Production Resources

Crop Rotation and Herbicide Rotation

Yield response data from MASC, recorded from 2011 – 2020 (10 year results), shows that flax responds best when seeded following a pea crop, with the next best response after corn (Table 2). It generally has the poorest yield response when seeded following any oilseed crop, for obvious reasons. Research has shown that flax performs poorly specifically after canola and/or mustard, and not only because of disease issues. The poorer performance of flax on canola stubble is attributed to mycorrhizae fungi which do not associate strongly with canola and decrease in presence during the canola crop’s growing season. When flax is grown on canola stubble, the mycorrhizae populations are lower, which leads to poorer early  season nutrient update, especially phosphorus, a relatively immobile nutrient in the soil that is crucial to early flax development.

Flax does well after cereals or corn. It also performs well after legume crops and alfalfa, but Rhizoctonia disease may be a problem. Flax does not do well after potatoes due to the loose seedbed and potentially Rhizoctonia in this rotation as well. According to MASC, the most common crop stubble that flax is seeded into is spring wheat in Manitoba and very few acres are seeded into pea stubble, so that flax-on-pea yield data in Table 2 could be seen as skewed. Crop rotation is extremely important when making all cropping decisions, but flax is a particularly sensitive plant to many outside factors and rotation should be paid considerably close attention to. It is recommended to have at least three years between flax crops on a field to control various soil-borne or stubble-borne diseases of flax, such as pasmo.

Table 1: Relative Stubble Yield Response (2011 – 2020). Source: Manitoba Agricultural Services Corporation.

Many crops, namely oilseeds, are sensitive to herbicide residues left in the soil from the previous year, or even longer. This is usually a result of a dry season that did not get enough precipitation to break down the herbicide residual in the root zone. When a sensitive crop to that herbicide is planted the next season, plant development can be affected. Knowing cropping and herbicide history is important as well as general historical precipitation events or amounts from the last 12 months is ideal to keep track of in order to seamlessly avoid development issues.

Manitoba Crop Alliance provides a succinct overview of Manitoba herbicide recropping restrictions in flax.

Variety Selection

In Manitoba 2024, flax market share was divided largely amongst five varieties: CDC Rowland (1), CDC Glax (2), AAC Bravo (3), CDC Sorrel (4) and CDC Esme (5), a brand new variety that was sold in small quantities.

• CDC Rowland covered the most flax acres in Manitoba in 2024, by a significant margin. It is identified by a violet flower, medium-sized bolls with characteristically large, brown seed. Rowland is defined as an early to mid-season maturation variety.
• CDC Glas was the second most popular flax variety in Manitoba last year. It has a blue flower, medium-sized brown seed found in a medium-sized boll.
• AAC Bravo is another blue-flowered and brown-seeded variety. Bolls will have a similar appearance to CDC Glas and a medium size.
• CDC Sorrel is the most mature variety in the top five list, referring to how long it has been available (2008). Sorrel is another variety with the typical medium-sized boll and brown-seeded, but can be more accurately identified by the medium blue coloured petals.
• CDC Esme is new to the Prairies and was made available to seed producers in 2025. It is characterized by its large, brown seed, slightly shorter stature and high yielding capabilities.

*All current Canadian flax varieties are immune to rust, moderately resistant to Fusarium wilt and powdery mildew.

Flaxseed varieties on the Prairies are improving consistently over recent years. Dr. Bunyamin Tar’an, flax and chickpea breeder at the Crop Development Centre at the University of Saskatchewan, developed CDC Esme and has more flax lines that have strong potential for registration on the Canadian Prairies. Dr. Tar’an has an experimental flax line that has been recommended for registration via Canadian Food Inspection Agency. This line will undergo a registration process and could be available for seed production in the next two years.

