Phacelia tanacetifolia
Lacy phacelia
Common names: Blue tansy, Purple tansy
At a glance
- Light
- Full sun
- Lifespan
- Annual
- Hardiness
- Cold damage below −5 °C
- Water need
- Low
Photo: Copyright by Curtis Clark, licensed as noted · CC BY-SA 2.5 · Source
Description
Phacelia is the universal green manure. It grows rapidly, shades the soil, suppresses weeds, and attracts masses of bees and hoverflies with its violet-blue tubular flowers. Because it is not related to any vegetable family, it can be used as a cover crop in any crop rotation.
Care instructions
Sow Phacelia from April to September in a wide scatter or in rows directly into the bed and lightly rake it in. It germinates in the dark, so cover the seed well. Water after sowing, then it tolerates little water. Cut or roll it down at the latest at flowering, before it senesces, and leave it as mulch or incorporate it flat; it will freeze safely over winter.
The care notes were machine-translated from German.
Garden year
SowingApr–Sep
Germination
- Soil temperature
- from 5 °C, ideally 18 °C
- Days to sprout
- 5 to 14 days
- Light
- Needs darkness to sprout
- Sowing depth
- 1 cm
- How to start
- Sow straight into the bed
Soil & site
Soil pH
Soil type
sandy, loamy, clayey, well-drained, lean
Lacy phacelia is remarkably tolerant of soil: it grows equally well on sandy, loamy and clay soils, as long as the soil is free-draining. It does not tolerate waterlogging. You can also sow it successfully on nutrient-poor and dry sites. With its fine, densely branched root system it loosens the topsoil and improves soil structure, especially as a green manure.
Feeding
Light feeder
Lacy phacelia needs no feeding; it is itself the fertiliser. If you use it as a green manure, work the plant material shallowly into the soil shortly before or at the start of flowering; as it rots, it releases nutrients and organic matter to the following crop. As a bee pasture, simply let it flower and mulch it afterwards. Fertiliser of its own is neither necessary nor sensible.
Overwintering
Lacy phacelia is an annual and dies back completely in the first harder frost. You do not need to overwinter anything actively; leave the dead stems lying as mulch over winter. For next year, let a few plants set seed or collect seeds and sow directly outdoors again from March.
Propagation
Methods
- From seed
Lacy phacelia is an annual and can be propagated only by sowing. Sow the seeds directly outdoors as soon as the soil is frost-free, typically from April to the end of August in Central Europe. Phacelia is a dark germinator: cover the seeds with about 1 to 2 cm of soil or work them in lightly, and keep the seedbed evenly moist. Germination takes about 10 to 15 days, and the first flowers appear after just 6 to 8 weeks. If you want to save your own seed, let a few flower heads ripen fully, harvest the seeds and dry them further in a cool, dry place. That gives you seed for next year. Note: phacelia self-seeds readily, and the seeds are viable just 2 to 3 weeks after flowering. If you leave spent stems standing, the seeds drop by themselves and germinate in spring; if you want to avoid that, cut back in good time. For continuous flowering from spring to autumn, you can stagger the sowing and make a new sowing every few weeks.
Companion planting
Good neighbors
nightshade family (Solanaceae)
Borage attracts pollinators and is supposed to keep tomato pests away from the nightshade family.
For example Sweet pepperCocktail tomatoEggplantCape gooseberryChiliPointed pepper and 12 more species in the catalogue
Source: organic greenhouse companion planting practice
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
Some of these explanations were machine-translated.
For your garden
Grow Lacy phacelia yourself
Gartenkern tells you when frost is coming, when to sow and when to harvest, for your location.
Free, no time limit
Notes from real gardens
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From the magazine
Green Manure Through the Winter Half-Year: No Bed Goes Bare Into Winter
Frost-killed or winter-hardy? How to cover empty beds with green manure in late summer, which type fits when, and how to work it in properly come spring.
Green Manure That Hums: Feed Your Soil and the Bees at Once
Sow a flowering cover crop after harvest and you protect the soil while filling the late-summer nectar gap for bees.