How to Grow Corn Salad in Australia

Corn salad (Valerianella locusta), also called lamb's lettuce or mâche, is a small salad green in the honeysuckle family, Caprifoliaceae. It keeps growing through frost and short winter days, giving soft, mild, nutty leaves in the months when most leafy crops stall. The usual mistake is sowing it into warm soil, where the seed simply lies dormant.

Three mistakes that matter

1. Sowing into warm soil. The seed goes dormant in soil above about 21°C, and seedlings that do come up in the heat soon run to flower. Sow from late summer to late autumn as the soil cools, in the months given in When to plant.
2. Letting the seedbed dry out. Corn salad is slow to come up, often 7 to 12 days and sometimes three or four weeks. A dry crust in that time loses the sowing, so water the row lightly every day or two until seedlings show.
3. Keeping the soil soggy. The plants need steady moisture, but the low rosettes rot in waterlogged soil and crowded rows. Grow them in free-draining soil, water when the surface starts to dry, and space them as set out in Thinning.

When to plant

Corn salad germinates best in soil between 10°C and 20°C. The sowing season opens as the late-summer heat breaks and runs to late autumn, with Anzac Day in the heart of the southern window. Sow a short row every 2 to 3 weeks through the window for a steady supply.

At the warm edge of the window, sow where a taller crop gives afternoon shade and keep the row damp until the weather cools. A late-winter sowing in cool districts gives a short picking before the lengthening days bring on flowering.

Site, soil and setup

No common vegetable shares its plant family, so corn salad slots into any gap in a rotation, including beds just cleared of summer crops.

Container growing

Its low, shallow-rooted rosettes make corn salad a good pot crop. Use a pot at least 30 cm across and 20 cm deep, holding 10 to 15 L of premium potting mix with some compost added. Both 'Large Dutch' and 'Verte de Cambrai' suit pots; sow thinly and thin to about 10 cm apart.

• Water: check pots every few days and water when the top 2 cm of mix is dry. Tip out any water left standing in the saucer.
• Feed: from the first true leaves, worm casting liquid diluted to weak tea colour, fortnightly.
• Position: full sun in autumn and winter; move the pot into afternoon shade as spring warms.

Sowing Seeds

Sow corn salad straight into the bed, or raise it in cell trays while the bed is still full of summer crops.

Choosing a variety

Despite its names, corn salad is no lettuce and no relation of sweet corn. The "corn" is the European grain fields where it once grew as a weed. Lettuce, rocket, spinach, cress and chicory are separate crops.

Starting in trays

• Sow two or three seeds per cell of seed-raising mix, 5 mm deep.
• Keep the tray in a cool, shaded spot and the mix damp.
• Snip all but the strongest seedling in each cell at mix level.
• Plant out at three or four true leaves, after hardening off (a week of gradually longer spells outdoors); see hardening off seedlings.

Sowing direct

Short rows are easier to keep damp through the long wait for seedlings than a broad patch.

• Rake the bed to a fine surface and water it the day before sowing.
• Sow in shallow drills 5 mm deep, seeds about 3 cm apart, with rows 10 to 20 cm apart.
• Cover with fine soil or seed-raising mix, firm it down and water gently.
• Expect seedlings in 7 to 21 days, and up to four weeks in cold soil.
• Thin in stages to the spacing in Thinning.

Care by growth stage

Cool weather and steady moisture decide the crop. Corn salad needs only light feeding, and too much fertiliser can reduce its flavour. Weeks count from sowing.

If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched into the soil can help. Corn salad shrugs off the frosts of a Canberra winter.

In cold districts, a low tunnel of clear plastic over the row speeds winter growth and keeps frosty-morning picking easy. Open it on sunny days, because a sudden rise in temperature can push the plants to bolt.

Thinning

Thin in two steps, because seedlings come up unevenly and a few always fail. The final spacing is 10 to 20 cm, the wider end for 'Large Dutch'.

