Wild opium lettuce seeds

Prickly Lettuce

Prickly lettuce (Lactuca serriola) seeds travel with the help of their downy, white plumes. Seedlings of this hardy annual appear in damp soil in spring and summer. Mature plants grow 3 to 5 feet tall, and produce small, yellow flowers. Broken stems and leaves bleed white latex sap. Found throughout much of North America, prickly lettuce can grow in any type of soil. Control young plants by pulling, cultivating, or spraying with an organic herbicide containing clove oil or acetic acid. Cut back older plants to reduce reseeding.

Weed Control Techniques

Pulling. Most young weeds can be pulled from the soil. They will slide out most easily if you pull them when the soil is wet. Getting the root up is crucial, so think of the main stem as the root’s handle, and grasp it as close to the soil line as you can. If you find that the weeds are breaking off at the crown as you pull, slip a kitchen fork, dandelion weeder, or similar tool under the weed, and pry and twist as you pull it up. Weeds that have taproots, such as dandelion and plantain, usually must be pried out. A flexible pair of waterproof gloves will keep your hands comfortable as you weed, and it’s good to have a nice sitting pad, too. Let pulled weeds bake in the sun for a day or so before composting them. If pulled weeds are holding mature seeds, compost them separately in a hot, moist pile before using this compost in the garden.

Cultivating. Slicing and dicing weeds with a hoe works best when the soil is relatively dry, and the same goes for cultivating with a tiller. With their tops mangled and roots cut, most young weeds will quickly shrivel up and die. Be careful to cultivate only the top inch or two of soil or you may injure nearby garden plant roots and drag new weed seeds to the surface. A sharp hoe works much better than a dull one, so refresh the edge on your hoe with a steel file between weeding sessions. After using either a hoe or tiller to cultivate weeds, go back the next day to nip out any survivors. When battling perennial weeds, you can weaken the plants by chopping them down with a sharp hoe, but it’s best to combine hoeing with digging to achieve good control. Never use a tiller in soil that is infested with bindweed, quackgrass, or other weeds that regrow from small pieces of root; they are easily spread by rototilling.

Organic herbicides. There are several herbicides made from natural ingredients. Those that contain clove oil (eugenol) give the best control of young broadleaf weeds. Products containing acetic acid, often in combination with citric acid, do a good job on young grasses. Some products contain both clove oil and acetic acid, so they are useful for a broad variety of weeds. Soap-based herbicides dehydrate leaves by cutting through their protective layer of cutin. All of these types of organic herbicides work best on young weeds and pose only a temporary setback to well-rooted perennial weeds. To minimize damage to neighboring plants, spray only in dry, still weather. To maximize effectiveness, spray young weeds when temperatures are above 70 degrees F and the sun is shining brightly. Be aware that repeated applications of a product containing acetic acid (which is very strong vinegar) can lower the soil’s pH, making it more acidic.

Reducing reseeding. Most weeds reproduce primarily from seeds, and the seeds of some weeds can remain viable when buried in the soil for decades. So it’s essential to keep weeds from shedding seeds in the garden. Garden weeds that are neglected until they reach seed-bearing age can be lopped off near the soil line with pruning shears, a stout knife, or a string trimmer with a blade attachment. Cutting back perennial weeds again and again not only reduces reseeding, it also forces the plants to use up food reserves stored in their roots. In a garden that has gone hopelessly weedy, mowing it down promptly, raking out the seed-bearing debris, and starting over next year is a big step in the right direction. Mowing regularly helps keep weeds under control in lawns. When mowing lawns where seed-bearing weeds are present, collect the clippings in a bagger and dispose of them in a shady place.

Image courtesy of Randall G. Prostak, University of Massachusetts

About this weed

This common summer annual, originally from Eurasia and North Africa, has been introduced as a genetic resource ( it is a genetic relative of lettuce) and as an ornamental plant and for use in medicines. It is easily identified by its prickly leaves and stem, but is sometimes mistaken for Skeleton Weed.

Description

Prickly Lettuce can also be a biennial weed and grows to about 2 m high. As plants get older the leaves become deeply lobed and the flower heads take on an open pyramid shape. The species has small yellow flowers. When damaged it exudes a white milky sap.

The seed germinates after winter or summer rain. Most seedlings emerge in autumn, grow slowly and form a rosette over winter, and then develop stems in spring. Long, warm autumns favour emergence and rosette establishment, and often result in large populations the following year. Plants emerging in spring have a shorter rosette phase before flowering and are often smaller than plants emerging in autumn. Seeds have an attached pappus for wind-dispersal, have no primary dormancy and only form a short term soil seedbank. Seed production is proportional to plant height, with taller plants able to produce as many as 2,300 seeds. It is possibly poisonous to mammals.

Impact on Bushland

Research has shown it has broadened its ecological amplitude, enabling it to invade a range of vegetation types.

Location

Distributed across parts of the Eremaean and South-West Provinces along roadsides, in gardens and in cultivated fields. It also likes disturbed habitats including wetlands.

