Phacelia: sowing, location & flowering


I studied horticultural sciences at university and in my free time you can find me in my own patch of land, growing anything with roots. I am particularly passionate about self-sufficiency and seasonal food.

Favourite fruit: quince, cornelian cherry and blueberries
Favourite vegetables: peas, tomatoes and garlic

Phacelia (also called scorpionweed) is a delight in the garden, not only to bees. We reveal what to consider when sowing, planting and caring for Phacelia.

A bee visiting phacelia
Phacelia offers bees in particular plenty of food [Photo: Robert Lessmann/]

Phacelia can be found in harvested fields in the autumn as a green manure and in many seed mixtures for the home garden or balcony box. In this article, you will learn what makes the Phacelia so attractive for people and nature.

Phacelia: flowering time, origin and characteristics

Phacelia is a genus of the family of hairy-leaved plants (Boraginaceae) native to the Americas, which also includes viper’s bugloss (Echium vulgare), comfrey (Symphytum officinale), and forget-me-not (Myosotis sp). The Phacelia genus includes about 150 different species that grow as annuals, biennials, or perennials. In our country, however, we use and know only the annual, non-hardy lacy phacelia (Phacelia tanacetifolia). Its leaves are double finned and resemble the foliage of tansy (Tanacetum vulgare) in shape. It can grow up to a height of 120 centimetres and forms long flowerheads that unroll outward and bloom starting from the centre towards the top. The individual flowers have five lobes and the petals are white, purple or blue. The stamens and stigmas protrude conspicuously far from the flower. The tansy-leaved phacelia blooms from June to October, depending on the sowing date, and offers large amounts of very sugary nectar to eager pollinators. This property also makes it a particularly popular plant with beekeepers.

The most beautiful varieties

  • Phacelia tanacetifolia ‘Angelia’ displays a strikingly beautiful light blue flower. This variety is undemanding and drought tolerant. It quickly forms a lot of biomass and is therefore well suited as a green manure plant.
  • Phacelia tanacetifolia ‘Stala’ bears light purple to white petals with darker stamens. It is an annual and well suited for freezing winter planting.
  • Phacelia campanularia ‘Blue Bonnet’ produces a stunning display of royal blue, accentuated by large white stamens. It can grow up to a height of about 25 cm and blooms already 8-10 weeks after sowing.
  • Phacelia grandiflora ‘Summertime Blues’ delights us with a blend of royal blue petals, white calyx and stamens. This annual variety grows 40-60 cm high.
Flower of the phacelia campanularia
The P. campanularia shines in a strong blue [Photo: SF photo/]

Sowing Phacelia

The Phacelia species and varieties used in our latitudes are annuals and are propagated by sowing. Everything you need to know about growing scorpionweed in your own garden can be found here.

The right location

Phacelia is generally quite undemanding and drought tolerant. It likes deep, humus-rich soils with good drainage, but will grow in pretty much any soil that does not become waterlogged.

How to plant Phacelia seeds

The small, brown and conspicuously fluted seeds are sown directly into the soil between April and September. The depth of sowing is between 1 and 2 cm. A row spacing of about 15 cm gives the Phacelia room to spread its leaves. Larger areas can be sown widely, lightly worked in then rolled over. During the short germination period of about 10 days, the soil should always be kept well moist.

A wild flower meadow
Species-rich flowering meadows provide habitat and food for numerous species [Photo: Jurgen Bauer Pictures/]

Plant care

The first flowers appear after only 5 to 8 weeks, depending on the variety. Until then, some watering should be done at least during extremely dry periods. Otherwise, the phacelia does not require any care. For propagation, you can let some flowerheads mature and harvest the seeds. Let them continue to dry indoors. The seeds are germinable for about 4 to 5 years.

Is Phacelia poisonous?

The scorpionweed is not poisonous, but all Phacelia contain skin irritants that can cause an allergic reaction. You should therefore wear gloves whenever handling this bee friendly plant. Phacelia is also harmless to animals, it is considered a harmless food plant.

Phacelia is non-toxic to humans and animals but can cause skin irritation

Use of phacelia as green manure

The tansy-leaved Phacelia does not require fertiliser during its short growing season; it roots to a depth of 60 cm and helps itself to the available nutrients. Many plants do not even reach such depths, but the Phacelia brings the minerals up, first incorporating them into its biomass and later serving as green manure itself. If cultivated in spring, scorpionweed is mulched and incorporated into the soil after flowering and before the seeds ripen. If sown in late summer or autumn, Phacelia can be left until the first frosts in October or November. It reliably freezes and remains as a storehouse of nutrients until spring. At this time of year, it is incorporated into the soil and as soon as it gets warmer, the hungry soil organisms start decomposing.

Phacelia is visited with preference by various species of bees, as it is one of the few nutritious flowering plants in summer, offering both nectar and pollen. This makes the plant highly appreciated not only by beekeepers and is popularly known as “bee friend”.