Ornamental · Boraginaceae
Lacy Phacelia
Phacelia tanacetifolia
Sow it once and watch the bees arrive, a haze of lavender-blue that pulls in pollinators all summer.
Full sun
Every 5–10 days
42–56 days
USDA 3–10
Overview
Lacy phacelia is a fast, easygoing annual from California and the western states, named for its fine, fern-like leaves and the coiled sprays of lavender-blue bells that uncurl like a fiddlehead. It belongs to the borage family, not the daisies, though the tansy-like foliage fools plenty of gardeners. Few plants this simple to grow pull their weight quite so hard.
Its real claim is the draw it has on bees. Honey bees, native bees, hoverflies, and parasitic wasps all work the flowers, which is why it turns up in cover-crop and pollinator mixes more than in flower borders. Gardeners also grow it as a green manure, since it scavenges loose soil nitrogen and smothers weeds while it grows.
Treat it as a quick annual that flowers a few weeks after sowing and lives only a season. Sow it in spring or fall, give it sun and soil that drains, and stagger a few sowings if you want bloom that lasts. Let it run to seed, though, and it comes back uninvited the following year.
Care
The short version: full sun and well-drained soil, water only until it settles in, then leave it nearly alone, sowing in succession for a long bloom and cutting it back before it seeds.
Light
Give phacelia full sun for the heaviest bloom and the strongest pull on bees. It will take partial sun or light shade, but flowering thins out in shade and the plants stretch and flop.
Water
Water young seedlings until they take hold, then ease off, because phacelia is drought tolerant once established and gets by on 7 to 18 inches of rain or watering a year. Let the top half of the soil dry between drinks, and never leave it sitting in wet ground.
Soil
It thrives in well-drained sandy, gravelly, or loamy soil and shrugs off poor, dry ground that defeats fussier plants. The pH range is wide, anywhere from 6.4 to 8.5, so most garden soil suits it as long as it drains.
Temperature
Phacelia handles a broad span, from about 18°F to 95°F (-8°C to 35°C), and young plants take light frost. A hard freeze near the low end of that range kills the foliage outright, which is why it works as a spring or fall plant rather than a winter one.
Humidity
Ordinary outdoor humidity is all it asks, so there's no figure to hit. Air movement counts for more than moisture in the air, since crowded, still plantings are where aphids and rot get a foothold.
Feeding
Skip the fertilizer in all but the poorest soil. As a cover crop phacelia scavenges nitrogen already in the ground rather than needing more, and an extra dose just grows soft, aphid-prone foliage.
Pruning
There's no real pruning to do. Deadhead spent flower clusters to keep the bloom coming and to head off self-seeding, and if you're growing it as a cover crop, mow or till the whole stand at flowering before it sets seed.
Repotting
none
Size & spacing
Plants reach 1 to 3 feet (30 to 91 cm) tall with a spread of about 8 to 18 inches (20 to 45 cm). Sown thickly as a cover crop they knit together and crowd out weeds, while a thinner stand gives each plant room and better airflow.
When to plant
Phacelia runs on a short clock. Direct sow it in early spring once the soil can be worked, or in fall where winters stay mild, and it blooms about 6 to 8 weeks later. Stagger sowings every couple of weeks for color that carries on, and know that a hard frost ends the stand.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Generally direct-sown; if starting indoors, sow 4 to 6 weeks before last frost in darkness (light inhibits germination)
- Plant: Direct sow in early spring when soil is workable, or in fall in mild-winter climates; sow seed about 0.25 inch deep when soil temperatures are below 68 degrees F
- Harvest: Late spring through summer; blooms roughly 6 to 8 weeks after sowing over a long period
Hardiness
USDA hardiness zones: 3–10
Temperature: down to -40°C
Troubleshooting
Phacelia has few real troubles, and most of what goes wrong traces back to wet soil or its own eagerness to reseed. Match what you see below and step in early. A small problem here is easy to head off before it spreads.
Volunteer seedlings popping up where you never planted them
Phacelia self-sows hard when the coiled seed heads dry and shatter, dropping a seed bank that flushes after the next rain. The fix is timing. Mow, till, or pull the stand at peak bloom before the seed matures, and deadhead spent clusters so they never ripen.