Priority for removal

High: major threat to the conservation values of habitat in the South-West Province.

Management (hand)

Manually remove small and/or isolated infestations, ensuring the entire plant is removed especially the taproot.

Management (herbicide)

Apply Glyphosate at early growth or rosette stages in spring, summer or autumn or metsulfuron methyl 5 g/ha (based on a minimum of 50 L/ha of water) + surfactant. Plants are difficult to control with herbicides once the flowering stems have begun to elongate. Many populations in southern Australia have developed resistance to Group 2 herbicides. Optimal spraying months are September to November but can also be done occasionally between December and March.

Flowering month/s

January, February, October, November, December

Flower colour/s

Yellow

Information source

Additional information

Prickly lettuce ecology and management

Take home messages

  • Prickly lettuce germinates at a wide range of temperatures, from 5 to over 35 °C
  • Emergence in a wheat crop mostly occurs between April and August in the first year after seed burial, with research showing 92% emergence in the first year and only 8% emergence in the second year
  • Control in winter crops is important in reducing the weed pressure over summer
  • Seeds of prickly lettuce are relatively short-lived, indicating prevention of seed set over two years should be effective in running down the seedbank
  • Prickly lettuce is a surface germinator but can emerge from beyond 5cm burial depth. Cultivation to bury seeds will be less effective for prickly lettuce control than for sow thistle or fleabane
  • Mature plants are often cut off during harvest and re-grow quickly with numerous branches. Prompt action through chemical control or grazing is required to stop seed set
  • Control within paddocks is not the only consideration. It is also important to control weeds on fence lines, roadsides and other non-cropping areas due to the wind-dispersal capability of prickly lettuce
  • Seedbank management is critical. It requires a combination of chemical and non-chemical options as there is no single “silver bullet”.

Background

Prickly lettuce (Lactuca serriola L.) is of Eurasian origin and is adapted to a summer-dry Mediterranean climate (Weaver and Downs 2003). It is distributed globally in Australia, Europe, North Africa, North America and West Asia (Prince et al. 1978). In Australia, it was first recorded in 1899 in the Upper Hunter, NSW and is now widely distributed across several states, particularly in NSW, VIC and SA (ALA 2018). It is a common weed of fallows, roadsides, waste lands and gardens, and it has recently become an increasing problem in cereals and lucerne pastures in southern NSW.

Prickly lettucecan grow up to 2 m high and is highly competitive with crops or pastures. If left uncontrolled, it consumes soil moisture and nutrients in the summer. L. serriola at a density as low as 0.2–1.2 plants /m2 has been shown to cause soybean yield losses of 10% and by up to 80% at densities of more than 50 plants /m2. However, it did not cause significant yield loss in winter wheat (Weaver et al. 2006). Similarly, no yield losses of cereals or grain legumes due to prickly lettuce were reported in Australia, but grain quality and harvesting efficiency were severely compromised (Amor 1986a). Flowering buds are cut together with grain during harvest, resulting in grain contamination and reductions in value. In addition, cut stems release a milky sap which can clog the harvesting machinery and increase the moisture content of the grain (Amor 1986a).

In Australia, Amor (1986b) estimated that a single prickly lettuce plant growing without competition in crop stubble produced 48,000 seeds/plant while it produced 900 seeds/plant in a wheat crop. The light-weight seed with a pappus is easily dispersed by wind and through surface water run-off. The tall stem also facilitates dispersal (Weaver and Downs 2003). Lu et al. (2007) reported that the seed can travel over distances of up to 43 km. The weed has evolved resistance to ALS inhibitors (Group B) herbicides and most recently to EPSP synthase inhibitors (Group M, glyphosate) in Australia. Plants are difficult to control with herbicides once the plants start to elongate. Mechanical control, such as slashing or mowing, is ineffective as it regrows with competitive branches after cutting or harvesting and progresses to set seed (Amor 1986a).

Information on germination ecology, emergence and effective herbicide options for control of L. serriola is limited in Australia. Effective herbicide control options are limited for mature plants. This study was conducted to compare the field emergence patterns of L. serriola with and without crop competition, and to evaluate a range of herbicide options of different modes of action on mature L. serriola plants.

Materials and methods

Germination factors

A series of experiments were conducted to determine factors affecting germination. A randomized complete block design with three replications was used in all experiments. Mature seeds of prickly lettuce (tall and short biotypes) were collected from a lucerne pasture paddock in Wagga Wagga in February 2018. Seed of willow-leaf lettuce (Lactuca saligna L.) was collected from a private garden and used for comparison. Thirty seeds of each Lactuca population were placed on Whatman No.2 filter paper moistened with 5 mL of distilled water in a 9 cm petri dish. Petri dishes were sealed with parafilm and incubated for 7 days under eight constant temperatures of 5, 10, 15, 20, 25, 30, 35 and 40 °C, and two fluctuating day/night temperatures of 25/20 and 30/20 °C, all with a 12-hr photoperiod. Seed germination was recorded after incubation for 7 days.

