conifers with low root damage potential

Can you suggest any larger growing conifers (ex. Lawson’s cypress) whose root systems are not invasive? The area I’m interested in planting is near water lines.

There are a number of conifers listed on the locally developed web pages of
Great Plant Picks.

I would suggest looking at some of these, and then checking the web page of
SelecTree, where you can select trees for low root damage potential.

For instance, if you are interested in planting a fir tree such as Abies
grandis or Abies pinsapo, you would find out from SelecTree’s full tree
record that both of these have moderate root damage potential. Calocedrus,
Picea orientalis, Sequoiadendron and Cryptomeria are also rated as moderate.
Cephalotaxus fortunei is rated low, as are Pseudotsuga menziesii, and
several Chamaecyparis species. The following conifers rated as having high
root damage potential:

Picea abies NORWAY SPRUCE

Picea brewerana BREWER’S WEEPING SPRUCE

Pinus cembra SWISS STONE PINE

Pinus nigra caramanica CRIMEAN PINE

Pinus taeda LOBLOLLY PINE

the color blue in conifers

What makes the blue color on some conifers?

I am by no means an expert on plant physiology, but I believe it is the waxy coating (cuticle) on the needles that makes them look blue, as confirmed in this article about a variety of Colorado blue spruce by Edward Gilman and Dennis Watson on the website of University of Florida Extension:

“[….] the wax coating on the needles of Blue Spruce which give
the blue color can be washed off by some pesticides.”

Here is similar information from Montana State University Extension (page 14):

Excerpt re: Colorado blue spruce:
“The bluish color of the leaves of some of the trees results from a wax (cutin) accumulation, which is genetically controlled.
This doesn’t satisfactorily explain why blue conifer needles would be any different from those of green conifers (whose needles are also waxy), though.”

The following article by John Clark and Geoffrey Lister in Plant Physiology, vol. 55, 1975 has a complex technical explanation:

Excerpt:
“The observed differences in relative pigment complements can, therefore, partially account for the differences between the action spectrum for red alder and those of the conifers as a whole. In particular, the increasing carotenoid-Chl ratios determined for red alder (0.38) and the two green conifers, Douglas fir (0.54) and Sitka spruce (0.67) would seem to be the factor responsible for the differences between their action spectra. The same explanation, however, cannot alone account for the range of differences seen in the action spectra for the four conifers. No evidence was found to support differential degrees of screening by an extrachloroplast blue-absorbing pigment reportedly present in some conifer needles (2). One is therefore led to believe that an additional factor must be
responsible for the differences between the green and ‘blue’ spruces. Differences in apparent leaf coloration, arising from changes in relative spectral reflectance attributable to varying leaf cuticle structure, seems to be the most plausible explanation.”

Silvics of North America

This is a full text electronic reproduction of Burns, Russell M., and Barbara H. Honkala, tech. coords. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654. USDA, Forest Service, Washington, DC. vol.2, 877 p.” The silvical characteristics of about 200 forest tree species and varieties are described. Most are native to the 50 United States and Puerto Rico, but a few are introduced and naturalized. Information on habitat, life history, and genetics is given for 15 genera, 63 species, and 20 varieties of conifers and for 58 genera, 128 species, and 6 varieties of hardwoods. These represent most of the commercially important trees of the United States and Canada and some of those from Mexico and the Caribbean Islands, making this a reference for virtually all of North America. A special feature of this edition is the inclusion of 19 tropical and subtropical species. These additions are native and introduced trees of the southern border of the United States from Florida to Texas and California, and also from Hawaii and Puerto Rico.”

American Conifer Society

This site includes a conifer database with photos, events calendar and a forum for questions and discussion.

Gymnosperm Database

“The Database provides basic information on the classification, description, ecology and uses for all species and higher-ranked taxa of the gymnosperms, i.e., conifers, cycads, and their allies. You enter the taxonomic tree at the Family level and then navigate to the Genus, Species or sometimes Variety levels. At each level, information on the taxon at hand is provided, along with bibliographic citations that will take you to more detailed information about the taxon.”

Garden Tip #94

The Pacific Northwest is an excellent climate for growing evergreens because our winters are generally mild. We can grow far more species than just Douglas Firs and Red Cedars, and in city gardens dwarf conifers are much more suitable. Explore the wide world of conifers, plants that produce cones, by joining the American Conifer Society. Membership costs $25 per year which includes a nice quarterly journal with color photos. Their website has a database with descriptions and photos, as well as information on becoming a member. Call (410) 721-6611 to join.

Favorite four conifers as voted on by members of the American Conifer Society:

Picea orientalis ‘Skylands’
Abies koreana ‘Silberlocke’
Tsuga canadensis
Chamaecyparis obtusa ‘Nana Lutea’

Designing with Conifers

book Richard Bitner has written three books about conifers in the garden; I think the best is the most recent, “Designing with Conifers.” Organized by notable features such as shape, color, or bark, the author uses his own photographs to illustrate a wide range of planting options. He clearly detests foundation plantings: “Why this mandatory dress code? It is time to break free of this tradition and change our practices.”

Specialty situations such as hedges and topiary are included, along with some unexpected chapters on recommended Christmas trees, dwarf cultivars for garden railways, and–the most curious–traditional plantings for German graveyards. Although the author is from the East Coast, I thought his best work was a case study of a garden near Eugene, with a photographic dissection of the different purposes for the plants used in the landscape–quite instructive.

Conifers of California

Conifers of California cover Conifers of California is a delightful introduction to many of our native conifers, as well as the incredible diversity of these cone bearing trees to be found further down the coast. Author Ronald M. Lanner writes what could be best described as a biography of each tree, telling the natural history and the interaction of each with humans and animals. While there are helpful descriptions, (including “At a distance”, “Standing beneath it”, and “In the hand”), this is not primarily a field guide.

The photographs are excellent, but a bigger visual draw are the botanical paintings by Eugene Otto Walter Murman (1874-1962), which besides being beautiful, clearly show the distinctiveness of the cones, cone scales, seeds, needles in a single bundle, and a growing tip. Adding to the history are quotes by some of the great describers of trees, including Charles Sprague Sargent, John Muir, and, one of my favorites, Donald Culross Peattie.

I’m adding Lanner to this list. His descriptions of the relationship between the Clark’s nutcracker and whitebark pine (Pinus albicaulis), or the unusual combinations of factors that lead to the long, long lives of the bristlecone pine (Pinus longaeva), are detailed and lengthy but totally engaging.

Of incense-cedar (Calocedrus decurrens) he explains how forestry practices have led to a population explosion of this tree little valued by the timber industry. This is “…good for those Americans who eschew the use of greasy-inked ballpoint pens, because incense-cedar is the unrivaled champion of available domestic pencilwoods. It may not be so good for those…who must past through thickets…for those thin dead, lower limbs seem always positioned to welt a cheek or poke an unsuspecting eye.”

Many of the rarer California conifers can be found in the Arboretum and this book is a good introduction. Look for the Coulter pine (Pinus coulteri) but don’t stand under its eight pound cones
“with talonlike appendages”, while from the Siskiyou Mountains comes the weeping Brewer spruce (Picea breweriana) with “long, dark-foliaged, pendulous branches.”