Sow Thistle (Sonchus)

Looking to increase the diversity of plants in your home garden? Well, one of the plants you can choose to grow is Sonchus, which is very commonly used in landscaping. While usually considered as a weed, it has numerous benefits too. Read on to learn more about the uses of Sonchus as well as the best way to grow and care for it.

I. Appearance and Characteristics 

Sonchus is a genus of flowering plants in the tribe Cichorieae within the family Asteraceae and are commonly known as sow thistles (less commonly hare thistles or hare lettuces). Sowthistles are annual, biennial or perennial herbs, with or without rhizomes and a few are even woody (subgenus Dendrosonchus, restricted to the Canary Islands and Madeira).

The genus is named after the Ancient Greek for such plants. All are characterized by soft, somewhat irregularly lobed leaves that clasp the stem and, at least initially, form a basal rosette. The stem contains a milky latex. Flower heads are yellow and range in size from half to one inch in diameter; the florets are all of ray type. Sonchus fruits are single-seeded, dry and indehiscent. Sow thistles are common roadside plants, and while native to Eurasia and tropical Africa, they are found almost worldwide in temperate regions.

Mature sow thistle stems can range from 30 cm to 2 m (1 to 6 ft) tall, depending upon species and growing conditions. Coloration ranges from green to purple in older plants. Sow thistles exude a milky latex when any part of the plant is cut or damaged, and it is from this fact that the plants obtained the common name, “sow thistle”, as they were fed to lactating sows in the belief that milk production would increase. Sow thistles are known as “milk thistles” in some regions, although milk thistle more commonly refers to the genus Silybum.

In many areas sow thistles are considered noxious weeds, as they grow quickly in a wide range of conditions and their wind-borne seeds allow them to spread rapidly. Sonchus arvensis, the perennial sow thistle, is considered the most economically detrimental, as it can crowd commercial crops, is a heavy consumer of nitrogen in soils, may deplete soil water of land left to fallow, and can regrow and sprout additional plants from its creeping roots. However, sow thistles are easily uprooted by hand, and their soft stems present little resistance to slashing or mowing.

Most livestock will readily devour sow thistle in preference to grass, and this lettuce-relative is edible and nutritious to humans—in fact this is the meaning of the second part of the Latin name of the common sow thistle, oleraceus. Attempts at weed control by herbicidal use, to the neglect of other methods, may have led to a proliferation of these species in some environments.

II. How to Grow and Care

Sunlight

Sowthistles predominantly thrives in open habitats where light is abundant. They require full sun to partial shade with high light intensity for optimal growth. Exposure should be around 6 to 8 hours of direct sunlight daily, which is crucial for their photosynthetic processes, ensuring robust growth and timely flowering. In settings with insufficient natural light, such as indoors or greenhouses, supplemental LED or fluorescent grow lights can be used to mimic natural conditions. Achieving the right balance of light is essential to prevent etiolation and to maintain healthy sowthistles.

Watering

Native to regions with moderate climates, sowthistles thrives in conditions that mimic its natural habitat, which is neither too wet nor too arid. This species exhibits a preference for consistent moisture without being waterlogged, maintaining a balance that supports its growth. It requires watering every week to sustain its health and vigor. As an herbaceous plant, sowthistles often favors outdoor cultivation where it can benefit from natural rainfall patterns, aligning its growth cycle with the availability of water in its environment.

Soil

Sonchus can grow well in a variety of soil types and is fairly tolerant of saline soils, but it prefers moist, well-drained soils with a pH range of 5 to 8.

Fertilizing

Most potting soils contain an abundance of nutrients that plants use to produce new growth. By the time Sonchus has depleted the nutrients in its soil, it will have grown large enough to require a larger pot. Repot your Common sowthistle after it has doubled in size or once a year, whichever comes first, to replenish its nutrients.

Planting Instructions

The sowthistles genus requires full to partial sun, well-drained soil of any type, and moderate water. Start by loosening the soil in the planting area and enrich with compost if needed. Position the plants, allowing space for spread, then backfill, ensuring the plant’s base is level with the soil surface. Keep soil moist without water logging for the first few weeks. Though all sowthistles species follow this pattern, individual care may vary, so research the specific sowthistles you’re planting.

Propagation

Primary propagation for sowthistles is through seed sowing, but cuttings and division are also viable. Key factors for success include well-draining soil, adequate light, and mild temperatures. It’s essential to consider sowthistles’ fast growth and possible invasiveness. Typically, propagation is not difficult, but care must be taken to prevent unwanted spread.

For seed propagation:

• Collect seeds after flowering;
• Sow seeds shallowly in moist soil;
• Place in a bright area without direct sun;
• Keep soil lightly damp until germination;
• Transplant seedlings once sturdy enough to handle.

Pests and Diseases

Aphids frequently choose Sonchus as their host plant. Aphids may spread from Sowthistle to other plants, while on the other hand, Sowthistle can promote the development of beneficial predators like hoverflies. Sonchus Oleraceus are a great choice for a sacrifice plant in this sense.

In addition to carrying some viruses, common sowthistle serves as a critical host for insects that transfer these and other vegetable crop viruses, such as the lettuce aphid (Nasonovia ribisnigri) and lettuce root aphid (Nasonovia ribisnigri) (Pemphigus bursanus).

The presence of Sonchus, specifically between lettuce crops (either in cash crops or fallows), permits the spread of a number of pertinent viruses to succeeding harvests.

The fungi black root rot (Chalara elegans) and corky rot (Rhizomonas suberifaciens), which can infect lettuce crops and significantly reduce yields, have also been observed to employ common sowthistle as an alternate host.

III. Uses and Benefits 

• Medicinal uses

In liver problems, Sonchus is helpful. Root extract is used in ointments for ulcers and wounds, while the stem is used as a sedative and tonic and the leaves and roots are used as febrifuges in ingestion. Latex-derived gum is used to treat ascites and hydrothorax.

In addition, the leaves of Sonchus Oleraceus can be cooked and eaten on their own or added to soups.

Sonchus stems can be eaten; however, before cooking, people frequently scrape off the outer layer. Because of their hardness, roots must be cooked thoroughly if they are to be consumed. 

Due to the low latex content of the plant, even the sap is helpful; the New Zealand Maori chew the sap like gum.

• Culinary uses

The greens were eaten by the indigenous people of North America. Edible raw when young, the older greens can also be eaten after cooking briefly.