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Lettuce

Crunchy lettuce is the smorgasbord of the salad bowl, select from the traditional iceberg lettuce that is the backbone of sandwiches, wraps and hamburgers or cos lettuce, the signature ingredient of the Caesar salad. For a mixture of leaves try Mesclun which can combine lettuce with rocket, chervil, mustard, radicchio or a variety of other tasty leaves.

The nutrient level of lettuce will vary depending on variety selected. The humble iceberg provides calcium, potassium, vitamin C and folate, while the red leaf varieties may also include biotin, omega-3 fatty acids, vitamin B2 and B6.

Lettuce varieties are easy to grow from seeds or seedling. Harvest times will vary between varieties and will depend on whether the whole plant is taken or just selected leaves. Leaves can be harvested from six weeks on, whereas allow ten to twelve weeks for the whole plant. To get a continuing supply of leaves, plant another batch about 4 to 6 weeks later.

Lettuce belongs to the Asteraceae family which also includes sunflowers, chicory, globe artichoke and safflower. For healthier lettuce crops, grow alongside beets, carrots, strawberries, broad beans, parsnips or radishes.

Follow our seven easy steps to successful lettuce harvest including tips along the way.

How to grow vegetables - lettuce
How to grow vegetables - lettuce

When to plant and location.

Position.

  • Lettuce is thought of as a cool season crop but with new modern varieties they can be planted in all regions of Australia throughout the year
  • Check hardware and garden centres to get the best local varieties

Location

  1. Lettuce are a cooler season crop so in cooler temperatures plant in at least six hours of sun a day.
  2. In summer, especially if areas are prone to high heat consider planting alongside living shade such as beans or sweet corn or erect a shade tent to protect them.

Soil

Get the soil right to harvest a bumper crop of delicious lettuce.

Follow our steps for easy soil preparation.

  • Turn the soil over before planting to a depth about 10cm before planting.
  • Add heaps of well-rotted compost and manure for strong growth and great leaf flavour. For a no-dig option consider Seasol Liquid Compost.
  • Lettuce can be grown in all types of rich, well-draining soil, with the pH around 6.5.
  • To boost the soil add Seasol Plant + Soil Booster and a fertiliser rich in nitrogen such as PowerFeed Controlled Release for Tomatoes & Vegetables.
  • Water in well and if possible, let the soil rest for two weeks or so.
  • Lettuces are surface rooting, so use mulch to prevent the roots from drying.
How to grow vegetables - lettuce
How to grow vegetables - lettuce

Step 1 – Sowing seeds.

  • Check the back of the seed packet as different varieties of lettuce require different spacings.
  • In the soil, dig shallow (1cm) trench rows 20 to 30cm apart. Sow seeds every 10cm apart and cover with Seasol Seed Raising & Cutting Potting Mix. Lettuce seeds buried too deeply will not germinate.
  • In seed trays, put a couple of seeds into every cell or make shallow row 1cm deep and scatter a few seeds along the rows. Lightly cover with seed raising mixture such as Seasol Seed Raising & Cutting Potting Mix.
  • In pots 20cm deep and wide, make a few small holes 1cm deep in each corner of the pot. Scatter a few seeds in each hole and lightly cover with potting mix.
  • Water in well with Seasol to help increase seed germination rates.

Step 2 – First growth.

  • Seeds will start to emerge out of the soil within 10 to 14 days depending on the temperature. It may take longer if the temperature is cooler.
  • When seedlings sprout, they have two, tiny rounded seed leaves.
  • Lettuces require a lot of water to keep the leaves juicy and fresh so check moisture levels daily.
  • Apply Seasol weekly to help stimulate strong root development and healthy growth.

Step 3 – Baby lettuce seedlings.

  • Thin out weaker seedlings so they are not competing for nutrients and space.
  • Lettuce leaves use a lot of water to keep them healthy, crisp and green so check moisture levels and water daily if required.
  • Apply a liquid fertiliser such as PowerFeed PRO SERIES for Tomatoes & Vegetables every week to the soil around the plants. Lettuces are a hungry crop, so they need the right blend of nutrients to encourage fast growth.
  • If required thin seedlings again a few weeks later.

Step 4 – Lettuce seedlings ready for transplant.

  • If transplanting seedlings you have grown in seedling trays, they should be around 4 to 6cm high. For leaf crops space at 20cm apart, for whole lettuce space around 30cm apart.
  • If transplanting seedlings from punnets you have purchased, check the seedling label for spacing and depth requirements.
  • Water your newly transplanted seedlings in with Seasol to get them over transplant shock.
  • Once a week feed your lettuce seedlings with a liquid fertiliser such as PowerFeed PRO SERIES for Tomatoes & Vegetables.

Step 5. Lettuce plant growth.

  • Watch your lettuce leaves grow over the following weeks as the rosette starts to form.
  • Lettuce leaves like to stay moist to stay juicy. If the soil dries out, the plant may bolt and go to seed.
  • Check mulch around plant and apply more sugar cane or pea straw if required.

Step 6 – Lettuce head formation.

  • Lettuce varieties that develop heads, begin by forming a cup shape.
  • Every 6 to 8 weeks apply another application of PowerFeed Controlled Release for Tomatoes & Vegetables to produce a bumper crop.
  • Additionally, liquid feed plants with a combination of Seasol and PowerFeed every week. Mix 30mL of Seasol concentrate and 50mL of PowerFeed concentrate per 9 litres of water (standard watering can).
  • Watch out for slugs and snails as they eat tender young leaves. Remove these little critters as you see them.

Step 7 – Lettuce harvest.

  • Keep a close eye on your plants and leaves. Either harvest the whole plant or just the individual leaves.
  • If harvesting the whole plant, cut at the base of the plant close to the soil.
  • If harvesting the leaves, pick the leaves off the plant one level at a time, giving the inner leaves more time to develop.
  • Harvest the outer leaves when there is at least six leaves 100mm long. Don’t wait too long to harvest as bitterness can set in.

Things to watch for…

  • Snail, Slugs and Earwigs They are the biggest pest for lettuces, with slugs and earwigs not far behind. Search plants regularly and destroy by hand. For an organic treatment, try coffee grounds; broken eggshells or wood savings around the plants or use ion-based non-toxic snail and slug baits.
  • Aphids These tiny pests can quickly destroy a crop, as they suck all the water and nutrients out of the leaves. The leaves will curl and wilt. Remove by hand or spraying with an appropriate insecticide such as EarthCare Natural Pyrethrum insect spray.
  • Bolting If it’s too warm or the leaves are left to long before harvest, the plant will bolt and go to seed. Check plants daily.
Tips for looking after warm temperate soils - Seasol Liquid Compost