They were cute when they were young, but it’s now time to say goodbye to these formerly dwarf conifers. Photo: natureworksct.blogspot.com
There is really no such thing as a dwarf conifer. All grow throughout their lives. So, the tiny little conifer that looks so good in your rock garden and which the label listed as 3 feet (1 m) high by 5 feet (1.5 m) in diameter may be one day as tall as your house and nearly as wide!
Why Do the Labels Lie?
They don’t really. It’s just that dwarf conifer labels offer different information than regular plant labels and no one ever seems to explain what they mean to the home gardener.
With a perennial, the dimensions given on the label are pretty much what the plant will reach at maturity and it will stay at that size all its life.
The dimensions of trees are also fairly close to the maximum size you can expect under average gardening conditions, although they can vary more, depending on local conditions. Still, a “small tree” will probably stay at less than 30 feet (9 m) in height and a “large tree” will eventually reach 70 feet (21 m) or more, so the label information is reasonably close to the reality of the situation.
But dwarf conifers are classified based on a different system. The dimensions listed don’t refer to its maximum size, but rather its expected dimensions when it reaches 10 years old. It will not just reach that size and stop growing, but will keep on at the same pace all its life.
The American Conifer Society developed four size categories for conifers, according to their growth rate. The problem is that this information is not always being shared with home gardeners. But now you know!
Miniature Conifer: grows less than 1 inch (2.5 cm) per year, so a 10-year-old specimen could still be under 1 foot (30 cm) in height and spread.
Dwarf Conifer: grows 1 to 6 inches (2.5 to 15 cm) per year. That means some might be 5 feet tall or wide after 10 years … possibly less dwarf than you had hoped.
Intermediate Conifer: grows 6 to 12 inches (15 to 30 cm) per year.
Large Conifer: grows by more than 12 inches (30 cm) per year.
As you can see, so-called “dwarf conifers” likely won’t look very dwarf after 10 years or so of growth and even most miniature conifers, since they grow all their lives, will become huge over time.
💡Helpful Hint: In spacing “dwarf conifers”, calculate the double of the height and diameter listed on the label. This will give you a more realistic estimate of its size in over its useful lifetime, about 20 years. And seriously consider removing them after about 20 years, because at that point, the term “dwarf conifer” really no longer applies!
I’m not trying to discredit dwarf conifers. I find them very useful in home landscaping … and 20 years of service is excellent, but to truly profit from them, you have to know how to properly space them and you also need to know when it’s time to replace them.