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Leeks

Last updated on September 18, 2024

Leeks

Growing Leeks

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Varieties

Summer Harvest

(August, September)

Kilima, Lancia.

Autumn Harvest

(October, November)

Jolant, Tadorna, Carleton.

Over-winter

Arkansas, Ashton.

See your seed dealer for the most recent variety recommendations.

 

Soils

Leeks should be grown on well-drained soils and should not be subjected to flooding at any time. They can be grown successfully on mineral soils but in heavy, clay soils harvesting may be held up and the removal of surplus soil from roots may require more labour.

 

Seeding and Transplanting

Leeks are normally transplanted. They should be seeded under protection early in the season (February to March) or in outdoor seedbeds (April to May). Leeks for harvesting in August to September should be seeded from mid-February to mid-March. For harvesting in early winter, seed from mid-March to mid-April. For spring harvest, seed may be started from April to mid-May. The right varieties (above) must be used for each harvest season.

At transplanting, leek seedlings should be placed in furrows 15 cm deep. Furrows are filled in during cultivation and as the plants develop, the rows should be hilled up. Leeks should have a white shaft that reaches almost to the base of the leaves. Care must be taken not to introduce soil between leaves as it will penetrate the shaft.

Another method of transplanting is to drop each seedling into an individual hole, 15 cm deep, pressed into the ground. This procedure eliminates the need for filling of furrows but ridging should still be done.

Leeks should be spaced 8 to 10 cm apart in 90 cm rows.

 

Fertilizer

A soil test is necessary to determine phosphate and potash requirements. Use the Vegetable Production Guide: Nutrient Management (PDF) for recommendations based on soil test results.

Prior to planting, broadcast and disc in 70 kg/ha (28 kg/acre) nitrogen and all of the required phosphate and potash.

A further 50 – 100 kg/ha (20 – 40 kg/acre) of nitrogen applied in one or more side-dressings is usually necessary to maintain growth.

For the overwintering crop, side-dress 50 – 100 kg/ha (20 – 40 kg/acre) nitrogen in early spring to promote greening-up.

 

Leek Weed Management

Weed control can be achieved by mechanical methods. Timely and frequent cultivation to fill in the trench and hill up the rows will effectively smother weeds. For chemical control, see tables below.

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Post-emergence

Post-emergence: Herbicide Application Rates
Product Rate PHI* Comments

Prowl H20

(pendimethalin)

Group 3

2.37 L/ha
(1 L/acre)

Apply in 200 L/ha (80 L/acre) of water

 30
  • Apply after transplanting and before weed emergence.
  • Destroy existing weeds before applying.
  • Do not use on muck soils.
  • Controls green foxtail and redroot pigweed.
  • Suppresses lamb's-quarters.
  • Rainfall or irrigation within 7 days of application improves control.
  • Do not enter treated area for 24 hours.

Gesagard 480SC

(prometryne)

Group 5		 Split application of 3.75 L/ha (1.5 L/acre) at each application

Apply in 200 to 1000 L/ha (80 to 405 L/acre) of water at 200 to 300 kPa 		N/A
  • Controls annual broadleaved weeds and seedling grasses, including redroot pigweed, lamb’s-quarters and groundsel.
  • Make the first application to well established transplanted leeks that have produced one new, fully expanded leaf.
  • Make a second application 10 days later.
  • Do not make more than 2 applications per year.
  • Temporary injury can occur to the lower leaves of some cultivars.
  • Treated fields can only be replanted with crops listed on the label in the same season.
  • For best results apply to moist soil.
  • Use on mineral or organic soils only.
  • Do not enter treated area for 12 hours.

Aim EC

(carfentrazone-ethyl)

Group 14

 37 to 117 mL/ha
(15 to 47 mL/acre)

Apply in 100 L/ha (40 L/acre) of water		 1
  • Controls annual weeds.
  • Must be applied using hooded sprayers to weeds between the rows of the emerged crop.
  •  Use an adjuvant such as Agral 90 or Agral-Surf at 0.25% v/v (0.25 L/100 L of spray solution) or Merge at 1% v/v (1 L/100 L of spray solution).
  • Precaution:  crop injury will occur when spray drift is allowed to come in contact with green stem tissue or leaves.
  • Apply only once per growing season.

