We love 'em. Picea abies 'Nidiformis' is called birdsnest and may be the most popular but 'Repens' and other varieties are quite similar. All are pruned as described below.
None of them read their catalog descriptions. They often reach a height of 4' or more, and we've seen them 10' wide and still growing.
Yet we've also been able to keep them small for decades -- 2' tall, bed-wide and softly -- at the same time preserving their soft, irregular shape.
We do it by pruning in late summer every two years. We cut during the second half of the growing season so we can leave the shrubs alone during their spring growth cycles. We design in part to feature the plants' beautiful, soft, bright green new shoots,* so why cut them?
(*Some readers wonder, why all these links?)
Besides, most people who cut in spring end up slowing the plant's increase in size but not stopping it. Take a look at Prune a mugo to see an example of how this develops. Dwarf pines have a similar growth habit and the same creeping tendency when pruned in spring.
So that we can cut only every other year, we shorten and narrow the plant by two years' growth each time. Growth rate varies with the plant and the place so "read" that rate on the plant(s) you're dealing with. (See photo 9.)
1. These shrubs, focus of aworkshop, have not yet gotten too big. That's perfect.
Start cutting in the year a plant reaches the size you want. It will be just right, then you cut it back and it can grow for two more years, then you cut it again... At no time in the cycle is it too big.
2. Here we are, cutting.
(A big thank you to Virginia Bergin who manned the camera to capture this group while Janet pruned, when Steven was called away from this session.) It may look like only Janet's cutting but that's because the clipping's just begun -- the pile of clippings at the arrow will almost triple in size by the end. People always start out timid but eventually get their hand in.
3. Done! Here are the plants after fifteen minutes of cutting.
(Okay, it's the next morning's photo; it was too dark when we finished. Those funnel weaver spiders netted them overnight!)
Otherwise, the shrubs look the same, right? Good! They should.
However, on second look you should notice there's now more space between the foreground plant and the curb, and that the back, right plant is showing a bit of an opening.
4. Here is the foreground plant, with a dashed line indicating its previous spread -- the mulch it covered has not yet dried. There is also an arrow pointing out a marker rock Janet set under the plant before the pruning began. That rock is under the plant in the first photo, too, but completely hidden under the branches. We didn't move the rock, only cut the branches back.
6. Look, too, at that plant in the back. It had an ungainly hump developing. (Arrow.) We removed it.
Now can you tell the plants have been pruned?
Here are other birdsnest spruces that had been allowed to get a bit too wide so that they were hanging over the walk.
7. Janet's already cut the foreground part of the first shrub. The arrow points out the clippings taken from that spot.
8. At each place where the foliage has crossed the line, she's reaching inside the plant to find a needle-clad branch with a tip that sits behind the line.
She cuts back to make that point the outer edge. If a branch that's overhanging has only bare wood within the limit we've set for the plant, she follows that branch 'way back and cuts it at its juncture with some other branch that does have room to grow. Sometimes we cut all the way back to the main trunk.
Here is a birdsnest branch and the cuts that you might make.
Like many birdsnest spruces, this one has an annual growth rate of about three inches.
How to know? The wood changes color, from light brown in its first year to darker.
Since the growth rate is 4-6 inches over two years, our goal is to cut the shrub back by 6 inches. We want graceful fluffy tips but six inches less on the top and each side.
10. So go for it - clip off that central piece where the pruners were poised in photo 9, since it extends too far.
11. Then clip that left side that extends too far...
12. ...and same for the right side.
13. See that we cut to just outside tiny new tips. They are there just waiting to jump into growth.
There are many such tips on this plant because each time we shear the outside we then feel our way around the shrub to find and remove the oldest, most branched limbs. That allows light to reach the interior and keep new growth coming. We call the second cutting ' pat and clip', since patting lets us feel those thick, much-cut stubs. This whole demonstration branch (photo 9) is one we took out as a thinning.
14. Done. About 5 inches back from where the tips were when we started, there is now a soft new tip pointed outward, ready to be the new leader.
Perhaps you have a dwarf globe blue spruce (Picea pungens glauca 'Globosa'), a weeping Norway spruce (Picea abies 'Pendula'), or a dwarf Serbian spruce (Piea omorika variety) -- cutting is the same for all of them!
Here is a branch from a Koster blue spruce with branch-shortening cuts marked. We hope you see that it's the same as photos 9 - 14.
Try it, and ask again if you have other questions. We improve at telling how-to only if we hear back from readers, or meet you in the field as we did for this birdsnest pruning at a recent Garden by Janet and Steven.
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We've received mail asking, "Why all the links?" and explaining that it takes too long to read "all you want us to read" now that we're on the website.
Sorry! We don't intend to take up your time. We send you a summary so you can pick and choose articles, and try to keep each article as short as possible.
Some of the links we include ("overall" and "details" in this article) are to help you skip forward in an article to exactly the points you want to read.
Other links we include are there so any reader -- including us -- can follow up on related or additional questions.
For instance, in this issue we mention the birdsnest spruce's beautiful spring greenery. That's point is the basis for the timing of our pruning but there is no reason to show the greenery here. Yet we know people ask, "What can be so pretty about a spruce?" and we have already illustrated its spring beauty in What's Coming Up 45, so we linked to that issue.
We don't think you should have to follow every link, only that you sometimes may want to go deeper on some item.
We have been writing on the website, and bringing our whole library here where you can use it, precisely because we wanted to check what we're writing now against what's gone before. It helps with our life goal to not write the same thing twice. However, we do know after 25 years of writing Q&A that some questions will be repeated. Links help us answer two questions with one article.