• Choose trees appropriate for the site


• Buy high-quality planting stock


• Plant with proper spacing


• Do not mulch up to the trunk and


• Water during dry periods. I planned to be more exact: site the conifer in a spot that drains well, so that the plant does not sit in water.

Phomopsis Tip Blight Fungus
The fourth species of fungus attacking conifers is Phomopsis juniperovora (Phomopsis tip blight), identified in 1917! Phomopsis causes the new growth on conifers, both on seedlings and mature specimens, to turn brown and wilt.

The infection begins with the germination of asexual conidia (asexual, non-motile spores of a fungus, also called mitospores), borne from pycnidia (asexual fruiting bodies produced by mitosporic fungi). The mycelia, the vegetative parts of a fungus, move inward down the branch and eventually into the main stem.

In order to check the spread of this fungus, the blighted tips should be removed and destroyed. You must also sterilize any pruning tools to avoid the spread of the pathogen (a very good IPM practice).

Researchers recommend choosing resistant varieties and spraying new growth with fungicide until the plant(s) has (have) matured.

 

Stigmina on the needle of Rocky Mountain bristlecone pine (Pinus aristata) at the

home of Leah Alcyon. Photograph by Leah Alcyon

 

Seeking Fungus-Resistant Conifers
I have never seen a plant tag labeling a plant as “Phomopsis-resistant." It is possible that, since 1917, certain conifers might have become resistant, or been even bred as such, but my now 15- feet tall Pseudotsuga menziesii (Douglas-fir), planted in 2003 as a 5-footer, did not come as a Phomopsis-resistant plant.

All of the tips of this Douglas-fir are limp and browning for the third year running. Unless I scale a very tall ladder—or rent a cherry picker—to remove the blighted tips, neither of which I will do, I am going to have to take that tree down.

Once the tree is felled, I will cut off the infected tips and cut up all the branches, seal the tips and pieces in paper garden waste bags, and transfer everything to my waste collector for disposal. The trunk of the tree will be cut up and burned.

My advice: caveat emptor (buyer beware)! Read the plant tag and hope that the plant you have chosen is Phomopsis-resistant, or resistant to any kind of fungus, for that matter!

Fungal Attacks: Conifers to Avoid

Phomopsis juniperovora is known to attack:

• Juniperus virginiana (eastern red-cedar)


• Pinus banksiana (Jack pine)


• Pseudotsuga menziesii (Douglas-fir)


• All Abies (true fir) species


• All Juniperus horizontalis (Rocky Mountain creeping juniper)


• All Larix (larch) species


• All Thuja (arborvitae) species

Stressed trees are more likely to fall victim to opportunistic pathogens or insects. Whatever the stress-producing agent, significant numbers of conifer species are succumbing to fungi. Every living organism on Earth is programmed to die, but the acceleration of the demise of some conifers comes directly from fungal infection.

 

Setomelanomma fungus on the bark of Scots pine (Pinus sylvestris). Photograph by Leah Alcyon

 

In an NBC News report by Jacelyn Jeffrey Wilensky, climate change, insect invasion, tree death, and deforestation are noted to increase the release of CO2. As a result, the amount of that greenhouse gas balloons and causes an ever-increasing hostile environment to life.

Add to that what Jill Wegryzn (University of Connecticut Stress Genetics professor) writes about the weakening of the immune systems of trees through drought and weather extremes, and certain of our conifers face serious challenges.

A former colleague of mine at Adrian College, Dr. Craig Weatherby (Emeritus Professor of Biology and Environmental Studies), has been studying box turtles (Terrapene sp.) all his professional life.

I once asked him why he dedicated his life to those animals. He immediately replied: “Because the way the turtles go, humans will go.” Box turtles are now an endangered species.

Click here to read more about other fungal diseases like oak wilt, cedar apple rust and white pine blister rust.

 

By Elmer Dustman
November 7, 2019

Find out how pruning creates consistent texture and appearance in conifers, while encouraging healthier growth in the long run.

There is a different concept of pruning, called Aesthetic Pruning. My Aesthetic Pruning definition is: controlling plant growth in a way which results in plants which look convincingly natural and untouched by human hands.

The gardener must have two arsenals of knowledge: the growth habit of the plant and the use of proper pruning tools. The reference I use is Edward Gilman’s 2012 book, An Illustrated Guide to Pruning (Third Edition), Chapters 5 and 18, Pruning Cuts, and in Pruning Landscape Trees and Shrubs, published by Delmar Cengage Learning.

There are three basic pruning terms that I will discuss:

Reduction Cuts
Removal Cuts
Heading Cuts
These are two additional cuts to be used:

Tipping
Shearing

Defining Pruning Terms
Reduction Cuts are used to “reduce” or shorten the length of a branch by pruning it back to a branch junction which is large enough to assume apical dominance. This branch varies by species, but should be 1/3 to 1/2 the diameter of the cut stem. To make the cut, bisect the angle between the branch bark ridge and an imaginary line perpendicular to the branch to be removed. This cut is used to maintain the size and shape of the tree or shrub.

