Lettuce and Salad Greens in Your Garden

By Tracey Srock, University of Minnesota Extension Master Gardener Crow Wing County

History of Lettuce

• Lettuce seeds were brought to North America from England in the 1700’s

• Iceberg lettuce became popular just before WWII

• The first named lettuce cultivars were listed in the U.S. in 1806

Nutrients

• Contains vitamins (such as A, C and K), minerals (such as iron, magnesium, potassium and calcium),

and carotenoids (antioxidants that protect cells and play a role in blocking the early stages of cancer)

• Excellent source of fiber and folate

• Low in calories and sodium. Lettuce is fat free and cholesterol free

Growing Lettuce Indoors

•Containers

~ Flat fairly shallow with good drainage

~ 4” to 6” plastic pots

~ Produce containers or take out dishes (poke holes for drainage)

• Growing Medium

~ Seed starting mix

~ DIY – equal parts peat moss, vermiculite or perlite, and sand

•Planting

~ Moisten soil and put in containers

~ Scatter seeds an inch apart, cover with thin layer of soil, spray with water bottle

~ Cover with plastic wrap or lid and keep moist

~ When sprouted, remove plastic and thin if needed

~ Keep soil moist but not water logged

~ Fertilize when first true leaves appear, diluted by half

• Selecting the right location

~ A minimum of 12 hours of light, 14 – 16 is ideal

~ Choose a room that isn’t too hot or too cold; 60 – 70° daytime, 10° cooler evening

~ A room with lots of natural light, but will also need supplemental fluorescent lighting

~ Adjust lights and keep no more than 4” above plants

Indoor Varieties

• Loose leaf varieties: Baby Oakleaf, Tom Thumb, Black-seeded Simpson

• Winter Density – early spring sowing in cold frame or even unprotected in the garden

•Spinach

•Arugula

Damping Off

•Cause: Fungi that are water loving organisms thrive in wet or poorly drained soils

•Control: Plant properly, avoid soggy soil

•Soak pots in a solution of 10% bleach for 30 minutes

•Do not reuse potting soil

Harvesting

•May be ready in a few weeks

• Trim larger leaves at base, leave smaller ones to grow.

•May be able to harvest 2 or 3 cuttings

Growing lettuce outdoors

Site Preparation:

• Soil testing on a regular basis and fertilizing according to recommendations

• Need a good supply of nutrients in the surface soil. Lettuce has small root systems

and is a poor forager

• Soil needs to be well drained and moisture retentive. The optimal ph is between 5.8 and 6.5

Planting

• Direct seed as soon as soil can be worked in the spring and 2 to 3 months before frost

• All leafy greens are generally direct seeded, although kale, some lettuces, and Swiss chard can be transplanted.

• Plant seeds according to package directions

• Thin accordingly after true leaves emerge

• Fall greens can be planted again in late July or beginning of August.

Watering & Mulching

• Soak the soil thoroughly when watering, to a depth of at least one inch each week during the growing season

• Mulching with herbicide free grass clippings, weed free straw or other organic material will help retain soil

moisture and suppress weeds while decreasing the need for frequent cultivation and keeps lettuce cleaner

Weeding

• Salad greens have small root systems so they cannot successfully compete with weeds

• You must cultivate shallow because their roots are close to the surface. Keep the surface of the soil loose

• Weeds take water, nutrients, light, and space

Harvesting

• Harvest leaf lettuce as soon as single leaves are large enough to use

• Spinach and some lettuce varieties can produce new leaves, especially if harvesting at the “baby” stage.

• Alternately, the whole plant can be harvested by cutting it off at or just below the soil surface

• Endive and escarole can be blanched before harvesting by placing a 4 – 8 inch cardboard disk over the head,

3 days before harvesting

• Harvest all lettuce early in the season except those varieties for hot weather. Hot, dry weather will

cause lettuce to become bitter and bolt because energy that had been producing leaves is now producing

seeds or flowers

• Pick leaves in early morning or evening and avoid the heat of the day

• Parsley - can be picked as needed all season. It may even be brought indoors in fall and kept during the winter

Cleaning

• Wash thoroughly in tepid water, swishing around or use salad spinner

• Wrap in damp paper toweling, place in perforated plastic bag, and refrigerate

• You may also use a waxed cardboard box lined with a clean damp cloth

Variety Selection

There are hundreds of varieties with many different sizes, colors, textures, and tastes. Also, varieties that are slow bolting and heat-resistant.

• 3 Types of Lettuce

~ Looseleaf – leaf, Romaine, and Spinach

~ Head or Semi-head

~ Boston or bibb

• Looseleaf

~ Black-seeded Simpson - has tasty, tender leaves and is an early producer

~ Red sails – one of the slowest bolting red leaf

~ Oakleaf – withstands hot weather and never bitter

~ Lolla Rossa Atsina – dark copper red fading to green, refreshing taste and easy to grow

• Boston/bibb

~ Kagraner Sommer – delicious buttery texture and flavor, heat tolerant

~ Buttercrunch – butterhead with tender leaves and slow to bolt

~ Tom Thumb – miniature butterhead about the size of a baseball, mild and creamy, tolerates

high temperatures, resists bolting

• Head

~ Rosy red baby leaves, delicate taste, pick when young

~ Summertime (Batavia) – first open then as it matures forms a tight head, sweet, without bolting

~ Panisse - Large, lime-green, lobed leaves form dense heads with a long harvest window.

