Natural Ranges: In listing the natural range of a species I often just list the approximate corners or extents, usually counter-clockwise but not necessarily! e.g. “Newfoundland/ Manitoba/ Tennessee/ Georgia” includes NS and most of the eastern half of North America except the extreme cold and warm bits. I often find that with newer plants for which hardiness ratings are not available or are unreliable, it is useful to look into the natural range and environment (including elevation) of the plant in deciding how to try to grow it or whether it might even be hardy here. Apart from that, it's just interesting to know where they are from! Much of the range information is adapted from the Phillips and Rix series from Random House (see Reference List in the General section).
Plant Hardiness and Zones: The zones to which hardiness is rated in my catalogue are the USDA zones, not the Canadian zones.
Reason? It’s not just the factors affecting the geographic Zone that the Canadian system modified: plants also have different hardiness ratings in the Canadian system (not much is said about this aspect of it!). But very little of the literature is concerning itself with ‘our’ ratings. Frankly, all the zone rating systems are just an estimate at best; a starting point from which to expand one’s horizons. And for NS’s maritime climate I don’t see anything in the Canadian zone assignments to lead me to believe that we’re better served by them (the opposite, in fact). So I’m sticking to USDA zones. (By the way, many outfits that use the Canadian zone maps use USDA plant ratings, which makes it all that much worse...).
At best the zones are only a guide. We’re learning that a lot of plants can be grown in colder zones than originally thought, if they’re given reasonable attention in siting and soil composition. (As a result there are now mail-order distributors who automatically rate a plant 1 or 2 zones hardier than the grower or the reference literature support: which really becomes a problem if the grower and the reference author already reflect absolute hardiness under optimum conditions!) Not to mention warmer winters since the beginning of this century.
Hardiness ratings I quote include the most recent information from the past few years, and may be different from what you will see elsewhere. In any event all are hardy here. Plants that have failed here have done so either because I wasn’t paying attention in siting or because stuff was mislabelled at source and so got the wrong care.
When you see "Zone 5 or colder" that should be interpreted to mean that I haven't found any hardiness reference that I'm prepared to accept, but that the plant has been hardy for me here (but the winters since 2000 have not been much of a test of cold, although they have been a test of wetness). "Zone 3 or colder" refers to seed from a source in that zone.
My Climate, roughly: (this describes the pre-2000 climate; since then we haven't really settled on a climate and have merely had "weather" which I can't really describe in polite terms): "Here" is in Nova Scotia, on the east coast of Canada, at 200m elevation (650ft), about 25km from the Atlantic Ocean in one direction and the same distance from the Bay of Fundy in the other. So while there is some ocean-induced moderation of the climate it is more extreme than along our coast; colder winters, usually with reliable snowcover for most of the winter and usually with at least one night down below -30°C and several below -25°C but sometimes with heavy rains during midwinter thaws; hotter summers, although not often above +30°C. This allows me to grow some plants that don't cope well with the wetter coastal winter, but I also have trouble with some that prefer the cool coastal breezes and fog in summer. Autumns are usually wet after sometime in October, and the ground is usually saturated going into the winter. Summer and autumn tend to be dryish. Formally, I am in a USDA Zone 5 but with a semi-maritime influence. The winters of 2001 and following have been warmer than the usual, at least with respect to minimum temperatures, with rain in place of some of the snow. As a result, some plants that used to be iffy here are now doing well, but some which used to do well are now gone or iffy-- the latter includes many alpine plants from the Rocky Mountains, which were fine in cold dry winters but can't stand the warmer wet ones that we have shifted to. By the way, did you know that Halifax (my nearest major centre, but it is coastal) gets more annual precipitation than Vancouver?
Benchmark Winters: In the catalogue and my database I make frequent reference to the winters of '96 and '97; these were, for me, real trial benchmarks: the sort of conditions of which one could say of a plant: “If it survived those, it’ll survive anything...” '96 was a year of very cold temperatures preceding any snowfall. '97 was a year in which cold temperatures alternated with rain, and a thick layer of ice formed and stayed on all surfaces, even slopes of 30 degrees. (The roots of a few rhododendrons were still frozen solid on 1 July! but amazingly although they had lost every leaf the buds did eventually open and the shrubs survived.) Since the winter of 2000 however, winters have been warmer, with wet snows preceeding heavy frosts so the ground did not freeze until sometime after the snows and in some winters it seemed that the ground didn't freeze much at all. This kind of winter has proved much nastier than extreme cold would have to many of my Alpine plants which had previously been very happy here.
