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Plant Answer Line Question

Keywords: Prunus padus, Styrax, Laburnum, Davidia, Ribes, Larix, Chamaecyparis, Picea, Tsuga, Cedrus, Fagus, Betula, Flowering trees, Pinus, Ericaceae (Heath family), Conifers

Are there any lists of shrubs/small trees that are best viewed from below, such as Styrax or Halesia?


While there are no lists of shrubs/small trees best viewed from below, there is a list of trees with weeping habits in The Pacific Northwest Gardener's Book of Lists (Ray and Jan McNeilan, 1997). Many genera of conifers - Cedrus (cedar), Chamaecyparis (cypress), Larix (larch), Picea (spruce), Pinus (pine), and Tsuga (hemlock) - have weeping forms, often indicated by a variety name 'Pendula' or 'Pendulum'. There are weeping birches (Betula), beeches (Fagus), and cherries (Prunus), too.

You are correct about Styrax and Halesia. Additionally, I ran across a few individual species that may be of interest to you as I researched this question:
--Davidia involucrata
--Laburnum anagyroides
--flowering currants, Ribes spp.
--flowering cherry trees, particularly Prunus padus
--various plants in the Ericaceae family have bell-shaped flowers that hang on the underside of the stem.

I would add that any tree which has a naturally graceful branching pattern and/or delicately shaped foliage (such as Japanese maples) would be pleasant to view from below, as well as from other angles.

Date 2018-08-23
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Plant Answer Line Question

Keywords: Shade trees, Conifers

We would like to plant a special evergreen tree that would be a large heirloom or heritage tree. We would like this to be the centerpiece of our back yard. We know the type of trees that typically fall into this category will be slow-growing, so we want to plant it soon so that it will be big enough for our grandchildren to climb in, swing from, play under, etc.

We would like a tree that is quite large and wide (possibly even wider than it is tall, around 40 feet tall x 40+ feet wide), with branches that start relatively low on the trunk, but do not go all the way to the ground (so you could both climb into it and have a picnic table under it).


I recommend visiting your local arboretum. If you are in the Seattle area, the Washington Park Arboretum is one place where you will find many examples of mature trees, some of which are coniferous evergreens, some of which are broadleaf evergreens. There are also many useful books to help you select the tree that best suits your needs. Since you are interested in evergreens, I particularly recommend Richard Bitner's Conifers for Gardens: An Illustrated Encyclopedia (Timber Press, 2007) and Portland, Oregon author Sean Hogan's Trees for All Seasons: Broadleaved Evergreens for Temperate Climates (Timber Press, 2008).

Here are websites that are useful in narrowing down tree lists once you have a few ideas in mind. (Note: Some of the sites have a zone option, i.e. where the trees grow best. Seattle is in USDA Zone 8b & Sunset Zone 5). In some cases, you can narrow down the selection even further, by selecting tree attributes (see the SelecTree site below).

Virginia Tech's Department of Forest Biology and Environmental Conservation has a series of Tree Identification Fact Sheets. This site is best for descriptions when you already have a species in mind.

Search the SelecTree database from CalPoly.
The best way to get a good list (with numerous options) is to click on Select Tree by Attribute.

A classic source is the USDA Forest Service internet version of Silvics of North America. It will not help with selection since you will need to know what species you want, but it will provide more information than you will ever need.

Date 2018-08-23
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Plant Answer Line Question

Keywords: Arborist, Pruning trees, Conifers

An issue has come up within our local homeowners association regarding some of the evergreen trees in our common areas. The issue is that about 20 or so trees have "deformed tops" - the tree has grown straight, but in the course of nature, the top has either broken off in a storm, or the tree has grown irregularly, developing a "hook" or "lever" at the top of the tree. This has lead to considerable discussion and (unfortunately) argument within our association. A tree service was hired by our association and they recommended "topping" the evergreens with the "lever" on the top. They stated these "levers" become "sails" in the wind and weaken the trees. One side believes these trees are hazardous and should be topped for safety, the other side believes they should be left as they are.