Seed Quality and Vigour Testing

Planting certified seed with good germination testing is extremely important with flax, as it is with all crops. Using certified seed ensures genetic purity for desired variety traits, such as disease resistance, lodging tolerance and maturity. Flax needs a strong start as it germinates and emerges from the soil, and choosing good quality seed that is free from pathogens and any cracking or surface imperfections is a simple and cost-effective way to promote good germination. Typically, bin-run seed can be affected by cracks and/or splits that occurred during harvest, which affects the germ and is an entry point for soil microorganisms or pathogens. Blighted or mouldy seed may also be found in stored flax, which is commonly a result of weathering.

All certified seed should be labelled with seed testing results. If not using certified seed, always send a sample for testing to a local seed testing laboratory. A germination test will determine the number of seeds that germinate under ideal conditions. Vigour testing determines the number of seeds that will germinate under less than ideal conditions. Some testing labs indicate that vigour results can be directly applied to seeding rate calculations by using as the emergence rate while others suggest that the difference between a germination test result and a vigour test result represents the expected mortality rate in the field (SaskFlax).

Fall-Applied or PRE Herbicide Application

“PRE” refers to either a pre-seed or pre-emergent herbicide application.

As mentioned earlier, flax needs a strong start in order to have a successful growing season, amongst other factors, of course. Flax does not compete well with heavy weed infestations, so fall or early spring applications of residual herbicides is an easy strategy to keep fields cleaner, longer and improve herbicide options in-crop. As of spring 2025, the following herbicides are registered for application head of a flax crop.

Table 2: Fall-applied herbicides registered for flax in Manitoba.

Table 3: Pre-seed herbicides registered for flax in Manitoba.

The following are registered additionally as a pre-emergent herbicide for flax, meaning they can be applied in spring prior to seeding OR up to three days after seeding flax safely.

Table 4: Pre-emergent herbicides registered for flax in Manitoba.

Please check Manitoba’s Guide to Field Crop Protection 2025 or the product label for full herbicide details prior to application in any situation.

Seed Bed Preparation

The ideal seed bed for flax is smooth, firm and moist for adequate seed to soil contact. Interestingly, flax has been found to have equal or better yields under reduced tillage (minimum or zero till) versus conventional tillage systems. This has been attributed to: (1) improved soil organic matter and soil moisture availability, (2) increased arbuscular mycorrhiza colonization and rooting capacity, and (3) reduction of early weed emergence compared with conventional tillage systems. If spring tillage is required, shallow tillage is recommended to maintain a firm seedbed. Deep tillage can reduce stand establishment therefore packing before or after seeding may be required.

Fertility and Placement

It is always suggested to soil test prior to seeding any crop in order to make an informed decision on fertilizer practices. Knowing what is currently in the soil and available to the crop is a great starting point that can avoid under- or over-fertilizing. Each crop has a range of removal rates of each nutrient that will aid in fertility practices as well.

Manitoba researchers were involved in the development of the Prairie Nutrient Removal Calculator, giving a general idea of nutrient removal rates for several key crops on the Prairies, including flax. Tools like this calculator are to be used as supplements for decision making and many factors need to be included when making an informed fertility plan, including soil testing.

Flax is very sensitive to seed-placed fertilizer and even low rates may cause seedling injury, so it is not recommended. Placing fertility requirements in a side- or mid-row band is typically safe with flax and depends more on the capacity of the equipment. Placing the full nutrient blend together does not reduce the efficacy of any of the individual components.

Fertility requirements for flax have not been updated in several years. Following soil test recommendations is an acceptable tactic, but there are may not be a soil test to support a decision. Current macronutrient recommendations are from 2001:

• Nitrogen:             2.6 – 3.2 lb Nitrogen per bushel of flax
• Phosphorus:        0.75 – 0.92 lb Phosphorus per bushel of flax
• Potassium:          1.6 – 2.0 lb Potassium per bushel of flax
• Sulphur:               0.5 – 0.6 lb Sulphur per bushel of flax

Seeding Timing

Typically, flax is seeded from May 1 to June 1. It may be seeded later as the bolls and seeds can stand and ripen in the fall without shelling while other crops like canola are being harvested. Prolonged exposure to fall weather, however, will reduce the quality of the harvested seed, make it ineligible for a food grade market and potentially affect overall yield. Early seeded flax can produce greater and more reliable yields, better control of later emerging weeds and reduces the risk of disease and insects by outgrowing the pest pressure.

