Harvesting organic vegetables

Towards the end of last summer, I harvested a bumper crop of organically grown peas. They were extraordinary in taste and quality. For several weeks I gathered them before dawn then packed them inside raw calico bags which stacked neatly inside the crisper section of my old twin door refrigerator. I offered them to relatives, friends, and neighbors.  Apparently there was no shortage of families who appreciated receiving small packages of freshly harvested garden peas. After my initial distributions I received a polite telephone request from a local restaurant. One of their patrons mentioned my crop of peas and the chef was hoping to obtain some for his special minestrone. No problem, I agreed.

The following day’s sunrise caught me unprepared. I was filling the bags and steadily loading my wheelbarrow when the eastern horizon expanded with the most brilliant glow of warm orange light. I walk to the edge of my garden, surveying and appreciating all that nature provides. Dogs are barking somewhere in the distance but my thoughts swirl with the songs and memories of my childhood, this perfect moment.

Harvesting is potentially the most enjoyable and rewarding of the activities associated with organic vegetable gardening. By fulfilling the need to provide ongoing food and sustenance, the harvest was originally experienced as a time of celebration and healing. Amongst traditional societies, there are numerous examples of harvest rites and celebrations which are usually associated with the religious and spiritual practices of their people. In Western Europe and North America, for example, the concept of Halloween extended from the combination of agricultural and religious ceremonies. These were established to accompany the annual harvest of grain and vegetables, before onset of the northern winter. Native tribes of Canada and North America frequently included dimensions of renewal and healing to their traditions of harvest celebration. Contemporary scientists have also reported the positive effects of gardening, including increased levels of serotonin and endorphin generated around the time of harvest. These are natural chemicals released in the brain to promote relaxation and a deep sense of well-being.

The optimum time for harvesting vegetable produce varies according to the influence of soil condition, seasonal factors, and personal taste for the flavor and texture characteristics of individual varieties. In many instances, the timing will be influenced by the metabolic rate and storage characteristics of individual vegetable types. Immature seeds and legumes like sweetcorn, fresh peas, and beans contain high water content and an elevated metabolic activity. These vegetables are generally harvested before their sugars are converted to additional starch. Vegetable varieties consisting of edible flowers, buds, and leaves can also have high metabolic activity and may be susceptible to mould and bacterial damage when their harvest is delayed. Most of the root, tuber and bulb vegetables have slower metabolic rates and are less likely to require early harvesting. Beetroot, carrots, onion, potatoes, parsnip, swedes, and turnip are classified as non perishable, and can be stored for prolonged periods if required.

Inexperienced growers tend to focus on the harvesting schedules published in popular gardening books and magazines.  The majority of winter vegetables should be picked towards the latter stages of their growing season. This is certainly true however each crop is unique and experienced gardeners must eventually develop strategies for consistently determining this point. I usually depend upon the physical properties of my produce. I’m more than satisfied with vegetables exhibiting a pleasing combination of color, firmness, and size. I also know that some gardeners employ scientific measures. I’ve listened to experts who use special instruments to evaluate the electrical and light transmittance characteristics of their vegetables. There are standardized tables which determine levels of maturity and ripeness according to these measurements. Less accurate comparisons are sometimes based on the chemical composition or respiratory behavior of vegetable samples.

Summer vegetables are frequently harvested before the onset of physical maturity. Commercial crops of sweetcorn, beans, and peppers are influenced by contemporary food styles as many distinguished chefs and providores demand the sweet taste and crisp texture of immature vegetables. Home growers and hobbyists can choose to ignore current fashion, although many prefer harvesting early to commence new crops or to encourage additional vegetables on plants which produce throughout the season. There is also an argument that early harvesting discourages the onset of troublesome plant diseases like sclerotinia, canker, and wilt.

The majority of commercial growers prefer harvesting their vegetable crops with high water content. This ensures optimum weight and appearance, particularly for the leafy greens which respond most rapidly to changes in their external environment. In some instances, maximum water content is encouraged through the use of chemical solutions, generally resulting in a bland or neutral taste. Skilled organic growers usually attempt to manipulate their watering to achieve maximum flavor in combination with high water content at the time of harvest. By carefully restricting watering throughout the early and middle stages of growth, vegetables are encouraged to increase the flavor characteristics determined by local influences such as climate, soil, and planting arrangements. When watering is increased during the final weeks of growth, most vegetables hold the additional fluid within their cells at the time of harvesting.

Efficient harvesting depends upon an ability to reject poor quality produce in coordination with handling and storage techniques which maintain an optimum standard of quality. In the first instance, harvested vegetables must be healthy and fully intact. This implies the absence of any symptoms relating to disease, pest infestation, or the physical signs of damage including bruising, cuts, and swelling. There are several reasons why damaged vegetables should always be discarded. Mechanical damage can easily distort the protective function of outer tissue layers, resulting in accelerated rates of gaseous exchange and water loss. Surface defects can also permit access to bacterial decay and disease causing microorganisms. Once detached from their parent plants, the capacity for wound healing and recovery is greatly diminished or negligible for most vegetable varieties.   

Some varieties of vegetable are particularly susceptible to water loss during the timespan between harvesting and secure storage. Water loss can occur through the combination of accelerated metabolic activity with a hot and dry atmosphere. Under such conditions, it is possible to lose approximately ten percent of the harvested weight for a perishable crop within several hours. This generally results in severe wilting and decreases the overall crispness and palatability of the produce. In the absence of protective measures, the rate of water loss depends primarily upon the ratio of surface area to volume. Leafy vegetables like spinach, for example, have large evaporative surfaces which suffer greater losses per unit weight than root vegetables like parsnip or swede.

Most commercial producers make considerable efforts to protect their vegetable harvest from water loss and several of their techniques may also apply to small scale organic growers. To ensure milder conditions, many crops can be harvested at night or early in the morning. The rate of water loss can also be reduced by providing physical barriers which limit the free circulation of warm air. These employ a variety of readily available materials including polythene films, fiber cartons, and sawdust. With current improvements in handling and storage techniques, it is now considered beneficial to quickly reduce the temperature of vulnerable vegetables at the time of their harvest. This can be facilitated with mobile chillers and air conditioned storage bins. Sometimes described as precooling, the technique is widely employed for highly perishable varieties of lettuce, broccoli, cauliflower, peas, and asparagus. Precooling restricts the rate of water loss, prevents undesirable changes in color, and protects important nutrients like vitamins C, A, and folic acid.