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                                 SUCCESSFUL PEA GROWING

                                                        PISUM SATIVUM


SUMMARY


Place in Rotation: before root crops and after brassicas.

Preparation of soil: rich in humus, moist and aerated.

Time of planting: March onwards and protect from frosts.

Control of major pests and diseases: good husbandry, optimised growing conditions, biological control where available, use of suitable sprays.

Harvesting: typically 12/14 weeks after sowing, pick regularly . Edible pod types just as peas are forming.



1.INTRODUCTION


Peas are annuals that grow from about 450mm to over 2m. Supporting twigs or nets are required dependent on the height. The time taken to mature is used as a method for grouping the pea varieties; these are ‘earlies’, ‘second earlies’, and ‘main crop’. The round seed types are generally hardier, and the wrinkled types less hardy but sweeter. There are also the specialist types ‘petite pois’, ‘mangetout’, and ‘sugar’. The growing conditions are similar for each, but sowing and harvesting times vary. Appendix 1 shows typical varieties, although some publications differ on the classifications.


2. PLACE IN ROTATION


Most vegetable crops, except perennials and perhaps some salad crops which do not fit into a rotation group benefit from regular changes of plot location. Salad plants which have short growing times can be used for intercropping or to fill temporary gaps in vegetable beds. There are several good reasons for changing the crop grown on a plot in successive seasons:


     2.1 Minimisation of transmission of pests and diseases and their rapid multiplication year on year. Typical problems include potato and tomato nematodes, clubroot on brassicas, and onion white rot.

     2.2 Smothering and hence reduction in propagation of weeds by ‘blanket’ coverage crops like potatoes.

     2.3 Use of nitrogen fixation by legumes to provide nutrition for subsequent crops such as leafy plants.

     2.4 Root crops such as carrots are used to help break up the soil with their deep tap roots.


It is the nitrogen fixing properties of pea root rhizomes that determine where in the rotation they should be planted.

The classic style seems to be to use a 3 year cycle (1)(4), but a 4 group cycle is the preferred RHS method which slots in the alliums as a miscellaneous category(3).

A typical 3 year cycle would be:


     2.5 Year 1 Plants that principally require phosphates and potash. Peas, beans, lettuce.

     2.6 Year 2 Plants that require nitrogen and potash. Root crops such as carrots, beet, parsnip.

     2.7 Year 3 Plants needing nitrogen and phosphates. Brassicas-cabbages, cauliflower, sprouts etc.


So, for example, if a specific plot has broccoIi in the current year, one would dig in humus the next year and grow legumes. The grouping of plants in a 4 year cycle is shown in appendix 2.


It is interesting to note that the 4 year groups include swedes (which are brassicas), turnips and radishes, along with the brassicas, and not in the root crop group.


3.SOIL PREPARATION


Peas will not tolerate cold, wet soil, or drought. Grow peas in an open site, reasonably fertile, moist retentive, well drained soil (3). Soil temperature should be a minimum of 10deg C for successful germination (5).Some sources say that deeply dug, really fertile soil which has been enriched with manure or compost some weeks prior to sowing is desirable (4).


Older references suggest that land should be thoroughly prepared in the winter months by double digging and heavy manuring (6), but this is not now considered the best approach. Indeed, current advice tends to avoid manure as the source could contain animal food and medical additives, and excessive digging can destroy the soil structure. A well drained, aerated soil avoiding excessive heat, drought and ‘fresh manure’ is suggested elsewhere(1). Rich, moist soil with a pH of about 6.5 is recommended, with the addition of lime if not done in the previous season (2). Lime dose rates should be carefully controlled as excess lime will ‘lock up’ nutrient availability. At most it should not be done more frequently than 3 year intervals. Work in plenty of well rotted humus (garden compost) before planting.


