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Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

Encouraging Chilean fire tree to bloom

I have a Chilean Fire tree (Embothrium) that I planted about four years ago. It has grown rapidly to about seven feet tall. It has not yet bloomed. At what size or age does this tree bloom? Does it require some encouragement, like root pruning, to get it to bloom?
I have not fertilized it because I have read in at least two sources that these plants should not be fertilized.

 

There are many reasons a plant may fail to flower, immaturity being one of them. You are correct to avoid over-fertilization, as that is often a cause of lack of flowers. Another cause is unusually cold weather.

I found an article by Roy Lancaster on Embothrium coccineum in Gardens Illustrated, May 2005. He mentions that if the tree is planted in a somewhat shady site, it will not flower as prolifically. Acid soil which is moist but well-drained, and a sunny but sheltered spot are ideal.

There is a discussion of the problem of Embothrium’s failure to flower on the NPR Talking Plants blog (no longer online) in 2007 (formerly hosted by Portland gardener Ketzel Levine). It appears that this is not an uncommon problem. Here is an excerpt, from a gardener responding to Levine’s complaint about the lack of flowers:

“Many have found Embothrium to be a slow bloomer. It is a polymorphous plant in many ways: some are evergreen, some deciduous, some are trees, some are shrubs. Some bloom in a 1-gallon container, others need to put on some size first.

“The danger of phosphorus toxicity rules out some of the usual bloom-stimulation therapies using fertilizer. Provided that it’s getting enough sun exposure, I’d say just sit tight and give it a few more years. If you’ve been watering it on a consistent basis all summer, hold back and let it dry out for a few weeks between good soakings.

“If you get really desperate and are contemplating its removal, you might first take a propane torch and try burning the leaves and twigs off when autumn comes (don’t scorch the bark on major limbs). I know that sounds a bit absurd, but some plants respond to environmental adversity by blooming, and the fire trick has been known to work on some other proteaceous flora. From the plant’s point of view, why expend the energy of going into a reproductive cycle when everything’s fine and there’s no threat to survival? Give ’em something to worry about.”

If you feel daring or desperate, I suppose you could try the blowtorch approach, or you could make sure to provide the ideal conditions, and wait patiently. Levine, like you, thought of root-pruning her Embothrium to induce flowering. You could try to contact her and ask if she tried it or the fire method, and if either worked.

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Speakers for a garden club

I would like to find a speaker for our garden club which meets at the Phinney Neighborhood Center in northwest Seattle. We are a small general interest club. Do you have any suggestions for resources for finding people willing to talk to our club, on topics such as winter interest in the garden?

 

Here is a link to the King County Master Gardeners Speakers Bureau, with a list of presentation topics and instructions for requesting a speaker. The Arboretum Foundation may still maintain a list of speakers; you can contact them directly at info@arboretumfoundation.org

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Bergenia, pig squeak, and elephant ears

I am trying to find out the difference between Bergenia Winterglut, elephant ears, and Bergemia pig squeak. The landscape plan I am following calls for the pig squeak, but I could only find elephant ears. Is Winterglut something special?

 

I think that the confusion arises from the fact that ‘pig squeak’ is a common name for Bergenia, as is ‘elephant ears,’ while ‘Winterglut’ is part of a cultivar name (Bergenia cordifolia ‘Winterglut’).
Bergemia with an “m” in the middle is just a typographical error.
‘Winterglut’ is also known as ‘Winter Glow.’ See the excerpt from Greer Gardens Nursery catalog below:

BERGENIA – PIG SQUEAK – (-40 F, USDA Zones 3-8) Bergenia are tolerant of a wide variety of conditions but soil that is too rich can cause soft foliage. Providing the plant with poorer soil conditions and some exposure, you will enhance the winter color. This plant prefers some shade, but will thrive in full sun if soil is deep and moist enough. Not for south Florida or the Gulf Coast.

30047 ‘Bressingham Ruby’ – The mound of rounded, deep green leaves are up to 8″ long. The foliage is maroon on the underside, and will turn beet red in the winter. In the spring, flowers of a very intense red are borne on nodding cymes. Will get 1′ tall.

