Introduction
Peas (Pisum sativum) are legumes (Fabaceae) and three main vegetable types are grown in Western Australia. Snow pea and sugar snap pea differ from the traditional garden pea in having less fibre in the pods and both pods and peas (seeds) may be eaten whole.
Compared with garden peas, they produce better yields and quality under higher temperatures. They are a good source of fibre, vitamin A and vitamin C. They may be eaten raw, lightly boiled, steamed or used in stir-frys.
Snow peas are sweet and crisp and popular in Asian cooking. The shoots from established plants may also be used for Asian cooking and in salads.
The snow pea (Pisum sativum var. macrocarpon) is called ‘mange-tout’ in England and France, which means ‘eat-all’. The pod is flat and is eaten before the seeds develop and start to swell. The main growing area in Western Australia is Wanneroo.
The sugar snap pea (Pisum sativum var. saccharatum) snaps like a green bean. The edible pods have thick walls and are sweet. Unlike the snow pea, the sugar snap is picked more mature and is fully rounded.
Pea sprouts are also popular, especially in Asian cooking, and are often marketed as ‘snow pea sprouts’.
Climate and soils
Snow peas and sugar peas can be produced throughout the year in the Perth area, but produce best yields and quality in spring and autumn. Temperatures above 30°C cause poor pollination, early maturity and lower yields. Cold temperatures cause curled pods. The plants are not affected by frost, but this may damage flowers and pods.
Peas thrive on a wide range of soil types, as long as the soil is well drained. The ideal pHCa range is 5.2 to 7.0. Lime should be applied if soil is below pHCa 5.0. The minimum soil temperature for growth is about 10°C.
Varieties, spacing and trellising
Cultivars can be either bush or tall types. Tall types mainly grow in Western Australia and require trellising, as they may grow to 2m high.
Check with commercial seed suppliers for new varieties and your destination market for their preferences.
Peas are sown directly into the soil, with about 10kg of seed needed for 1000 square metres. Sow seeds 2 to 3cm deep. Spacing within the rows should be 7 to 10cm and the distance between rows of bush varieties should be 60 to 70cm. For trellis production of tall varieties, rows should be 1 to 1.5m apart. Space them wider in winter to reduce diseases.
Snow peas are vigorous plants and trellising is necessary to manage the growth, to keep pods off the ground and to facilitate harvesting.
Fertilisers and irrigation
Fertilisers
If there is no recent history of trace element application to the site, apply the following rates of magnesium and trace elements to the soil before planting:
- 50kg/ha magnesium sulphate to supply magnesium
- 20kg/ha manganese sulphate to supply manganese
- 18kg/ha borax to supply boron
- 18kg/ha iron sulphate to supply iron
- 18kg/ha copper sulphate to supply copper
- 18kg/ha zinc sulphate to supply zinc
- 2kg/ha sodium molybdate to supply molybdenum.
Using compost at up to 30 cubic metres per hectare to other crops in the rotation will be beneficial. It will supply organic matter, add nutrients and help to retain moisture in the soil.
Peas are a legume crop and so are capable of fixing their own nitrogen, but to do this the seeds need to be inoculated with a suitable Rhizobium bacterium before planting. However, this is not often done in commercial practice because artificial fertilisers containing nitrogen are commonly topdressed throughout the life of the crop.
Immediately after planting, broadcast 200kg/ha of a compound fertiliser with an analysis of around 4% nitrogen, 7% phosphorus and 7-10% potassium plus trace elements. Continue to apply this product, banded 15cm either side of the planted rows, once a fortnight at 80kg/ha for 10 weeks. This practice can be continued beyond 10 weeks depending on the vigour of the plants. If they are very leafy and vigorous, discontinue applications because too much nitrogen will encourage vegetative growth, leading to poor flowering and pod set.
Analyse soil and irrigation water for nutrients before planting, plus one to two analyses of the youngest mature leaves during the season. This will help adjust your fertiliser program and provide information on nutrients that are deficient or toxic. Some suggested nutrients may be deleted or reduced if they are sufficiently high in the irrigation water and soil, including sources from compost and fertilisers from previous cropping.
Do not apply excess fertilisers because nitrogen, phosphorus and potassium are easily leached through sandy soils by rainfall and irrigation. This may lead to pollution of groundwater, rivers and estuaries.
Irrigation
Sprinklers on 2m or higher risers are mainly used for irrigation of high trellised crops. Drip irrigation is also suitable for snow peas. Peas must be kept well-watered, particularly at flowering and pod development.
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 online by using the irrigation calculator.
Pests, diseases and weeds
The pests most likely to damage pea crops are thrips (spotting of pods), Heliothis spp. caterpillars (leaves and pods), redlegged earth mite (base of stems and young leaves), two-spotted mites (leaves), aphids (leaves), thrips (pods), cutworms and root knot nematodes (roots).
The main diseases are downy mildew, powdery mildew, black spot on the leaves and Fusarium root rot and Rhizoctonia (base of stem). An interval of three years should be allowed between successive pea crops to reduce root diseases.
Weed control in snow peas is restricted to hand weeding and shallow cultivation along the pathways between rows. Snow peas are easily damaged by herbicides registered for use on green peas, so they should not be used. Hand weeding is economically viable for this high value crop.
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. The information on the APVMA website helps meet this requirement.
Harvesting
Peas are self-pollinated and snow peas are harvested about 10 days after flowering.
Harvesting commences 8 to 12 weeks after planting and may continue for 8 to 10 weeks. Pods may average 7g in weight and pickers can harvest about 11kg per hour. This may take longer in wet weather, as old flowers may stick to the pod. Yields range from 2 to 7t/ha.
Snow peas are harvested every two days when the pods are flat, without any development of seeds and are 7.5 to 10cm long and 2.5cm wide. Old pods should be picked and discarded.
Sugar snap peas are harvested when the pods are up to 7.5cm long and the seeds are almost full size. These may be harvested for four to six weeks. A good picking rate is about 20kg per hour per person.
Marketing
Snow peas and sugar peas may be marketed in 22 litre containers or cartons or polystyrene containers. After they have been pre-cooled to 2°C, they may also be prepacked into polystyrene trays of varying sizes from 175g to 2kg and covered with plastic wrapping. Snow pea shoots are tender and must also be kept cool.
Local production is lower in late winter and early spring and there are significant imports of snow peas from overseas. These are usually well presented and free of blemishes. In summer there are significant imports from interstate.
Snow peas may be stored at 0 to 2°C and 90 to 95% relative humidity for up to one to two weeks in a high humidity coolroom.
Acknowledgement
The original content of this page was authored by John Burt.