Frontier Max

(dimethenamid - P)

Group 15
Mineral soils:
963 mL/ha
(389 mL/acre)
 
Muck soils:
1.29 L/ha
(522 mL/acre)

Apply using 200 to 300 kPa spray pressure. 
 30
  • Registered for transplanted leeks.
  • Apply alone as a single application a few days after transplanting when plants are established and soil has settled around plants.
  • Use low rate on mineral soils to control red root pigweed and nightshade.
  • Use high rate on muck soils to reduce competition from red root pigweed and to suppress yellow nutsedge.
  • Apply before weeds emerge.
  • Avoid application under cool conditions.
  • If crop failure occurs, do not replant potato, dry bulb shallots or onions until the following year.
  • On mineral soils, observe a plantback interval (PBI) for 100 days for cereals other than corn and 11 months for all other crops not listed.
  • On muck soils, observe a PBI of 11 months for carrots, transplanted celery and onions.  See label PBI precautions for other crops grown on muck soils.
  • Early crop development may be delayed for carrots and celery used in rotation, but this should not have a negative development on yield.
  • Do not enter treated area for 24 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Leek Insect Management

Both onion maggots and thrips can cause damage to leeks, but to date have not been major problems in B.C. There are no products registered on leeks for onion maggot control. If experience has shown thrips control to be necessary, use one of the products listed in the tables below.

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Thrips

Chemical Control of Thrips
Product Rate PHI* Comments

Malathion 85E

(malathion)

Group 1B
1100 to 1345 mL/ha
(445 to 545 mL/acre)
 
Apply in 1000 L/ha (405 L/acre) of water
3
  • Do not make more than 1 application per year.
  • Toxic to fish.
  • Do not apply where runoff is likely to occur.
  • Best control when the temperature is above 20°C.
  • Do not apply after expiry date on the container label.
  • Do not re-enter treated area for 12 hours.

Delegate WG

(spinetoram)

Group 5

200 to 336 g/ha
(81 to 136 g/acre)

Apply in 300 to 500 L/ha (120 to 200 L/acre) of water

 3
  • Suppression only.
  • For optimal performance, final solution pH should be in the range of 6 to 8.
  • Apply at egg hatch or to small larvae.
  • Ensure spray solution penetrates to leaf axils.
  • Repeat at 7 to 10 day intervals.
  • Maximum of 3 applications per year.
  • Toxic to bees. Avoid spraying when bees are foraging.
  • Do not re-enter treated area for 12 hours.

Entrust 80

(spinosad)
 
Group 5
 
Used in organics

131 to 158 g/ha
(53 to 64 mL/acre)

Apply in 300 to 500 L/ha (120 to 200 L/acre) of water

 3
  • Suppression only.
  • Apply when onion thrips first appear targeting egg hatch or small nymphs.
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than three times per season.
  • Highly toxic to bees.  Do not apply if bees are visiting the area.  
  • Harmful to parasitoids and predatory mites.  Slightly harmful to foliage-dwelling predators.
  • Entrust products are OMRI-USA listed.  Check with your certification body before using in an organic operation.
  • Do not re-enter treated area until residues have dried.

Entrust SC

(spinosad)
 
Group 5
 
Used in organics

437 to 527 mL/ha (177 to 213 mL/acre)

Apply in 300 to 500 L/ha (120 to 200 L/acre) of water

 3
  • Suppression only.
  • Apply when onion thrips first appear targeting egg hatch or small nymphs.
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than three times per season.
  • Highly toxic to bees.  Do not apply if bees are visiting the area.  
  • Harmful to parasitoids and predatory mites.  Slightly harmful to foliage-dwelling predators.
  • Entrust SC (PCP# 30382) is OMRI-Canada listed.  Check with your certification body before using in an organic operation.
  • Do not re-enter treated area until residues have dried.

Success 480SC

(spinosad)

Group 5

218 to 262 mL/ha
(88 to 106 mL/acre)

Apply in 300 to 500 L/ha (120 to 200 L/acre) of water

 3
  • Suppression only.
  • Apply when onion thrips first appear targeting egg hatch or small nymphs.
  • Repeat at 7 to 10 day intervals.
  • Do not apply more than three times per season.
  • Highly toxic to bees.  Do not apply if bees are visiting the area.  
  • Harmful to parasitoids and predatory mites.  Slightly harmful to foliage-dwelling predators.
  • Entrust products are OMRI-USA listed.  Check with your certification body before using in an organic operation.
  • Do not re-enter treated area until residues have dried.

Agri-Mek 1.9% EC

(abamectin)
 
Group 6

600 to 1200 mL/ha
(242 to 485 mL/acre)

Apply in 200 L/ha (80L/acre) of water

 7
  • Repeat at 7 day intervals.
  • Do not apply more than 4 times per season.
  • Highly toxic to bees exposed to direct treatment, drift or residues from blooming plants.
  • Do not re-enter for 13 days for hand weeding, 4 days for hand-set irrigation, 1 day for thinning and 12 hours for all other activities.

