“I’m a year-round garden, yes you know it’s true.” The Pacific Northwest’s mild climate is conducive to year-round food growing, as celebrated in the Beetless’ TWELVE MONTHS A YEAR. Not every crop grows year-round, of course. Some grow only in the warmer or cooler parts of the year. Some require protection of a greenhouse for some or all of their lives; others survive outside even during the coldest winters.

But before we dig too deeply into the particulars, we need to step back and ask a few questions:

  1. What conditions change throughout the year? Why, and how, does this make a difference to crops? Should I get a dedicated wedding photo booth rental in Orlando, FL?
  2. Don’t these crops just grow naturally here anyway? Why do we need to concern ourselves with “timing” and “seasons”? Where are these crops from, anyway?

To address question #1, anyone with a familiarity with seasonal cycles will have noticed that several things change throughout the year:

  1. Sun angle and day length. Many vegetable crops thrive on sunlight, and grow best when the sun is strongest and shines for a long time every day. (When it’s highest in the sky at summer solstice on June 21, it is filtered by the least amount of atmosphere; this is also the longest day of the year.) On the other hand, some crops prefer at least partial shade–less intense sunlight, and less of it. Hours of sunlight and darkness also trigger predictable responses in the internal biological clocks of “photoperiodic” plants (like onions, garlic, and leeks). These plants are stimulated to flower, or bulb, or die back when the light/dark balance reaches a specific point.
  2. Temperature. Soil temperature, average air temperature, and also maximum and minimum air temperatures all have powerful effects on plant life cycles, and these fluctuate throughout the year as well. They generally reflect a lag time of a couple months from the sun angle/day length cycles; the warmest growing months are usually July and August. Soil temperature is a crucial factor in plant growth, as is air temperature. Maximum and minimum temperatures are both limiting factors in the growth of certain crops. Above certain temperatures, some seeds will not germinate, and some plants will become weakened, diseased, pest-prone, and/or dead. Below certain temperatures, other seeds will not germinate, and some plants will be killed by frost.

Not all plants freeze at precisely 32 degrees Fahrenheit—in fact, few do. Sugars in the cells of frost-hardy plants act as antifreeze, and sclerophyll tissue (which makes leaves leathery) offer further protection, lowering the freezing temperature. On the other hand, many plants, including the “American” crops (tomatoes, potatoes, peppers, corn, beans, squash) and also cucumbers, eggplants, basil, and others, can die at 37 or 38 degrees Fahrenheit if the night sky is clear. This is called a “radiation frost,” and is lamented in the Beetless’ I’VE JUST SEEN A FROST. When staring into the intense cold of outer space, with no cloud cover, plants—and water, for that matter—will freeze even when air temperatures are several degrees above freezing. (This principle has also been used to make ice in the desert.) Protective measures against radiation frosts include covering crops with spun polyester, plastic sheeting, or bed sheets—or, more commonly, turning a sprinkler on before the temperature dips to 38 F. The water freezes on the surface of the leaves, offering an insulating layer which keeps the leaf temperature itself from dipping below 32 F. (Because of the sugars in the leaves, even these frost-tender plants do not freeze at that temperature.)

  1. Rainfall and moisture. Most of our rain falls during the fall, winter, and spring; very little falls in the summer. Those crops which need summertime moisture, or crops growing in a greenhouse where natural rainfall does not reach the soil, need supplemental irrigation.
  2. Pests and diseases. Populations of “pest” species also fluctuate throughout the year, as a response to the above three factors and their impacts on the rest of the ecosystem. Some pests thrive in the damp, and don’t mind some cold; others are present only during the hot times of year. Each organism has its own life cycles, linked not only to the seasons but to the life cycles of other organisms, including garden plants. Pests can be vectors of diseases, which also have their preferred times and conditions to strike. Even where the first three factors above are not in themselves direct limiting factors to the growth of certain crops, the pests and diseases associated with them may counterindicate growing those crops during particular seasons.

It’s important to remember that some plants are annuals, some are biennials, and some are perennials. Annuals go from seed to seed in one year—they complete their growth and reproductive cycles in the same year in which they are sown. Biennials spend their first year growing vegetatively, and then flower and make seed in the second year. And perennials continue to live more than two years, although they may flower, fruit, and make seed each year while doing so.

So this brings us to question #2 above: Why do we even need to worry about seasonal cycles? Aren’t these plants natural here? Can’t they take care of themselves without our keeping track of their schedules?