|Parsley (Petroselium crispum)
Parsley General Background and Basic Agronomy
Parsley used to be one of the few mainstay culinary herbs in New Zealand cuisine and although much trendier vegetables and herbs have gained attention over the years, parsley remains an important plant for fresh market production. It is a very tasty and healthy herb with high quantities of vitamins A and C and many other nutritious components.
Parsley can be autumn, spring (main crop) or summer sown and has notoriously slow germination (2 weeks in good conditions even in seedling trays with bottom heat). Direct seeding can be utilised and a stale seed bed technique is useful for weed management (see weed management below).
Parsley is usually quite pest free although slugs can attack seedlings and aphids can also infest (although mostly on plants going to flower). Parsley is biennial and the flowers in the second year are beneficial for natural enemies of many garden pests.
Curly leafed varieties are the most easily recognisable types but the flat leaf types lend themselves very well to commercial growing with faster establishment and ease of harvest.
Leaves are cut by hand and bunched in the field. They are best cooled straight away and the crop will store for as long as 10 weeks at 0oC (ideally 95-100% relative humidity) – must be > -0.2oC to avoid freezing damage. Turnip rooted varieties are pulled whole, washed and can be stored for several months at 0oC with the leaves removed.
Parsley should not usually be grown in the same area for more than one in every three years. An exception is taking the crop through to seed which involves two seasons of growing in the one area.
Soil and Fertiliser
Prefers medium to rich loam soils – well drained and free of compaction. Optimal pH around 6.0 to 6.5. Liming is recommended to maintain the soil pH at around 6.2 to 6.4 (above this level, there may be some issue with the uptake of metal trace elements like iron, manganese, copper and zinc).
At 15 and 28 days after emergence, (or at transplanting and again a fortnight later) it can be beneficial to apply a biofertiliser with the aim of improving the yield. A liquid fertiliser including fish or some other nitrogen source can be especially helpful.
An initial base dressing rich in nitrogen (e.g. with restricted input permission: fishmeal or blood and bone @ 300 kg/ha) can be particularly successful in cool conditions to ensure vigorous growth.
Control perennial and grassy weeds prior to cropping and manage annual weeds through false seed bed technique. A variation on the false seedbed is the stale seedbed and this very effectively takes advantage of the slow germination and emergence of parsley (see below). Interrow cultivation is likely to be important before the parsley canopy is sufficient to smother weeds. Intrarow weeding is more difficult but could be achieved by interrow cultivation being designed to leave some soil on the row to smother weeds. Some hand weeding may make harvesting easier but the main concentration should be on the stale seed bed technique to reduce the issue. With any weeding operation, control while the weed seedlings are still small (e.g. three or four true leaves) is importance for speed and effectiveness of weed removal.
The false seedbed technique is to cultivate a seedbed as if for planting and then allow a flush of weeds to occur (if necessary irrigating to bring on the weed flush). The weeds are then controlled by undercutter bar or thermal weeding avoiding disturbing the soil to trigger deeper weed seeds. This should be repeated once or twice if weed burden is high or if a high level of seed exhibiting dormancy is expected (e.g. mature fathen that had been ploughed in several years ago and the area has been once more ploughed).
Some extra tips for false seed beds are…
Control of weeds is ideally done when weeds are very small (less than four true leaves) as regrowth after thermal weeding or light cultivation is not an issue.
Established perennial weeds should be controlled before going into the false seed bed method.
Grassy weeds are more able to regrow from thermal weeding or undercutter bar work. They should ideally be controlled before starting a false or stale seed bed programme.
Stale Seed Bed Technique
This technique is very effective for parsley – taking advantage of the long period between sowing and seedling emergence. The final seedbed preparation is done and then the crop is sown say four to seven days later. Emerging weeds are then controlled by flame or steam weeding prior to the emergence of the crop seedlings. By placing old windows around on the field to accelerate crop emergence and give a few days advance warning of crop emergence so that you are able to control weeds just before this time. Thus you maximise weed control and avoid crop loss.
The pests of parsley include aphids and slugs.
Also see general information on aphid management. Aphids are a concern for causing poor growth of parsley, transmitting viruses and reducing marketability of the produce.
Floating row covers are effective in keeping out the pest. And generally there should be an encouragement of beneficial flowering plants to increase levels of natural enemies of the aphids. Flowers include phacelia for feeding hoverflies and buckwheat for general natural enemy improvement.
Slugs aid decomposition of dead plant matter but are also major pests of living vegetables being a particular concern for the survival of young seedlings. They can also reduce marketability of crop due to damaged areas of leaf and stem and their presence (they can hide in harvested bunches of parsley). Slugs leave a slimy shiny trail though not as pronounced as that of snails.
On an intensive scale, trapping or barriers may be feasible. A small container or lid sunk into the soil with diluted beer in it attracts and drowns slugs. If the lip of the trap is raised two centimeters from the soil surface and two or three small sticks rest inside, beneficials such as predatory ground beetles are less likely to be trapped. Various materials such as wooden planks and comfrey leaves (high attractive to slugs) can be laid around a garden area and the slugs taking residence underneath them regularly collected.
On a larger scale, attention to relatively fine tillage is useful as cloddy soil tends to provide habitat conducive to slugs. The predators of slugs such as hedgehogs and thrushes can be enhanced through the provision of hedgerows and a diversity of plants with undergrowth and alternative feed for these predators.
Parsley Disease Management
The main disease in parsley is leaf spots. Bacterial and fungal spots affect mostly leaves but can still result in a decrease in yield and the non saleability of outer leaves.
Management is through avoiding excess wetness on the foliage and humidity in the air. This can be by avoiding overly dense plantings, providing good shelter that still allows airflow, avoiding irrigation or spraying of biofertilisers etc late in the day as this may leave leaves wet for a prolonged period. Copper sprays can control the fungus but the use of these should be minimised to avoid build up of copper levels in the soil (harmful to soil life including earthworms). Copper sprays are restricted input items with the most effective organically allowable type being Bourdeaux mixture.