Q:
I'm losing most of the evergreens that give me privacy along one of my property lines. They're mainly blue spruce, and they're getting thin from the bottom up. I'm trying to bring them back by fertilizing, but if that doesn't help, do you have some suggestions for replacements? I have plenty of space, so big evergreens are fine.
A: That's a fairly common problem with older Colorado blue spruce – and a lot of other evergreens, for that matter. As the tops grow and take in the necessary sunlight, the bottoms start to become more shaded and less needed for producing chlorophyll. Sometimes disease is a factor as well.
I doubt that fertilizing will do anything to restore the bottoms of your spruce, but if you want to give that a try for a year or two, fine.
One other possibility before yanking them is planting a lower evergreen around the base to give yourself "tag-team screening." Something like spreading junipers or blue hollies or cherry laurels could give you privacy for the first 5 to 8 feet, then the spruce would pick up from there.
If you get to the point of just replacing the aging spruce, here are five larger evergreens I like for sunny screening situations:
* Bosnian pine (Pinus heldreichii var. leucodermis). Has stiff green needles and is about as good as any pine at fending off the numerous bugs and diseases that threaten pines. Fairly sleek in habit. Figure on about 30 feet by 12 feet wide in 20 years.
* Oriental spruce (Picea orientalis). Has shorter needles than most spruce and a dark-green color. The red spring blooms are especially interesting. 60' by 20' in 20 years.
* Serbian spruce (Picea omorika). Has a narrow, graceful form and a bluish-green color. 50' x 20' in 20 years.
* Japanese red cedar (Cryptomeria japonica). Narrower still at about 20 to 25 feet tall and 10 to 12 feet wide in 20 years. Lighter green color and soft needles. Especially good are the cultivars 'Kityama' and 'Yoshino.'
* American holly (Ilex opaca). A good native option with wider leaves that have little spines at the edges. Best feature is the red berries. Can tolerate some damp soils as well. 30' by 15' in 20 years.
A few others to check out: Nordmann fir, arborvitae 'Green Giant,' concolor fir and Swiss stone pine.
I've got photos and more details on most of these on my web site under the Plant Profiles and then Evergreens button.
You don't have to pick just one, by the way. You can do a screen planting by patterning out two or more different species, i.e. two or three of one species on both ends with one or three of a second species in the middle.