Most of the symbols are pretty easily remembered after the first time that you have seen what they mean. There are three that might need clarification:
This generally represents lower- growing plants suitable to a rock garden, but more importantly it represents plants that require good drainage. Keeping the plant out of soggy areas, and mixing sand or gravel in the immediate area is wise.
2) Part Shade:
This is a really broad designation. It can mean anything from “this plant tolerates very little sun”, to “you can get away with 5 minutes of shade at noon” to “we thought we’d label it this way ‘cos we weren’t sure, and we know we can get away with it”. Individual gardens vary, and so please remember that if the plant doesn’t seem to be happy within 3 weeks, relocate!
The most important single symbol. Because it is important, and confusing to describe, Americans and Canadians have developed separate systems, just in case you get too confident . It works like this: based on average lowest minimum winter temperatures, countries are divided into numbered areas that give an indication of what plants that environment is likely to allow. Both systems give the coldest areas the lowest numbers.
The values run from 1 to 10. And so you would see Hudson’s Bay with areas of Zones 2 and 3, while you would see Florida with Zones 9 and 10, and so forth. However, how cold it gets over the winter isn’t strictly a matter of lattitude. Prevailing wind patterns and geological features like lakes and mountains change the macroenvironment in odd ways that will create zone areas that are no longer straight lines- in fact, you could be surprised to find, for example, that parts of British Columbia are in the same zones as parts of Florida. Find your location on either the map of the States or Canada, and look for the corresponding zone. (American maps always give American values, and Canadians their own,too…)
This number given (for example, Z. 6 in Toronto) means that when you shop for plants, you can buy any plant that says “Z.1-10″, or “Z.2-10″, or “Z.3-10″, anything up to and including “Z.6-10″. The first number of the “Zone” symbol is the coldest zone the plant will tolerate. The second number is the hottest zone that plant will tolerate. It’s usually only the first number that will cause concerns. If I were to buy any plant that said, for example, “Z.7-10″, I would be taking chances that the damn thing wouldn’t come back next year.
You can shop, then, for any plant where the zone symbol shows that first number lower (colder), or equal to, your zone. And do check, because garden centers make mistakes, too. Most of what your local garden center chooses is likely to be quite hardy for your area. They do have a vested interest in your happiness, even if they do not offer a guarantee. Two situations that might cause you to run into the problem of zoning differences between the U.S. and Canada is when you are researching information from texts that happen to have been published in the other country, or when you first import plants. In general, American zones differ from ours by one zone- usually what they will term Zone 5, we will term Zone 6. Try to be sure that you have at least one good reference text that refers to plant hardiness in your own terms.
Now, we’ve talked about macroenvironment, the big climate picture, but there are ways of trying to bring thru plants that are warmer by nature than the rest of the area, or your garden. Most gardens have hot and cold spots. These microenvironments are often a zone or more warmer or colder than the prevailing zone, and so may be able to support special plants that you really would like to try. Full sun areas that face south, especially those close to walls, are usually warm. In addition, snow cover (or mulching) will help to mitigate some of problems faced by plants in winter. If you have pets, you can get to know your own garden’s microsystems pretty soon. Cats know microsystems. On a sunny cool spring day, they will always find the warmest spot. And in the heat of summer, you’ll find them in the cool zones.
A word of unsolicited advice: if you are just beginning a garden, wouldn’t it be wisest to invest in plants that you know are truly hardy? I am not recommending zone extension as a matter, really, for only experienced gardeners to delve into. In fact, anyone who is taking a novel plant unsuited to their zone and trying to nurse it through is on new ground. But experiments like this might be best later when you have invested in the spine of the garden you wanted. Putting your money, time, and heart into plants that might not make it can lead to giving up on gardening, and leave you with funny gaps in your border, besides. As a matter of fact, it may not be a bad idea to shop for plants that are at least a zone hardier than your own zone, at least at the beginning. Your first objective should likely be a full, lush garden, and that’s most likely to happen by using suitably hardy material.