4. PLANTING TIME


Peas are a cool season crop, growing best at 13-18deg C., and will not tolerate frost. Selection of the appropriate variety for the time of planting is necessary (appendix 1). Sowing can commence once the soil temperature has risen above 10deg C. for successful germination. First sowings in February can be made under cloches or floating mulches for frost protection using dwarf varieties. In mild areas with warm soil early varieties can be sown in Autumn or Winter.


The usually accepted time for early varieties is March onwards, followed by repeat sowings every 14 days, or use different varieties to provide a succession of harvests. Mid Summer sowing is to be avoided as excessive heat inhibits germination.


Sowing method is normally in flat bottomed drills about 230mm wide and 30mm deep, spacing seeds 50mm apart in a zig-zag pattern 3 seeds wide. Reference (1) suggests 50-75mm deep and 25mm apart, but depth may depend on variety. Appendix 3 shows the back of a seed packet (Onward) which suggests 150mm wide and 50mm deep.


5. CONTROL OF MAJOR PESTS AND DISEASES.


The most common problems are birds(jays, pigeons), mice, pea moth, thrips, aphids and weevils. Other problems may include damping off, foot and root rots, seedling blight, fusarium wilt, slugs and snails, and mildews.


     5.1 Birds. Use pea guards, horizontally disposed netting or twigs.

     5.2 Mice. Damp the seeds in paraffin (old books suggest red lead, but this should NOT be used) before sowing. Use traps or poisoned baits ( even though baits are suggested in RHS publications, this is dubious and more likely to be when voles and rats are encountered).

     5.3 Pea moth (Cydia nigricana) .

 (Comprehensive protection methods for insects, viruses and nutritional problems are to be found in reference 7, and approved chemicals listed in reference 8.)

Eggs are laid on flowering plants in June/July. Eggs hatch inside pods and 5mm long pale yellow caterpillars with black heads eat the seeds. Restrict by sowing early or late to avoid damage during flowering time. Timing is essential to kill before entering the pods. Pheromone traps can be used to catch the males before mating, or spray 1 week after first flower with fenitrothion, pirimiphos-methyl, or permethrin. Repeat after 2 weeks.

     5.4 Pea thrip (Kakothrips pisivorus)

Leaves, flowers and pods are misshapen. Pods stay flat and appear silvery-brown. Orange-yellow nymphs develop into 2/3mm long narrow bodied, black/brown adults. Eggs hatch into adults in about one month at 20deg C, and some are parthenogenetic.  They thrive in hot, dry weather. Water plants regularly, try to retain a cool atmosphere and good soil condition. Predatory mite amblyseius cucumeris can be used in glasshouses. Otherwise spray with dimethoate, pyrethrum, permethrin, pirimithos-methyl, malathion or fenitrothion. Repeat after2/3 weeks.


     5.5 Pea aphid (Acyrthosiphon pisum)

Colonies of large, long bodied pale green/yellow aphids damage plants by feeding, and can spread viruses such as bean yellow mosaic and pea leaf roll. Suitable systemic or non-systemic insecticides can be sprayed in late May or early June before flowering.


     5.6 Pea weevil (Sitona lineatus)

In Summer small, short snouted weevils up to 5mm long eat semicircular edges in the leaves, and drop off when disturbed. Treat young plants only if required, as older plants are not seriously damaged. Encourage rapid germination and growth with good soil conditions, protect young plants with a suitable dusting insecticide.


6. HARVESTING


Harvest early varieties 11/12 weeks after sowing, and main crops at 12/13 weeks. Water regularly and pick young pods frequently, as this will enhance further cropping. Harvest edible pod types just as the immature seeds are forming. Mid-season types such as Onward can be sown in March for first harvests in early June.


7.CONCLUSION


There are variations in the recommendations depending on which publication is used. Older books are not to be regarded as reliable: for the best and latest advice use RHS publications, supplemented with specialist reference books, for example on pests and diseases. However, old books often have tips which have been out of fashion but return in modern times, so they are still useful.

Ian Shepherd    Abingdon  October 2000