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Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

Leaf-out date for deciduous trees

Can you direct me to a list of deciduous trees whose leaves generally emerge in early spring, or a list of trees ranked in order of their leaf emergence? I know this will vary from year to year and from individual tree to individual tree due to climate and genes, but if there is a list out there with a general sequenced time schedule, it would be a great tool for design.

 

An early American observer of the varying timing of leaf emergence was Henry David Thoreau, whose journals list leaf-out dates for the trees and shrubs he saw in Massachusetts in 1854. In fact, his data is now being used in climate change research. Though it’s a subject that hasn’t been much approached from a garden design standpoint, the increased interest in climate change means that more research on phenology and the leafing out sequence is becoming available. There are several articles by Richard Primack in the Arnold Arboretum newsletter, Arnoldia. Primack (of Boston University) is a specialist in this topic. Primack and Caroline Polgar co-authored “Leaf-out phenology of temperate woody plants: from trees to ecosystems” (Arnoldia, Volume 68, Issue 4,2011) which states that “maples (Acer spp.), birches, alders (Alnus spp.), and poplars” tend to leaf out earlier, while “oaks, ashes (Fraxinus spp.), and hickories (Carya spp.)” are among the later-leafing trees.

The article “Why Do Temperate Deciduous Trees Leaf Out at Different Times? Adaptation and Ecology of Forest Communities,” (The American Naturalist December 1984, Martin J. Lechowicz) has a chart (p. 825) showing the tree species the author studied leafing out in this order:

 

  • Acer rubrum
  • Populus tremuloides
  • Betula papyrifera
  • Sorbus americana
  • Acer saccharinum
  • Betula alleghaniensis
  • Ulmus americana
  • Tilia americana
  • Quercus macrocarpa
  • Fraxinus pennsylvanica
  • Populus grandidentata
  • Fraxinus nigra

 

 

Another chart on the same page compares 1980 and 1981 leafout dates, with Populus tremuloides and P. balsamifera and Betula species consistently leafing early, followed by Acer and Prunus, then Fagus and Populus grandidentata, then Fraxinus and Tilia, and finally Carya and Juglans.

You may want to read a short article in the March 11, 2015 online version of Conservation Magazine on predicting the future of forests, based on two centuries of data from citizen scientists in England. Here is an excerpt:
“It is likely that the variation in each species’ sensitivities to both spring forcing and winter chilling will mean that forests will look quite different in the future. Those species for whom spring forcing is most important will grow leaves earlier in the year; those for whom the autumn and winter chill is more critical could leaf later in the year. Eventually, a late-leafing species like oak might wind up growing its leaves earlier than an early-leafing species like birch.”

Another resource that may help you determine the leaf-out date of specific trees is The Botanical Garden: volume 1: Trees & Shrubs by Roger Phillips and Martyn Rix (Firefly, 2002). The book presents photos of branch samples from many tree species, often showing the young leaves associated with a date (though not with the geographical location; bear in mind that the authors reside in England). While it doesn’t have such a photo for every tree, it might have enough trees for you to get useful data.

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Controlling liverwort

Both my front and back gardens have become covered in moss and/or liverwort. It has intermingled with groundcovers such as sweet woodruff and blue star creeper. I have dug up the liverwort in the past but it comes back. Any suggestions towards eradicating it would be greatly appreciated.

 

It would be important to distinguish among mosses, lichens, and liverworts. Mosses and lichens are not harmful to garden plants. One species of liverwort is known to be a bit of a pest, mainly in greenhouse-grown plants. A first step would be to bring samples to a Master Gardener Clinic for identification. See the following on moss and lichen in gardens:

There are researchers at Oregon State University who have done work on the species which is prevalent in greenhouses, Marchantia polymorpha, but the following information may not be relevant if that is not what you have growing in your garden. The first thing to do–if this is indeed the liverwort you are seeing–is to make sure you are not providing the ideal conditions for liverwort growth. Note that high nitrogen and phosphorus levels encourage growth: if you use fertilizer, check the levels of these nutrients. Avoid quick-release synthetic fertilizer. Below is information on methods of greenhouse (not garden) control of liverwort, from the OSU website:

“Before talking about how to kill liverworts, let’s talk about conditions in which liverworts thrive. Liverworts grow vigorously in conditions with high humidity, high nutrient levels (especially nitrogen and phosphorus), and high soil moisture. In an environment that has any of these 3 conditions, it will be difficult to control liverworts (even when using herbicides). In order to effectively control this weed, you must make growing conditions for the liverworts as difficult as possible. To do this, you should attempt to create an environment where the ambient air is dry, the surface of the container is dry (as dry as possible), and nutrients are not available on the container surface.”

