NRCS−Montana−Technical Note−Plant Materials−MT-113 1 

United States Department of Agriculture

NATURAL RESOURCES CONSERVATION SERVICE

Plant Materials Technical Note No. MT-113

August 2016

PLANT MATERIALS TECHNICAL NOTE

LACY PHACELIA

Phacelia tanacetifolia Benth.

A Native Annual Forb for Conservation Use in Montana and Wyoming

Robert Kilian, Rangeland Management Specialist, NRCS Plant Materials Center,

Bridger, Montana

Honeybee utilizing lacy phacelia (NRCS photo).

General Description

Lacy phacelia, Phacelia tanacetifolia, is a cool season annual forb, native to the southwestern 

United States, (Arizona and California) and northern Mexico, but not native to Montana and 

Wyoming. It has several alternate common names including lacy scorpion-weed, tansy leaf 

phacelia, blue tansy, and purple tansy. Phacelia is listed in the top 20 pollen producing flowers 

for honeybees, and is highly attractive to pollinator insects including bumblebees and hoverflies. 

It provides a source of high quality nectar and pollen. It also is desired as a cut plant for its 

persistence in floral arrangements.

Lacy phacelia is in the Hydrophyllaceae (waterleaf) family, and is a rapidly growing broadleaf 

with branched cyme inflorescences, one-sided with dense buds and flowers on a coiled rachis. 

Flowers are radial, five-lobed lavender-blue, bell-shaped, with long and feathery stamens. It has 

a single-sided inflorescence that curves into a fiddlehead shape, producing nectar and pollen.

Larger leaves are helically alternate, pinnately compound, with toothed to lobed leaflets, 

creating a tansy leaf appearance. Stiff hairs are found on the leaves and stem. Rooting depth 

has been reported from 10 to 30 inches, and the species is considered tap rooted with fibrous 

side roots. Growth form is a single stem at the base with 2 to 3 ascending branches off the main 

stem, reaching 6 to 40 inches in height.
NRCS−Montana−Technical Note−Plant Materials−MT-113 2 

Adaptation or Range

Lacy phacelia performs well in many soil types, but grows best in open, fertile, light-textured, 

and well-drained soils within a pH range of 6.4 to 8.5. It is fairly drought tolerant, and grows well 

given 7 to 18 inches of annual precipitation or irrigation. Lacy phacelia is not considered winter 

hardy and suffers winter kill at approximately 18o F. It should be seeded in early spring when

attracting pollinators and seed production is desired. It should be planted late fall when used as 

a winter killed cover crop for biomass production or to scavenge excess nitrates in the soil. 

Seeds germinate within 15 to 30 days, and germination rates increase with rising soil 

temperatures above 37o to 68o F. At soil temperatures greater than 68o

 F, the percentage

germination decreases with total germination inhibition at 86o

 F. It has not been found growing 

outside of cultivation in Montana or Wyoming.

Lacy phacelia, Bridger Plant Materials Center, Carbon County, Montana (NRCS photo).

Conservation Uses

This non-leguminous forb initiates flowering 45 to 60 days after emergence and has a flowering 

period lasting from 6 to 8 weeks, making it desirable in pollinator enhancement and cover crop 

plantings. Lacy phacelia is fairly competitive and establishes well in cover crop and pollinator 

mixes. It forms arbuscular mycorrhizal fungi associations, and rates “fair” for increasing soil 

organic matter as its biomass decomposes quickly.

Lacy phacelia is used extensively in Europe in “catch crops” (cover crops), pollinator plantings, 

and for intercropping for bio-control benefits. When planted as an intercrop it attracts hoverflies 

which feed on nectar and pollen, and then lay their eggs on the underside of leaves of 

associated crops. The hoverfly larvae, a predator of leaf aphids, have shown a significant 

reduction of this insect pest in sugar beets. 

