Leek Harvest, Yields and Storage

How much a leek crop can yield

After years of practice, a good yield for leeks is from 12 to 40 tonnes per hectare or 5-16 tons per acre (on average 15-25 t/ha, or 6-10 t/acre), depending on the plant density. For example, growers have reported yields of 3600 cartons with 12 bunches each from a population of 160,000 plants. Such a population results from distances 60 cm (24 in) x 10 cm (6 in) between rows and plants.

When and how to harvest leeks

The right time to harvest leeks varies depending on the leek variety we cultivate. Leeks are categorized into 4 types depending on their maturity period:

• Summer leeks. 
• Autumn leeks 
• Autumn-Winter leeks
• Winter leeks

All leek types are planted during spring and harvested at the time their type suggests. For example, summer leeks are planted in early spring, have the shortest life cycle, and are harvested within summer. On the other hand, winter leeks are planted in spring, maybe a bit later than summer-type leeks, and harvested in early winter. There is no strictly defined moment regarding the harvesting time. Broadly speaking, leeks grown from seed are ready for harvesting 6-7 months from sowing in the field. On the other hand, leeks produced by seedlings (transplants) are ready approximately after 3-4 months from transplanting. The goal is to harvest leeks that have formed a white shank with an acceptable commercial size of 15-20cm (6-8 in) and 3-7 cm (1.2-3 in) diameter. To obtain the highest prices possible, the leek shanks should have good quality [optical characteristics, taste, and texture (tender)]. 

Producers usually harvest leeks consecutively every 3-4 days. Leeks are harvested early in the morning to prevent wilting from intense transpiration. The entire plants are uprooted manually (by hand or with garden forks) or mechanically. In mechanical Harvesting, the machine first cuts the leaves of the plants and then, extracting the leeks from the ground is much easier

How to handle and store leeks

After harvested from the field, the roots of the leeks and part of the leaves are trimmed (10-15 cm or 4-5 inches remain), and then they are transferred to rooms where the excess outer leaf sheaths are removed, the shanks are cleaned, and tied into groups of 4-6. Then, they are either stored or transferred directly to the market. It is essential in order to preserve leeks quality to cool them soon after harvest by using hydrocooling, vacuum cooling or crushed ice. Leeks that are large (15-20 cm (6-8 in) long, 3-5 cm (1.2-2 in) thick-diameter and 200-300 g weight), white, clean, with small or no bulbing at the base and with deep colored leaves with fresh green tops can obtain the highest prices in the market. Leeks can be stored for up to 2-4 months in 0-2 °C (32-35 °F) temperature and 90-95% relative humidity. Poorly stored leeks are expected to lose weight and if this loss reach 15% then moderate wilting will be noted. 

References

https://southafrica.co.za/leeks-crop-management.html

https://horticulture.oregonstate.edu/oregon-vegetables/leeks-0

https://www.dpi.nsw.gov.au/agriculture/horticulture/vegetables/commodity-growing-guides/leeks

https://www.agric.wa.gov.au/leeks/growing-leeks-western-australia?page=0%2C4

https://extension.usu.edu/yardandgarden/research/leeks-in-the-garden

https://datcp.wi.gov/Documents/mk_fc_82_web%20pdf%20-%20Adobe%20Acrobat%20Pro.pdf

https://extension.umn.edu/vegetables/growing-leeks#harvest-234413

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