Sophie Jobin
- Aug 17, 2022
- 4 min read

How to Grow: Lettuce

The Green Everyone Knows About: The Lettuce (Lactuca sativa)

If you haven't gotten a chance to read it yet - definitely check out: what type of lettuce should you grow.

Once you have done that you will have a better understanding of what type you want to grow!

Now that we know which type of lettuce we want. Let's find out just exactly how to grow this wonderful vegetable. It's not complicated but it can be tricky, I know that sounds like the exact same issue but what I mean by that is: it is easy to grow but hard to keep from bolting and away from pest. Don't let that stop you from growing your own! Let's find out just how to do that.

Once you've gotten your lettuce seeds picked out, purchased and brought home, it's now time to start those seedlings indoors or outside.

When to Plant Lettuce

Lettuce is a cool season vegetable and doesn't need a long time like most vegetables. You can either grow them as a cut leaf or as a full head, that will be the deciding factor on how long you will need. Start them in late-winter, early spring, late-summer or early fall, For me in zone 6b, I start them around March and September.

Sow Direct or Starting Seeds Indoors

Depending on your zone, you may direct sow or start your seeds indoors rather than in the garden.

Direct Sowing

- The simplest way to sow is by dragging a line in the surface of the soil, 1 cm deep.

- To help avoid seeds from floating around, pre water the line before sowing.

- Water every four days.

- This leads to the cutting method of harvest and sowing again every month.

Starting Seeds Indoors

Here in zone 6b, I start mine around March + August indoors.

Reasons for March: Lettuce is not frost hardy and will die from the cold. However hardened off seedlings are tolerant (-5 to -7°C) to frost but mature plants are more sensitive to frost (-1°C).

Reasons for August: Lettuce should be pregerminated in cool rooms during the summer. The conditions are generally too hot for good germination. At soil temperatures over 27°C germination is poor.

Lettuce also has specific needs:

Sow seeds in plug trays or 6 cell trays of soilless mix.
A minimum temperature for seed germination is 5°C
An optimum temperature range for growth is 16 to 20°C.
They should be sown 8 to 10 weeks before transplanting outside.
Learn how to: Sow seeds

Soil Type

Warm sandy soils are preferred for the early harvest, good drainage and high organic matter content are essential.

Watering

Salads need more watering than most vegetables, their leaves are filled with 95% water making it need a constant stream of moisture.

Winter: in a polytunnel, it's best to water every three or four weeks. We want to help avoid overwatering to attract slugs, leaf mildew and germination of weeds.

Spring and Fall: the in-between seasons of wet/dry weather it's not necessary to water all the time, twice weekly, try and make sure to keep the surface moist but not soaked.

Summer: in dry weather and in containers, plants should be watered every day.

PROTIP: high humidity and excess water close to time of harvest can be destructive to the yield.

Pests & Diseases

Salads can be Disney world for some pest to eat, causing a lot of damage. It can become overwhelming to try and fight off but stop it early and you won't have any issues. There are some tricks you can use to help avoid this type of damage.

- Sow seeds in the best season for each kind of salad plant.

- Keep plants tidy while picking, always bring two bowls: one for fresh salad and one for dried up old leaves.

- Space evenly to avoid any shaded areas where pests love to hide or disease likes to creep in.

- Lay mesh or fleece covers over the plants to prevent their entry and avoid early damage.

Growing & Harvesting

Depending on how you planted your seeds. Pick and come again, cut and come again, or hearts.

Cut and Come Again

- This methods works when seeds are sown 1cm (1/2in) apart in rows of about 15cm (6in) apart.

- Cut the plant with a fresh knife or scissors when leaves are 7-10cm (3-4in) long. Make sure to cut above the height of the smallest leaves,

- Cutting above the height of the smallest leaves will allow time for regrowth within 7-10 days.

- Make sure to clean up any dead or diseased leaves.

- Flavour is milder when you cut them into small leaves.

Pick and Come Again

- This method works for when they are past the cutting stage only and start forming heads.

- Pull off the outer leaves to harvest the oldest ones first, this allows the plant to regrow more quickly when their baby leaves have not been touched.

- Make sure to clean up any dead or diseased leaves.

- Flavour is milder when you pick them into small leaves.

PROTIP: Even if you aren't in need of lettuce, continue picking weekly so that the plants stay youthful and productive.

Hearts

- Hearting plants mostly need more space from 25-30cm for lettuce.

- Growing full heads take upwards of 6-10 weeks longer compared to leaf harvests.

- Harvest at the bottom of the plant. Cut with a really sharp knife at the base of the plant.

- Remove any dead leaves before storing.

Store

Depending on the type of lettuce they all have different storage lives. Avoid storing lettuce with apples, pears, tomatoes or other produce that omit ethylene.

FYI: Lettuce turns pinkish-brown due to oxidation (being but and exposed to oxygen) or when exposed to ethylene.

- Head lettuce that is rapidly cooled in good conditions can be stored for up to 2-3 weeks at a temperature of 0C with 98% humidity or over.