Light

The influence of light was tested at two constant temperatures (5 and 20 °C) and one fluctuating temperature (25/20 °C) by wrapping petri dishes in aluminium foil during incubation.

Burial depth

The effect of seed burial depth on seedling emergence was conducted in a glasshouse by placing 100 seeds of each population in 15 cm-diameter plastic pots on 28 March 2018. Seeds were placed on the soil surface (0 cm) or covered to depths of 2, 5 and 10 cm with field soil (brown clay, pH 5.4; and organic carbon, 0.6%). Treatments were replicated four times and emerged seedlings were assessed and removed on a weekly basis until no further emergence was noted.

Prickly lettuce field emergence

Seeds of four populations of prickly lettuce were each collected from low and high rainfall areas in southern NSW in January 2016. On 1 February 2016, 150 seeds of each of the eight populations were placed in seedling emergence trays (34 cm x 28 cm) filled with a mixture of coco peat potting mix and garden soil (1:1). Seeds of each population were evenly spread across the tray surface and then lightly covered by the peat/soil mix. The trays were maintained in the field under natural conditions in Wagga Wagga.

Two populations (one each from the high and the low rainfall zones) were used to determine the emergence pattern in wheat. Glyphosate was used as a pre-sowing knockdown. Wheat cv. Corack was sown at 60 kg/ha on 14 June 2016 and on 8 June 2017, respectively, with a 6-row cone seeder at 23cm row spacing using coulter knife points and press wheels. A basal fertiliser DAP was applied at 135 kg/ha each year at sowing. Prickly lettuce seeds (1000 seeds/m2) were sown in plots (3 x 1.3 m) on 15 April 2016. Any surviving or late emerging plants of prickly lettuce were counted and manually removed to prevent any new seed replenishment. Field emergence of prickly lettuce was recorded at monthly intervals from April 2016 to December 2017.

Herbicide options

Two trials were established after wheat harvest in December 2015, one at Lake Cowal and the other at Temora, NSW. Average prickly lettuce density was 9.5 plants/m2 at Lake Cowal and 10 plants/m2 at Temora. The plot size was 2 x 16 m. A range of herbicide treatments were imposed, respectively at the Lake Cowal and Temora sites, each including an untreated control. After the initial application, each plot was equally sub-divided with one half of the plot receiving an additional application of paraquat as a ‘double-knock’ treatment.

Herbicides were applied using a hand-held boom sprayer, calibrated to deliver 100 L/ha at 2 bar pressure. The first application of herbicides was applied at the Lake Cowal and Temora on 10 and 15 December, respectively, and the ‘double-knock’ paraquat application (600 g.a.i. /ha) at Lake Cowal and Temora on 16 and 21 December 2015, respectively. At the time of herbicide applications, prickly lettuce plants were at the elongation/re-branching stage after being cut during crop harvest and not under moisture stress.

A visual rating (% of control) in the single-knock treatments was conducted on 8 January 2016. The number of surviving prickly lettuce plants was also recorded in a 1 x 6 m strip in each plot on February 2, 2016.

Results and discussion

Constant and alternating temperatures on germination

The Lactuca species have wide germination temperatures, ranging from less than 5°C to more than 35°C, depending on the species and population (Figure 1). Willow-leaf lettuce (L. saligna) had 80% germination even at 5°C. The optimum temperatures for germination were 15 – 25°C for L. serriola and 10 – 30°C for L. saligna. Alternating temperatures did not improve the germination of L. serriola (tall) and L. saligna, but reduced the germination of the short biotype of L. serriola (Figure 2).

Figure 1. Germination temperature requirements for prickly and willow-leaf lettuce

Figure 2. Impact of alternating temperatures on the germination of prickly lettuce and willow-leaf lettuce

Higher temperatures induced secondary dormancy in prickly lettuce (Figure 3) (Secondary dormancy is the dormancy induced in the originally non-dormant seeds due to unfavourable environmental conditions). L. serriola seed (short biotype) underwent induced dormancy at 30 °C with only 49% germination at this temperature. The un-germinated seeds gave an additional 46% germination after being placed under 20/25 night/day temperatures. Both biotypes of L. serriola as well as the L. saligna entered secondary dormancy at 35 and 40 °C.

Figure 3. Dormancy of prickly lettuce and willow-leaf lettuce induced at higher temperatures of 30, 35 and 40 °C followed by (fb) exposure to alternating temperature regimes of 20/25 °C

Light stimulated the germination of L. serriola for tall and short biotypes, while light was not required for the germination of L. saligna (Figure 4).

Figure 4. Impact of light on the germination of prickly lettuce and willow-leaf lettuce

Prickly lettuce had major emergence (40 to 76%) from the soil surface (0 cm), depending on the species and population, with L. saligna still having 19% at 2 cm burial depth (Figure 5). Both Lactuca species can emerge (0.25-0.5%) at deeper depths (5 and 10 cm), which is different to sow thistle, indicating cultivation to bury seeds will be less effective in prickly lettuce than sow thistle.