Agri-Mek SC

(abamectin)
 
Group 6

135 to 270 mL/ha
(55 to 110 mL/acre)

Apply in 200 L/ha (80L/acre) of water

 

 7
  • Use with 0.25 to 0.5% v/v non-ionic surfactant.
  • Repeat at 7 day intervals.
  • Do not apply more than 4 times per season.
  • Highly toxic to bees exposed to direct treatment, drift or residues from blooming plants.
  • Do not re-enter for 13 days for hand weeding, 4 days for hand-set irrigation, 1 day for thinning and 12 hours for all other activities.

Exirel

(cyantraniliprole)
 
Group 28

1000 to 1500 mL/ha
(405 to 605 mL/acre)

Apply in 200 L/ha (80 L/acre) of water

1
  • Suppression only.
  • Do not make more than 4 applications per growing season.
  • Repeat at 5 day intervals.
  • Do not apply more than 4.5 L/ha (1.8 L/acre) per season.
  • Use with an adjuvant such as Hasten NT at a rate of 0.25% v/v or MSO Concentrate with Leci-Tech at a rate of 0.5% v/v.
  • Toxic to bees and certain beneficial insects.  Apply early in the morning or late in the evening when bees are not active.
  • Note:  Do not tank-mix or apply in sequence with strobilurin-, copper- or captan-containing fungicides.
  •  Observe a plantback interval of 30 days for legume vegetables, cereals, grass, crop group 1A (inlcuding beets, carrots, radish, parsnip, turnip) and crop group 2 (inlcuding beet greens and turnip greens). 
  • Observe a plantback interval of 1 year for crops not on this label.
  • Do not enter treated area for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

OMRI-USA = Organic Materials Review Institute of USA

OMRI-Canada = Organic Materials Review Institute of Canada

 

Leek Disease Management

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Botrytis Leaf Blight

Chemical Control of Botrytis Leaf Blight
Product Rate PHI* Comments

Switch 62.5 WG

(cyprodinil & fludioxonil)

Group 9 & 12
 775 to 975 g/ha
(314 to 395 g/acre)

Apply in 200 L/ha (80 L/acre) of water		 7
  • Repeat using a 7 to 14 day application interval.
  • Do not make more than 3 applications per year.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not enter treated area for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Suppression of Stemphylium Leaf Blight

Chemical Suppression of Stemphylium Leaf Blight
Product Rate PHI* Comments

Aprovia

(benzovindiflupyr)
 
Group 7
 750 mL/ha
(300 mL/acre)

Apply in 150 to 600 L/ha (60 to 240 L/acre) of water		 7
  • Apply when plants are 5 to 10 cm high.
  • Repeat using a 7 to 14 day interval.
  • Do not apply more than 4 times per season.
  • Do not apply more than 3 L/ha (1.2 L/acre) per season.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).

 

Suppression of Purple Blotch

Chemical Suppression of Purple Blotch
Product Rate PHI* Comments

Inspire

(difenoconazole)

Group 3

364 to 512 mL/ha
(147 to 207 mL/acre)

Apply in 150 L/ha (60 L/acre) of water.		 7
  • Provides control.
  • Repeat using a 7 to 10 day interval.
  • Do not apply more than 1.53 L/ha (619 mL/acre) per crop per season.
  • Do not make more than 2 sequential applications before alternating to a fungicide with a different mode of action.
  • Observe a plantback interval of 60 days for crops not on label.
  • Do not re-enter treated area for 12 hours.

Miravis Duo

(pydiflumetofen & difenoconazole)

 

Group 7 & 3

1.0 L/ha (405 mL/ac)

 

Apply in 150 L/ha (60 L/ac) of water		 7
  • Repeat using a 7 to 14 day interval.
  • Do not make more than 2 consecutive applications before switching to a non-Group 7 & 3 fungicide.
  • Do not apply more than 3.0 L/ha (1.2 L/ac) per season.
  • See label for details on plantback interval.
  • Do not re-enter treated area for 12 hours.

Switch 62.5 WG

(cyprodinil & fludioxonil)

Group 9 & 12
 775 to 975 g/ha
(314 to 395 g/acre)

Apply in 200 L/ha (80 L/acre) of water		 7
  • Repeat using a 7 to 14 day application interval.
  • Do not make more than 3 applications per year.
  • Observe a 30 day plantback interval for crops not listed.
  • Do not enter treated area for 12 hours.

*PHI = Pre-harvest interval
BUFFERS – Refer to product label for buffer requirements, and consult the Vegetable Production Guide: Pesticide Regulations and Safety (PDF).
PESTICIDE GROUP DETAILS – see the Vegetable Production Guide: Pesticide Toxicity Table (PDF).