Phacelia tanacetifolia - Green manure

Phacelia tanacetifolia is a panacea for the garden: it is honey-producing, very aesthetic and fragrant, and it prevents leaching of the soil. Its roots aerate the soil and provide it with necessary nitrogen.

Phacelia tanacetifolia or Tansy-leaved Phacelia is an annual plant from the Boraginaceae family. Native to North America, it is useful in the vegetable garden for several reasons. As a highly honey- and nectar-producing plant, it attracts insects to the benefit of all other plants present. To attract these pollinators, it has developed a delicious scent. It also fits perfectly into an intelligent crop rotation system that enriches, aerates, and allows the soil to rest. Its abundant root system aerates the soil and prevents leaching during heavy rainfall. Crop rotation allows for the cultivation of plants with different nutrient requirements each year without depleting the soil too much. Generally four types of plots are considered, which are not necessarily grouped together:

• Plot 1 is dedicated to leafy vegetables
• Plot 2 is dedicated to fruiting vegetables
• Plot 3 is dedicated to grain vegetables
• Plot 4 is dedicated to root vegetables

A rotation is carried out from one year to the next, with leafy vegetables giving way to root vegetables, and so on. To allow the soil to rest and regenerate, a fifth step is increasingly added: the use of green manure, such as Phacelia.

This undemanding plant thrives in any type of soil, even the most difficult and dry, as long as it receives enough sunlight. Despite its wildflower appearance, it has a very sculptural habit with its scorpioid inflorescence curling up like a crozier as the small lavender-blue to deep blue flowers bloom. Its deeply cut foliage resembles that of tansy and quickly forms beautiful clumps over 1 m (3.3 ft) in height.

Finally, at the end of the season, this beautiful Phacelia serves as green manure, either directly buried in the soil or incorporated into compost to enrich it with nitrogen.

Harvesting: after flowering, the flowers form dehiscent capsules containing 4 very dark seeds. It is then time to mow it, grind it, and bury it in the soil to enrich it with nitrogen.

Storage: Phacelia tanacetifolia can be buried in the soil to enrich it with nitrogen or incorporated into compost with the same objective.

Gardener's tip: the dense root system of Phacelia tanacetifolia prevents the establishment of adventive plants. Knowing this, it can be beneficial to cultivate it in an area where you want to get rid of "weeds". However, it is necessary to weed before cultivating it.