Ornamental · Boraginaceae
Lacy Phacelia
Phacelia tanacetifolia
Coiled sprays of lavender-blue bells uncurl over ferny foliage, alive with bees all summer.
Full sun
Every 5–10 days
42–56 days
USDA 3–10
Overview
Lacy phacelia is a fast annual from California and the western states, and its whole look lives up to the name: the leaves are cut into fine, fern-like segments in a soft gray-green, and the flowers ride in coiled sprays of lavender-blue bells that unroll from a tight curl like a fiddlehead. It belongs to the borage family rather than the daisies, though that feathery, tansy-like foliage often suggests otherwise. Up close it is all fine texture and cool color.
The flowers are the plant's real spectacle. Each coiled, one-sided cluster opens bell by bell, and from every small bloom the long stamens push well past the petals in a soft fringe that bees crowd over. It shows up in cover-crop and pollinator mixes far more than in flower borders, and it doubles as a green manure, its quick, leafy growth scavenging loose soil nitrogen and covering bare ground.
As an annual it moves fast, throwing up ferny growth and coiled flower spikes within a few weeks of sowing, then finishing in a single season. Sow it in spring or fall, give it sun and soil that drains, and stagger a few sowings to keep fresh blue clusters opening. Let the coiled heads ripen and dry, though, and it seeds itself back in the next year.
Care
The short version: phacelia wants full sun and well-drained soil, water only until its ferny growth settles in and then very little, succession sowing to keep the lavender-blue clusters coming, and a cutback before the coiled heads set seed.
Light
In full sun phacelia flowers most heavily and holds its ferny foliage upright and full. It will take partial sun or light shade, but the flowering thins there and the stems stretch pale and lean over.
Water
Water the young, ferny seedlings until they take hold, then ease off, because phacelia is drought tolerant once established and lives on 7 to 18 inches of rain or watering a year. Let the top half of the soil dry between waterings, and never leave the roots sitting in wet ground.
Soil
It grows best in well-drained sandy, gravelly, or loamy soil and holds up in the poor, dry ground that defeats fussier plants. The pH range is broad, from 6.4 to 8.5, so most garden soil suits it as long as the water drains away.
Temperature
Phacelia takes a wide span, from about 18°F to 95°F (-8°C to 35°C), and young plants shrug off a light frost. A hard freeze near the low end blackens the soft foliage outright, which is why it runs as a spring or fall plant rather than a winter one.
Humidity
Ordinary outdoor humidity is all it asks, so there is no figure to reach. Air movement counts more than moisture, since crowded, still plantings are where aphids film the stems and rot sets into the roots.
Feeding
Skip the fertilizer in all but the poorest soil. As a cover crop phacelia scavenges the nitrogen already in the ground rather than needing more, and an extra dose only forces soft, sappy, aphid-prone growth.
Pruning
There is no true pruning. Deadhead the spent, coiled clusters to keep fresh bells opening and to limit self-seeding, and as a cover crop, mow or till the whole leafy stand at flowering before it sets seed.
Repotting
none
Size & spacing
Plants stand 1 to 3 feet (30 to 91 cm) tall with a spread of about 8 to 18 inches (20 to 45 cm), the ferny foliage building into a soft mound. Sown thickly as a cover crop they knit into a dense sheet and crowd out weeds, while a thinner stand gives each plant room and better airflow.
When to plant
Phacelia moves on a short clock. Direct sow it in early spring once the soil is workable, or in fall where winters stay mild, and the first coiled clusters open about 6 to 8 weeks later. Stagger sowings every couple of weeks so fresh lavender-blue keeps unrolling, and know that a hard frost blackens the ferny foliage and 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 gives little trouble, and the few problems it does show read plainly on the plant, from yellowing ferny leaves in wet soil to specks massed on the stems. Match what you see below and step in early. A small change caught now rarely spreads through the stand.
