Bolt-free, sweet summer lettuces

"Magenta" Batavian lettuce

Sunday, July 12, 2015

Lettuce is not a crop that thrives in the heat of summer, but there are varieties that are more resistant to the heat than others.  If you want fresh lettuce through spring, summer and fall, you will need to plant seeds every two to three weeks.  This way, as one batch bolts (grows a flowering seed stalk), you have another batch ready to harvest.

In late spring and early summer, plant varieties that are resistant to bolting. Colorado State researchers tested to see which varieties held up the best in summer heat.  Here were the winners:

Leaf lettuce-”New Red Fire”, “Simpson Elite”

Butterhead-”Optima”, “Winter Density:

Romaine-”Jericho”, ”Green Towers”

Batavian-”Magenta”, “Nevada”

Simpson Elite was very slow bolting for leaf types and Magenta was almost “boltproof”.

"Green Towers" Romaine

Loose leaf lettuces are those that do not form heads.  They are the quickest to be able to harvest from.  We love these as you can take off the outer leaves and they just keep going for months.

Butterhead, also called Bibb or Boston lettuce, have crumbled leaf heads.

Romaine have tall leaves and have crisp center veins.  Red romaines did not hold up as well as the green.  Green Towers lasted 3 months of summer.

Batavian has loose heads with crisp hearts.  Batavian lettuce is also called French Crisp or Summer Crisp lettuce.  They resisted bolting longer than any other type of lettuce.  Some lasted more than 100 days!

A few others that I have read about recently that look interesting to try:
Red Sails-looseleaf type that stays sweet even when bolting and one of my all time favs
Brown Goldring-Romaine that retains is sweetness into summer
Grandpa's Admire's-Butterhead with good heat tolerance with red tipped leaves
Monoa-a Hawaiian tropical green lettuce.  If it grows in Hawaii any time of the year, that is a good sign!
Webb's Wonderful-crispleaf green lettuce well suited for the south

Lettuce does not germinate well in soil temperatures greater than 70 F and will not germinate at all when soil goes above 85 F.  You can either start seeds indoors, start seeds in a shady spot, or buy transplants when the temperatures hit summer highs.  I start mine outdoors in a shady spot.

Some ideas for keeping your lettuce producing sweet leaves:
Use a shade cloth over your lettuce.
Move your potted lettuce to a shady spot
Start your seeds in cooler spots in the garden like the north or east side so they have protection against the afternoon sun
Plant under, behind or between taller vegetables.

Prepare your bed by adding a 1" layer of compost and a balanced fertilizer.  After planting, do not fertilize.  Keep evenly moist to keep the lettuce sweet.  Getting too dry will cause the lettuce to turn bitter and bolt in warmer temperatures.