Phacelia, a great green manure

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Best known as a green manure, phacelia is an annual plant that fertilizes and improves the soil, while preventing the proliferation of weeds.Very melliferous, it is also appreciated for the beauty of its lavender blue flowers.

Latin namePhacelia tanacetifolia
Common name : Phacelia, tansy-leaved phacelia
Family: Hydrophyllaceae

Type:  Annual herbaceous plant
Height:  Up to 1 m
Exposure : Sun
Soil : All

Planting : Spring/late summer – Flowering : Summer – Harvest : 2 months after sowing

Phacelia is a herbaceous plant , grown as an annual here, essential for permaculture or organic gardens. Indeed, this green manure has many advantages to improve the soil :

  • Rich in nitrogen and phosphorus, it fertilizes the soil and improves its composition
  • Its very deep root system aerates the earth and decompacts the soil
  • Endowed with a compact tuft, it limits the proliferation of weeds and avoids the beating of the rains , that is to say the formation of a crust on the surface of the soil.
  • Its flowers, very melliferous and nectariferous, attract foraging insects , useful for pollination, but also hoverflies and beetles , auxiliary insects very useful in the fight against pests.

To understand everything: Green manures, think about it!

Phacelia sowing

Where to sow it?

Phacelia is sown in the vegetable garden to improve the soil before vegetable crops . You can therefore sow it on a free plot or between rows of vegetables to prevent the growth of weeds. Or in the orchard!

It can also be sown in a bed or a border because it has pretty fine, cut foliage, quite similar to that of tansy, and very decorative lavender blue flowers. This flowering is also very useful because it attracts pollinating insects. It will be of the most beautiful effect in a massif of naturalistic or rural inspiration.

Undemanding, phacelia adapts to all soils , even the most difficult, with a preference for light soils.

It needs full sun.

When to sow it?

Phacelia is sown mainly in spring, from March until May. As it is fast growing, it mows 8 to 10 weeks after sowing. This makes it possible to take advantage of its benefits for the cultivation of summer vegetables.

Spring is the best time to sow phacelia because its ideal germination temperature is between 10 and 15°C.

You can also sow in late summer, in September . If you live in a region with a rather mild climate, it can bloom before winter. Otherwise, she will wait until next spring. And, in areas with harsher winters, it will freeze to the surface but its roots will continue to enrich the soil as it decomposes.

Sowing at the end of summer remains more uncertain than sowing in spring.

How to sow it?

Phacelia is sown broadcast at the rate of 1.5 g per m2.

  • Hoe and loosen the soil with a claw
  • Break up the clods well and remove the stones
  • Rake to level the ground
  • Broadcast sow very lightly, adding a little sand to the phacelia seeds
  • Cover with 1 cm of soil by scratching with the rake
  • Tamp lightly with the back of the rake
  • Water in fine rain.

Since Phacelia seeds are photosensitive , they need to be covered with a thin layer of soil to germinate. The emergence occurs in about ten days.

What maintenance for phacelia?

Phacelia requires regular watering during the emergence phase . Then, watering continues only in case of hot weather.

Otherwise, it does not require any special maintenance and grows very quickly. She is not susceptible to any disease.

Mowing phacelia

Phacelia mows but does not tear . Indeed, it is essential to leave the roots in the ground because they will enrich the soil by decomposing.

This mowing occurs just after flowering and before seed formation . Do not skip this step because phacelia reseeds itself easily and can become invasive.

Once you’ve cut your phacelia down to ground level, there are two ways to take advantage of it:

  • Either you leave the stems and foliage in place which will serve as mulch for future plantings. If you sowed in March, you can plant your tomatoes, courgettes, peppers…
  • Either you dry the leaves and stems for a few days before incorporating them into the ground. You can then plant your leeks, your cabbage…

You can also keep a few flowering plants in place to feed the pollinating insects. Before harvesting some seeds for the following season.

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