How big is a boxwood?

[ponderosae]

I got a common boxwood shrub (Buxus sempervirens), which says its mature height (without pruning) is 4-6ft tall and 4-5ft wide (on the label). Although, other sources say it can grow much larger. I'm aware that there are dwarf versions, like Buxus microphylla, but the descriptions of common boxwood don't seem to distinguish between tall and short versions with the naming of them (all being Buxus sempervirens). Am I missing something, or does a 4ft tall boxwood have the same name as a 24ft tall one?

"Buxus sempervirens is an evergreen shrub or small tree growing up to 1 to 9 m (3 to 30 ft) tall, with a trunk up to 20 centimetres (8 in) in diameter (exceptionally to 10 m tall and 45 cm diameter)".

"Buxus sempervirens, American boxwood is a classic, large-growing upright rounded boxwood. In an ideal environment, the plant will continue to grow for 75 to 150 years and develop into a massive shrub (sometimes as large as 15 ft. tall and wide or more)".

"Buxus sempervirens, North Star Boxwood...  Use North Star boxwood as a low-growing hedge... Garden Height: 24 - 32 Inches Spread: 24 - 32 Inches."

Well, maybe "common" was the keyword for the kind of boxwood I got, since the others are called something else, even though they're all Buxus sempervirens, but the first article doesn't distinguish, and says the common boxwood can be any size: "Buxus sempervirens, the common box, European box, or boxwood"...

[Southside]

We have one "English" Boxwood that is about 4' tall and maybe 6' across - it's old and does not grow very rapidly.  Then we have two "American" Boxwoods that are 20' tall and easily 20' across at the base, I have been told they were put in at the same time as the English variety was.  They put on probably 6" or so a year in width.  

[Don P]

Also read up on boxwood blight, it has become a serious and widespread problem of late.

[ponderosae]

This one says it's a product of Canada (maybe an English boxwood then).

[Southside]

Can you post a close up of the leaf shape?  The two types I have are slightly different. 

[ponderosae]

Not right now, but I'll see if I can find a similar image for comparison.

[btulloh]

When you rub the leaves of English boxwood, it leaves a smell like cat pee.  The American boxwood doesn't.  It's a surefire way to tell them apart.  (I'm NOT making this up.)

The smell of the English boxwood seems to even fool the cat as well, because he likes to back up and spray it just in case there's been another cat in his territory.  

[ponderosae]

Boxwood – Varieties, this page notes that the two different leaf shapes are between common and dwarf versions (of Buxus sempervirens vs microphylla), and it is also says that English boxwood is the same as Common boxwood, but there are different cultivars... so this simply wasn't specified on the label (except it must be one of the shorter cultivars, going by its description, or I'll just call it the Canadian cultivar).

Well, there are more pages or even books about cultivars. This one implies that the common boxwood is a cultivar for low hedges, and other sizes have different names, as pictured: Available wholesale boxwood cultivars in the United States, and this one has a chart of different sizes: Boxwood nursery & Cultivar information, and another one says that The American Boxwood Society lists 365 cultivars for boxwoods! Maybe that's in one of the books they publish, but one of their bulletins says "The dramatic increase, with 270 new names, between the 1987 and 2006 editions, is indicative of both a heightened interest in boxwood and more effective methods in identifying new releases".

Apparently some are hybrids between Buxus sempervirens and Buxus microphylla, or have different leaf shapes too.

Anyway, I got some tips on mulching from a couple of those sources... "Boxwoods in the southern United States can have root problems if a thick mulch is applied. For this reason gardeners should only mulch lightly"... "Only 1/2 to 1 inch of leaf mulch around your boxwood. Do NOT use bark mulch". Actually, I'm thinking pine needles would be a good mulch, because they are said to make the soil more acidic, which is recommended for the boxwood.

I've just read about boxwood blight too, and they say that some cultivars are more resitant than others. Also, I didn't notice a foul odor (whatever cat pee smells like, I can't remember ever sniffing it like some kind of wine taster), but I'd imagine it would be variable across so many cultivars (or cats in the area). I'll probably just pee on them myself (free fertilizer). Coincidentally, they are said to be one of the few deer-resistant evergreens.