Lacy phacelia is considered non-toxic, but it is a nitrate accumulator and should be used in a 

mix when fed to livestock. Protein content ranges from 6.7% to 19.8% at the pre-bloom stage. 

Ease of Establishment

Lacy phacelia seeds germinate readily in 15 to 30 days without treatment. Germination is 

inhibited by light and temperature, so plant seeds 1⁄4-inch deep and plant when soil 

temperatures are below 68o F. Soil temperatures can vary greatly depending on location and 

should be considered when planning late spring or summer plantings.
NRCS−Montana−Technical Note−Plant Materials−MT-113 3 

Planting Rates (all recommended amounts based on pure-live-seed [PLS])

Direct Seeding. The full stand drill seeding rates listed in Table 1 are based on 12-inch wide, 

between-row spacing on a favorable (non-critical area) site, and should be used as approximate 

guidelines. With its potential for slow establishment and relatively shallow roots, a 

recommendation for lacy phacelia seeding in critical areas is not provided. Forbs are seldom 

seeded in pure stands except for production purposes. Seeding rates vary by percentage in the 

mix, row spacing, and planting method (drill versus broadcast). Seeding rates by planting 

method and site condition are shown in Table 2.

Table 1. Seeding specifications for conservation plantings of lacy phacelia.

Seeds/

Pound 1/

Seeding

Date

1 PLS

Pound/Acre 

Rate 2/

Full Stand Rate 3/ 

PLS seeds/ft2 lbs. PLS/ac

244,944

spring/early 

summer 5.6 20 3.5

1/ Number of pure live seeds (PLS) per pound. 2/ Number of PLS seeds per linear or square foot at 1 pound PLS/acre rate. 3/ Full stand drill seeding rate in PLS pounds per acre with 12-inch, between row spacing on a favorable site. 

Table 2. Seeding rates for lacy phacelia as determined by planting method and site condition.

Non-Critical

Drilled

lb. PLS/ac

Non-Critical

Broadcast 1

lb. PLS/ac

Critical Area

Drilled 1/

lb. PLS/ac

Critical Area

Broadcast 2

lb. PLS/ac

3.5 7 N/A N/A

1/ Multiply the non-critical drill rate times 2. 2/ Multiply the non-critical drill rate times 4.

Seeding rates for annual phacelia in cover crop mixes depend on the desired percentage of 

annual phacelia in the stand. If there is an erosion concern, add a faster germinating species 

such as annual buckwheat Fagopyrum esculentum to the mix. 

Stand Establishment

For best results, seed should be planted into a firm, weed-free seedbed in early spring after the 

soil has reached a temperature of 40o

 F, and the danger of a killing frost has passed. It is 

recommended to drill the seed to a 1⁄4-inch depth to ensure a uniform seeding depth, although 

broadcast seeding followed by cultivation may also be successful. Seeding a forb component in 

alternate-row or cross-planting (forb in one direction and grass in the other) configurations may 

ensure better forb establishment. Adjust seeding rates accordingly for these types of plantings.

Refer to Plant Materials Technical Note, MT-78 (Rev. 1), Calculating Seeding Rates when Using 

Alternate-Row and Cross-Seeded Planting Techniques. 

Seed Production

Seed production specifications for lacy phacelia are shown in Table 3. Harvest by direct 

combine before more than 10% of the seed heads have turned brown and fluffy. Harvested 

material must be dried to prevent mold and decay. Seed production rates are highly variable 

and have been reported from 150 lbs. in eastern Texas to 800 lbs. in eastern Oregon. Table 3 

lists seed production from the Mediterranean region of Turkey and eastern Oregon. 

 
NRCS−Montana−Technical Note−Plant Materials−MT-113 4 

Table 3. Seed production approximations for lacy phacelia.

Row Spacing Seeding Rate Irrigated Seed Yield

inches PLS/ft2 Lbs. PLS/ac bulk lbs./ac

7 26 4.6 438

Biomass Production

Lacy phacelia produces relatively abundant biomass, especially in temperate climates. The 

biomass, however, breaks down quickly, and may not increase long-term soil organic matter. 