30965 ‘Bressingham White’ – Has large, dark green foliage which is adorned by blooms that start out light pink and then fade to a pure white. They reach 12-15” in height and blooms appear in the spring.

31673 ciliata – (-20 F, USDA Zones 5-8) Large (12”) fuzzy, rounded leaves and white flowers in early spring make this deciduous Chinese species a standout. Part shade and moisture retentive soil. Low growing to 10”.

cordifolia – (-30 F, USDA Zones 4-8)

31562 ‘Eroica’ – Dark purple flowers in early spring. Foliage changes from light green to deep copper in fall, then a brownish red after first frost.

31035 ‘Winter Glow’ – Deep reddish pink flowers bloom in spring, held above evergreen leaves. In the winter the leaves turn deep red. Will be 1′ in height.

From Thimble Farms in British Columbia:

Bergenia `Winterglut’ Ht.45cm. Z2. Thick clusters of florescent red flowers and dark green foliage. Fantastic red fall highlights

You may find this information from the website of a Seattle area gardener, Paghat’s Garden, and this additional page, of interest. Excerpt:

“A good plant nearly impossible to kill is Bergenia, named for the 18th Century German botanist Karl August von Bergen. It is called Elephant Ears because it has giant round or heart-shaped leaves. My grandparents called Bergenias the Elephant Plant, because if an elephant stomped on it, it wouldn’t die. But I notice the Sunset Guide only calls it by its scientific name, giving it no common name at all, so Elephant Ears may be somewhat a regional name, & Elephant Plant just the name our family used without authority.

“We get good red winter colors on our B. cordifolia ‘Winterglut’ & B. cordifolia ‘Abendglocken.’ The first photo at the top of this page shows both of these when they were first stuck into the hillside as tiny starts. In that early-April 2002 photo, the ‘Abendglocken’ on the left has already turned from red back to green & is starting to bloom, showing a glint of color in its buds. But ‘Winterglut’ on the right still shows a chocolaty-colored leaf, which began to green shortly after photographed.”

Eradicating English ivy

In trying to eradicate English Ivy I am considering using Clorox on the roots. I have cut off all of the leaves. Is this safe and do I need to guard against nearby roots from trees that I want to save? If the Clorox will work I am assuming that I would use it undiluted for maximum effect. Any other ideas on English Ivy eradication?

 

Ivy is a tough plant to eradicate, as I imagine you already know. The resources I have consulted indicate that manual removal methods are more effective than chemical methods. Ivy apparently has an excellent defense system against chemicals. I could find nothing in the literature that suggested using bleach to kill the roots of Hedera helix (English ivy).

Here are links which may be of use to you.

From King County Noxious Weed Control.

From Portland, Oregon’s No Ivy League.

Local garden writer Ann Lovejoy’s article in the Seattle Post-Intelligencer. Excerpt:

“Why not just poison it? Using herbicide on ivy is both futile and dangerous. Ivy’s waxy foliage repels herbicides, which run off to damage nearby plants and pollute water systems.

“To safely and steadily get rid of ivy, begin by cutting all vines that have scrambled up trees or posts. Remove as much as you can reach from each trunk. If you miss a few stubborn scraps here and there, don’t worry about it. Just be sure that none of the vines remain uncut or are left dangling.

“Now remove all ivy at ground level by pulling strands and prying roots with a small hand-mattock or hori-hori (Japanese farmers’ knife). Even if you miss a few roots (as you will), they won’t all sprout back.

“Finally, mulch with a combination of woodchips and compost if you plan to replant soon. If you just want to keep the ground clear for a while, use coarse wood chips for mulch.

“To keep the mulched area clear, check it two or three times a year. You can quickly remove any new shoots that appear, along with as much root as possible.”

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Cutworms on strawberry plants

My small patch of strawberry plants has this year suffered from green fruit dropping off, forming neat piles under each plant. Each fallen fruit has a short bit of stem still attached. A few fruit are still attached. No sign of slug or squirrel damage, no signs of fungus of insect attack. The weather has been colder and wetter than average. Owing to natural layering, the plants are closer together than when first planted. This happened a couple of years ago, but we had a good crop last year. Any idea what’s going wrong?