Searching through resources on the internet has led me to believe that topping these trees is the worst thing that could be done for the future health of the trees, not to mention the effect on property values due to the unsightliness "topping" causes.

I am interested in obtaining any information on the subject and would be open to discussing this with an arborist if possible, preferably someone who is very familiar with northwest evergreens.


You are right to be concerned about topping. The discussion probably should be whether to remove the trees if they pose a true hazard, or leave the trees if they do not pose a hazard. A damaged leader can be remedied, but do not take my word for it! You need a CERTIFIED arborist. If the arborist is hired as a consultant he will not have any incentive to recommend work that is unnecessary (this is why I am suspicious of the tree-service company).

Here are two organizations to contact for referrals:
Plant Amnesty: Plant Amnesty (See also Plant Amnesty's page about topping trees.)
PNW Chapter of the International Society of Arboriculture (the organization that grants certification) www.pnwisa.org or Trees Are Good, the website of the International Society of Arboriculture.

You want someone who has experience with tree hazard evaluation.

Another source is Arboriculture by Harris, Clark and Matheny that discusses what to do when a conifer loses its leader.

Date 2018-08-23
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Plant Answer Line Question

Keywords: Arborist, Hillside planting, Slope stabilization and soil erosion, Conifers

I live in a condo. The conifers on the site are beginning to obstruct the view of the neighbors. Our covenant with these neighbors says trees must not exceed a height of 25 feet. Last year several of the conifers were topped and others removed. Our concern now is that we may have to either top or remove more trees. We don't want to block the neighbors' view but we also don't want to destabilize the ground - we all live on a hillside. What can we do over the next 5, 10, 15, 20 years to decrease the number of conifers and replace them with other trees that will be neighbor-friendly and keep our hill stable?


The short answer is to plant shrubs and groundcovers.

The long answer is that slope stabilization is a serious concern and deserves expert advice. Get started in your research by reading the articles produced by the Washington Department of Ecology:
Slope Stabilization and Control Using Vegetation.

Your condo association may want to hire a consulting arborist and/or a civil engineer ("To locate technical experts such as experienced registered engineers specializing in geotechnical and/or drainage projects, use local telephone directories or call the Seattle or Kitsap branch of the American Society of Civil Engineers (ASCE) for membership references." from DOE site)

For an arborist referral try:
Plant Amnesty

The Pacific Northwest chapter of the International Society of Arboriculture has information about hiring an arborist.

The International Society of Arboriculture can also help to narrow the search to your area.

Date 2018-10-25
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Plant Answer Line Question

Keywords: Tree roots, Conifers

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:




Pinus nigra caramanica CRIMEAN PINE


Date 2018-08-15
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Plant Answer Line Question

Keywords: Cupressus, Tree planting, Transplanting, Soil amendments, Conifers

I am going to take my 6-foot tall Wilma Goldcrest out of the giant pot it is currently in, and plant it in the ground. I am seeking some sort of consensus on how to prepare the hole into which the tree is going. Someone said that I should not put compost in the hole because that will encourage the roots to just stay in the area of the hole. If that's the case, then shouldn't the "no compost" rule apply to all new plantings (which, of course, it does not)? Also, when should I fertilize the tree and what kind of fertilizer should I use? I always use organic fertilizers. What about putting some bone meal in the planting hole to feed new root growth?


I refer you to the following information from Washington State University Extension horticulturist, Professor Linda Chalker-Scott, who discusses planting procedures in her book, The Informed Gardener (University of Washington Press, 2008). She says that the planting hole need only be the depth of the root system, but should be twice the width. She advises against amending the planting hole in any way: Backfill the hole with native soil, not a soil amendment. The idea is not to 'spoil' the plant by putting rich compost just in the hole, which will deter the roots from spreading out into the surrounding area.

Her debunked gardening myths may also be found online. This one addresses soil amendments and planting. She also addresses the use of bone meal as a planting amendment.