MASC data has shown that flax has good yield potential until the last week of May (Figure 1), but yields decline as the calendar turns to June. MASC seeding deadline is June 20 for all of Manitoba.

Figure 1: Seeding Date vs. Average Yield Response (2010 – 2019). Source: Manitoba Agricultural Services Corporation.

Seeding Rate and Depth

Flax seeding rate reflects plant stand goals and the seed lot germination rating. A plant population of 30 – 40 plants/ft² is an average goal for Manitoba farmers. Some farmers note that increasing plant stand to greater than 40 plants/ft² can lead to lodging and have no benefit on yield. Factors like date, soil temperature or the use of seed treatment can be considered when making seeding rate decisions.

Flax should be seeded at a depth of 1 – 1.5 inches deep and into warm, moist soils for quick germination. Small, frail flax seedlings do not emerge well in soil crusting situations and are prone to drought if seeded too shallow.

More details on early season success of a flax crop can be found at https://mbcropalliance.ca/directory/production-resources/growing-flax-production-management-diagnostic-guide/.

Early Weed, Insect & Disease Pressures

Flax is well known for being an uncompetitive crop and having limited weed control options. In-crop herbicides are restricted to Group 1’s for grassy weed control and some Group 4 & 6 herbicides for broadleaf weed control. Due to the very specific herbicide options and herbicide resistant weed populations, it has become regular practice (as it is in most crops) to include a fall-applied, pre-seed or pre-emergence herbicide into the weed management program ahead of flax. In-crop herbicides are commonly registered for application for flax at 2 – 6 inches tall. A grassy weed herbicide, like clethodim, will be safe for a longer period of time.* For best weed control using any herbicide, target weeds at their seedling stage, when they are at their most vulnerable and use appropriate water volumes for good coverage.

Weed control is not only reliant on herbicide applications. Some effective cultural management strategies include:

• planting a competitive variety
• use narrower row spacing
• higher seeding rates
• fertilizer placement to optimize uptake by the crop
• early seeding dates

*Always check herbicide label prior to applications and follow carefully.

Insects are not a typical concern in flax until a little later in the season, when there is more plant tissue to feed on and/or flower or boll development.

Cutworms are not often an economic threat to flax, though they are fairly non-selective feeders. In fact, it may be more common for present cutworms to feed on weed populations in a flax crop than the actual flax itself.  Economic threshold for cutworm presence in flax is 4 – 5 larvae/m², however loss of some plants may be compensated for by neighbouring plants.

Early disease development in flax is less common than it once was because of varietal improvements. Fusarium wilt and seedling blight can still be spotted on the odd plant and hopefully maintained within a small population.

Early fusarium wilt infections can kill seedlings after emergence, while later infections may cause chlorosis and wilting of leaves, followed by necrosis and death of plants. An identifying factor when dead plants are found is ashy grey roots when plants are pulled up. Affected plants may form a “shepherd’s crook” where the top of the plants is turned downward, though this can also be a symptom of improper herbicide applications.

Seedling blight is another difficult diagnosis because early season death or yellowing can be so many different things, most commonly attributed to environment. In this case, blighted seedlings turn yellow, wilt and die and this can occur in single plants or in patches. Roots of recently affected plants show reddish to brown lesions, later turning dark and shriveling up.

Flax relies on a good crop rotation for success, and 3 years between crops would tend to be the shortest break that would be recommended. This is not unlike other oilseed crops that do have significant disease pressures to avoid. Use of certified flax seed is highly recommended to avoid diseases coupled with resistant varieties and solid, uncracked seed. Use of seed treatment is also suggested in flax to promote good vigour in germinating seed as well as protection from seedling diseases.

More details on early season success of a flax crop can be found at https://mbcropalliance.ca/directory/production-resources/growing-flax-production-management-diagnostic-guide/.