• Make the first thinning at two or three true leaves, to about 5 cm apart.
• Thin again a few weeks later to the final spacing, and eat the thinnings in salads.
• Snip unwanted seedlings at soil level so the shallow roots of their neighbours stay undisturbed.
• Hand-weed between the rows while the plants are small.
• Pull off yellowing or rotting lower leaves so air can move around each rosette.

Companion planting

Corn salad sits low through the cool months, so its best neighbours are slim winter crops that leave it the light.

Grows well with

• Onion, whose upright, narrow leaves cast little shade over the rosettes.
• Garlic, planted in the same autumn window and just as slim above ground.
• Radish, which is pulled within weeks, before the corn salad needs the room.

Keep apart

• Kale, broccoli and other tall winter brassicas on the sunny side of the bed, which shade the small rosettes when the winter sun sits low.
• Silverbeet, whose broad leaves spread over and crowd small plants.

Harvesting Leaves

Start picking once plants have six to eight leaves or stand 7 to 10 cm tall, usually 5 to 8 weeks from sowing.

• Pick the outer leaves one at a time, leaving the centre to keep growing.
• Or cut the whole rosette just above the soil once it is 10 to 15 cm across; the stump often reshoots.
• Pick in the cool of the morning, when the leaves are crisp.
• Handle the leaves gently, because they are tender and bruise easily.
• Cut whole plants as soon as a flower stem shows, before the leaves turn bitter.

Corn salad is best eaten on the day it is picked. Wash it well in cold water, since the low rosettes collect soil. Keep it in a bag or lidded container in the fridge for 5 to 7 days at most. Serve it raw with lemon juice and olive oil, or wilt the bigger, older leaves as you would spinach.

Common problems

Slow or no germination. In cold soil the seed can take three or four weeks, so wait before resowing; the other causes are in Three mistakes. Read more

Running to flower in spring. Lengthening days, rising heat and dry soil all make corn salad bolt, after which the leaves turn bitter. Time the last sowings to finish before late spring.

Seedlings everywhere next autumn. A plant left to flower drops seed that comes up again in autumn, and corn salad has naturalised in parts of Victoria. Pull flowering plants early, or leave one or two only where a self-sown patch is welcome.

Pests and diseases

Corn salad is seldom badly troubled in the cool months, and slugs and snails do most of the damage. Use only sprays whose label names the pest and the crop, or a crop group that includes it, and keep to any withholding period.

Common garden snail (Cornu aspersum) and slugs. They chew irregular holes and leave slime trails, worst in wet autumn weather. Pick them off after dark, or scatter iron-based snail bait thinly, never in heaps. Keep bait away from dogs, since even iron baits can poison them. Read more

Aphids (Aphididae). These small, soft-bodied sap-suckers cluster under the leaves, distorting and stunting the rosettes. Wash them off with a strong jet of water or spray insecticidal soap, and let ladybirds and lacewings do the rest. Read more

Cutworms (Agrotis species). These moth caterpillars hide in the soil by day and cut young seedlings off at ground level at night. Scratch the soil beside a felled seedling to find the caterpillar, and clear summer and autumn weeds well before sowing. Read more

Damping off (Pythium species and Rhizoctonia solani). Seed rots before it emerges, or seedlings collapse at soil level, most often in wet soil. Sow into free-draining soil or fresh seed-raising mix, and water only enough to keep it damp. Read more

Prevention first

• Clear boards, pots and leaf litter from bed edges, where snails hide by day.
• Check leaf undersides weekly for aphids.
• Space plants as in Thinning, so air moves freely between the rosettes.
• Water the soil rather than the leaves, and in the morning, so plants go into the night dry.

Tips

1. Sow more than you expect to need. The plants are small and slow, and it takes a good number to fill a salad bowl through winter.
2. Leave the first big picking until after a frost or two, when the leaves are often at their sweetest.
3. For a winter salad with more bite, sow mustard or rocket in the same window and mix the peppery leaves with the mild ones.