Posts Tagged ‘leafy greens’

Continuing Vegetable Sales in Fall and Winter

Friday, September 21st, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

While most vegetable growers finish up with fall crops around Thanksgiving, there is potential to produce throughout the fall and winter. There are fall and winter sales potentials with schools, institutions, and restaurants; for CSA’s; and for specialty wholesale markets.

One strategy is using storage to have products available out of season. This has been a common practice on a large wholesale scale with potatoes and apples where large controlled environment storage facilities are used. On a smaller scale, there are many vegetables that can be stored in sheds, cold boxes, or greenhouses as long as products are kept above freezing and have adequate humidity. It should be noted that critical minimum temperatures will vary according to the type of produce.

Probably the easiest vegetables to store are hard shelled winter squash such as butternuts. If kept around 50°F, most of the hard shelled squashes can be kept for at least 3 months, some for over 6 months. Potatoes store best at 45°F in high humidity and sprouting can be a problem for longer storage. Sweet potatoes, once cured, can be stored for months as long as the storage temperature is kept around 60°F. Colder temperatures damage the roots. Onion storage depends on the type but longest storage is just above freezing in dry conditions. Cabbage can also be stored for long periods. The key is to grow storage varieties that are dense. Longest storage is at 32 F° in high humidity. Napa type chinese cabbage also stores well in refrigeration (several months). Other crops successfully stored include carrots, parsnips, rutabegas, and turnips. In fruits, long keeping apple varieties can be stored for months in cool temperatures.

Field storage is another way to extend sales of some vegetables. Root crops such as carrots, parsnips, and beets can be kept for extended periods in the field if kept from freezing with row covers or straw mulch. Certain cabbage varieties can field store into winter if protected from hard freezes with row covers. Green onions and leeks also field store well.

An alternative strategy is to make used of high tunnels, low tunnels, row covers, or a combination to grow cool season crops for fall and winter harvest. Greens crops in the mustard family (mustard, turnip, kale, collard, cress, many asian greens); spinach, chard, and beet greens; and lettuces and endive can be planted in the late summer or fall and harvested repeatedly through the fall and winter in these protected systems without additional heat. Some day neutral strawberries can be harvested into the late fall in high tunnels or low tunnel/row cover systems. The use of row covers can also extend harvest periods for crops such as broccoli where side shoot production can be maintained after main heads are harvested, often through Christmas, and Brussels sprouts where sprout production can be extended into winter.

Of course, there is potential for production of many crops in heated greenhouses. The choice of varieties becomes important for greenhouse production because of the lower light and reduced daylength conditions in fall and winter. Specific greenhouse varieties of crops such as tomatoes, lettuce, and cucumbers have been developed for fall and winter production.

UMD Researchers Seek Tomato and Leafy Greens Farm Participants

Friday, June 22nd, 2012

Sasha Marine, UMD Postdoctoral Research Associate;

In recent years, outbreaks of Salmonella, Listeria and E. coli in fresh vegetables and the resulting public concern over food safety has prompted regulators to re-evaluate production and post-harvest practices. Research has demonstrated the importance of Good Agricultural Practices (GAPs) and Good Hygienic Practices (GHPs) for preventing contamination and the subsequent growth of pathogenic microorganisms. As a result, protocols (referred to as “metrics” by the food industry) have been established by specific commodity groups and retailers, as well as by state and federal organizations. However, knowledge gaps remain as to the risk factors and adaptability of these protocols to different climates, regions and types of farming operations. It is important that any protocols be suited to implementation on small- and medium-sized farms, which are typical to Maryland and Delaware.

Thanks to a multi-state grant from the USDA National Institute of Food and Agriculture, University of Maryland researchers Kathryne Everts and Christopher Walsh will be collecting data from several small- and medium-sized farms in Maryland and Delaware to examine the influence of water sources and environmental parameters on the microflora on tomatoes and leafy greens. The scientific and technological knowledge gained from the 3-year project will be used to develop, refine and defend national food safety protocols for domestic and imported produce. Data generated from this project will also be incorporated into an upper-division undergraduate course being developed by Walsh and faculty at the University of Delaware and the University of Florida.

Farmers wishing to participate in this project may contact Sasha Marine (

Bolting in Spring-Planted Vegetables

Friday, May 20th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Bolting is the term used for flower stalk formation in vegetables. Bolting response may be related to temperature, daylength, or a combination.

Bolting in spinach, lettuce, and some radishes (oriental types) will occur naturally as days get longer. High temperatures will accelerate bolting in spinach and lettuce.