What do I mean by Low Maintenance or Not? Low Maintenance plants are the stuff of complacent gardeners: plant them and then forget about them and they will come back year after year with no bother (assuming the soil was appropriate when you planted them). Some plants are unqualified Low Maintenance, others are qualified “in the right conditions”. For the latter I describe the conditions required to qualify; doesn’t mean you can’t grow them in other conditions, just that if you do they will tend to be short-lived, or will try to take over, or will develop some other habit that some gardeners will find a nuisance in some situations (could I be more vague?).
Keep in mind that Low Maintenance is also a state of mind or a philosophy of gardening. If you like a cultivated garden look, nicely raked bare soil between the plants with no hint of the first leaf of a weed, no plant is going to reduce your basic maintenance requirement! Similarly for those who are in the habit of moving plants around almost yearly to try to colour-match with precision... LM involves use of mulch and letting things look at least a bit natural-ish: and mainly leaving plants be!
Then there are the ‘Not Low Maintenance’ plants. These are plants that will take some effort to grow well, either because they are short-lived, or seed around excessively, or require constant fertilizing, debugging, checking for disease, propping up, cutting back etc. Whether or not these are worth the trouble of growing depends on the gardener. And of course several of those with invasive tendencies may well combine very happily in a meadow effect where one has such a spot, or do very well where natural boundaries will limit their wanderlust. In fact, LM gardeners will often use non-LM plants as LM groundcovers in specific bounded areas...
A very good reference for Low Maintenance garden plants is “Low Maintenance Perennials” by Robert S Hebb. Sadly no longer in print, and the 1 copy that was in the Halifax library system has disappeared. The book was written on experience at an area of the Arnold Arboretum in Boston but is very applicable to our climate, and one of my primary references.
Cultivation recommendations: these are fine-tuned for optimum long-term growth in our Nova Scotian environment. May not produce the showiest plants, but they won’t grow to death quickly either. However the plants will usually do well in conditions other than those recommended; consider it a starting point rather than an absolute necessity (usually!) In general, many perennials can be grown here quite easily if planted in a non-puddling location in a soil with not too much clay. Bark mulch also helps against temperature extremes; I leave it on year-round. Doubters may consider that I’m growing close to 2000 taxa (species and varieties), covering over to 1200 species here, mainly by application of the above. Any spot that grows ice crystals or ice pillars in winter or spring will be a problem for perennials!
The Big Deal About DRAINAGE: As you read the various cultural recommendations, you’ll probably get tired of almost always seeing some reference to “good drainage”. Because of our wettish winters with rather more freeze and thaw than much of the continent experiences, most of our perennials will drown before spring if they’re in a soil which holds water too well (Prairie gardeners are less likely to encounter drainage problems even in heavy clay because of the much drier climate and times of year when precipitation occurs or doesn't occur!). Drainage is best provided by using a proper soil mix and by growing plants in slightly raised beds (6” or more) or on slopes, while avoiding digging down into clay which then traps the water in the dug area. If the soil has a large proportion of clay, mix in a large proportion of sand or grit as well as organic material such as compost or manure. I advise against the use of milled peat moss in wet climates except in very limited specific circumstances.
What do I Mean With the Term ‘Peat’ or ‘Peaty’ Soil?: Well, not peat moss! I use these terms to mean the sort of thing that makes up the upper few inches of soil in old woodlands. (I think I’m in step with the general horticultural usage in this.) It’s a light mix of leaves, twigs, evergreen needles, dead plants, and dead roots in various stages of decomposition. Sort-of chunky garden compost. So a ‘peaty loam’ would be a Loam soil with an extra generous helping of compost, preferably not completely finished.
Requirement to Divide Clumps: Some references indicate that plants may require division every x years. You won’t see this info in the catalogue but it will be with the full data printout on your receipt; I frankly haven’t often seen that makes a huge amount of difference with most of the plants over 6 years. Whether this has to do with my cultivation habits or not is an open question... (still).
Plant width information is still in a bit of confusion: sometimes I enter the width of a mature single plant, sometimes of a mature clump: still trying to make up my mind which to stick with! I've been saying that for about 10 years now...