'Wilma Goldcrest' is a cultivar of Cupressus macrocarpa, or Monterey cypress. The University of California's Garden Information publication on "Pines and Other Conifers"(including Monterey cypress)says:
"Pines and conifers require less fertilizer than most other trees and shrubs. Heavy fertilizing can promote rank, unsightly growth, destroying their natural, symmetrical, picturesque form." If you do wish to use fertilizer, a dilution of something like seaweed or fish fertilizer would probably not be harmful.

Here is more about fertilizing conifers from University of Minnesota Extension Horticulture.
"Why Fertilize?
The plant itself will often indicate when it needs fertilizer. If growth rate and needle color are normal for a particular variety, fertilization is not necessary. If new growth is sparse or slow, or the needles are not a healthy color, or are shorter than normal, you should probably fertilize. Keep in mind, however, it is not unusual or abnormal for newly transplanted evergreens to exhibit slow growth until they're re-established.
Regular fertilization may be recommended if you are trying to grow evergreens in a less than ideal site, such as very sandy or heavy clay soil, or if the plant has suffered damage from insects or disease. You might also wish to fertilize to encourage more rapid growth in relatively young evergreens."

Local garden writer Ann Lovejoy says the following in her book, The Handbook of Northwest Gardening (Sasquatch Books, 2007): "I rarely feed plants directly, preferring to feed the soil with what are called 'feeding mulches,' made of materials such as compost, seed meals, kelp, and fish meals."

Date 2018-09-08
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Plant Answer Line Question

Keywords: Tree planting, Conifers

The nursery recommended waiting to plant a Cedrus deodara until after the first hard frost. As we are in USDA Zone 7 (the lower limit for a deodar), I'd think we would want to get it in the ground as early as possible. Any idea what the rationale is behind this advice?


I am really not sure what their rationale might be. I agree with you that planting in the fall is preferable. Here is information which supports this:
Excerpt from Brooklyn Botanic Garden booklet on conifers:
"Across most of the country, spring (early or late, depending on how far north you are) and early fall, when temperatures are cooler and rainfall more abundant, are the best times to plant conifers. To reduce transpiration or water loss from the tree, plant on an overcast day when there is ample soil moisture."

I don't know if your tree was a bare-root specimen or container-grown. Here is what Keith Rushforth says in his book Conifers (Christopher Helm, 1987):
"Bare-rooted stock can only be planted during the dormant season. This restricts planting to the period November to April. Planting during midwinter is better avoided, because cold, dry winds during the winter can desiccate the young plants before the roots have been able to make new growth. Planting after April is only feasible if the plants have been held dormant in a cold store.
Container-grown stock can be planted out during most of the year, although the period of maximum growth from late May to early August is better avoided unless watering is no problem. A check should be kept on whether winter-planted stock needs watering; it is very easy for the compost to dry out during dry periods in the winter."

Based on the above, it seems like a good idea to plant now (fall).

Date 2018-09-08
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Plant Answer Line Question

Keywords: Thujopsis, Pruning trees, Conifers

I'm looking for resources on proper pruning or rejuvenation for Thujopsis. We have a 50-60 year old specimen.


According to Michael Dirr (in Dirr's Hardy Trees and Shrubs: an Illustrated Encyclopedia), Thujopsis dolabrata is "too beautiful to mutilate with pruning shears." This website of a Seattle-area gardener suggests that you may be able to prune it lightly by candling the leader.

According to George Brown's The Pruning of Trees, Shrubs and Conifers (Timber Press, 2004), specimens of this tree vary widely in habit. Some form a definite leader, while others are "untidy, spreading shrubs. Of those which grow out of this shrubby habit, a number produce rival leaders and the result is a small tree made up of slender upright trunks with their supporting branches." If your tree has multiple leaders, it is probably too late to prune them--this kind of pruning would be done on a younger tree.