New seedlings surfacing where nothing was sown
Watch the coiled seed heads as they age: they dry to a papery brown, split along their curl, and shed a heavy seed bank that stirs to life after the next rain. Timing is the answer. Mow, till, or pull the stand at peak bloom before the seed hardens inside those tight curls, and clip the finished clusters so none 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
Yellowing, slumping plants over blackened roots
In soggy ground the ferny leaves go slack and yellow and the whole plant slumps, while below the surface root rot softens the roots to a dark, mushy pulp and eats into the crown at the soil line. Once a plant has flopped there is no firming it up again, so lift it and mend the drainage. Sandy, gravelly, or loamy soil keeps the roots pale and firm.
Fix:
- Improve drainage and stop overwatering
- Remove and discard collapsed plants
Blue clusters browning and the plants sagging early
The brief flush is written into the plant. Phacelia is a short-lived annual whose lavender-blue clusters carry a few weeks per sowing before they fade and the stems sag, and the soft, ferny foliage turns black once a hard frost nears 18°F (-8°C). Sow a fresh patch every 2 to 4 weeks to keep that blue coming, and sow again once the cold has lifted.
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
Soft-bodied specks massed along the stems
Those pale, soft-bodied specks packed along the stems are aphids, drawn to the tender new growth and coating it in a shining, sticky film. A firm jet of water strips them off, and a scattered few are no real loss. The flowers keep their own patrol of hoverflies, lacewings, and parasitic wasps that thin the aphids down.
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 leaf, stem, or flower. The one thing to know is that the fine, glandular hairs on the foliage can leave an itchy rash on people who handle it and react, so wear gloves before pulling or mowing a stand.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat is safe among the ferny foliage. A nibbled leaf does no harm, since phacelia holds no toxin that affects them.
Dogs None
A dog can push through the soft, divided leaves or chew one without harm, and phacelia never appears on poison-control lists.
Horses Safe
Grazing horses take no harm from phacelia, foliage and lavender-blue flowers alike, since none of it is toxic to them.
Rabbits Safe
Rabbits can browse the feathery leaves freely, with no harmful compounds anywhere in the plant.
Livestock Safe
Cattle, goats, and sheep tolerate phacelia well, and the leafy, flowering growth is grown right in their pasture cover-crop mixes.
Birds Safe
Birds are safe here. Many pick at the dried, coiled seed heads, and the plant poses no poisoning risk.
People Safe
Nothing here will poison a person. The catch is the foliage itself, since its fine glandular hairs can leave an itchy rash on sensitive skin, so wear 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, though a close relative with deeper blue bells turns up in wildflower plantings. These are the two worth telling apart by eye.
Lacy phacelia (Phacelia tanacetifolia)
This is the standard cover-crop and bee-plant type, its foliage cut into fine, fern-like gray-green segments and its flowers held in coiled, one-sided sprays of lavender-blue bells whose long stamens push out well past the petals like fine threads.
California bluebell (Phacelia campanularia)
A related ornamental annual whose bells glow a deeper gentian-blue than the lacy type, carried on a lower, bushier plant and admired 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 its dried, coiled heads scatter on their 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 rises from small seed sown straight into its spot, set about a quarter inch under the surface once the soil cools below 68°F (20°C), since light and warmth above that hold the seed dormant. The first ferny seedlings break the surface in 15 to 30 days, the coiled lavender-blue clusters open about 6 to 8 weeks after sowing, and an established patch scatters its own seed freely from there.
Myths
Names like scorpionweed and fiddleneck mean phacelia is a dangerous garden plant.
Those names only trace the shape of the flower spike, the way each coiled, one-sided cluster curls over like a scorpion's tail or the crook of a fiddlehead, and they warn of nothing. Phacelia is one of the finest bee and beneficial-insect plants going, and it is non-toxic to pets and people. The single caution is a possible skin rash from handling the hairy leaves if you are sensitive.
Phacelia fixes nitrogen like clover or vetch.
Phacelia sits in the borage and waterleaf family, not among the legumes, so it adds no new nitrogen to the soil. As a cover crop its fast, leafy growth instead pulls up the nitrogen already there and stores it in stem and leaf, then releases it back as the plant breaks down.