I like a good garden salad. Its a shame that at the peak of summer, when tomatoes are abundant and cucumbers out of control, lettuce can go downhill quickly. Many varieties will bolt and go bitter before producing anything usable. Others will get tip burn or produce flat cloth-like leaves that you can’t seem to even stab with a fork. While lettuce is easier grown as a cool-weather spring, winter or fall crop, I have always aimed for year-round lettuce. In my square foot garden, the 3 varieties I have used for summer lettuce were:
- Jericho Romaine – a romaine type bred in the deserts of Israel for bolt resistance
- Red Sails – a gorgeous red loose-leaf type with deep crinkly leaves
- Black Seeded Simpson – a reliable green loose leaf type with large ruffled leaves
These have always gotten me through summer so I continued to grow them this year, but decided this year was the time to do a trial on more heat resistant varieties to give myself a bigger arsenal. I started my garden too late to research and buy seeds from the internet, so I scoured the local nursery seed sections for varieties specifically mentioning heat resistance. Here’s what I ended up with:
- Green Star – a green, loose-leaf variety with lofty ruffled heads
- Kagraner Sommer – an heirloom butterhead type with soft buttery leaves
- Nevada – a green Batavian type, popular for summer growth
- SloBolt – a green loose leaf variety with large frilly leaves
I also threw in my standard Bibb variety for a total of 8. This trial wasn’t 100% scientific since their location in may garden dictates how much sun they receive which can affect bolting, but its close enough for me. So how did everything fare?
This variety produces beautiful heads in cooler weather. I love using it in salads and using whole leaves as lettuce wraps a la PF Changs. For summer, this variety was a no-go. I planted at a density of 4/sf and they looked good early on but bolted before producing anything usable.
Black Seeded Simpson²
I did these at 9/sf which works well for continually harvesting individual leaves. If you want to harvest full heads, 4/sf would work fine as I found these a little crowded for my liking. Black Seeded Simpson has always been reliable for me and you can find seeds almost anywhere. Its a little paler green than my other green loose-leaf’s for what that’s worth. I’ve reliably harvested these in July-September in the past and expect this year to be no different. With more varieties to choose from, I may find myself planting less Black Seeded Simpson in the future.
This ones a winner. I planted at 9/sf which left them shoulder to shoulder when harvesting. I don’t have a scale to be Mr. Scientific, but Green Star seems to be a very good use of space. When I stripped the outer leaves I didn’t want, I found almost everything usable. This will make for a good versatile lettuce for salads, sandwiches or shredded for tacos. I’ll definitely be planting Green Star again.
Kagraner Sommer is an heirloom French Butterhead lettuce that I found impressive. After the failure of my standard Bibb, I was excited to see it perform well in the heat of summer. I planted at 4/sf which seems ideal. They were slower growers than my other lettuce varieties but well worth it. I also had some germination issues, which may or may not be about the seeds – more on that in a future blog post. The leaves are soft, buttery and attractive. Can a man describe lettuce as elegant? I probably shouldn’t.
I’ve grown Jericho Romaine for several years now during summer and it has always been reliable. I plant them at 4/sf which seems to be about the perfect spacing as they are slightly crowded right before they would bolt. I’m a picky lettuce eater who really only wants the crisp juicy leaves. When I strip the Jericho down to the heart, I’m generally left with a single serving or so per head. The hearts never seem to be dense for me, but since I’m generally harvesting a square foot or two at a time it doesn’t really matter.
When researching summer lettuce, Nevada came up time and time again. It is a Batavian type that forms large open heads. I planted at 4 per square foot which worked out well. They grew quickly, filled the space well and have nice flavor and texture. There was a little bit of tip burn on leaves that still would have been composted, but it deserves mentioning. Like the others, no signs of bolting even at full size. I will be growing Nevada again.
Red Sails is a variety that I grow year-round. It is a loose leaf variety with crinkly textured leaves that can be deep bronze red, though some plants have a lot more green. Red Sails is worth growing for the contrast alone – it looks great in a mixed salad, but its great flavor and texture make it a keeper. I did 9/sf but they’ll fill the space if you do 4/sf for fuller heads.
With the name Slobolt it must be perfect for summer. Its a green loose leaf with ruffly leaves. It seemed to fill in a little slower than my other varieties, but has yet to show signs of bolting with August almost here. I’m still up in the air on this one – I have yet to even taste it but the leaves felt a little “dry”, though ruffly in texture. I’ll update when I’ve got a better opinion. At least I have another bolt-resistant variety up my sleeve.
With all said and done, I was pretty successful at upping my summertime lettuce variety. Of course, since I live in coastal Southern California, your mileage will vary. There are strategies you can employ other than just the varieties you choose. The life cycle of a lettuce plant inevitably ends at going to seed, so preventing that is an impossibility.
Plant in Partial Shade
Bolting is a response to heat, air temperature, soil temperature, humidity and day length. In hot conditions, planting in partial shade can buy you time. Some backyard gardeners use shade cloth for the same effect, though I have never done so.
Lettuces are shallow rooted and respond to dry soil with bolting. Keep them evenly moist with regular hand waterings or a sprinkler timer. If you really love your lettuce, you can use a timer and brass nozzle sprayers to mist them several times a day like they do at the grocery store. With a miniscule amount of water, you can lower the leaf surface temperature by 10 degrees or more.
You’re racing the clock with summer lettuce. Whether you’re using organic compost teas or a sprayer filled with Miracle-Gro, keep your lettuce fed and you will cross the finish line sooner.
Cut and Come Again
Many varieties of leaf lettuce start putting out usable food when they’re just a few inches. Cutting leaves as you need them, rather than waiting for a “mature” head means you’re getting it while the gettings good. With a lot of varieties, by the time they have bolted, the entire plant is bitter meaning missed opportunity.
While different varieties have slightly different DTMs (days to maturity), most are in the same range. Spread out your plantings for regular picking so you don’t end up with 10 bags of lettuce followed by a month long hiatus.
Planting other greens
Most of my salads end up with 25% or so greens that aren’t standard head or leaf lettuce. Some of my favorites are baby beet and chard greens, spinach leaves, kale, arugula, mizuna, shredded cabbage and baby pak choy. If the heat is keeping you from cranking out lots of lettuce for a summer salad, think outside the box.
Have a tip or favorite variety for summer lettuce production? Let me know in the comments section.