rhizoctonia. These may partially controlled with fungicide drenches.

Some fungicides may be phytotoxic to the seedlings, so use these with caution and never exceed the recommended rate and always read the label. Keeping out diseases by good hygiene is always the best means of control.

Young waratahs are also very susceptible to moisture stress, therefore great attention needs to be paid to watering of the pots.

Seedlings take at least 2 years, and usually 3 years, to flower. And there are large variations in vigour, leaf shape, inflorescence shape, size, colour and possible disease resistance.

 

Vegetative

Cuttings as a means of propagation have many advantages over seedlings. They allow selected clones to be established, with desirable vigour, inflorescence shape, size and colour, and they flower in the first year after planting into the field. Selected clonal material will usually out-perform seedlings in the field.

Availability of such material at the present time, however. is restricted.

Terminal or stem cuttings may be taken. Spring is the optimum time for taking cuttings. just after growth has started. Cuttings taken during winter will be slow to strike.

Make the cuttings 15 cm long with 4-5 leaves attached.

Dip the cuttings in a systemic fungicide to control infections of Guignardia citricarpa (Black spot of citrus). Failure to do so may result in high percentage losses. especially if the cuttings are taken from plants in a cultivated area. Treat the basal 5 mm cuttings for five seconds with 2.000 ppm IBA (in 50% ethanol solution) or with semi-hardwood hormone powder (0.3% IBA in talc). Do not use higher rates as a delayed toxicity may occur.

Use of intermittent mist to strike the cuttings will usually give the best results. Use a coarse, well drained medium (such as perlite/peat). Bottom heat (24C) will also speed up root formation.

A strike rate of close to 100% should be achieved in 4 - 5 weeks if cuttings are taken at the optimal time and are in good condition (i.e. just after growth has started in spring) and then are correctly treated.

When struck, transplant the cuttings into containers of 1 - 2 litres using the medium and fertilisers suggested for seedlings in pot sizes of 1 litre or above. After about 6 months in the pots, the waratahs will be ready for transplanting into the field.

 

Culture

Soil aeration

Soil aeration is perhaps the most critical aspect in the successful cultivation of the waratah. They grow naturally in sandy soils over 1.5 m deep, however it has been demonstrated that they will grow in a wide range of soil types. provided the soil is well-drained. For example. they thrive on well-drained red basaltic clay soil in the Silvan (Victoria) area.

A site with a mild slope can often greatly improve drainage.

Shallow soils, particularly those overlying an impervious sub-soil, are not suitable unless provision is made for drainage. There is a dramatic improvement in the survival and growth rate of plants when shallow soils are drained.

Poorly structured clay soils (such as those derived from shale in the Sydney basin) are generally unsuitable.

 

 

Aspect

Although they occur naturally in a woodland situation. waratahs grow and flower best in full sun. Plants grown in heavy shade are generally not vigorous and produce few inflorescences. Plants which are heavily shaded or on southerly slopes can flower 2- 4 weeks later than those in the full sun. Waratahs should be protected from strong winds, especially at flowering.

 

Planting

Early spring or early autumn planting is preferred. Waratahs should be planted at least 1.5 m apart. and 2 m apart when vigorous selections are used. Close spacing results in weak plants and few flowers. Inter-row spacing will be determined by the cultural methods to be used. Dig in fertiliser around each planting hole - not in direct contact with the root system. Take particular care when applying fertilisers to young seedlings as they are extremely sensitive to them. Use 100 g (per plant) of blood and bone or other slow release organic fertiliser. The original pot level should be level with the surrounding soil. Water thoroughly. It is essential that the plants be kept moist (not waterlogged) until the root system becomes well established. This usually takes 2 months, when the plant is actively growing. Use a soil drench, at least initially, to control both Phytopthora and Rhizoctonia. Most losses will occur in the first 3 months. Good weed control is essential. Use mulches, weed mats and, as the plants become larger, contact herbicides.

 

Irrigation

After establishment, waratahs in the higher rainfall areas can grow without irrigation. However, it may be required to ensure high quality blooms during a dry spring and to minimise bract browning.

