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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Plant diseases--Diagnosis, Juniperus

My Sky Rocket junipers are declining. To me it looks like mite damage accompanied by winter damage. The top of the plant is still healthy looking. There are spider mites present. It does not resemble phomopsis, but could be phytophthora. Please let me know what you think.


I checked Diseases of Trees & Shrubs by Sinclair, Lyon and Johnson and Juniper virginiana does not get phytophthora (or at lease this good authority does not list that disease.) It does list a number of other diseases including blight, canker, phomopsis, among many others.

The HortSense website of WSU Cooperative Extension mentions Juniper webworm, which creates heavy webbing, which could resemble mite webbing.

Of course it could be winter damage, like you guess or nitrogen deficiency if the Ph is high (near a lot of concrete?), or salt damage (from melting ice in past winters?).

You should take a sample in to a Master Gardener clinic. If they do not know the cause, you can ask that they "submit it to the diagnostic center at the Center for Urban Horticulture."

Locate a Master Gardener Clinic within King County at this website.

Date 2017-05-26
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Plant Answer Line Question

Keywords: Screens, Thuja, Juniperus, Viburnum, Hedges, Ceanothus

I will be having a very overgrown, rarely pruned laurel removed from my back garden. It has been, if a monstrosity, an effective visual screen. The bare area that it leaves is appproximately 40' in length, is atop a rockery, approximately 3' high, and will look up into the neighbor's back hillside, while they peer down at us in dismay. Can you suggest one or several fast growing, shrubby plants or suitable trees that will act as an attractive visual screen? I do not want bamboo.


Here are a few ideas:

Morella californica

Thuja occidentalis 'Smaragd'

Osmanthus delavayi is also a good choice, but it doesn't get quite tall enough--my own hedge, which is pruned at least twice a year, is about 8 feet tall, so if I really let it go, maybe it would be 10-12 feet.

Juniperus scopulorum 'Wichita Blue'

Juniperus virginiana 'Manhattan Blue'

Viburnum tinus

Ceanothus would also be striking, with blue flowers, but you'd need to find the tallest possible species, and they tend to be short lived.

You could plant a mixed hedgerow, which would allow you to include some of the flowering plants you prefer. King Conservation District has more information on hedgerows.

Date 2018-06-22
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Plant Answer Line Question

Keywords: Juniperus, Pruning

I have a young 5-foot tall Hollywood juniper. How do I prune it to shape and train it so it looks good?


Because of the natural beauty of its form, Hollywood juniper, or Juniperus chinensis 'Torulosa', is not a good candidate for pruning, and I would recommend only pruning branches which are interfering in some way, such as intruding into a walkway. Below are links to information on pruning junipers:
University of Georgia Extension
"Junipers do not tolerate heavy pruning because of the lack of new growth on old wood. This makes it important to know the growth habit of a particular juniper prior to planting so that future pruning can be minimized. Junipers can be tip pruned and thinned, but not cut back to large limbs. Pruning out old. dead foliage underneath creeping junipers will often contribute to better air circulation and thus better health of the plant."
University of Florida Extension
Excerpt: "Torulosa Juniper develops into a showcase specimen without pruning and is probably best used for this purpose."

In her Guide to Pruning (Sasquatch Books, 2006), local pruning expert Cass Turnbull advises strongly against shearing and cutting into old wood, because you will be looking at woody stubs for a long time, if not forever. You can remove lower limbs which may be blocking sidewalks, but in general, avoid pruning. "Junipers, like most conifers, are difficult to prune. This is because the barren portions of the branches can't produce new greenery (break bud) once the exterior green has been removed (headed back). Never expose those ugly, barren internal branches . . . What little can be done to help an overgrown planting involves removal of the lowest limbs, and/or selective heading (grab and snip) or thinning off the worst, most interfering branches. Always hide the cut beneath some natural-looking greenery."

Your young plant should shape and train itself without the intervention of pruning.

Date 2017-08-11
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Plant Answer Line Question

Keywords: Juniperus, Economic botany

Our microdistillery is going to be making gin. I'd like to know which species of juniper to use for the berries which will flavor it. Also, someone said that the berries were toxic. Is that true? Any other information about the use of juniper as a flavoring would be helpful, too.


Here is what Amy Stewart says about the use of juniper for gin in The Drunken Botanist (Algonquin Books, 2013):

"The juniper most widely is J. [Juniperus] communis communis, a small tree or shrub that can live up to two hundred years. They are dioecious, meaning that each tree is either male or female. The pollen from a male shrub can travel on the wind over a hundred miles to reach a female. Once pollinated, the berries--which are actually cones whose scales are so fleshy that they resemble the skin of a fruit--take two to three years to mature. Harvesting them is not easy: a single plant will hold berries in every stage of ripeness, so they have to be picked a few times a year."

North Carolina State University's Poisonous Plants database lists juniper as having low toxicity if consumed, and simultaneously describes the fleshy cones ("berries") as both poisonous and edible, which I understand to mean that if you ingested large quantities of them it might be unwise, but there is a long tradition of using them for flavoring.

A 1998 article by J. Karchesy of the Department of Forest Products at Oregon State University discusses the uses of juniper for specialty products:
"The juniper berry oil of commerce is an essential oil produced by steam distillation of Juniperus communis berries. This oil is composed mainly of monoterpenes, including a-pinene, myrcene and sabinene as major components, lesser amounts of sesquiterpenes and other volatile compounds. Commercial production is carried out in several European countries including Italy, France, Germany, and Austria. Perhaps the most famous use of this product is to flavor gin and alcoholic bitters. It is generally recognized as safe for human consumption (GRAS) and also finds use in many other food products such as frozen desserts, gelatins,puddings, and meats."

Date 2017-05-12
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May 31 2018 13:14:08