Start from seed: March-May
Optimum soil temperature for germination: 10-20°C
Plant spacing: 10-20 cm
Days to maturity: 35-60 days
Introduction
Corn salad (Valerianella locusta), also known as mâche, lamb’s lettuce, or field salad, is a delicate, cool-season annual leafy green that belongs to the family Caprifoliaceae. Despite its name, it has no relation to corn.
This humble plant has been harvested for centuries in Europe, where it was originally found growing wild as a weed in grain fields, which is how it earned the name “corn salad” (“corn” referring to grain crops in Europe). It has been cultivated since the 17th century, first becoming popular in France and later spreading throughout Europe and beyond.
Corn salad grows in low rosettes of small, spoon-shaped, dark green leaves with a subtle, nutty flavour that is often described as milder than spinach with a slight butterhead lettuce taste. It’s prized for its tender texture and nutritional value, being rich in vitamin C, beta-carotene, iron, and potassium. It’s a valuable addition to Canberra gardens seeking year-round salad production.
Site and soil
Corn salad thrives in Canberra’s cool temperate climate and is particularly well-suited to growing during autumn and, winter. It is extremely frost hardy and will actually continue to grow through winter. It prefers full sun during the cooler months but appreciates some afternoon shade as temperatures warm up in spring.
Prepare the soil by incorporating compost or and aged manure and complete organic fertiliser. Corn salad grows best in well-drained, moderately fertile soil with a pH between 6.0 and 7.0. If your soil is particularly acidic, add lime to bring the pH up. While it can grow in poorer soils, the flavour and yield will be better in enriched soil.
For container growing, use pots at least 20 cm deep with good quality potting mix enhanced with compost or slow-release organic fertilizer. Containers work well for corn salad, allowing you to position them in optimal growing locations as the seasons change.
For details on preparing soil and pots, including the use of lime, dolomite, gypsum and fertilizers, please refer to the COGS guide to garden bed preparation.
Planting Seeds and Seedlings
Corn salad is primarily grown by direct seeding. Sow seed in March, April and May for autumn, winter and early spring harvest.
Sow seeds to a depth twice the size of the seed in rows 10-20cm apart. Seeds can be slow to germinate, often taking 7-12 days but sometimes up to 3-4 weeks, so patience is required. Keep the soil consistently moist during germination. Once seedlings have developed a few true leaves, thin them to about 10-20 cm apart. The thinnings can be used in salads.
Corn salad can also be succession planted every 2-3 weeks during the growing season to ensure a continuous harvest. In Canberra, succession planting works well from March through May.
Cultivation
Corn salad is relatively low-maintenance once established. It requires consistent moisture but is susceptible to rot if overwatered. Water regularly to keep the soil moist but not soggy, especially during dry periods.
A monthly foliar spray with seaweed solution; a mix of worm juice, seaweed and compost tea; or trace elements will help boost growth and resilience to pests and diseases. Avoid excessive fertiliser use, as this can reduce flavour.
Mulching around plants with a fine organic material like compost or well-rotted leaf mould helps retain soil moisture and suppress weeds, which can compete with the shallow-rooted corn salad.
Corn salad is very cold-hardy and can withstand Canberra’s winter frosts. In fact, frosts will improve the flavour by increasing sugar content in the leaves. Caterpillar tunnels clad in horticultural plastic erected over the crop will increase growth, allow harvesting on frosty mornings and provide protection from severe frosts.
As temperatures warm up in spring, corn salad will quickly bolt (flower and set seed). Once this happens, the leaves become bitter and less palatable. Plan your sowings accordingly to maximize harvest before bolting occurs.
Harvesting
Corn salad can be harvested in two main ways:
- Cut-and-come-again method: Harvest the outer leaves when plants are about 7-10 cm tall, leaving the growing centre intact to produce more leaves.
- Whole plant harvest: Cut the entire rosette just above soil level when plants reach about 10-15 cm in diameter.
Harvest in the morning when leaves are crisp and full of moisture for the best flavour and texture. Corn salad is ready to harvest 35-60 days after sowing, depending on growing conditions and the harvesting method used.