Micro jet irrigation with one nozzle per plant (or per 2-3 plants if in offset rows) has proven to be both satisfactory and reasonably economical, especially on the sandy soils.

 

Fertilisers

Addition of some fertiliser is required to achieve maximum production. After establishment waratahs are not particularly sensitive to high rates of fertilisers, unlike many of the Proteaceae, although it is safer to use slow release fertilisers (e.g. most organic fertilisers) at low rates.

Use of organic fertilisers has the advantage of providing a wide range of nutrients as well as stimulating Proteoid root development.

Waratahs respond to applied phosphate, especially on soils derived from sandstone. Use 9 kg/ha P annually (on a root zone area basis). Do not exceed this rate without prior experimentation.

Apply it as single super phosphate (about 100 kg/ha) or in another form such as fowl manure or blood and bone (at a higher rate because of restricted availability of P).

Application of high levels of immediately available nitrogenous fertiliser may result in a high death rate, especially in young plants. A slow release form, such as coated slow release fertilisers or an organic fertiliser, is better. Use up to 600 kg (dried) fowl manure per ha or 300 kg blood and bone per ha, twice a year (early spring and early autumn). after the plants are established

There is only a limited response of waratahs to potassium fertilisers.

Proteoid root development is inhibited by high levels of N and P. If they are not present reduce the rate of fertiliser application.

 

Pruning

Regular pruning of the plants is essential and falls into two parts:

Annual pruning. During harvesting or immediately after harvesting, remove excessive growth and short stems. The aim is to produce flowers with stems at least 30 cm long for the next flowering season. If the number of shoots left is excessive. flowers will be of poor quality and have short stems. However, do not prune heavily as this will weaken the plant. Pruning later in the season may remove next year's flowers.

Rejuvenation. At intervals of about 10 years prune the plants severely, mainly to reduce the height of the plant This makes picking easier and encourages the development of longer stems. This will reduce the yield of inflorescences for the next 2-3 years so should be done on a rotational basis.

 

Bract burn

One defect of inflorescences often encountered is browning of the bract tips. This appears to be related to environmental conditions, particularly water stress.

To minimise burn, maintain the water supply to the plants during bud development and opening and protect them from strong winds. Covering with very light shade cloth and selection of resistant clones has also been reported to reduce the incidence of burn.

 

Postharvest handling

Flowering mainly occurs from early September to late October, depending on locality. Flowering time in individual localities may also vary slightly from year to year. Stems need to be at least 0.8m long to obtain the best price.

The optimum stage for harvesting inflorescences of the waratah is when they are fully mature (with no more than 5% of the individual flowers open). When harvested at this stage they have a vase life of about 13 days at 20C.

They will keep longer at temperatures lower than 20C, and temperatures higher than 20C will cause a greater reduction in their subsequent vaselife.

Some hybrids, and other species, may have a significantly shorter vast life than this.

Storage at 0.5C for 9 - 10 days will reduce their subsequent vase life by about 30%. This is the maximum permissible reduction in vase life recommended by many workers.

Where flowers are stored at high temperatures (e.g. 20C) and high humidities (e.g. in a plastic bag during transport) it is essential to treat the inflorescences with a fungicide to prevent the development of Botrytis.

A wide range of floral preservatives have been tested to date but they may not greatly improve the vase life of inflorescences. However, some of the commonly used preservatives may prevent stem plugging and thus may be useful for maintaining vase life in adverse environmental conditions (e.g. air conditioned rooms) or where contaminated water is used in vases.

Sugar in pulsing solutions will result in increased nectar production, and thus increased susceptibility to Botrytis.

Waratah flowers need to be treated with the same care that other cut flowers generally require. Failure to do so will result in a reduction both in quality and post harvest life.

Agnote DPI/102 First edition, May 1994

Edited by Megan McDonald Produced by the Communications Unit NSW Agriculture, Orange, May 1994

Agdex 280/11 Approval no. PL (V&O) 67

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