Leaf Lettuce Variety and Adaptation for WNC

PROJECT LEADER(S): Diane Ducharme, NC Cooperative Extension - Buncombe County Center
Dr. Doug Sanders, NCSU Horticultural Extension Specialist
TYPE OF PROJECT: On-Farm Trial
LOCATION: Buncombe County, North Carolina

IMPACT


Production of leaf lettuce represents a potential means for growers in western North Carolina to diversify crop production in an established and profitable market. However, most research to date has focused on the suitability of different varieties for production in eastern NC. The purpose of this study was to evaluate lettuce varieties for production in the western part of the state, in both conventional and organic settings. By providing variety recommendations and discussing best production techniques and marketing strategies, we aim to enable growers in western NC to grow this commodity effectively and with significant economic benefit.


INTRODUCTION

While leaf lettuce varieties have been investigated extensively for production in eastern NC, research in the mountains has been limited. Increasing interest from both commercial growers and markets in the western part of the state indicate the significant value of lettuce to this region. Field or greenhouse production of lettuce offers potential diversification and market extension for growers in this area. The objective of this research was to evaluate lettuce varieties in both conventional and organic production systems. Optimization of leaf lettuce production in western NC will provide season extension of lettuce supply, and help growers to establish new markets or maintain previously held markets.

METHODS

Research took place on two separate farms-one conventional, one organic-in Leicester, NC. Lettuce had never been grown commercially on the conventional farm, while the organic farmers had past experience growing 40 different varieties. Pre-plant field preparations for the conventional setting included:

Green and red varieties of Iceberg/Summer Crisp (5 varieties), Butterhead/Boston (4 varieties), Romaine (4 varieties), and Leaf (10 varieties) were grown by the conventional farmer. A standard conventional method called plasticulture was utilized: methyl bromide (67:33, 100 lbs./acre) chiseled into soil, beds pulled into raised beds, drip-line laid and covered with black plastic. Overhead irrigation was used to start lettuce and converted to drip irrigation after two weeks. Typically lettuce was set at 10-12" intervals in 2 rows along the beds. The head varieties were sown into 128 cell trays at 21-day intervals, planted into the field at 4-week intervals (3 weeks between seed sets, 1 week to harden off outside prior to planting in field). For growing leaf lettuce varieties, the black plastic was pulled off raised beds, and seed was either hand-seeded or a Planet Junior (Cole manufacturer) was used to sow directly into field at two-week intervals; 4 rows across beds at recommended seeding rates. Seeding started on 4/8 through 4/29/02, providing first harvest on 5/20/02 and weekly after that. Leaf lettuce was cut and super cooled with spring water, boxed, and refrigerated. There was no harvest of heads due to hail damage. While there was limited weed break-through on plastic, hand weeding was required in leaf lettuce beds. Produce was sold at roadside market, loose leaf in bags, and to brokers as loose leaf in wax boxes.

For the organic farm, the fertility regime included chicken manure, lime, and colloidal phosphate. Green and red varieties of Iceberg/Summer Crisp (2 varieties), Butterhead/Boston (2 varieties), Romaine (2 varieties), and Leaf (9 varieties) were grown. All lettuce was sown into 48 cell trays and allowed to germinate. Plugs were hand planted at 12" spacing in landscape cloth covered ground, in 3 rows 9" apart. Seeds were started on 4/24/02, germinated on 5/7/02, transplanted to field on 5/22/02, and harvested weekly. Limited hand weeding of beds was required. Produce was sold at tailgate markets in bunches with roots.

