Growing Phacelia

Phacelia, also known as bee's friend, comes from the dry uplands of North America and belongs to the borage family (Boraginaceae). Since it is unrelated to any common vegetable family, it shares very few diseases and pests with them. That makes it an ideal companion plant in the vegetable garden.

As a green manure, phacelia is one of the most versatile plants in the home garden. It covers the soil quickly and densely, keeps weeds down and protects against erosion. Its fine, dense roots create a crumbly topsoil. After harvest it takes up leftover nitrogen and holds on to it over winter, then releases it again once you work it in. It does not fix nitrogen from the air, though, that job stays with the legumes. It won't break up a compacted subsoil either, and it is no help against nematodes. For those jobs, combine it with clover, vetch, lupins or nematode-resistant oil radish.

The blue-violet flowers are a magnet for bees, bumblebees, butterflies and hoverflies. If you grow phacelia in your garden, you do your pollinators a big favour.

Sow phacelia straight into the bed, raising seedlings indoors is pointless. The sowing window runs from mid-April to the end of September, depending on what you are after. Earlier isn't worth it, because the young plants won't survive harder late frosts. For a flowering bee pasture or a few blooms to draw in pollinators, sow from late April after the last frost. Sowings up to July still come into flower, later ones mainly give you the green manure effect.

The seeds germinate from 5 °C, ideally at 12 to 18 °C, and germination takes 7 to 14 days. Phacelia shrugs off light frost, at around -5 to -7 °C it dies back. If you don't want it to self-seed, mow the plants in good time before the seed ripens.

Phacelia is undemanding: sun to partial shade, and almost any soil will do, whether sandy, poor or loamy. The only exception is waterlogging, which it won't tolerate.

Keep the soil evenly moist for the first two weeks after sowing, after that it copes well with dry spells. It needs no feeding, it gets by on whatever is still left in the soil.

For the vegetable garden you don't need a fancy variety. Standard phacelia seed without a cultivar name does the job perfectly well.

Phacelia is easy to look after. After sowing, keep the soil evenly moist for about one to two weeks. Watering is only needed in extreme drought, feeding not at all.

There are two ways to work it in as a green manure. With spring or summer sowings, it is best to mow the plants when flowering starts, so roughly 5 to 8 weeks after sowing. Don't wait too long, because the first seeds are already setting at the bottom while flowers are still opening at the top, and cut seed heads carry on ripening. Let the plant remains dry off briefly, then work them shallowly into the soil without digging it over. That protects the soil structure. If you only sow in late summer or autumn, simply leave the plants standing. From about -5 °C phacelia reliably freezes off, and the dead remains stay on the bed as a protective mulch layer over winter. In spring you then work these remains in. If a late sowing does come into flower during a mild autumn, mow it anyway.

Whatever you do, cut the plants before the seed ripens, otherwise you'll have little phacelia seedlings everywhere next year.

In the home garden, phacelia is practically trouble-free. Diseases such as mildew or sclerotinia can show up now and then, but they are rarely a serious problem. Among pests, only slugs and snails are really worth mentioning, as they may go for fresh seedlings.

One important point: phacelia can carry verticillium wilt and should therefore not be grown before strawberries.

Phacelia is no help against nematodes, even though you often read otherwise. It is not a host for the beet cyst nematode, but it does multiply the northern root-knot nematode and can encourage the nematodes that transmit spraing in potatoes.

If you have sensitive skin, wear gloves when handling the plants, as phacelia can trigger contact allergies.