Swathing, Desiccation and Harvest
Harvest Timing:
Flax is ready for swathing or application of most desiccants when 75% of bolls or capsules have turned brown (90% in 2015 North Dakota Flax Production Guide). When 75% of bolls have turned brown, the boll and seed moisture contents are about 30% and 20%, respectively. Bolls that have turned yellow but still retain green tips/pedicels or have not begun to split between capsule sections are not classified as turned brown.
Swathing:
If you decide to swath, a stubble height of 4 – 6 inches is recommended to hold the swath off the ground and facilitate drying.
Flax stems are difficult to cut, especially when green and sharp cutter bars are necessary. Green stems are a major reason that desiccants are applied to flax.
Desiccants for Flax in Western Canada:
Diquat (Reglone, Reglone Ion, Desica or Diquash): Apply when 75% of bolls have turned brown. Stem degreening and dry down will normally occur within 10-14 days to allow harvesting.
Refer to the Guide to Crop Protection for pre-harvest intervals.
Desiccated flax should be combined as soon as the seed sample tests dry, to avoid capsule loss (boll drop) and weathering (dull grey/black) of seed.
Pre-harvest Perennial Weed Control:
Glyphosate: Do NOT apply if you intend to keep the crop for seed as glyphosate may reduce germination. Recommended stage for application is less than 30% seed moisture or when majority of bolls (75-80%) are brown. Manitoba research in the 1990’s reported highest yield when glyphosate was applied after 90% brown boll stage. Glyphosate is not a desiccant and therefore the rate of stem degreening and dry down is up to 2 weeks later than desiccants like diquat.
Flax with pre-harvest glyphosate application should be combined as soon as the seed sample tests dry, to avoid capsule loss (boll drop) and weathering of seed.
Straight Combining Flax:
Flax can be straight-combined since shatter losses are generally quite low (<1-3%). Short flax crops may be better suited to straight combining if a good swath can’t be anchored in the stubble. Although a few bolls may drop off standing plants during windy periods, this loss is usually very low. Standing crops can tolerate wet weather with less seed discoloration and grade loss than swathed flax.
During harvest, the flax seed coat can be damaged leading to grade loss and/or emergence issues if used for seed, so take care to properly adjust the combine. Turn fan speed down to avoid losing seeds. Check harvest losses when setting combine to make sure not too much seed is being lost with the chaff (especially critical if your field was subject to drought as seeds will be light). Straw choppers need to be sharp to cut and spread the straw evenly and this is important since poor straw distribution is very difficult to manage next spring in the field.
For more information on harvesting please refer to the Flax Grower Guide Chapter 10 – Harvesting, which is posted on the Flax Council of Canada website. For more information on desiccants or glyphosate, please refer to your Provincial Guide to Crop Protection and/or herbicide label.