 

I wonder if this might be the work of cutworms. You can take a close look just under the soil surface, along the stems, and inside curled or folded leaves during the day, or take a flashlight at night, which is when they feed, and see if that may be why your strawberries are being cut away from the plant. If you find them, cut them with garden pruners.

Washington State University’s pest and disease site does list the cutworm as a known pest of strawberries. Excerpt:

“Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4″ to 1″ in length and tend to curl up when disturbed. They may climb into the plant and feed on foliage, buds, flowers, or fruit. Armyworm behavior is similar to that of cutworms, but armyworms feed in large groups instead of individually. They tend to be voracious feeders. The caterpillars typically spend the day just beneath the soil surface or under debris near the host. Weeds are a primary food source for both cutworms and armyworms.”

I looked at Pests of the Garden and Small Farm by Mary Louise Flint (University of California, 1990), but could not find any strawberry disease resembling what you have observed in your garden, which leads me to believe it is a pest problem. Here is a link to U.C. Davis’s Integrated Pest Management page on strawberries.

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Micropropagation of Japanese maple

Do you have any information about micropropagation of the Japanese maple?

 

I found a series of replies to a question like yours on the University of British Columbia Botanical Garden’s online forum.

An article formerly available online from the Oregon Association of Nurseries states the following:

“Keeping up with the demand for ‘newness’ means learning about and trialing different propagation techniques. That’s where tissue culture, or ‘in vitro micropropagation,’ has been used as one propagation tool of many in the tool chest, said Gayle Suttle of Microplant Nurseries Inc. in Gervais, Ore. The company focuses on shade trees and shrubs. “No technique will dominate,” Suttle said. ‘What’s going to work for the industry is, number one, focusing on quality and, number two, efficiency. If you sacrifice quality for cost, then you lose.’

“Micropropagation helps many nurseries get a jump-start on production of new items, improve the reliability of plant performance and start with clean stock. In the area of woody plants, micropropagation has had a particular impact on the nursery industry, allowing growers to cut the time needed to establish mother blocks and meet production demand, Suttle said. Also, there are some plants where branching is hard to come by, and micropropagated plants tend to branch more. ‘If you can grow a plant by seed, there’s nothing that beats throwing a seed into the ground,’ she said.

“But there are plants for which normal propagation has problems — the seed source is unreliable or unavailable, a graft is incompatible with its scion, budding problems arise in the field or roots fail to form on cuttings. Micropropagation fits as one way to keep growers successful and efficient.

“‘Twenty-five years ago, there was a fear that micropropagation was going to take over the world,’ Suttle said. ‘That’s never been a concept that’s panned out. The industry is such a variable industry, with different people doing things differently. The goal is to be successful. You can save all kinds of money, but if you have a rotten plant, no one’s going to buy it. Customers may buy a cheap plant one year, but if the quality is not behind it, they won’t be back next year. They’ll be looking for something else.’

“It was plant health and survivability that drove Dieringer Nursery Company toward organic growing practices nearly 13 years ago, and those goals keep the nursery from fully jumping into use of tissue culture. The company grows rhododendrons, relying mostly on vegetative propagation with a small smattering of grafting and an even smaller sample of plants produced via micropropagation.

“‘Every couple of years we will bring in some tissue culture to evaluate the plant under our growing procedures, we’ll get a new variety and it comes in by tissue culture,’ said Jeff Dieringer, president of the Hubbard, Ore.-based company.

“The advantages of propagation by cuttings over other methods are exact replication of desired genetic characteristics and the more rapid time frame to finished product compared with starting from seed. Nearly all of the hundreds of thousands of rhododendrons Dieringer nursery handles in a year are grown using vegetative propagation, while maybe only a couple hundred are started from in vitro micropropagation.

“‘It’s a way to introduce a plant, but we don’t get tissue culture starts and turn them into production plants,’ Dieringer said. ‘We watch that plant, its habits under our growing condition for three to four years to see if it exhibits normal growth. We do vegetative cuttings then, if they don’t exhibit any juveniles.'”

