Phacelia tanacetifolia

Sowing and growing tips

Phacelia tanacetifolia seeds are best direct-sown where they are to flower. Wait until after the last frost and when the soil is workable; in mild climates, autumn sowing can provide winter cover and earlier blooms. Choose full sun and well-drained, moderately fertile soil, though this adaptable plant tolerates poorer ground. Prepare a fine seedbed, sow thinly, and keep the surface evenly moist until germination. Thin seedlings to maintain airflow; final spacing can follow packet guidance for medium-tall growth. Water to establish and during prolonged dry spells, avoiding waterlogging. Succession sowing every few weeks can extend the flowering window. Cut back spent stems to tidy and encourage fresh growth where conditions allow.

• Full sun; well-drained, moderately fertile soil; tolerates poorer soils.
• Direct-sow after last frost; autumn sowing in mild climates for winter cover and early bloom.
• Sow thinly, keep evenly moist to establish, then allow airflow; follow packet spacing for medium-tall plants.
• Pollinator-friendly: nectar-rich flowers support visiting insects.
• Ornamental: ferny foliage and coiled blooms add soft texture in mixed plantings.

How do I grow Phacelia tanacetifolia from seed?

Prepare a weed-free, fine tilth in full sun and well-drained soil, then broadcast or drill Phacelia tanacetifolia seeds thinly and cover very lightly (about a few millimetres). Keep the surface evenly moist until germination, which usually occurs quickly in warm soils. Direct sowing is preferred, as seedlings dislike root disturbance. Once established, thin gradually to allow airflow and reduce competition. Growth is fast, so keep moisture steady but avoid waterlogging. For a longer display, make small repeat sowings rather than a single dense sowing that matures all at once.

When should I sow phacelia in relation to the last frost?

Sow after the last frost when soil is workable and warming, as cold, wet ground slows emergence. In mild climates, an autumn sowing can provide winter cover and earlier blooms the following season. For continuous flowering, make successive sowings every few weeks through the growing period, pausing during extreme heat or drought. Where spring (Northern Hemisphere) / autumn (Southern Hemisphere) arrives early, earlier sowings are possible; where late frosts linger, wait until risk has passed to avoid seedling damage.

What spacing and height should I allow for lacy phacelia plants?

Phacelia tanacetifolia is medium-tall, typically reaching about knee to waist height depending on fertility and moisture. After seedlings establish, thin to roughly 20–30 cm between plants or clumps, keeping rows or patches open enough for good airflow. Sown thickly as a cover or filler, reduce density by thinning or cutting to limit lodging. In open, windy sites, taller stands may benefit from nearby support or from being grown in mixed plantings that offer shelter.

What are the cover crop benefits of phacelia, and how do I use it as green manure?

As a quick, soft-tissue cover, phacelia shades soil, helps suppress weeds, and produces fibrous roots that improve surface structure. It is often used to bridge gaps between crops or to protect bare ground. For green manure, cut it before seeds form—ideally at bud or early bloom—then chop and leave as a surface mulch or incorporate lightly into the top few centimetres of soil. Allow a short interval for residues to break down before sowing the next crop. In mild climates, autumn sowings can provide winter cover and early biomass.

Why is phacelia valued by pollinators and beneficial insects?

The blue-lavender, nectar-rich flowers open progressively along curled spikes, offering a steady resource over many days. This supports a wide range of pollinators, including various bees, and often attracts hoverflies and other beneficial insects that can help moderate pest populations. Staggered or successive sowings extend the flowering window, which is helpful when nearby crops or ornamentals need consistent pollinator activity.

Does lacy phacelia reseed easily, and how can I manage it?

Yes, if allowed to set and drop seed, phacelia readily self-sows, with seedlings appearing where soil is lightly disturbed. To limit spread, cut or pull plants soon after peak bloom, before seeds ripen; this also aligns with best practice for green manure use. If some self-seeding is desired, leave a few seed heads to mature and monitor volunteers the following season. Self-sown seedlings are usually easy to thin or hoe while small, helping keep phacelia where it is wanted.

Growing information provided here is general. Outcomes vary with microclimate, soil composition, drainage, and seasonal factors such as temperature range or rainfall. Product pages include specific instructions, including sowing windows (such as after last frost or when soil is workable), spacing, and other cultivation details tailored to each item’s characteristics.

Pollinator-Friendly Cover Crop Notes

Phacelia tanacetifolia seeds produce a fast-growing annual valued as a pollinator magnet and versatile green manure. Sow direct after the last frost when soil is workable and warming; in mild climates, autumn sowing may be possible for earlier spring color. Broadcast over a fine, weed-free seedbed or drill shallowly, covering 0.5–1 cm and keeping evenly moist. Germination is quick in warm conditions, with seedlings establishing rapidly into ferny foliage and airy, violet-blue blooms. For continuous flowering, make small, successive sowings through the suitable season. Plants typically reach medium height, smothering weeds and providing nectar for bees and beneficial insects. For soil improvement, cut down before seed sets and incorporate as a fresh mulch, or leave some plants to finish blooming where extended forage is desired. Works well as a gap-filler between crops, beneath young perennials, or as a stand-alone cover crop. Suitable for a range of soils with good drainage and full sun.