Figure 5. Impact of burial depth on the emergence of prickly lettuce and willow-leaf lettuce under glasshouse conditions

Field emergence

Prickly lettuce populations differed in their final cumulative emergence, ranging from 39 to 341 plants/m2 (Figure 6). However, they had similar emergence patterns, with 69% emergence in late autumn and early winter, 27% in later winter, 2.4% in spring in the first year after burial and only 1.6% emergence between autumn and winter in the second year (Wu et al. 2018).

Figure 6. Emergence of prickly lettuce in seedling trays without crop competition under field conditions from April 2016 to December 2017. The number of seeds sown onto each tray was expressed as seeds/m2

Figure 7. Emergence of prickly lettuce in a wheat crop grown under field conditions from April 2016 to December 2017 (the populations COOT07 and BARM 01 were collected from high and low rainfall zones, respectively)

The two prickly lettuce populations from different rainfall zones had similar emergence patterns, with major emergence occurring between April and August 2016 in the first year after burial, followed by limited emergence between May and September in the second year after sowing. On average, there was:

  • 69% emergence in late autumn and early winter,
  • 22% in later winter and 1.4% in spring in the first year after burial, with
  • 7.5% emergence between autumn and winter in the second year.

The final cumulative emergence at 18 December 2017 was 32 and 24 plants /m2 for the high and low rainfall populations, respectively, while the final cumulative emergence for the two populations (COOT07 and BARM 01) in the above seeding tray trial in the absence of crop competition was 228 and 341 plants/m2, respectively. These results indicate that the emergence of prickly lettuce in a standing crop is only one tenth of that in a bare ground.

Thus, to achieve effective control and to reduce weed pressure in the summer, prickly lettuce management should focus on the major emergence cohorts in autumn prior to elongation in winter crops. A fallow control soon after harvest is also necessary to control the spring emergence cohort.

Effects of herbicides on prickly lettuce in summer fallow

At the Lake Cowal site, single-knock applications of different herbicides differed significantly in controlling prickly lettuce (Table 1). Five treatments, glyphosate, 2,4-D amine + glyphosate, metsulfuron-methyl + glyphosate, glufosinate ammonium and fluroxypyr achieved good control with more than 90% mortality, while the remaining 11 treatments only controlled 30–88% of prickly lettuce. The follow-up ‘double-knock’ treatment with paraquat at 600 g.a.i. /ha provided 100% control on prickly lettuce, even in the untreated plots which did not have the first knock of herbicide applications (data not shown).

The control of the single-knock herbicide application at Temora was generally less effective than at Lake Cowal. Only four treatments had >80% control efficacy including 2,4-D amine + glyphosate, a prepacked mixture of 2,4-D amine and picloram + glyphosate, glufosinate ammonium and a prepacked mixture of amitrole (250 g ai/L) and ammonium thiocyanate (220 g ai/L). The other 14 treatments resulted in poor control of prickly lettuce (7–72%, Table 2). The follow-up “double-knock” treatment with paraquat also provided near 100% control on prickly lettuce, with less than 0.1 surviving plant m-2.

In general, no single treatment, except paraquat, achieved 100% control of mature prickly lettuce plant after crop harvest. Many plants, even though severely damaged, managed to survive and re-branch. Further research is needed to evaluate other double-knock options for prickly lettuce control.

The major emergence of prickly lettuce occurs between late autumn and winter, management focus should be directed to target the young seedlings in crops, minimising the weed pressure at the end of the season when climatic conditions are often not favourable for spraying. The weed plants are also mature and often under moisture stress, making herbicides less reliable.

Table 1. Herbicide control efficacy as a visual % rating and plant density (plants/m2) on mature prickly lettuce plants at Lake Cowal.

ATreatments applied on 10 December 2015 and a visual rating was conducted on 8 January 2016.
BThe surviving prickly lettuce plants were recorded on 2 February 2016.

Table 2. Herbicide control efficacy as a visual % rating and plant density (plants/m2) on mature prickly lettuce plants at Temora.

ASingle_knock treatments applied on 15 December 2015 and the “Double knock” paraquat on 21 December 2015, followed by a visual rating in the single-know treatments conducted on 08 January 2016.
BThe surviving prickly lettuce plants were recorded on 02 February 2016.

Amor, R.L. (1986a). Incidence and growth of prickly lettuce (Lactuca serriola L.) in dryland crops in the Victorian Wimmera. Plant Protection Quarterly 1, 148–151.

Amor, R.L. (1986b). Chemical control of prickly lettuce (Lactuca serriola) in wheat and chick-peas in the Victorian Wimmera. Plant Protection Quarterly 1, 103–105.

ALA, Atlas of Living Australia (2018). (accessed 10 April 2018).

Marks, M.K. and Prince,S.D. (1982). Seed physiology and seasonal emergence of wild lettuce Lactuca serriola. Oikos 38, 242–49.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC — the author would like to thank them for their continued support.