The link above discusses postemergence control, but bear in mind that if something like acetic acid is used on liverwort growing on your plants it will affect the plants as well.

The Royal Horticultural Society says that liverwort will not harm plants (except by causing competition for small plants) but its presence indicates compacted, acidic, and/or bare soil.

The only time I have encountered liverwort is when transplanting nursery-purchased plants. With these, I physically remove the liverwort from the pot before planting into the garden. I wonder if your soil drains poorly, gets too much water, and/or too much fertilizer. I hope the information above will give you some ideas. Again, I recommend getting a conclusive identification before proceeding.

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Wings or ridges on tree branches

There are a number of trees in my neighborhood which seem to be abnormal. The branches are changing shape, and instead of being round, they have ridges growing lengthwise along them. It makes the branches look misshapen, almost like elongated stars. It looks unnatural, maybe like a disease. I think the trees are maples. Do you know what could be causing this?

 

There are some trees and shrubs whose branches normally take the form I think you are describing, which is sometimes referred to as winged or alate. I am not aware of maples which do this, so I wonder if perhaps you were seeing sweet gum trees, or Liquidambar styraciflua. According to information from the Mathilda Mathias Botanical Garden in Los Angeles,
“One diagnostic character is the presence of corky wings on young stems. In some cases, wings are due to stimulation of localized phellogens along a stem angle, as in winged euonymus (Euonymus alatus). Wings also occur on young stems of sweet gum (Liquidambar). Longitudinal splitting is the cause of stem wings in certain species of elm (Ulmus.)

Here are more images:
Euonymus alatus
Ulmus alata
Liquidambar styraciflua

According to the book Plant Form: an Illustrated Guide to Flowering Plant Morphology by Adrian Bell (Oxford University Press, 1990), these wings can be part of the way a particular plant grows. The book shows an illustration of metamers (also called phytomers), which are repeated constructional units
(like building blocks) in the plant’s development. From my unscientific perspective, I wondered if the wings might have a leaflike photosynthetic function. I did find an article from the Botanical Gazette from February 1889 (yes, 19th century!) by Emily Gregory which examines this issue. It seems to suggest that the corky wings on the branches may have the function of increasing branch circumference and this may provide the tree with extra protection.

A version of this question and answer appeared in the Spring 2014 issue of the Washington Park Arboretum Bulletin.

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Encouraging Acidanthera or Gladiolus murielae to bloom

This summer my several Acidanthera bulbs (which have flowered in past years) sent up many new shoots which grew to normal height. I had used a bulb fertilizer on them as they emerged from the ground. However, I only got one bloom from the entire lot.

Do you have any suggestions for getting them to bloom?

 

I’m either the best or the worst person to ask about Acidanthera, having planted 50 of them and lost them all within a year. I assumed it was because I did not dig up the corms and store them over the winter. According to The Brooklyn Botanic Garden’s Summer-Blooming Bulbs (edited by Beth Hanson; 2001), Acidanthera bicolor, also known as Gladiolus murielae (this is the preferred name) or Gladiolus callianthus, is hardy from Zone 7 and up, but won’t bloom after the first summer unless you pull up the corms, clean them, and let them dry. They should be stored over the winter in a dry place at 50 to 70 degrees. Pacific Bulb Society concurs, and adds that you may replant the corms after the last frost.

Other possibilities if you are already digging them up and replanting them after all danger of frost: Are your corms planted in a well-drained, sunny, wind-protected site? Did the fertilizer have a high proportion of nitrogen (this can cause a lot of leafy growth and no flowers)? You may find the following article from Portland garden writer Ketzel Levine of interest. Here is an excerpt:
“Clearly, you need this plant. The trick is growing it. In regions where winter temperatures are major league, plant acidantheras in April, then lift in fall and overwinter in paper bags. In more temperate regions, they should be hardy barring a catastrophic winter (read: 10 F). In the maritime Northwest, a greater challenge is preventing rot; the best advice I’ve heard is to top your already well-drained soil with several inches of sand or gravel and plant directly in that.”

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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