Varieties in 2002 trial:
Varieties are green unless otherwise stated

    Iceberg/Summer Crisp - 54 - 60 Days (plugs set at 12" apart, 2 rows)
      Desert Storm (iceberg-Harris Moran)
      Ithaea (iceberg -Harris Moran)
      444 Crispino (iceberg)
      2021 Cardinale (crisp -Red)
      439 Nevada (crisp)
    Butterhead/Boston - 52 Days (plugs set 8 - 10 " apart, 2 rows)
      Amazon (Harris Moran)
      Tania (Harris Moran)
      2125 Mikola - red
      481N Marvel of four seasons - red
    Romaine - 60-70 days (plugs set at 10" apart, 2 rows)
      Green Tower (Harris Moran) Triton (Harris Moran)
      2129 Medallion
      2381 Eruption - red
    Salad/Braising Mix - 28 Days (plugs set 4-6" apart, 4 rows)
      2850 Wildfire lettuce mix
    Leaf - 28 - 48 Days (plugs set 8 - 10" apart, 2 rows)
      Slobolt (Harris Moran)
      Xena (Harris Moran)
      2897 Tatsoi - (Organic)
      2233N Red Salad Bowl - red oakleaf
      2304 Hussarde -red oakleaf
      406N Royal Oak - oakleaf
      2235N Salad bowl - oakleaf
      2409 Blackjack - red grand rapids
      433 Lollo Rossa - red grand rapids

RESULTS

Seeding and Germination: Because it is very small and flat, lettuce seed is difficult at best to seed by hand. Pelletized seeds offer a cost-effective option for precision planting, decreased loss of seed, ease of use with the Cole Planet Junior, and decreased thinning of beds. These advantages translate to decreased labor, resulting in savings or at least a break-even for the farmer. Germination for both leaf and head lettuce ranged from 56% to 92%. No distinction was made between pellitized and non-pelletized seed in the measurement of germination rates.

Planting and Harvest: Planting in early to late May allowed for 2 months of harvesting that was easily supported by the markets, and avoided bolting and bitter leaves. Future investigations of both early spring (March 20-25th) and late summer to fall plantings (Late August - October) would be desirable. Plant spacing was effective for heads at 12" on center, 2 rows across; ideal spacing for leaf was 8-10", 2 rows across. While optimal planting intervals depend largely on the needs of particular markets, this study found that planting at 2-week intervals for leaf and 4-week intervals for heads was most effective. Harvest times depend on the market: baby leaf is harvested in 28 days, mature lettuce is harvested in 48 days. A well-supported market was found for mixtures of baby, mature leaf lettuce, as well as mixtures of red and green varieties.

Performance: All leaf lettuce had good growth and limited disease and insect pressure this season, with one noted exception. Tatsoi variety (Johnny's organic seed), which has a heavy leaf similar to spinach, had extensive flea beetle damage. This variety is not recommended without further insect controls. Xena (Harris Moran), a dark green leaf lettuce, sold well at tailgate and roadside markets. Cardinale (Johnny's), a red crisp, did not get bitter, and also sold well at markets. Red/Green Salad Bowl (Johnny's) oakleafs did not get bitter, even when starting to bolt. Red Lolla Rossa (Johnny's) was quick to bolt, and become bitter fast.

Challenges: While both leaf and head lettuces were investigated in this trial, results for head lettuce varieties (Summer Crisp, Butterhead, Romaine) were limited due to hail damage and subsequent disease. The crop was knocked down prior to disease identification to prevent spread, but likely culprits were Rhizoctonia solani or Sclerotinia sclerotiorum. This unfortunately prevented the collection of harvest and yield information; market investigations indicate that pricing of this commodity was highly variable.

CONCLUSION

Leaf lettuce production in western NC can be highly profitable for growers in both organic and conventional markets. Leaf lettuce varieties do well in springtime; additional planting times need to be considered to extend marketing season. Environmental damage and subsequent disease pressures limited assessment of head lettuce and prevented the organization of field days. Results from these trials will be published in the Buncombe County Commercial Horticulture Newsletter this spring, which reaches over 850 people.

The funding for this project allowed growers to diversify their commodities, find new profitable markets, and limited the financial risk of trying new crops. Potential economic impact of this commodity for the grower (using current parameters of production) is estimated as an additional weekly income of $200 - $300.

Special thanks to Micheal Hannan of Harris Moran and Steve Bellavia of Johnny's Seeds for donation of all seed used in this trial.

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Updated April 2003
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