Contact details

Hanwen Wu
Wagga Wagga Agricultural Institute
NSW Department of Primary Industries
Pine Gully Road, Wagga Wagga, NSW 2650
Ph: 02 6938 1602
Email: [email protected]

Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994

® Registered trademark

GRDC codes: UA00149 and UA00156

Wild Lettuce vs Dandelion – What’s the Difference between Dandelions and Wild Lettuce?

There are some Dandelion look alikes to look out for when you’re foraging for Dandelion. For example, there’s Wild Lettuce, Hawkbit, and several Cat’s Ears species. It’s really important to know you’re foraging for the right plants, and to know what’s the difference between Dandelion and Wild Lettuce. Let’s compare Wild Lettuce vs Dandelion!

Dandelion Identification

Taraxacum officinale – Buy Dandelion Seeds

Dandelion Leaves

Dandelion is a perennial plant with bright green leaves to 30cm long. The name “Dandelion” comes from the French “dent de lion”, meaning lion’s tooth. This name refers to the ‘teeth’ on Dandelions’ leaves. They’re not sharp, but they are indented, jagged edges.

Taraxacum comes from the Greek taraxos (disorder) and akos (remedy). It may also come from the Persian “tark hashgun”, meaning Wild Endive. The name ‘officinale’ indicates that Dandelion was officially listed as a medicinal herb. It was listed in the US National Formulary until 1965, and dried Dandelion root is listed in the US Pharmacopeia.

Dandelion Flowers and Seeds

Flowers stems are up to 30cm tall. One of Dandelion’s most identifiable features is that is has only ONE yellow daisy flower per stem. Flowers mature into a puffball seed head. The seed head is well-known for a lot of fun – blowing the seeds! Dandelion flowers throughout the year, almost continuously. Most profuse flowering occurs in May and June. The seeds are like little fluffy parachutes, easily carried by the wind. This is how Dandelion propagates in nature. You can propagate them the same way in the garden! Grab a puffball seed head, take it to your garden, and blow. The Dandelion seeds will sprout where they see fit, growing beautiful, strong plants.

Dandelion has a thick tap root that is edible. The flower stem exudes a milky juice when it’s picked and this juice turns brown on your skin. The brown stain is difficult to remove. Dandelion flowers are very responsive to weather conditions. On a nice sunny day, the flower will be fully outstretched. However, on a rainy day, the whole flower closes up. It performs the same action for night time.

Eating Dandelion for Humans and Animals

Dandelions are valuable food for humans animals. Many birds love Dandelion seeds, and pigs and goats will happily forage on it. Sheep and cattle might not like it very much, nor do horses. Rabbits love to eat Dandelion though, and it’s well-worth growing it for feeding your rabbits.

Humans can add young leaves (mature leaves are very bitter) to salads and juices. Use Dandelion like lettuce on a sandwich, in stews, curries, and stir-fries. Dandelion seeds can be used for the same purposes. Young leaves taste similar to endive or spinach and can be used in the same way.

Dandelion beer is a fermented drink, common in many parts of the USA and Canada. Dandelion wine is made from the flowers. Dandelion roots are roasted as an alternative to coffee. I love a tea called ‘Dandy Chai’ which is a spiced Dandelion-root tea. Dandelion coffee is completely caffeine free and has many health benefits, including promoting healthy liver, kidney, and bowel.

Dandelion Identifiable Features:

  • One flower per stem
  • Jagged, pointed leaves
  • Hollow stems
  • No hairs
  • Flowers continuously, but most profusely in May and June

Dandelion Other names

Buy Dandelion Seeds

Wild Lettuce Identification

Lactuca virosa – Buy Wild Lettuce Seeds

Wild Lettuce is a biennial (grows for 2 years) up to 6 ft tall. The Latin name “virosa” means “unpleasantly strong taste or smell” or “toxic” and “lactuca” is “milky extract”. I’m sure this plant sounds very attractive by now: toxic milky extract with unpleasantly strong taste or smell!Wild Lettuce has a brown tap root with a smooth, pale green stem. This stem sometimes has purple spots. The plant has some prickles on the lower parts. The broad, oval leaves have jagged edges. Wild Lettuce flowers look like Dandelion flowers.

It’s best known for its slightly narcotic and pain relieving properties, although all lettuces contain some of these narcotic properties to some degree. Wild Lettuce has the most of all and is often made into a skin lotion for irritation, sun burn, or redness.

These properties are found in the milky juice that flows freely from the whole plant when you cut it or it is wounded. The sap tastes bitter (Bitter Lettuce!) and smells like medicine. When this milky sap dries it hardens and turns brown. This dried, hardened sap is known as lactucarium.

The drug resembles a feeble opium without its tendency to upset the digestive system. It is used to a small extent as a sedative and narcotic.

Dissolved in wine it is said to be a good anodyne.

