5 Steps to Successful Summer Lettuce

When summer is hot, the perfect accompaniment to any meal is a juicy succulent salad. Lettuce loves the coolness of Spring and Autumn so here in Southern Victoria, the long days and sometimes high temperatures of Summer can make head lettuce production a challenge.

Here are four steps to help you negotiate the trickiest months and keep you crunching on salads all through Summer!

1) GERMINATE LETTUCE UNDER 25C

Lettuce WILL NOT germinate over 27C - it has a gene that inhibits seed germination in high temperatures! We over come this by sowing our lettuce in flats, watering them with cool water and then sitting those on the cool concrete floor of our shed. The position, while completely shaded is bright and the lettuce seed cracks open in 24-48 hours. If the day is especially hot, we will water it with cool water to keep the soil temperature low.

Do watch carefully as if you leave it for too long in the shade, it will be very leggy. Once germinated, we transfer the flats to our glasshouse where we have shade cloth and fans so that it is to too hot.

If there will be a period of forecasted weather above 35C, wait to sow your lettuce OR sow it in flats and put them in a fridge for a day and then in the coolest bright spot. To ensure head lettuce harvest each week, we have done both of these work arounds with great success.

In summer, lettuce seedlings are ready for transplant in 21 days.

2) SOW HEAT TOLERANT and/or QUICK HEADING VARIETIES

Variety matters! Many of the traditional butter lettuces originated in the high altitudes of mountains where weather was cool throughout summer. These are not the best choice for the often very hot, dry summers in Southern Victoria.

Choose iceberg, gem and romaine varieties which are quick heading and/or heat tolerant. As market growers, we had standing lettuce orders for our CSA and restaurants every week. We have not only trialed all of the following varieties throughout the hottest of summers with great results, many of these are in their third or fourth generation - regionalized biodynamic seed!

SOW in Mid Jan and February for HARVEST in Mar, Apr, May

SOW in Nov, Dec, Jan for HARVEST in Jan, Feb and Mar

• Butter/Crisphead

  • Carmona

• Iceberg

  • Crispino

  • Salinas 88

• Crispheads

  • Reine de Glace

  • Jester

  • Joker

  • Rosencrantz

• Romaine

  • Flashy Troutback,

  • Jadeite,

• Gem/Romaine

  • Pandero

  • Sweetheart Gem

• Iceberg

  • Crispino

  • Salinas 88

• Crispheads

  • Jester

  • Joker

• Romaine

  • Flashy Troutback,

  • Jadeite,

• Gem/Romaine

  • Pandero

  • Sweetheart Gem

3) KEEP LETTUCE MOIST

Heat and water stress lead to bitter lettuce that goes to seed early!

We water early in the morning and/or late in the evening in summer- some days required both. If you allow your lettuce to wilt and dry out, the leaves may turn bitter.

Also the dryness may signal the lettuce that it is time to go to seed and it will bolt, also turning the leaves bitter. So keep it moist!

4) SHADE DURING INTENSE HEAT

During periods of intense heat, we would create shade in the field by attaching shade cloth over hoops made from poly pipe. We would choose the degree of shade depending on the weather.

In the home garden, you can make use of shade created by large plants, popping the lettuce in on the southern or eastern side of taller plants so that they shade it in the afternoon. You can also set up a shade cloth lean-to to shade your lettuce through the hottest afternoon sun during periods of intense heat.

Sometimes the white netting above was enough shade- sometimes we would use green shade cloth over the poly pipe - depending on how hot it was. We also add shade to the caterpillar tunnel in the background, using it for summer lettuce production as well.

5) SOW SEVERAL VARIETIES AT THE SAME TIME WITH DIFFERENT DAYS TO MATURITY

In summer, a gem lettuce can be ready for harvest at 35 days from transplant! While an iceberg may take 55 days and there is a speckled crisp head which takes 45 days. You can take advantage of this by sowing all three at the same time and harvesting each variety at maturity over a 3-4 week period! One month of head lettuce just by paying attention to the days to maturity. We have listed these on our website and on each seed packet.

Although you may have no shortage of lettuce right now at the end of Spring, successive plantings ensure you are ready when your Spring lettuce bolts to seed. Some of the gem lettuces are as quick as 56 days from seed to harvest - giving you a wonderful treat to eat raw or barbecue in January!

Bolted Spring Lettuce