The plants will bolt in spring as daylength increases, so harvest promptly once they reach a suitable size.
For the best flavour, use corn salad immediately after harvesting. If needed, it can be stored in the refrigerator for up to 5-7 days in a plastic bag or container, though its delicate nature means it doesn’t store as well as other greens.
Problems
There are numerous pests and diseases that can affect cabbage. The best approach is to have a reliable Australian reference book to identify problems. Garden Pests, Disease and Good Bugs by Denis Crawford is recommended.
A general strategy to follow with any problem is to observe the plant carefully before taking action. Identify the problem then carefully consider the course of action. For example, with pest insects, you often can see a predator nearby. If you watch and wait the predator may deal with the problem for you. Beneficial predatory insects which feed on pest insects can be purchased from suppliers such as Bugs for Bugs. If the problem needs further action the above recommended book has suggestions.
Practicing good garden hygiene, crop rotation, and maintaining plant vigour by providing adequate nutrients are key strategies for prevention.
Corn salad is generally resistant to many pests and diseases, particularly when grown during its preferred cool seasons. However, it can face a few challenges:
Slugs and Snails are the most common pests of endive, especially during wet periods. They leave irregular holes in leaves and slime trails. Control methods include beer traps, copper tape barriers, organic snail baits (iron EDTA), or manual removal in the evening.
Aphids: These small sap-sucking insects can transmit celery mosaic virus. They often cluster on the undersides of leaves, causing distortion and stunting. Small populations can be controlled by washing them off with a strong stream of water or using insecticidal soap. Alternatively, neem oil or pyrethrin can be used. Beneficial predators like ladybugs and lacewings should be encouraged and can be purchased for release on the crop. Look for aphid mummies which are evidence that the aphid has been parasitised. Eggs can also be parasitised and will appear bronze in colour. Generally speaking, plants that are high in soluble nitrogen (nitrates and ammonia) are prone to attack by sap sucking insects. Ideally avoid using soluble nitrogen fertilisers and ensure plants have adequate trace elements. This can be achieved by using foliar sprays.
Powdery Mildew: A fungal disease appearing as white powdery spots on leaves. Occurs more commonly in humid conditions with poor air circulation. Improve spacing between plants, avoid overhead watering, and apply organic fungicides if necessary.
Bolting: This is more of a physiological issue than a disease. Corn salad bolts (flowers and sets seed) quickly in response to: Increasing day length, rising temperature and, water stress. Prevent premature bolting by planting at the right time, keeping plants well-watered, and providing afternoon shade in warmer weather.
Recommended Varieties
There are two types of corn salad: the Dutch varieties, A Grosse Graine, which have pale leaves that are not as winter hardy; and smaller, dark leaved varieties, such as Vit and Elan. Several varieties of corn salad perform well in Canberra’s climate:
Vit versatile, vigorous, mildew-resistant variety. Long, oval, glossy green leaves form tight rosettes. Mild, slightly nutty flavour also reminiscent of roses
Verte de Cambrai A traditional European variety with small, dark green leaves in tight rosettes. Very cold hardy and excellent flavour.
Verte d’Etampes: Features larger, thicker leaves than many varieties, making it easier to harvest. Good resistance to bolting.
Dutch: Forms compact plants with rounded leaves and excellent nutty flavour. Well-suited to container growing.
Large Seeded: As the name suggests, has larger seeds and produces bigger plants than traditional varieties. Slightly better heat tolerance and slower to bolt in spring.
Medallion: A productive variety with uniform growth and good bolt resistance.
References
- Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
- Coleman, Eliot. The New Organic Grower. Chelsea Green, Vermont, USA. 1995.
- Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
- Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023.
- Fanton, Michel and Jude. The Seed Savers Handbook. The Seed Savers Network, Australia, 1993.
- Lambley Nursery. (2024). Corn Salad (Mache) Valerianella locusta. https://lambley.com.au/product/corn-salad-mache-valerianella-locusta/