Dr. Collins stated that twenty-three out of twenty-four cases of dropsy were cured by taking doses of 18 grains to 3 drachms of extract in twenty-four hours. It is used in Germany in this complaint, but combined with more active drugs. It is said to be also a mild diaphoretic and diuretic, easing colic, inducing sleep and allaying cough. —https://botanical.com/botanical/mgmh/l/lettuc17.html

Wild Lettuce Other Names

Lactucarium, Opium Lettuce, Strong Scented Lettuce, Bitter Lettuce, Green Endive, Poisonous Lettuce, Tall Lettuce, Great Lettuce

Buy Wild Lettuce Seeds

Wild Lettuce vs Dandelion Comparison

Dandelion Wild Lettuce
Flower per stem One flower per stem Multiple flowers per stem
Perennial/Biennial Perennial Biennial
Height max 12″ 6ft
Prickly No prickles Prickles
Bloom time Flowers continuously, but most profusely in May and June Flowers July-August
Parts used All parts are used Lactuarium (dried sap) and leaves are used

This prickly lettuce rosette is not too happy, but you can get a sense of the color and form from the photo.

This year I’m ready for the prickly lettuce—not just a few, scraggly, rescued rosettes from the xeriscaped yard of my parents-in-law, but for vast, tender carpets of prickly greens, like what grows in the fields and old agricultural places on the outskirts of Denver, Colorado.

I really only discovered the merits of prickly lettuce last season. An introduced Eurasian species, prickly lettuce (Lactuca serriola syn. L. scariola) is found throughout the United States and Canada. It is distinctive in its mature form, with leaves that turn to face sideways, sometimes pointing east and west, Euell Gibbons relates in Stalking the Faraway Places (1973). Prickly lettuce leaves twist to optimize exposure to the sunlight, Sam Thayer explains in Nature’s Garden (2010); the result is a plant that looks as if it “has been pressed between two pieces of plywood.”

Mature prickly lettuce has a solid stem with deeply lobed leaves that clasp it in an alternating pattern (Weeds of the West, 2004, 9th ed.). In contrast, the margins of young leaves can have few or shallow lobes. Prickly lettuce buds and flowers are numerous, borne in a panicle or branched cluster of beaked buds that open into small, yellow ray flowers. Later, the seedheads look a bit like dry, dandelion seed puffs.

I’d chased edible wild plants for years before paying much attention to prickly lettuce. I knew from the guidebooks that it was edible—but also that it possessed an extremely bitter latex coursing through stems and petioles and covering the mature leaves. Furthermore, as it bears thin, needle-like bristles on the leaf margins and midveins, I figured it would probably not be very fun to eat.

Mature plants turn their leaves sideways to optimize exposure to the sun.

A few years ago I tasted a mature leaf despite my misgivings at Colorado forager Cattail Bob Seebeck’s house, only to discover that it was indeed too bitter to eat. Still, a forager in Colorado is a desperate forager indeed, for her warm seasons are short and the pickings slim compared to other regions.

So last spring, hungry for green forage in April, I experienced a brief love affair with the scraggly yard rosettes of prickly lettuce in Gregg’s parents’ backyard in Aurora on Denver’s outskirts. It was early enough in spring that they had not yet sprayed the unwanted Asteraceae with yard poisons, so they invited me to scavenge what I could.

The specimens were still in their young, spring rosette forms, but the latex in the dandelion-like leaves and small prickles in a line along the underside of the leaf midvein helped to confirm that I’d found prickly lettuce.

Wild Lettuces

Lettuces are members of the Aster or Sunflower family (Asteraceae), the second largest family of flowering plants, which worldwide includes about 920 genera and 19,000 species (Elpel, 2013). Within that there are a number of tribes, including Lactuceae— the lettuce tribe, whose members have strap-shaped flower petals and milky or colored sap.

Within Lactuceae, Thayer (2010) identifies seven genera as the most common, widespread, and useful wild food plants: Cichorium (chicory), Hypochaeris (cat’s ear), Lactuca (lettuce), Prenanthes (white lettuce), Sonchus (sow thistle), Taraxacum (dandelion), and Tragopogon (salsify). He calls these the “lettuce-dandelion” group. Once you know you have a member of the lettuce-dandelion group, his dichotomous key in Nature’s Garden (2010) is useful for figuring out which genus it is while the plants are still young, since the key focuses on leaf and stem features rather than relying on buds, flowers, and seeds.

Prickly lettuce has a distinctive line of bristles on the underside of the leaf midrib. These are reddish in color. On less mature specimens, they can be light green like the midrib.

Among the distinguishing Lactuca or lettuce features I found on the young rosettes, based on the key, were leaves with “toothed, lobed, or with wavy or irregular margins,” leaf midribs that were triangular in cross section “forming a sharp or nearly sharp keel,” white or light brown latex, and “erect hairs or spines found along the keeled bottom on midvein” (present in all Lactucas except L. muralis).

In the youngest specimens, however, I had to cut and squeeze the midveins well in order to spy just a hint of the latex, which becomes more plentiful as the plant matures.

I rinsed and chopped and tasted one. The prickles had not yet firmed up enough to be bothersome, and the flavor was far less offensive than the mature plant I’d tried at Cattail Bob’s, though it was still bitter like a dandelion.