The decomposition of lacy phacelia residue can be slowed by growing this species in 

combination with a cereal grain or other durable residue species. 

On January 30, 2015, a frost planting study at the Bridger Plant Materials Center (BPMC) that 

included VNS (variety not stated) lacy phacelia was seeded. Plots were sown as solid stands, 

on 14-inch between-row spacing, at a seeding rate of 35.5 seeds per linear foot, and maintained 

as a dryland planting. Shoot biomass of lacy phacelia ranged from 1,492 pounds per acre to 

1,924 pounds per acre with a mean production of 1,650 pounds per acre (see Figure 1). This 

was greater than 7 of the 11 other tested species/varieties. Root biomass was not sampled.

Figure 1. Mean biomass weights, cover crop frost seeding study, Bridger, Montana. 2015.

A spring planting date study was installed at the BPMC (planting dates of March 30, 2015 and 

April 22, 2015), that included VNS (variety not stated) lacy phacelia. Plots were sown as solid 

stands, on 14-inch between-row spacing, at a seeding rate of 15.5 PLS seeds per linear foot, 

and maintained as a dryland planting. Shoot biomass of VNS lacy phacelia when planted on 

March 30 ranged from 2,222 pounds per acre to 5,144 pounds per acre with a mean production 

of 3,570 pounds per acre (see Figure 2). This was greater than 8 of the other 11 tested 

species/varieties, and was only less than Dwarf Siberian forage kale (3,912), Bayou rapeseed 

(4,298), and Defender radish (5,391). Mean shoot biomass increased to 3,876 pounds per acre 

when sown on April 22, resulting in production greater than all other tests species/varieties 

except Defender radish (5,150).

0 500 1000 1500 2000 2500 3000 3500 4000

Dwarf Essex rapeseed

VNS yellow sweet clover

Bayou rapeseed

Dwarf Siberian forage kale

Selby flax

Whistler winter pea

Richlea spring lentil

VNS lacy phacelia

Purple Top turnip

Defender radish

Lavina barley

Rockford oats

MEAN BIOMASS (pounds per acre)
NRCS−Montana−Technical Note−Plant Materials−MT-113 5 

Figure 2. Mean shoot biomass weights, cover crop spring seeding study, Bridger, Montana. 

2015.

VNS lacy phacelia established at a rate of 6.8 plants per square foot when planted on March 30, 

which was approximately a median value for tested species/varieties for that planting date (see 

Figure 3). Number of stems of lacy phacelia per square foot increased to 8.4 for the April 22 

planting, which was greater than 8 of the 11 other test species/varieties.

Soil temperatures at the time of planting for the three study plots are 27.6o F (January 30 frost 

seeding) with mean production of 1,650 lbs.; 44.5o

 F (March 30 spring seeding) with mean 

production of 3,570 lbs., and 45.1o

 F (April 22 spring seeding) with mean production of 3,876 

lbs. Biomass production was significantly reduced when seeded at soil temperatures below 37o 

F.

0 1000 2000 3000 4000 5000 6000

VNS crimson clover

Purple Top turnip

VNS yellow sweet clover

Richlea spring lentil

Whistler winter pea

Indianhead lentil

4010 spring pea

Dwarf Essex rapeseed

VNS lacy phacelia

Dwarf Siberian forage kale

Bayou rapeseed

Defender radish

MEAN SHOOT BIOMASS (pounds per acre)

22-Apr Planting Date 30-Mar Planting Date
NRCS−Montana−Technical Note−Plant Materials−MT-113 6 

Figure 3. Mean stand counts, cover crop spring seeding study, Bridger, Montana. 2015.

In non-replicated sampling of root biomass production in the March 30 planting, mean root 

biomass production of VNS lacy phacelia measured 370 pounds per acre, which was slightly 

below the median production for all test species/varieties (see Figure 4). For the April 22 

planting, root biomass of VNS lacy phacelia decreased to 301.1 pounds per acre, which was 

again below the median production for all species/varieties tested.

