Acclimatization, zones, and how plants adapt to weather

You know when you go on a tropical vacation in the winter and at your destination, the locals are wearing hats, long sleeves and pants. You strip down, head to the beach only to get sunburn and heatstroke? Eventually, after a week, you get used to it. Upon return, that first blast of cold at the airport feels like the Arctic, yet people are wearing shorts!

Plants experience the same affect, perhaps even more because it happens gradually at a cellular level. The more robust the cell walls become, the hardier the plant.

Every living thing has preferred conditions. Plants are grouped into zones to help guide gardeners to choose plants that will survive in their climate. It is based on the worst weather extremes for the area: Coldest temperature, number of frost free days and exposure. It’s good to know your zone before you waste your time and money on something that won’t thrive. Zones can be pushed higher by starting plants indoors, protecting them with cloth, overhangs, windbreaks, a south facing wall and   greenhouses. Global warming is also changing things and most areas will be up-zoned in the near future.

Microclimates exist in all zones. Sunny south facing protected areas can be a full zone or more higher than a cold, windy, shady frost pocket. Understanding your microclimates on your property can determine whether you will succeed or not. It’s something you need to constantly pay attention to, and even make notes, if you have to. The smallest changes can make a big difference.

Slowly, plants need to adapt from one environment to the other. Our intervention is called “hardening off”. Plants started indoors are used to the warm cosy, calm and diffused light. If you put those out right away they will most likely get shocked by cold nights, wind, pounding rain and scorching sun. The trick is to, over the course of several days, slowly leave them out in their new environment a little more each day, paying attention to extremes in which case you will have to leave them indoors or add extra protection.

When buying plants in the spring it’s good to ask the grower to what extent they’ve been hardened off, if at all. You may have to do it yourself. Something few consider. Many tropical plants in Florida, grown for export as houseplants are raised under shade cloth, not because they don’t tolerate sun, but because they will eventually live in someone’s living room. It works both ways.

When to plant your starts or seeds outside is also tricky. Seed packages are only a rough guideline as they can’t possibly know everyone’s circumstances. Even experienced gardeners can’t rely on calendar dates, as every year is different. It’s part intuition, part trial and error and partly luck. Those in tune with nature will know when to plant something by biological clues related to the weather, like when the crocuses sprout, the ice on the lake melts, you see the first Robin or the forsythia blooms.  This study is called Phenology  and is the most accurate method. The even more in tune will take biodynamic guidance into account such as moon cycles, the almanac  and spiritual doctrines to plan schedules, making things  even more complicated to organize.

Regardless, all good farmers are aware of the weather and check the forecast constantly.

Starting some things early can be as detrimental as starting them late. A root-bound start can suffer and be stunted. A plant left too long indoors on a windowsill can get leggy and fall over searching for the sun. It’s good to know how many days it takes a particular variety to mature. Transplanting earlier may serve no benefit.

Most plants will survive marginal temps above freezing. Few do anything and stay in a state of statice between 1-6 degrees celsius. Some tender annuals such as basil will perish at a damp 1-2 degrees. Transplanting on a windy day is terrible as it knocks them over, and sucks the moisture from the plants and soil, through transpiration. Some things that have a short lifespan may need successive planting to stagger the harvest. Cool loving crops may only work in spring and fall. and will quickly bolt in the summer. Late maturing species may need to be brought indoors to finish off or  to spend their dormancy. Hardening off is also required to adapt in this case , now humidity and introducing pests indoors becomes a concern. Plants are fickle,  you need to get to know them personally.

There are obviously so many factors to consider: The bottom line is that you have to treat all your plants like dependents and provide the best care for them from the elements as possible. You have to guide them through life, like children, until they are strong enough to go at it with little intervention. You can never assume anything, be complacent or lazy. What if it was your infant out there? How would you care for it?