This makes sense because dandelions and chicory belong to the lettuce tribe too. All members, including wild lettuces, contain a bitter, milky sap. Despite the modern aversion to bitter foods, this milky juice is valuable as a digestive aid and spring tonic, useful for cleansing the liver after a long winter of eating hard-to-digest foods, Elpel writes in Botany in a Day (2013 ed.). So the fact that young prickly lettuce is a touch bitter can be considered a good thing—both for those who enjoy bitter greens like endive, and for those who relish tapping into the wisdom of our refrigerator-less forbears who enjoyed annual health benefits from the bitter greens of spring.

There are 12 species of Lactuca in North America—all edible, Thayer writes, though they vary in palatability. He says L. canadensis or “good lettuce” is the best to use for food, and also describes L. biennis, or “bitter lettuce” in his account. Both are native and neither is prickly.

Western Lettuce

Young leaves look a lot like young dandelions, but with prickles on the edges.

In Colorado’s Front Range, Weber & Wittmann distinguish prickly lettuce (L. serriola), a disturbed area-loving annual, from other Lactucas based on the presence of spiny-margined leaves, and spines along the midrib and veins (Colorado Flora, 2012 ed.).

But the West is also home to the native Western lettuce (L. ludoviciana), a biennial reported by Rydberg (1905) to occur in Denver. This lettuce may also appear spiny along the margins—distinguishing it from non-prickly lettuces like L. muralis, L. canadensis, L. biennis, and L. pulchella. But the margins of Western lettuce have teeth with points, compared to prickly lettuce’s “nonvascular, hardened, non-tapering projections well beyond the photosynthetic surface,” Thayer explained when I wrote for clarification (personal communication, 2014).

The upshot is that I spent a long time questioning whether all the “prickly” Lactucas I was eating were the same species. One of the distinguishing factors is how the leaves react to the sun, since Thayer also notes that the leaves of L. ludoviciana do not twist in the sun, whereas those of L. serriola do.

The native Lactuca ludoviciana is found throughout the West, starting in western Kentucky and Indiana, though it is federally protected in Indiana and should not be foraged there (USDA). According to Daniel Moerman’s database of ethnobotanical resources at the University of Michigan-Dearborn (http://naeb.brit.org), leaves of L. ludoviciana were eaten by the Gosiute people of Utah (Chamberlin, 1911), and the Cherokee cooked and ate L. canadensis leaves as greens (Hamel & Chiltoskey, 1975). Lactucas also served medicinal purposes among native groups, with recorded usage as sleep inducers, stimulants, treatments for gastroenteritis, pain-killers, and lactation inducers, among others.

The West is also home to blue lettuce (Lactuca pulchella syn. L. tatarica), a non-spiny species with lance-shaped or linear leaves and blue-purple flowers.

Cultivating the Wild

Interestingly, our modern lettuces—like iceberg, Romaine, butter, green leaf lettuce, and stem lettuce or celtuce—are cultivars of Lactuca sativa, thought to have been bred from prickly lettuce (L. serriola) thousands of years ago in Egypt.

To this day, prickly lettuce hybridizes with cultivated lettuces, though the resultant seeds from interbreeding apparently produce tough, bitter leaves. The good news is that because of its interest in cross-breeding, prickly lettuce can help diversify the gene pool, protecting lettuces in perpetuity.

I collected this spring bounty in the Denver region at the end of April 2013. The prickly lettuce rosettes are at lower left.

Forager on a Bed of Lettuce

Last spring, around the same time I was experimenting with my first scraggly lettuce rosettes in Aurora, I started noticing lush patches of a young green I did not know. I photographed and wondered about these lovely patches, only to later discover that they, too, were wild lettuces with prickly margins and midveins and latex that became more copious later—just growing under different conditions than the tough, solitary invaders of my father-in-law’s carefully tended landscape.

Once I made the connection I started picking light green rosettes where the leaves looked healthiest—some from forested areas with dappled sunlight and others from open fields in direct sunlight. Some of the young lettuce I picked had the distinctly twisting leaves and deep lobes of prickly lettuce, whereas other young specimens were less lobed and not so obviously turned.

Back at the house, I swirled the leaves in a bowl of cold water to refresh them, followed by a forceful spraying with the faucet. They damaged more easily than the mustard greens I’d also been collecting, but not too badly after their two-hour journey back to the high country. Because some of the greens I collected were a little too close to a dog-walking zone for comfort, I soaked them in a water-and-vinegar bath in the hopes of killing any unwanted microbes.

Last spring’s lettuce greens went a long way into dinner salads, pack-along salads, and spring rolls. This summer I also hope to try them in the style of the ancient Romans, poached with a warm oil-and-vinegar dressing poured overtop.

Warm Welcome & Fond Farewell

The lettuce beds turned out to be the gift that kept on giving, for they lasted—fresh, green, and unbolted—into summer. Then, to my pleasant surprise, they reawakened again in fall. My friend Butter wrote to tell me about it. “I can’t believe I never noticed them in fall before,” she said. “I must have been too busy with my head turned to the sky, looking at the fruit in the trees.” Since they were still going strong in late November last year, I headed down for a last wild food mission of the season. We got prickly wild lettuce and prickly pears on those last few sunny days before the weather changed and my world turned white once more.