Fix:
- Mow, till, or pull plants at flowering before seed matures
- Deadhead spent flower clusters before they dry and shatter
- Hand-pull or hoe volunteer seedlings while young
Wilting, yellowing plants with dark rotted roots in wet soil
Phacelia hates wet feet, and soggy ground brings on root rot that turns the roots soft and dark and rots the crown at the soil line. There's no saving a collapsed plant, so pull it and fix the drainage. Plant in sandy, gravelly, or loamy soil and steer clear of low spots that stay wet.
Fix:
- Improve drainage and stop overwatering
- Remove and discard collapsed plants
Flowers fade fast and the planting fizzles out early
This is just the plant's nature. Phacelia is a short-lived annual that flowers for a few weeks per sowing, and its tender foliage blackens once a hard frost hits near 18°F (-8°C). Sow a fresh patch every 2 to 4 weeks for bloom that carries through the season, and replant after the cold passes.
Fix:
- Make successive (succession) sowings every 2 to 4 weeks to extend continuous bloom
- Replace winterkilled plantings with a new sowing once frost danger passes
Sticky stems crowded with small soft-bodied insects
Those clusters are aphids, which gather on lush or stressed new growth and leave a sticky honeydew behind. A strong jet of water knocks them off, and light numbers are worth leaving alone. Phacelia draws in hoverflies, lacewings, and parasitic wasps that clean up aphids for you.
Fix:
- Spray off colonies with a strong jet of water
- Tolerate light infestations, as phacelia attracts predatory and parasitic beneficial insects that help control aphids
Toxicity
Phacelia is safe company in the garden, non-toxic to pets, livestock, and people alike, with no poison in any part of the plant. The one thing to know is that the hairy foliage can leave an itchy skin rash on people who handle it and react, so glove up before pulling or mowing a stand.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to be around. A cat that nibbles the foliage isn't at risk, since phacelia carries no toxin that troubles them.
Dogs None
No concern here. Dogs can brush past or chew a leaf without harm, and the plant is absent from poison-control lists.
Horses Safe
Grazing horses come to no harm from phacelia, which holds nothing toxic to them.
Rabbits Safe
Rabbits can browse the leaves freely, with no toxic compounds to worry about.
Livestock Safe
Cattle, goats, and sheep tolerate phacelia well, and it's often grown right in their pasture cover-crop mixes.
Birds Safe
Birds are in no danger. Many visit the seed heads, and the plant poses no poisoning risk.
People Safe
Nothing here will poison you. The one caveat is the foliage, since its glandular hairs can leave an itchy skin rash on sensitive people, so pull on gloves before handling or mowing a stand.
Phacelia foliage bears glandular hairs and contains skin-sensitizing compounds (geranylhydroquinone and related substances). Some people develop allergic contact dermatitis (an itchy skin rash) from handling the leaves. Wear gloves when handling or terminating the plants if you are sensitive, and supervise children who handle the foliage.
Varieties
Most seed sold as phacelia is the standard lacy type, but a close cousin shows up in wildflower plantings. These are the two worth telling apart.
Lacy phacelia (Phacelia tanacetifolia)
The standard cover-crop and bee-plant type, with finely cut fern-like gray-green leaves and coiled, one-sided sprays of lavender-blue bell flowers whose long stamens stand well clear of the petals.
California bluebell (Phacelia campanularia)
A related ornamental annual grown for its deep gentian-blue bells, staying lower and bushier than lacy phacelia and prized as a desert wildflower rather than a cover crop.
How to propagate
Phacelia grows from seed and nothing else, and it does so readily, both from a packet you sow and from the seed a standing patch drops on its own.
SeedEasy
Direct sow in early spring, or in fall in mild-winter climates; make successive sowings to extend bloom · Germinates in about 15 to 30 days; flowers roughly 6 to 8 weeks after sowing
Phacelia comes easily from seed sown right where it will grow. Set it about a quarter inch deep once the soil drops below 68°F (20°C), since light and warmth above that point hold germination back. Seed breaks ground in 15 to 30 days and flowers about 6 to 8 weeks after sowing, and the plant self-sows freely once a patch is going.
Myths
Names like scorpionweed and fiddleneck mean phacelia is a dangerous garden plant.
Those names just describe the coiled, scorpion-tail shape of the flower clusters, not any danger. Phacelia is one of the best bee and beneficial-insect plants you can grow and is non-toxic to pets and people. The only real caution is possible skin irritation from handling the hairy foliage if you're sensitive.
Phacelia fixes nitrogen like clover or vetch.
It belongs to the borage and waterleaf family, not the legumes, so it adds no new nitrogen to the soil. As a cover crop it pulls up and stores the nitrogen already there, then hands it back as it breaks down.