Introduction
Brussels sprouts belong to the Brassica genus of plants and are related to cabbages and cauliflowers. Plants grow to between 100 and 140cm high and are slower growing than other brassicas. The sprouts are the small, cabbage-like buds produced in the axils of the leaves.
Brussels sprouts are produced locally and imported from eastern Australia. Less than half of the Brussels sprouts sold in Western Australia are grown here.
Most Brussels sprouts are marketed from January to October, with peak supply in September.
Climate, varieties and transplanting
Brussels sprouts require a warm climate to develop a good plant frame but low temperatures to produce high quality sprouts. The plant is the most cold tolerant in the brassica family and frost may improve the quality of the sprouts.
Commercial vegetable varieties change constantly with changing consumer preferences; before planting, check with specialist seedling nurseries.
Plants are five to seven weeks old when ready for planting out of cell-packs, which are normally produced by a specialist nursery.
Plant from late December to February in the Perth Hills and January to March in Perth. In the South West, transplant from October to January. Planting too late will not allow sufficient foliage and stem growth to support a high yielding crop of good-sized sprouts.
Space plants 1.2m between the rows and 0.6 to 0.8m within the rows. Wider spacing helps reduce bacterial and fungal infection as air flow between the plants prevents leaves remaining wet for long periods.
Soils and fertiliser
Well-drained loams, peaty sands or gravelly loams are preferred, but good crops can be produced on sandy soils providing they are fertilised well. A neutral to slightly alkaline soil is optimum; apply lime if the pHCa is less than 6.0.
Before planting on loamy or gravelly loam soils, apply 1500kg/ha of a compound NPK fertiliser with an analysis around 8% nitrogen, 12.5% phosphorus, 11% potassium and trace elements in strips 20cm wide and incorporated to 15cm in the planting lines.
One week after planting, apply 50kg/ha of urea by broadcasting or spraying — with immediate sprinkler wash off to avoid foliage damage — plus 20kg/ha of a soluble boron containing product such as borax. Thereafter, at two-weekly intervals, apply 150kg/ha urea.
About four weeks before the first harvest, switch to calcium nitrate at 150kg/ha at 14 day intervals and continue until harvesting ceases. After heavy and prolonged rain, apply more fertiliser. At monthly intervals, include dressings of 50kg/ha of magnesium sulphate with the above.
Before planting on sandy soils, broadcast and incorporate 30 cubic metres of compost per hectare. On the day of planting, broadcast a mixed granular NPK product with an analysis of around 12% nitrogen, 5% phosphorus and 14% potassium plus trace elements directly over transplanted seedlings. Thereafter, broadcast this NPK product at 100kg/ha at three to four day intervals until 17 days after planting. About 21 days after planting, increase the rate to 400kg/ha and apply it by banding about 15cm either side of the rows at weekly intervals for the next 7 to 8 weeks.
Thereafter and during the harvest period, apply calcium nitrate by fertigation at 150kg/ha weekly.
At monthly intervals, include dressings of 50kg/ha of magnesium sulphate and apply a soluble boron product soon after planting and again at around 10 weeks after planting at 10kg/ha each time by spraying (with immediate wash off) or fertigation.
Trace elements may be required at 12 to 18 month intervals in the vegetable program. A suitable mixture would include manganese sulphate (25kg/ha), copper sulphate, ferrous sulphate, zinc sulphate and borax (each applied at 18kg/ha) and sodium molybdate (2kg/ha).
Preventive sprays of some trace elements may be needed at the following rates in the seedling stage:
- Molybdenum: sodium molybdate at 1g/L, especially where soils are acidic. Spray seedlings in trays before planting.
- Manganese: manganese sulphate at 8g/L, especially on alkaline soils if symptoms appear. Spray in the field within four weeks of planting out.
Soil analysis before planting and leaf analysis after planting, plus nutrient analysis of the water, will help you adjust your fertiliser program.
Irrigation
Comprehensive information on the principles of irrigating vegetable crops in WA can be found on the vegetablesWA website. Irrigation rates for your specific location and circumstances can be calculated using the irrigation calculator.
To minimise salt damage and associated yield loss, irrigation water should have total soluble salts content of less than 220mS/m or about 1200mg/L.
Pests, diseases and weeds
Aim for a rotation of at least three years between crops in the brassica family.
Clubroot (roots), ring spot (leaves) and black rot (leaves) are the main diseases, but bacterial soft rot (sprouts), black-leg (base of stem), downy mildew (leaves), peppery leaf spot (leaves and sprouts), sclerotinia and Rhizoctonia (base of stem) may cause problems at times. Click on the links for further information on the identification and control of these diseases.
Aphids (leaves) and diamond back moth (leaves) are the main pests, but African black beetle (roots), beet cyst nematode (roots), root-knot nematode (roots), redlegged earth mite (young plants), slugs (stems and leaves), snails (stems and leaves) and vegetable weevils (stems and leaves) may also cause damage. Click on the links for further information on the identification and control of these insects.
Click here for detailed descriptions of brassica insect pests.
Herbicides are available to control most weeds before and after planting.
The registration and availability of chemicals for pest, disease and weed control changes regularly. Consult a trained and experienced horticultural agronomist or the Australian Pesticides and Veterinary Medicines Authority (APVMA) website for chemicals which are currently registered or have a permit for use on this crop.
The information on the label or permit for a chemical must be followed including the directions for use, critical use comments, withholding period and maximum residue limit. Quality assurance (QA) schemes for horticultural crop production require producers to have current information on chemical registrations and permits readily available.
Yields, harvest and marketing
Yields can be 1 to 3 kilograms per plant (15 to 40 tonnes per hectare) and a single plant may produce 50 to 80 sprouts which vary from 20 to 40g in weight.
Brussels sprouts are ready for harvest about 14 weeks after transplanting and can be picked for two to three months.
Plants are picked by hand three times per week from April to September in Perth districts and extending beyond September into early summer from the lower South West and South Coast.
Begin harvesting as the sprouts mature at the base of the plant.
Removing two to three leaves above the current level of harvest exposes sprouts for the next harvest and helps sprouts dry quickly after rain, minimising disease.
Some growers top the plants of late crops when the first sprouts are picked, to increase the size and time to maturity of the rest of the crop.
A good variety has sprouts that are easy to pick. Top quality sprouts are of good size throughout the season (30 to 45mm), round, tight with no internal browning and bright green. Discard loose, split, diseased and 'blown' sprouts then wash and grade, cool with forced-air or hydro-cooling and store at 0oC with humidity of 98%.
Sprouts are normally loose packed into 10kg cardboard cartons, or 22 to 30 litre plastic crates. Packing in five or 10kg polystyrene containers and covering with ice will keep the sprouts in good condition when sent to distant markets.
The stumps are large and fibrous and need to be well rotavated in order to break down prior to planting the next crop.
Acknowledgement
The original content of this page was authored by John Burt.