In retrospect it’s funny to have spurned a plant for so many years, only to be suddenly reawakened to its merits. As my joy over wild lettuce grows with each new epiphany, I find myself eagerly awaiting those small miracles still in store. Though I have been intimate with it now for only one season, wild lettuce seems a fitting way to put foraging to bed each season, and to welcome spring once more.

UPDATED 4.19.19

Family:

Sunflower Family (Asteraceae)

Other Names:

Lactuca scariola, compass plant, horse thistle, milk thistle, wild lettuce, wild opium.

Origin and Distribution:

Originally from Eurasia, prickly lettuce immigrated to North America from Europe around 1860. Later, it spread through southern Canada and over much of the U.S. except for areas in extreme northern Maine and southern Florida. Currently, it is naturalized in about 3/4 of the counties in Ohio. Prickly lettuce grows along roads, railroads, and sidewalks and in alleys, vacant lots, waste areas, pastures, orchards, and cultivated fields. The plant prefers dry conditions, although it tolerates and can often be found growing on moist ground such as that in low areas or irrigated fields. Prickly lettuce grows most abundantly on nutrient-rich soils.

Plant Description:

Prickly lettuce is an erect biennial (rarely an annual) that grows as a rosette of basal leaves during its first year. Each rosette gives rise to a solitary stem that is usually erect and sometimes branched, especially the top portion where small, daisy-like, yellow flowers are borne. Stem leaves are irregularly-lobed and have prickly edges and a distinctive row of stiff, sharp prickles on the underside of midribs. Nearly half of the length of each seed consists of a beak having a tuft of silky white hairs (pappus) at the tip. All plant parts exude a milky juice when cut or broken. The plant reproduces only by seeds.

  • Root System:

    Plants produce a large white taproot that exudes a milky juice if cut or crushed.

  • Seedlings and Shoots:

    Emerging first are two seed leaves (cotyledons) that are round and have short hairs scattered on the upper surface, lower surface, and edge. Subsequent leaves are club-shaped, light green above, paler green beneath, and have a few short hairs on the upper surface, lower surface, and midvein. Short, knob-tipped hairs develop along the leaf edge. Young leaves form a rosette resembling that of dandelion.

  • Stems:

    Flowering stems are 2 to 7 feet tall, stiff, hollow, and filled with milky juice. Stems are usually leafy and may bear a few prickles on the lower portion. The stem surface is covered with a waxy coat giving it a whitish cast and it is sometimes flecked with red. Stems are typically erect, usually solitary, and frequently branched throughout the upper portion that becomes dotted with small, daisy-like, yellow flowers.

  • Leaves:

    Leaves are alternate (1 leaf per node), 6 to 12 inches long, coarse, and variable in size and shape. Basal leaves are larger than stem leaves. Leaves located on the lower part of the stem may be deeply or irregularly lobed or may lack lobes. Leaf bases typically consist of ear-like lobes that clasp the stem. The upper leaf surface is hairless, but there are prickles along the edge, and the midrib on the lower leaf surface is lined with sharp prickles. Prickles are generally absent from upper stem leaves, which are small, lance-shaped, and lack lobes. Leaves taste like lettuce and exude a milky juice when cut or crushed.

  • Flowers:

    Many small flower heads, each borne singly at the end of a short branch, are grouped in open terminal clusters. Unopened flower heads resemble a tight green teardrop. Opened flower heads are less than 1/2 inch wide and consist of 5 to 12 yellow ray flowers that often fade to blue as they dry.

  • Fruits and Seeds:

    The single-seeded fruits are oblong, about 1/10-inch long, brownish, and end with a slender beak that is nearly as long as the fruit. A soft white tuft of bristles (pappus) arises at the end of the beak.

Similar Species:

Prickly lettuce can be confused with sowthistles (Sonchus spp.), which have prickly leaf margins but smooth midribs. Tall lettuce (Lactuca canadensis) and tall blue lettuce (Lactuca biennis) look similar to prickly lettuce except they have leaves with smooth edges and midribs without prickles.

Biology:

Prickly lettuce is a highly variable plant that may be difficult to identify until the row of prickles on the underside of the leaf margin is evident. Experts sometimes distinguish two varieties of prickly lettuce based on the presence or absence of leaf lobes. The plant blooms from July until frost. Only about a third of the flower heads open at a time. Flowers mature into small, fuzzy seed heads from which pappus-bearing seeds disperse. The overall appearance of the reproductive plant resembles a tangled, feathery web.

Toxicity:

Regrowth of plants in autumn has caused poisoning in cattle, but mature and dried plants appear to be harmless.

Facts and Folklore:

  • ‘Lactuca’ refers to the white milky juice contained in this plant, which has been investigated as an alternative source of rubber.

  • Basal leaves often twist and face the sun such that leaves point north and south, hence the origin for the common name ‘compass plant’.

  • The juice in prickly lettuce is reported to have narcotic properties and said to be useful for sunburn.

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