I spoke with a docent at Seattle's Japanese Garden, which has Thujopsis, and she said that they are not pruned, except to remove dead, damaged, or diseased branches. You may find this general information on pruning conifers from Brooklyn Botanic Garden useful.
"As with any plant, dead or diseased conifer branches should be removed immediately, regardless of the time of year. Any other pruning should be done when the plant is dormant. Unlike many deciduous shrubs, most conifers can't re-sprout from older wood (yew, arborvitae and podocarpus are exceptions), and so a good rule of thumb is never to remove more than one-third of the total growth at a time. If you prune too drastically, the plant may never fully recover. Many of the dwarf varieties never need to be pruned, but do appreciate some thinning to allow air and sunlight to penetrate to the interior of the plant.
The most common method of pruning evergreens is known as 'cutting' or 'heading' back. Only part of the branch is pruned; the terminal or tip growth is trimmed to side or lateral buds or branches. This promotes thicker, more compact foliage and a smaller overall plant."

It sounds as if you should do the bare minimum in terms of pruning. If you really need to reduce the tree's size, it would be wise to consult a certified arborist.

Date 2018-09-08
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Plant Answer Line Question

Keywords: Effect of storms, Pruning, Conifers

There's a self-described tree service knocking on doors in my street, trying to get people to pay them to do "wind sail reduction" on their trees. My neighbor just agreed to have them prune 17 of her conifers. Bad idea, right? Can you point me toward resources so I can dissuade her from going ahead with this plan?


Yes. The Washington Department of Natural Resources published an article, "Trees Don't Wind Sail, Do They?," in their online newsletter, Ear to the Ground, 12/20/2011. Here is an excerpt:
"Some people claiming to be tree experts will tell you that 'wind sailing' is a great way to protect your trees from wind damage. You may have heard this fabricated notion of thinning limbs from trees in order to make them stable during wind storms. This improper pruning technique is promoted to supposedly make trees safer in the wind by allowing wind to pass through the canopy of a tree, thus reducing movement and strain on a tree. Not so!
"This may sound reasonable and may even seem to have some logic behind it. But beware--the truth is, there is no scientific study that shows thinning is wise or safe way to decrease resistance during a wind storm. "Actually, many studies have shown that the outside limbs can divert some wind from the center of the tree and act as a buffering shield. Aggressive thinning, on the other hand, can make the remaining branches more vulnerable to failure; left isolated, these limbs must take on the elements alone. Pruning out a major portion of a tree's canopy for the sake of staying upright during a wind storm harms most trees in the long run."

The DNR has another, similar article from 12/6/2012 in their Tree Link News entitled 'Windsail Reduction:' A Northwest Controversy.

You can also suggest that your neighbor speak to someone at Plant Amnesty, a local organization dedicated to teaching the community about proper pruning techniques (as well as informing them about ill-advised methods!).

Date 2019-04-05
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Plant Answer Line Question

Keywords: Color, 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:
"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."

Date 2019-05-22
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Garden Tip

Keywords: Plant and garden societies, Chamaecyparis, Picea, Tsuga, Abies, Dwarf conifers and shrubs, Conifers

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:

  1. Picea orientalis 'Skylands'
  2. Abies koreana 'Silberlocke'
  3. Tsuga canadensis
  4. Chamaecyparis obtusa 'Nana Lutea'

Date: 2007-04-03
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Conifers of California   by Ronald M. Lanner, 1999

Reviewed by: Brian Thompson on 2012-06-01

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."

Edward Anderson was for 30 years a biology professor at Whitman College in Walla Walla before finishing his career at the Desert Botanical Garden in Phoenix. The Cactus Family is the culmination of his life's work as, sadly, he died shortly after publication, but more importantly because it will be a long-time standard reference for these popular plants.

While not a gardener's book--a chapter on cultivation is included but is by a different author--this provides a superb view of the remarkable diversity of cacti, well captured by excellent photographs, most by the author and many in situ. Highly recommend, too, are the chapters on ethnobotany and conservation of cacti, which illustrate how important these plants have been and continue to be throughout their range in North and South America.

Excerpted from the Summer 2012 Arboretum Bulletin.

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