Figure 4. Mean root biomass weights, cover crop spring seeding study, Bridger, Montana. 2015.

0 2 4 6 8 10 12 14

Dwarf Siberian forage kale

Purple Top turnip

VNS crimson clover

Defender radish

Whistler winter pea

VNS yellow sweet clover

VNS lacy phacelia

Dwarf Essex rapeseed

Richlea spring lentil

4010 spring pea

Bayou rapeseed

Indianhead lentil

MEAN STAND COUNTS (plants per square foot)

22-Apr Planting Date 30-Mar Planting Date

0.0 500.0 1000.0 1500.0 2000.0 2500.0

Whistler winter pea

4010 spring pea

Indianhead lentil

Richlea spring lentil

VNS crimson clover

VNS lacy phacelia

Dwarf Siberian forage kale

Defender radish

VNS yellow sweet clover

Bayou rapeseed

Dwarf Essex rapeseed

Purple Top turnip

MEAN ROOT BIOMASS (pounds per acre)

22-Apr Planting Date 30-Mar Planting Date
NRCS−Montana−Technical Note−Plant Materials−MT-113 7 

Limitations

Lacy phacelia is an excellent pollinator attractant, but when planted in large solid stands, may

deter pollination of other target species. Lacy phacelia readily self-seeds, so termination before 

seed set will be needed to limit volunteer plants from establishing.

Releases

There are no varietal releases of lacy phacelia from the United States. There are several 

released varieties from Europe. Seed of VNS is available from commercial seed companies. 

References

Dieter H. Wilken, Richard R. Halse, and Robert W. Patterson. 1993. Phacelia: Treatment from 

the Jepson manual. 

Leslie Gilbert. 2003. Horticulturist, Small Farm Success Project, USDA, Sustainable Agriculture 

Systems Laboratory. Fact sheet number 2a. 

Phacelia tanacetifolia Benth. Lacy phacelia, PHTA. USDA, NRCS. 2016. The PLANTS 

Database (http://plants.usda.gov/core/profile?symbol=PHTA, 5 February 2016). National Plant 

Data Team, Greensboro, NC 27401-4901 USA.

USDOI, NPS, SAMO NRA. 2016. 

(http://www.smmflowers.org/bloom/species/Phacelia_tanacetifolia.htm) 

Lindley, J. 1969. National Plant Germplasm System, Edwards, Bot. Reg 20:t.

Brianna, D. 2008. Phacelia tanacetifolia Benth. CSU Stanislus, Valley flora propagation center

species profiles. 

Young-Mathews, A. 2015. Personal communication, USDA-NRCS, Corvallis, OR.

Kamer, T. 2016. Personal communication, Wild Seed Farms, Fredericksburg, TX.

Wilson, D. 2016. Personal communication, Applewood Seed Company, Arvada, CO.

Tiraki, I., and H. Keles. 2012. Reversal of the inhibitory effect of light and high temperature on 

germination of Phacelia tanacetifolia seeds by melatonin. Journal of Pineal Restoration. 

Garen, H., R. Aucioglu, and D. Kaymakkauak. 2009. Effects of different row spacings on the 

seed yield and some other characteristics of Phacelia tanacetifolia Benth. varieties. Journal of 

Food, Agriculture and Environment Vol. 7 (2):383-386.

Layberitie, E., S. Wratten, and J. Hemptinne. 2012. The contribution of potential beneficial 

insectary plant species to adult hoverfly (Dipter: Syrphidae) fitness, Journal Biological Control, 

61 1-6.

Scianna, J., R. Kilian, and R. Hybner. 2014. Calculating seeding rates when using alternate-row 

and cross-seeded planting techniques. Plant Materials Technical Note MT-78 (Rev. 1). USDANRCS, Bozeman, Montana.