Sowing & Growing: Phacelia

Phacelia (Phacelia tanacetifolia) does not fix nitrogen but is a fast growing, high biomass, annual nitrogen holding crop. The flower is eye-catching, lavender to pale blue/white in colour and very attractive to bees. It takes 6-8 weeks for phacelia to flower from sowing.

Phacelia is effective at preventing nitrogen leaching and suppressing weeds due to its fast establishment. Although not known as a deep rooted species, its dense zone of shallow roots are very good at conditioning the top 3-4 cm of soil.

It can be combined in a mixture with other fast establishing species like mustard, the annual clovers or buckwheat.

When to Sow: As it is a fast establishing species, sow from mid spring until early autumn after the risk of frost has passed.

Sowing Rate: 1.0 g/m2 - 4 kg per acre - 10 kg per ha.

Preparation: The most successful results come from sowing into a newly prepared seedbed. Aim to cultivate the top soil to about 5cm, with a light cultivator or discs. The finished seedbed should be fine but firm, with no clods. Several passes with a cultivator may be needed to achieve this.

Sowing: The seed of phacelia is very small, it should be shallow sown at no more than a few mm under the surface to ensure it has some darkness to germinate.

Management: Phacelia generally does not need topping and may survive through very mild winters however prolonged frost will normally kill the plant. 

Be aware that phacelia can quickly produce viable seeds 2-3 weeks after flowering. If allowed to drop, these could become a nuisance. If seed drop is a risk, destroy at or just after flowering by flailing.

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Date Posted: 20th January 2023