Today, regardless of the season, the variety of commercially available vegetables and fruits shows no sign of decreasing. However, there is a saying that vegetables and fruits are tastiest when they are in season, and that out-of-season ones are actually harmful to health, especially for children. I would like to ask, are out-of-season vegetables and fruits really problematic in terms of nutrition and food safety?
Traditionally, vegetables and fruits are planted and harvested during specific "seasons." Out-of-season produce disrupts this centuries-old convention, making many people uneasy. This unease is not because they are actually harmful, but rather an instinctive fear of the new. On this psychological basis of "seeking a crime where there is none," various "harmful" legends have emerged.
Out-of-season produce is not a scientific monster
There are three sources for out-of-season vegetables and fruits:
The first is异地种植、长途运输 (Planting in different regions and long-distance transportation). A plant that is "out-of-season" in one region may be in season in another. For example, almost no vegetables can grow in Beijing during the winter, while they thrive in the south, such as in Guangdong and Hainan. Thanks to the advanced logistics capabilities of modern society, transporting these "in-season" southern vegetables to the north leads them to be called "out-of-season."
The second is应季生长、长期保存 (Growing in season and long-term storage). In the past, northerners stored Chinese cabbage to eat all winter, which was a primitive form of this type of out-of-season vegetable. With advancements in agricultural technology, people have gained a deep understanding of the preservation and storage of fruits and vegetables. By controlling storage conditions, they can remain fresh for extended periods. The vast majority of "out-of-season fruits" are produced this way, such as bananas, grapes, apples, pears, citrus fruits, pineapples... These fruits can be supplied year-round with little change in quality.
The third is由“大棚种植” (Greenhouse cultivation). This method is mainly for vegetables and is what people are more concerned about. So-called "seasons" and "timeliness" are merely the ancestors' summary of how to utilize natural conditions. In modern society, humans' ability to manipulate these conditions has greatly increased, so instead of adapting to plants, we make plants adapt to us. A greenhouse creates a localized environment artificially suitable for plant growth, allowing them to grow according to our needs. Before the concept of "out-of-season vegetables" appeared, people were already able to grow bean sprouts year-round.
The exaggerated difference between out-of-season and in-season
Whether through异地种植、长途运输 (planting in different regions and long-distance transportation) or长期保存、售前催熟 (long-term storage and pre-sale ripening), fruits and vegetables must be picked before they reach their optimal state. This is not a big problem for vegetables, but for fruits, it means that the conversion of various components has not been completed. In other words, they are equivalent to "unripe" fruits—ripened before sale, their state is still somewhat different from those that ripen naturally. Furthermore, during storage, fruits and vegetables are in a "dormant" state, but some biochemical reactions still occur slowly, and some nutrients are lost to a certain extent.
For greenhouse-grown vegetables, people can well control temperature, humidity, and fertilizer, but they cannot change the light, which has a significant impact on the growth of some vegetables, leading to differences in the content of certain nutrients.
In other words, out-of-season vegetables and fruits do have some differences compared to those produced "in-season" and "locally." However, this difference is only that the levels of certain "nutrients" vary, which does not mean they are "nutritious-less," let alone that they "might be harmful." In fact, the difference between an out-of-season vegetable and its in-season counterpart is often less than the difference between it and another variety of vegetable.
Demonized pesticide residues and plant hormones
Many people's concerns about out-of-season produce come from pesticide residues and plant hormones. In greenhouse cultivation, the temperature and humidity inside are very suitable for plant growth, and also for bacteria and fungi. To control them, more pesticides may be applied. But it's important to know that "the need to apply pesticides" is not the same as "excessive pesticide residues," which is not the same as "being harmful." Greenhouse cultivation is more conducive to large-scale and standardized management—highly toxic pesticides are now rarely used. Reasonable and standardized use of pesticides can effectively control pests and diseases while ensuring food safety. Moreover, even if one occasionally encounters "unscrupulous farmers" who "abuse pesticides," as long as the fruits and vegetables are thoroughly washed, this risk, which was only a "one-in-a-million" chance to begin with, can be avoided.
The ripening of fruits after vegetable cultivation and storage sometimes involves "plant hormones." Many people, upon seeing the word "hormone," jump to conclusions and worry unnecessarily. In fact, plant hormones only have a hormonal effect on plants and have no effect on humans at all. Worrying that plant hormones can cause "precocious puberty" in people is as absurd as worrying that "pollen can make women pregnant"—it's important to remember that pollen is the sperm of plants.