Removal Cuts are made back to the collar, or to the point of attachment. This cut is often used to thin-out the plant’s foliage. This encourages light and air circulation resulting in a healthier specimen. Removal cuts can be used to lighten the weight of branches and removal of dead wood.

Heading Cuts shorten a branch to a stub or to a bud or a lateral branch not large enough to assume the terminal role. This can cause the tree to sprout excessively from the cut.

Other Pruning Techniques in Conifers: Tipping
Tipping/pinching is a technique of removing the last few buds, leaves, or sprouts from the end of a stem. It is performed for a number of reasons. It can slow down a tree’s rapid growth; it can redirect a tree’s energy into smaller, more desirable shoots or buds, and it can give a consistent texture and appearance to the newly pruned plant.

Tipping is easiest during the soft-lush-growth stage by using the fingers. For pines, breaking the new growth candles to the desired length before hardening controls the total yearly growth. The use of hand shears for removals must be done on new growth after it has hardened, which can cause browning of foliage and needles.

Other Pruning Techniques in Conifers: Shearing
The overuse and misuse of sheared shrubbery is one of the most common forms of landscape mismanagement. Because shearing is non-selective heading, you will stimulate bushy growth. You create a twiggy outer shell on sheared plants. This layer of twigs shades out the interior, which then becomes leafless and full of dead leaves and dead wood.

Meanwhile the outer shell becomes thicker and larger farther out to retain its greenery. The dense outer shell makes size reduction difficult because cutting back too far exposes the ugly dead zone. Although most plants will bud back and eventually reform, there are some species like junipers which won’t regenerate.

Power hedge shears do tremendous damage with [lots of] broken and crushed stem tips, torn bark and chewed leaves. This leads to wound responses and both bacterial and fungal invasions.

Alternatives to Shearing in Conifers
The only plants I shear are Boxwood and Privet, using manual hedge shears held in the horizontal position. This is because they have small leaves and are formal in appearance. The highest quality “shearing” isn’t even shearing at all. Instead it consists of the carefully performed “snip-by-snip” technique, which leaves no heading cuts at all; the manual head shears are held in an vertical or right angle position for “targeted” cuts on junipers, barberries, Spiraea, hemlocks and many more species with follow up use of hand shears for fine pruning removals.

Targeting cuts to inner branchlets opens up the plant to let in more light and air circulation, allows new growth to emerge from buds or side branches, and controls plant size. I prefer that certain shrubs be pruned in a semi-spherical and not a ball-like shape.

The preferred ratio of height to width is 1 to 3. This allows the entire bush to have new foliage or flowers and appear ground-hugging. Many shrubs with sheared tops have exposed sides which have little new foliage and the shape is of little interest.

Things to Consider Before Pruning
What does the tree or shrub look like in nature in its most mature form?
Find examples in the landscape as you drive down the street and in books and garden magazines!
Check branch forms: hanging or upright shapes?
Observe ratio of height to width to inform your pruning goals!
Where are the empty spaces between branches and note branching pattern?
Information selected from The Journal of Japanese Gardening, published by Douglas M. Roth, Plant Amnesty Newsletter, www.plantamesty.org.

Photograph by David Rangel.

 

 

 

 

 

1. Location. Obviously if you are in the native range, you should be able to grow Picea pungens successfully. Areas bordering on the native range are likely also to have climatic conditions conducive to success with this tree. The summer-dry Mediterranean climate of coastal California and Oregon also seems to produce long-lived, healthy landscape trees. If you are outside of these areas, careful cultural practices will improve your chances of success. There are ample examples of healthy, decades-old blue spruce in the Midwest and the Northeast and even in parts of the Southeast.
2.  Age. Unless you are the steward of a family estate or the curator of a public garden or other public space, it is unrealistic to think in terms of centuries when planning your garden. You have no control over what happens after you move or die; the next owner may chop the trees down and put in a swimming pool. So for most of us, it is logical to think in terms of a few decades at most. Thus, even if disease is going to get the tree in the end, but you can enjoy a few decades with it, that may not be a good enough reason to avoid a blue spruce. Dennis Groh notes that from what he has read, "the species spruce are disease resistant when they are young and growing vigorously. It seems that at about 25 years something happens and the spruce become highly susceptible. One article speculated it could something to do with the tree's inability to move adequate water to all parts of the tree and a resulting inability to then defend against disease attack. Another speculated the tree at some point exhausts all available elements in its rather limited root zone and requires supplemental fertilization to support its rapid upward growth and maintain its defense against disease. I have seen the root system on 70 foot spruce and it is much smaller than I would have expected based on deciduous trees."
3. Disease-resistant cultivars. This is the most difficult factor to assess. There is no hard evidence that Picea pungens cultivars in general, or any specific cultivars, are more resistant to disease than the species trees. While most of the examples of success are, indeed, cultivars, that could well be due to the fact that most conifer enthusiasts plant cultivars, not species trees; that the cultivars are newer to the market, thus younger and not yet affected with disease; or that more care has been taken with the cultivars as they are generally thought to be more 'special' and are certainly more expensive than the species. (What's the difference between a species and a cultivar?) It should go without saying that choosing a cultivar with a slower growth rate than the species is also a good idea, unless you are landscaping vast parkland.
4. Cultural practices. This is key. If you have decided, despite the issues, to plant a blue spruce, your best chance of success is to plant and care for it properly.
   