Many mustard family plants need a cold period along with lengthening days to flower. The amount of cold needed depends on the species and variety. Mustards are very prone to cold initiated spring bolting; turnips, Chinese cabbage, and salad radishes require more cold to initiate the bolting response.

In the cole crop group, cabbage planted very early in cold springs may bolt and premature flowering in broccoli, cauliflower, kale, and collards also occurs when planted too early, or if the spring is abnormally cold. However, cole crop transplants have to be of a certain age to be susceptible to this cold-initiated bolting.

Other biennial vegetables such as beets, carrots, and onions also can be induced to bolt but only once plants have reached a certain size (they are past the juvenile growth stage). This is uncommon in our region.

Controlling bolting starts with planting during the recommended planting window. Early planting will contribute to bolting in some crops (such as cabbage), late planting in others (such as lettuce).

Select varieties that are adapted to the spring planting season (an example would be Savannah mustard). Chose slow bolting varieties of spinach and lettuce. Choose spring adapted varieties of oriental radishes and Chinese cabbage.

One issue that complicates this is the use of high tunnels for early production. High tunnels allow for earlier planting but cold snaps still may drop temperatures enough to cause the cold induced flowering response in many of these crops.


FDA Has Released Draft Food Safety Guidelines for Melons, Leafy Greens, and Tomatoes

Friday, August 14th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.;

As part of the continued emphasis on improving produce food safety, the Food and Drug Administration has recently published draft guidance documents for reducing microbial food safety hazards in 3 crop groups – melons, tomatoes, and leafy greens. These publications are available for viewing at the FDA website at the following locations:
Leafy Greens

The FDA is currently accepting public comments on these guidelines. The following are some excerpts:

FDA recommends:
● Conducting environmental assessments on the topography, land history, risk of flooding, adjacent land use, and domestic animal and wildlife presence associated with the production environment, using concepts that are outlined in the GAPs Guide (to the extent that any of these environmental factors are present).

● Monitoring and reducing, to the extent possible, domestic animal, wildlife, and insect activity in melon production environments that may contaminate water and soil with human pathogens and directly or indirectly contact melons, thereby increasing the risk of product contamination.

● Evaluating whether to harvest portions of melon fields when there is evidence of unusually heavy wildlife pest infestations (e.g., presence of wildlife feces, large areas of animal tracks, or burrowing).

● Training harvest employees to recognize and report signs and evidence of wildlife pest infestations (e.g., feces) and take appropriate actions.

● Delaying harvest and performing extra washing when heavy rains have recently occurred. Heavy rains may increase the likelihood of soil-to-melon contamination.

Multiple Melon Harvests
Multiple melon harvests may increase the likelihood of melon contamination due to increased wildlife and insect pressures because of the presence in the field of melons mechanically damaged during prior harvest operations.
FDA recommends:
● Training harvest employees to recognize and not harvest melons that have mechanical damage or possible contamination from previous harvest operations.

● Evaluating ways to reduce flying insect access, to the extent possible, to animal feces and other likely sources of human pathogens that may contaminate non-harvested melons in the field.

● Evaluating ways to dispose of culled melons which reduce the potential for melon culls to serve as animal and insect pest attractant. This will reduce the potential for insect/pest-to-melon fruit contamination.

FDA recommends:
● Determining the previous usage of land. Assessing and mitigating conditions that may pose a food safety risk in and near production fields.

● Conducting an environmental assessment (e.g., considering topography, land history, near-by land use, and domestic animal and wildlife presence) including a consideration of the potential for flooding to create conditions that may pose a food safety risk.

● Locating tomato fields away from any area that may receive run-off or drainage from an animal operation or any other source of contamination that may pose a food safety risk.

● Avoiding, preventing, or minimizing run-off into the tomato field from any animal operation or other conditions that may pose a food safety risk.

● Avoiding the harvest of tomatoes in areas that have been contaminated by run-off from an animal operation or other potential source of contamination.

Tomato Equipment and Containers
FDA recommends:
● Cleaning and sanitizing any surface or equipment intended to contact fresh tomatoes (i.e., any food-contact surface), at a frequency sufficient to prevent the surface or equipment from becoming a source of contamination.

● Constructing reusable containers and food-contact equipment, and utensils of impervious materials that can be cleaned and sanitized.

● Checking any tomato containers that are received back from a packing house for cleanliness prior to use.