Best for early or late plantings, but suitable for summer in the north.

~ Cherokee - Thick, crisp, dark-red leaves with good flavor.

Very slow bolting with excellent tolerance to heat and bottom rot.

High resistance to downy mildew

• Upright/Romaine

~ Little Gem – miniature green romaine, 4” across, best tasting, very heat tolerant

~ Jericho – good for baby leaf and full size, tolerant to both heat and tipburn

• Spinach

~ Carmel spinach – fast growing, 25 days

~ Red Kitten spinach – red veined and fast growing, 23 days

~ Lakeside (New!) – Big, smooth, leaves that are 6” long and 3” wide, mild flavor with a touch of tang

~ Bloomsdale – great flavor, suitable for early spring or fall

• Salad greens

~ Arugula – fast growing. It has a distinctive peppery taste and is best picked young

~ Mesclun – combination of flavors, textures, and colors

~ Tatsoi – commonly known as spoon mustard, mild flavor, sweet and nutty, for salads or stir fry

• Chicory, radicchio – Indigo – remarkably sureheading, very tolerant to tipburn, resistant to bottom rot

• Kale

~ Winterbor – excellent yield and better cold hardiness

~ Toscano – heavily blistered leaves have a softer texture and rich and tender leaves

• Swiss chard

~ Bright Lights – multicolored and strong bolt resistance

~ Perpetual – extremely resistant to bolting and can grow the whole season

Disease Management

• Plant pathogen-free organic seed

• Adding organic matter can help reduce diseases caused by soil borne pathogens

• Overwatering or poorly drained soils must be avoided – do not apply water to foliage

• Remove diseased plants and soil immediately around the infected plant

• Disinfect tools to help prevent spread of pathogens such as gray mold and others

Problems

• High temperatures (above 75) produce flower stalk and seeds causing leaves to taste bitter

• Tipburn – brown and rotted areas on the edges of leaves. Occurs when plant loses more water than it takes up from the roots

• Calcium deficiency – leaves turn yellow and eventually wilt

Diseases

• Lettuce mosaic virus

~ Description: Leaves have random patches of yellow and green in mosaic/mottled pattern

Leaves are misshapen, usually curled and deformed

~ Management: Plant seed that has been tested for virus

• Septoria Leaf Spot

~ Description: Leaves have small irregular shaped yellow to brown spots

Tiny black dots can be seen in center with a hand lens

~ Management: Use disease-resistance seed

• Downy Mildew

~ Description: Yellow to brown leaf spots

Fuzzy white growth on the underside of leaves

Infected leaves often rot from secondary fungi and bacteria

~ Management: The most effective is to grow resistant cultivars

• Bacterial Leaf Spot

~ Description: Leaf spots are angular and water soaked; quickly turning black

Leaf spots grow together and leaf wilts

~ Management: Use pathogen-free seed and when possible, avoid sprinkler irrigation

• Anthracnose

~ Description: Somewhat circular, dry brown leaf spots

Sunken oval dark lesions form on midrib and larger leaf veins

Center of leaf spot turns white and falls out, leaves appear ‘shot hole’

~ Management: Use pathogen-free see and avoid sprinkler irrigation

• White Mold (lettuce drop)

~ Description: White, cottony mold with small hard, black raisin like fungal structures at the

base of the plant

Plant wilts and outer leaves drop to the ground

Rot progresses into the heart of the head

~ Management: The disease is favored by wet and humid conditions. A level planting bed is best

Water plants in the morning to promote drying of the soil surface and foliage

• Root Rot Complex - spinach

~ Description: Leaves turn yellow and wilt

Roots have dark sunken areas and few or no root hairs

~Management: Plant spinach in well-drained soil. Carefully manage watering schedule to prevent

flooding and saturated soil conditions

Websites

• extension.umn.edu

• wimastergardener.org

Articles

• University of MN Extension, Growing Leafy Greens in MN Home Gardens, by Cindy Tong

• University of MN Ext, Planting Greens, by Beth Berlin

• University of MN Ext, Suggested Vegetable Varieties for Home Gardeners in MN, by Mike Zins,

David Wildung, Jackie Smith, Robert M. Olen

• University of WI Master Gardener, Grow Your Own Salad Greens, April 25, 2000

• University of Florida, Growing Lettuce Indoors, by Kathleen Marshall

• University of Vermont Extension, Seedling Damping Off, by Anne Hazelrigg

Catalogs

• Johnny’s Selected Seeds, 2017 Catalog

• Territorial Seed Company, Spring 2017