My wife and I were outside, enjoying a very nice spring day, trying to complete some important garden chores the other day. We hoped the rain would hold off as long as possible – at least until we were finished with one major project. While we were working in the front garden, one of our neighbors dropped in and began to slowly walk around the path, carefully observing every conifer as he passed. He had a distinct expression on his face as he wandered around – something between a sneer and a look of suspicion. Finally he made his approach.
“Ed,” he said, “I thought you told me these trees of yours were dwarf.”
“Yes, many of them are dwarf cultivars, though, some are miniatures and others would probably be considered intermediate growers—” I said before he cut me off.
“Then explain to me again how it is that my dwarfs have turned into giants!”
Fortunately for me, going through this lesson is much easier with the visual aids readily available in the conifer garden than, say, in a coffee shop.
First, I pointed over to the group of our native Douglas fir (Pseudotsuga menziesii). I explained that these truly giant trees were very likely 80 to 100 years old. Then I walked him over to where I have allowed a few seedlings from these trees to grow for the past eight years. I showed him the length of last year’s growth. The central leaders of these young trees averaged 30 inches! Had I not been pruning these trees every year to encourage a nice Christmas tree shape, they would likely be 20 feet tall (remember that’s in just eight years). Then I walked him over to a nice old specimen of Picea abies ‘Sherwood Compact’. This tree is close to twenty years old and is just over ten feet tall.
“Ok, but how is that a dwarf then, it’s still too big.” He said, arms folded over his chest.
I took a deep breath and tried again.
I reminded him about the giant Douglas firs, their eight year old seedlings, and then I took him to a very special cultivar called Picea abies ‘Tompa’. This specimen is fairly young – about 15 years old – but it is less than three feet tall.
“See this one; it is just about the same height, after 15 years of growth, as just one year of growth of those young trees over there.” I said pointing back to the young Douglas fir seedlings. “The Douglas fir grows at an average of 30 inches per year. It continues to grow and grow over its lifetime into the giant forest trees you see at the corner of my property. This dwarf form will also continue to grow throughout its lifetime – just at a greatly reduced rate. Conifers don’t just grow to a certain size and then stop… if they do, they’re dead.”
“So, if this ‘Tompa’ grew for 300 years, it could be… 50 feet tall?” My friend’s eyes grew wide as everything began to make sense. “But Ed, when my wife brought home one of those conifers – at your suggestion – the tag said it would grow to 10 feet tall.”
“Well,” I answered, “depending on the grower, that listed size may have been for a 10 or 15 or even a 20 year plant. The better growers will give specific information. But remember, that’s not 10 years from when you buy the plant – you need to keep in mind that you may have just purchased a 5 year old tree.”
When considering a new conifer for your garden, remember that it will continue to grow throughout its lifetime. Upright growers continue to grow taller and taller, low spreading forms become wider and wider. Simple math skills are sufficient for anyone to gain a pretty good idea how large a particular conifer may grow. Determine the length of the growth of the central leader for the past year or two. Multiply a single year’s growth by as many years as you wish, and you will have a very good estimate at how large that conifer will grow in your garden.
A very large tree will grow at a rate of greater than 12” per year. Intermediate sized trees grow from 6” to 12” per year. Dwarf forms grow from 1” to 6” per year and finally, miniature conifers grow at less than one inch per year. If you purchase a true miniature conifer that is 15 inches in height or diameter, you have found a fairly old specimen and it will very likely cost you a good amount of money at the local garden center. On the other hand, an intermediate growing cultivar, that is 15 inches tall may only be three or four years old and to the uninformed, could seem like a real bargain in comparison.