● Cleaning and sanitizing harvest containers, bins, food-contact equipment, and utensils at regular intervals during use (e.g., daily), or more often as needed, to remove sand, grit, dirt, and other residue.

● Establishing routine cleaning and sanitizing procedures (i.e., standard operating procedures).

● Maintaining all equipment and surfaces in such a way as to minimize the risk of contamination of, and injury to, tomatoes.

● Maintaining records of cleaning procedures and their implementation.

● Removing broken or damaged containers that are not easily cleanable from food contact use. If they are retained for other uses (e.g., trash), clearly marking them for their intended use.

Leafy Greens
FDA recommends:
● Conducting environmental assessments prior to the first seasonal planting, within one week prior to harvesting, and during harvesting operations.

● Assessing near-by land use and waterways for activities or conditions that may pose a risk of contamination such as livestock, wildlife, landfills, sewage treatment, chemical plants, or other conditions.

● Determining land history to identify microbial and chemical contamination from previous land use.

● Evaluating the risk to subsequent crop production on production acreage that has experienced recent postharvest grazing of domesticated animals.

● Evaluating production field locations and proximity to wildlife especially if the production field is isolated from other non-contiguous production areas.

● Evaluating whether heavy rains or irrigation practices may increase the likelihood of soil-to-leafy greens contamination.

Practices FDA recommends to reduce the risk of microbial contamination of leafy greens in the production environment include:

● Locating production sites (to the degree feasible) to minimize potential access by wildlife. For example, considering the proximity to water, wildlife harborage, open range lands, non-contiguous production lots or blocks, and urban centers.

● Controlling risks associated with production fields that are encroached upon by urban development.

● Considering risk factors including septic tank leaching and domestic animal fecal contamination of production fields and harvest equipment.

● Exercising care to reduce the potential for windborne soil, water or other media that may be sources of contamination to come into contact with the edible portions of leafy greens.

● Monitoring and minimizing domestic animal and wildlife activity in leafy greens fields and production environments (e.g., reducing potential harborage and standing water, and utilizing animal repellents and attractants).

● Considering whether or not to harvest any portions of a field affected by unusually heavy wildlife activity or evidence of wildlife activity (e.g., presence of wildlife feces).

● Assessing the field at the time of harvest to ensure that no new food safety risks have occurred.

● Using harvest practices such as removing outer soiled leaves and not harvesting whole soiled heads of leafy greens when excessive soil or mud builds up on leafy greens.

● Training harvest employees to recognize and report for appropriate action any evidence of wildlife activity or infestations (e.g., feces).

Water and Leafy Greens
Water used in production and harvest operations may contaminate leafy greens if it contains human pathogens and contacts edible portions of leafy greens or transmits pathogens by means of water-to-soil and soil-to-leafy greens contact. In addition, irrigation methods vary and each method may have varying potential to introduce human pathogens or promote human pathogen growth on leafy greens.
FDA recommends:
● Preparing a description of the irrigation water system. Using maps, photographs, drawings, or other means to communicate the location of permanent fixtures and the flow of the water system (including any water captured for re-use). Documenting permanent fixtures, including wells, gates, reservoirs, valves, returns and other above-ground features that make up a complete irrigation system, so as to enable location on the field. Documenting water sources and the production sites they may serve.

● Performing a sanitary survey prior to the use of water in agricultural operations to determine if the quality of water meets applicable State and local requirements, and then monitoring water quality with regular testing.

● Evaluating irrigation methods (e.g., drip irrigation, overhead sprinkler, and furrow) for their potential to introduce, support or promote the growth of human pathogens on leafy greens. Considering issues such as the potential for irrigation methods to deposit soil on the crop or cause pooled or standing water that attracts animals.

● Considering the impact of storm events on surface waters used to irrigate crops. Bacterial loads in surface water are generally much higher after a storm than normal and caution should be exercised when using these waters for irrigation.

● Considering the potential for pathogen contamination and growth when combining water from different sources (e.g., water systems that convey untreated human or animal waste should not be combined with conveyances used to deliver irrigation water).

● Storing irrigation pipes and drip tape in a manner that reduces potential pest infestations and developing procedures to ensure safe use of irrigation pipes and drip tape if a pest infestation does occur.

● Ensuring that water used on harvesting equipment or during harvesting is of appropriate microbial quality for its intended use. Testing the water source regularly to ensure that it is of appropriate microbial quality for its intended use.

● Evaluating risks of using reclaimed (primary or secondary) water, including use in operations such as road dust abatement. Reclaimed water may be subject to State and local requirements.