   

 

 

• In the Mountain West or near it, you can grow blue spruce successfully.
•  In Mediterranean climates from Central California through Oregon, blue spruce tends to do well, although it may require supplemental irrigation. The cool summer nights and dry summer air are similar to those in the tree's native range. Established trees seem to be more drought-tolerant.
• In the upper Pacific Northwest, the weather tends to be too wet and fungal pathogens are too numerous. Another choice would likely be better to ensure long term success. Blue spruce is extensively produced in Oregon, where growers focus on using disease-resistant stock, avoiding overhead watering and avoiding pruning when the foliage is wet.
• In the upper Midwest and Northeast, blue spruce have been extensively planted and there are almost as many success stories as there are those of decline and death. This is where cultural practices may make a significant difference. Longevity (or lack thereof...), cultivar selection and luck may also have had a hand in the results! It is worth noting that one of the most popular blue spruce cultivars, 'St Mary' (also called 'St. Mary's Broom') not only has anecdotal evidence of success in the Northeast, but was actually found on a tree growing in Morristown, NJ.
• In the lower Midwest, according to Edward Gilman, professor emeritus of horticulture at the University of Florida, blue spruce 'is not for Dallas and south Texas, but Lubbock and into Oklahoma is suitable'.
• In most of the American Southeast, you will likely want to select a different conifer than a blue spruce. Tom Cox, who, with John Ruter, wrote 'Landscaping with Conifers and Ginkgo for the Southeast', firmly believes that summer nighttime temperatures regularly have to dip below 70 degrees F by 10:00 pm in order for blue spruce to be successful. In addition, he suggests that the heavy summer rainfall in much of the Southeast tends to dissolve the waxy coating that gives the blue spruce its blueness, making them a dull green instead of an arresting blue. In fact, he says that if he were to revise the book, he would not recommend Picea pungens for any parts of the Southeast, with the exception of higher elevations, such as Asheville, NC. Those that do survive, he notes, are not particularly attractive.
• In the few parts of the US that are tropical, you will also have to find your garden blue elsewhere, but there are conifers for you, too!
  

 

 

 

 

• Blue spruce prefer acidic, moist, well-draining soils. If your soil is heavy and poorly draining, or is basic, plant in mounds of high quality soil with grit, pumice or pebbles added to increase drainage. DO NOT dig a hole and backfill with non-native soil. This creates a bathtub effect whereby the hole, with looser, lighter soil, simply fills with water during rain or irrigation.
•  Plant your blue spruce so that the beginning of the root flare is evident. This is good practice for almost all woody plants, but with those that need good drainage it is particularly important.
• Blue spruce should always be planted in full sun.
• Maintain good air circulation around the plant. This means not overcrowding the plants in the bed or area. Remember to consider the tree's mature size when planning! If lower limbs are touching the ground, remove the entire limb or prune the underside or tips to lift the skirt so that it clears the ground.
• Pruning is fine; in fact, pruning to open the architecture and increase air flow is likely a positive. However, avoid shearing, as shearing produces dense, congested growth that holds water longer than the tree's natural foliage. There is anecdotal evidence that keeping the foliage as open as possible is helpful, which means getting inside and removing dead or unattractive branches and allowing the air and sunlight to reach as many needles as possible.
• Spread and maintain a layer of mulch covering the root zone of the tree (roughly to the edge of the branches) of several inches. This will keep the soil moister and cooler and reduce weed growth. Do not mulch up to the trunk; leave an inch or two so that the damp mulch is not piled up against the trunk.
• As noted above, blue spruce grow best in their native habitat when they are near streams and lakes. Make sure that your tree gets enough water, especially when young. Older trees may be more drought-resistant, but still need supplemental irrigation at times of scarce rainfall. Extended periods of drought can weaken the trees and make them more susceptible to pathogens.
• If you are in a summer dry climate, or in the mountain west, you can use overhead irrigation in summer, as the water evaporates quickly from the needles. If you are in most of the US or Europe, you should water using drip irrigation or a hose at the base of the tree. Avoid getting water on the needles, as the moisture promotes fungal growth and transmission.
• Fertilizing is not necessary when the tree is young, however, as Dennis Groh notes, "The key is to keep the tree well watered, fertilized, healthy and growing." So after its been in the ground for a few years, regular fertilizing is a good idea.
• If your tree does exhibit evidence of needle cast disease, you should seek confirmation of the specific pathogen before applying fungicide. Most county extension offices can review samples of infected foliage and provide a diagnosis. You can also search on line for examples of needle cast disease and compare with your plant. Different pathogens require different fungicides, so don't start spraying indiscriminately!

 

 

 

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