Let's Talk Lettuce

Hey Everyone,

I thought with the amount of bolting we experienced growing lettuce this past fall; it might be nice to write a post to assist us in achieving greater yields this spring.

First, it is important to note that all lettuce will eventually bolt, as its life cycle will be complete. However, most lettuce should not bolt as rapidly as what many in the garden experienced. Furthermore, the lettuce grown during the cooler temperatures of brisk fall days should be different to that chosen for the warmer weather that will rapidly approach in mid-spring and early summer.

 

Lettuces that bolted this fall at the garden

How to Choose the Correct Variety

Choosing the appropriate varieties that can take some heat, having a few tricks up your sleeve, and avoiding the common mistakes which lead to premature bolting, can go a long way to increasing your yields for a wonderful harvest.

Selecting the right variety to plant on a scale of 1 to 10 importance's, is a 10.  I love the resource comparison charts on High Mowing Seeds.  The High Mowing Seeds Lettuce-comparison-chart has lettuce listed by variety and type, days to maturity, disease resistance, and tolerance to heat and cold.  
 

The second link from High Mowing Seeds is a direct comparison of how well the special characteristics of one variety (such as Nevada Summer Crisp) will perform against others within the same type or class. (Click on a variety and then click the second tab, comparison chart.)  High Mowing Seeds - Organic Seeds Nevada

Much like we look at cars in the same class and weight, one may have a timing chain, one might have a drive belt, and one may get better gas mileage over and above the other.  Each vehicle will have certain characteristics that may stand out and be more desirable.  Okay, so I threw this analogy in there for the guys!  Lettuce is much the same and it is amazing how different many of the varieties are.
 

In choosing a lettuce variety for spring and early summer planting, it is imperative to look at varieties touting things such as bolt-resistance, heat-tolerance, and resistance to tip-burn, etc.  Any downy mildew resistance is a plus for some protection against warm and damp weather.  Keep in mind the darker color the lettuce, the more heat it will absorb.  The darkest reds and greens should be grown in the fall.  The more subtle reds and limey greens are a better choice for spring plantings.  Looking at these simple characteristics starts stacking the deck in your favor for success at a wonderful and lengthy harvest.  

This picture has unbolted lettuce in the first bed and the bed in the background

has bolted lettuce. Notice how deep red the lettuce is as well.

In doing any research you will see many of the loose-leaf varieties recommended to be the best for growing in the spring and early summer.  However, it is important to note that there is a wide range of heat-tolerances within those varieties.  This is where the comparison charts will come in handy at helping you to choose the more appropriate ones for our climate.

This year I want to try some of the more heat-tolerant Batavian's from Kitchen Garden Seeds and see where that takes me.  I cannot wait to challenge myself and get these seeds going for a spring trial run. Once you have a type in mind, it is important to understand what causes the bolting process and then utilize some tricks up your sleeve to get around it.  This enables you to get as much out of your lettuce as possible and then let nature take its course to give you some viable seed for a few years to come. Remember only to save the seed of non-hybrids.

Bolting is the term used when the plant is past its prime, starts to send up a stalk, and goes into seed setting mode (see picture below). Dreadful, of course, as this renders the leaves bitter and inedible unless using some of the bitter lettuce recipes found in Asian cuisine.

  Common Mistakes that Cause Bolting &

  Tricks to keep your lettuce producing as long as possible.

1. Choosing the wrong variety for the season - See discussion above.
2. Mishandling of seedlings - Lettuce will bolt more readily if exposed to temperatures below 50 degrees during the first few weeks of germination and growth.  Keep all seedlings growing at temperatures above 50 degrees and transplant into the garden at 3 - 4 weeks.
3. Purchasing stressed seedlings - Has anyone walked by the seedlings at a big box store or nursery and seen them completely wilted and limp?  Unfortunately, more often than not, this happens on a daily basis.  Seedlings are set out on concrete lots with intense full sun, they wilt, and then someone will eventually douse them with a hose and they are ready to go.  It is wise to call ahead and see when the deliveries arrive to get them fresh off the truck or grow your own from seed. Stressed seedlings tend to bolt more rapidly no matter how heat tolerant the variety. 
4. Improper transplanting - Make sure your lettuce is properly hardened off before moving to the garden and avoid transplanting in the morning or heat of the day.  Transplanting your lettuce during the late afternoon or evening allows the most time for plants to settle in before faced with the next day's sun and heat.  This avoids transplant shock that leads to plant stress and setback.
5. Spacing - It has been shown that lettuce can bolt when overcrowded.  Keep lettuce well trimmed and leave a little space between plants.  Most varieties will tolerate 5 to 6 inch spacing in intensely planted beds if they are maintained properly.
6. Temperature - The upper end of temperatures that most lettuces will tolerate is the low 80's.  When exposed to this temperature for a week, lettuce will start the bolting process.  To get around this keep the air temperature around your plants cooler.  Full sun is only essential when it isn't too hot. Mulch your plants well to keep the soil temperature cooler and tuck your plants either behind or under some taller ones to cut temps 5 to 10 degrees.  One trick I use is to put some type of shade cloth over the area to dapple the light.  Simple cheesecloth, window screen, and bait netting all work incredibly well.  
7. Water and nutrient stress - Lettuce is shallow rooted and can dry out easily.  In addition to providing a steady supply of water, it also needs to have a consistent supply of nutrients.  Any lack of water or food will cause stress and setback.  As I am sure you have picked up by now; stress and setback only lead to two things in lettuce, premature bolting and poor quality eating.  I often use water retention crystals when transplanting to have a steady supply of moisture available or I water my plants every other day if they are mulched well and protected from intense sun.  I provide nutrients on a systemic approach that is repeated small doses of a fertilizer with lower numbers on a strict schedule.  
8. Lack of proper harvesting - Trick your loose-leaf lettuces into thinking they haven't matured yet by continuously harvesting the outer leaves when they are 4 to 6 inches long.  This keeps the plants focus on producing more food and not seed. 

Park Seed Company has a general seed starting guideline on their website Park Seed -Seed Starting for those that may need some help. 

I hope this gives some insight on how to achieve a longer and more bountiful harvest from your lettuce.  I cannot wait to see what we all grow.  If I missed anything, or if anyone has some additional tricks up your sleeve that work well, please let us know.

Take care and strive to eat healthy this New Year!

Denise, Beds 25 &29