How to count 10-50% flower

June 28, 2017 - Issue 14

The spray window for sclerotinia stem rot is 20-50% flower and for cabbage seedpod weevil is 10-20% flower.

To assess flowering stage, count all “flowers” — which includes flowers, aborted flowers and developing pods — on the main stem. These numbers are based on plant densities above 8-10 plants per square foot. A thin stand can have more flowers on the main stem.

Count main stem flowers at a few sites in the field and take an average to come up with flowering stage for the field. For example, if you check 10 random plants and 3-4 are at 30% flower and some are at 0%, the average is probably around 15%.

Canola at 20% flower. Source: NDSU

Canola at 20% flower. Source: NDSU

At 10% bloom, the main stem will have around 10 “flowers”. It takes 2-4 days to go from first flower to 10% bloom.

At 20% bloom, the main stem will have 15 “flowers”. Canola can reach 20% bloom in 4-5 days after first flower

Petal drop starts after 30% bloom.

50% bloom is when the crop is at its “most yellow.” This is roughly when there are 20 “flowers” on the main stem, and side branches are starting to flower. This stage can last a week or more in crops with lower plant counts that result in higher numbers of secondary branching.

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