The Miller Library has several titles on micropropagation in general, but I did not find anything specifically addressing use of this method with Acer palmatum. A good general text with several chapters on in vitro culture is A Color Atlas of Plant Propagation and Conservation by Bryan G. Bowes (New York Botanical Garden Press, 1999).

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Thuja bark injury

I have a mature Western red cedar with an inverted-V gap in the bark,
right at ground level. The point of the V is about 2 ft. off the ground;
the base of the gap is perhaps 9-10″ across. What’s the current thinking on protecting this exposed area from diseases and critters? Paint with some sort of goop? Leave it alone? Or something else?

 

Here is a link to information on managing bark injuries, from
Cornell University’s Plant Disease Diagnostic Clinic, which includes
illustrations. Excerpt:

“When a split occurs on a tree, what should you do? In recent years,
quite a bit of research has been done on closure of tree wounds. These
investigations have indicated that tree wound paints are of little value
in helping a tree to callus over. For this reason, do not paint or try to
seal a split with paint or tar. Tracing the bark around the split can be
very helpful in aiding wound healing (Fig. 2). With a sharp knife,
starting from one end of the split, trace around one side of the wound,
about 1/2 to 1 inch back from the split bark. Stop at the other end and
do the same procedure on the opposite side of the split. Knives should be
sterilized between cuts by dipping them for several minutes in a 1:10
bleach:water solution or a 70% alcohol solution to avoid contaminating
the cuts. Carefully remove the bark from inside the traced area. You
should now have a bare area resembling the diagram in Fig. 2. Remember to
leave this untreated. A tree growing with good vigor usually calluses
over quickest. Encourage vigor in the tree with yearly spring fertilizer
applications — and be sure to provide adequate irrigation in hot, dry
weather. Bark splits will often close over completely leaving a slight
ridge in the trunk where callus tissue has been produced.”

The book Practical Tree Management: An Arborist’s Handbook by T. Lawrence
et al. (Inkata Press, 1993) confirms the method described above. Trim
back the bark to healthy tissue around the wound using tools such as a
chisel, gouge, hammer, and sharp knife. Wound margins should be rounded,
and damaged wood within the wound should be smoothed with a chisel or
gouge, but only to the most minimal level (don’t go deep).

If in doubt, I would recommend contacting a certified arborist for
assistance. You can obtain a referral from Plant Amnesty
or the directory of the Pacific Northwest chapter of the International Society of Arboriculture.

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Green beans and pests

I have planted green beans three times because I have an
annual problem of the leaves either being completely chopped off or they
appear lacy and nearly gone. I have seen slug slime, so that may be some
of the problem, but what does the lacy leaf indicate? I also have a lot
of “potato bugs” or “sow bugs,” could that be the problem?

 

According to The Organic Gardener’s Handbook of Natural Insect and
Disease Control edited by Barbara Ellis (Rodale, 1996), lacy leaves on
your bean plants might be the work of Mexican bean beetles. Parasitic
wasps (Pediobius foveolatus) can be used to control the Mexican bean
beetle. As a last resort, you can spray or dust your plants with
pyrethrin. See links here:

From the Connecticut Agricultural Experiment Station

From the University of California

Large holes in the leaves may be caused by other beetles as well, such as
the cucumber beetle, which can be managed by protecting your plants with
row cover like Reemay. If damage is severe, you can use pyrethrin or neem
spray.

Small holes in the leaves may be the work of flea beetles, and the
management is the same as above.

The chopping off at ground level sounds like it could be the slugs eating
shoots as they emerge, or climbing up the plant and eating it down to the
ground. It could also be the result of cutworms. Look for these at dusk, and look during the day at or just below the soil surface. I manage these
pests by looking for them frequently, and squishing them or cutting them
in half with my pruning shears.

I had never heard of sow or pill or potato bugs (isopods) being a
vegetable pest, but apparently they do have that potential if the
population is large enough. See the discussion among gardeners on Houzz.

You might try fooling the pests by planting your beans in a different
location, especially a raised bed.

Deciduous or evergreen Dendrobium?

I just got a Dendrobium, it is Dendrobium eima x impact. The
flowers are pink and white. I was wondering how I can tell if it is a
deciduous one or an evergreen one. I still have months before winter,
but want to make sure I give it the rest it needs when the winter does
get here.

 

There are deciduous and evergreen types of Dendrobium. Unfortunately, I could not find information about the variety you are growing. If yours has soft canes, it is deciduous; hard canes are characteristic of the evergreen type. Here is information from Orchids Made Easy:
“Dendrobiums are separated into two main groups: hard-caned and soft-caned.
Hard-caned Dendrobiums have tall pseudobulbs that are very thin and their leaves are generally a little darker in color than the soft-caned. Hard-caned Dens are evergreen and often keep their leaves for many years before they drop them. Hard-caned Dens grow spikes from the top of the cane and produce gorgeous flower sprays.

“Soft-caned Dendrobiums have leafy pseudobulbs that are long and slim. Their leaves are generally a little lighter in color than the hard-caned Dens. They grow leaves along the length of the cane and the blooms sprout from the individual stems that are along the cane itself. Soft-caned dendrobiums are deciduous and drop their leaves
when the weather gets cold.”

The American Orchid Society has a guide to growing evergreen Dendrobium for beginners.

There is also good general information on caring for orchids in the Brooklyn Botanic Garden guides on the subject. Generally, winter is the time to hold back on watering a bit, but also be careful about the plant’s need for humidity–our heated homes in winter can be exceedingly dry. According to Orchids by Joyce Stewart (Timber Press, 2000), most orchids prefer 65-75% humidity during the day. She recommends “damping down last thing at night” during the winter (using a spray bottle or mister), if you have heat on in your house overnight.

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Cryptomeria and dieback

My Black Dragon Japanese Cedar has a lot of dead branches. The tree is healthy otherwise. A foot of new growth this year. The nursery told me this was normal. Can you give me an opinion?

 

Apparently, dieback is often seen on Cryptomeria, as the following
information from North Carolina State University Cooperative Extension, no longer available online, suggests:

Cryptomeria can have leaf blight or spot. Branch dieback is common.
Dieback has not been associated with a disease but has been touted as the
nature of the tree. Pathologists are still researching this. There may be
some tip dieback associated with a disease.

There is another discussion of a Cryptomeria with dead branches on
University of British Columbia Botanical Garden’s forum which mentions
rust and needle blight (both fungal diseases) as possible causes.

You may want to bring samples of the affected branches (along with your
photo) to a Master Gardener Clinic for diagnosis.

You may find this University of British Columbia Botanical Gardens Forum discussion of interest.

The growth rate of a foot a year makes sense, considering that this is
not a large tree. See below what Great Plant Picks, a Seattle-based website, has to say about this tree. An earlier version of the page linked here, from Iseli Nursery, indicates a growth rate of only 3-6 inches a year.

Information from Iseli Nursery: Cryptomeria japonica ‘Black Dragon’ (Japanese cedar )

Cryptomeria japonica is one of the most variable conifers you can imagine, with plants ranging from very dwarf rounded shrubs, trees with golden or contorted leaves, and wild forest trees to 80 feet high and 20 feet wide. ‘Black Dragon’ takes the middle road,
neither too small nor too big. It has the deep green, needle-like leaves characteristic of this species and grows to about 7 feet high and 8 feet wide in twenty years. This very dark-foliaged conifer is easy to grow and combines well with plants having larger or variegated leaves.

Japanese cedars thrive in full or part sun in well-drained, humus-rich, acidic soil and average moisture. May grow quickly when it first comes home from the nursery, due to the added fertilizer it gets there, but within a year it will settle into its dense, compact habit of growth.

Cryptomeria japonica ‘Black Dragon’ is an evergreen, coniferous shrub. It grows wider than high, with an overall pyramidal shape. In 20 years it will reach only 7 feet high and about 8 feet wide.

Hardiness: USDA zones 6 to 9