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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Acer palmatum, Tree planting, Transplanting

I would like to transplant a Japanese maple, probably 5 years old and about 8 feet tall. Can I do it in late October/November safely in St. Louis? And what is the best method?


Japanese maples are best transplanted when they are dormant---usually late fall through early spring if the ground does not freeze in your area.

The following information comes from Japanese Maples (by J.D. Vertrees, 2001, pp.61-62). This book also contains good information about mulching and general care:

When moving a plant to a different location within a garden, the plant must be dug with an earthen ball intact around the roots. If the plant is of any size or age, this root protection is important. It is also desirable that the planting hole be prepared in advance, ready to receive the plant with its root ball, as soon as it is dug up. Having the new planting hole ready minimizes the risk of the fine feeding roots drying out. For this reason it is imperative that, whatever method, material, or timing is used when planting a Japanese maple, the roots are not exposed to air or direct sunlight for any length of time. Such care will help prevent them from becoming desiccated, which would cause too much transplant shock and possible loss of the tree.

The planting hole should be dug slightly larger than the root mass of the plant. To enable the root system to establish itself quickly, it helps to mix with the soil organic compost, such as composted conifer bark mulch, rhododendron or azalea planting mix, or rose compost. In tight , heavy clay soils the compost helps condition the soil, while in light, sandy soils the compost assists in water retention. Sawdust or wood chippings should never be used as, during their breakdown, they use up the available soil nitrogen and render it unavailable to the newly planted tree.

The planting hole should be deep enough so that the root collar of the plant, the ground line at which the young plant was grown, is level with the ground surface. The exception to this rule applies to tight, heavy soils, like clay, where success will be greater if the hole is rather shallow so that the root system is partly above the ground level. When filling in the hole, the soil should then be mounded up to the root collar to protect the roots from drying out. If deep holes are dug in heavy soil, it is like planting the tree in a large iron kettle with no drainage. Surely the plant will soon drown and die.

Whatever the soil conditions, the tree should never be planted deeper than the root collar. After the first season or two, the plant will find the level of root activity at which it can exist in particular soil conditions. I have observed maples growing in some surprisingly dry, shallow, and exposed conditions.

Date 2017-05-26
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Plant Answer Line Question

Keywords: Acer palmatum, Control of wildlife pests

The bark on a Coral Bark Maple is peeling away on one side of the trunk...about 1 1/2 to 2 feet long. The tree looks healthy otherwise. Cause? Anything to do?


Trees (maples and others) are attacked by various diseases and pests, but nothing that removes sections of bark on a trunk. Damage might be from larger pests such as raccoons, deer or squirrels. In the city, squirrels often strip bark from trees for their nests. You might want to:

1. Put chicken wire or other protective barrier around the tree. The tree will heal itself as long as the entire trunk is not girdled (that is when bark is stripped all the way around the trunk so moisture and nutrients can't flow).

2. Have an arborist look at the tree for an accurate diagnosis. To locate an arborist in your area, contact Plant Amnesty's referral service or call their Referral Service Coordinator at 206-783-9813 and leave the following information:

General Location (city or town)
Phone Numbers (work, home, cell)
Email (will get the quickest response!)

Date 2017-08-15
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Plant Answer Line Question

Keywords: Acer palmatum, Plant diseases

I have a lovely, 3-ft. Japanese Maple (Acer palmatum) that has access to full sun. I am guessing it is over 3 years old at least. The tree is leafing beautifully, but last week I noticed there are "pustules" all over the stems and branches. They are yellowish-brown in color and somewhat mottled looking. They form in irregular clusters along the branch. Each pustule is about the size of a ladybug; in fact, at first I thought they were beetles, but they do not move and when I removed one, it was liquid-y inside and left a thin, white streak along the branch. I am a beginner/ homeowner, so I do not know what this is. Do you have any ideas? What can I do to treat this? I would hate to lose my Japanese Maple.


The best way to determine if your tree is diseased is to bring a sample to a Master Gardener Diagnostic Clinic and ask a Master Gardener to diagnose it for you. This service is free to home gardeners.

What you describe sounds like several quite different problems (canker, or scale, for instance), which is why having a hands-on diagnosis is so important. Below is general information about maple diseases which you can compare with your tree. Additionally, I recommend the book Japanese Maples by J.D. Vertrees and Peter Gregory (Timber Press, 2009). It has sections on the most common pests and diseases affecting Japanese maples.

My Garden Guide from Bartlett Tree Experts has a document about Japanese Maples including extensive information about diseases.

Clemson State University has a factsheet on Maple diseases and insect pests (read the entry on scale).

Try searching for "maple" in Pacific Northwest Guide to Plant Disease Control, and compare the descriptions to see if any ring true with what you are seeing. Ultimately, though, the best thing is to get a hands-on diagnosis from the Master Gardeners, as mentioned above.

Date 2017-06-09
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Plant Answer Line Question

Keywords: Micropropagation, Acer palmatum

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).

Date 2017-01-13
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Plant Answer Line Question

Keywords: Wind-tolerant plants, Acer palmatum

I want to find an Acer palmatum cultivar that can manage full sun and high winds. Is this asking too much of the dainty thing? Can you suggest a type, or a source that lists palmatums and their various needs and attributes?


Interestingly enough, Acer palmatum is listed as possessing medium-high wind resistance by University of Florida Extension in their trees-and-hurricanes information.

The following comes from Mississippi State University Extension:
"The U.S. Forest Service conducted a study after Hurricane Camille devastated the Coast in 1969. The study indicated that the best wind resistant trees are compact and have major tap roots. Trees with a tapered trunk have a low center of gravity and are more stable."

I would be concerned about scorching from exposure to hot wind, and damage from winter wind even if the tree is not likely to lose limbs. Here is what J. D. Vertrees's book, Japanese Maples (Timber Press, 2001, 3rd ed.) has to say: "A spot with a constant strong wind will misshape the plant and may burn the leaves. In winter, the wind-chill factor may cause bark and cambium damage (...) In areas of strong marine breezes, leaf damage from salt deposits may occasionally occur. Anyone growing plants under such conditions should be familiar with the necessary protection and the need for periodic washing of the foliage with fresh water."(p. 63)

A commercial nursery, Maple Ridge groups Acer palmatum cultivars by type. University of British Columbia Botanical Gardens offers additional information.

Date 2017-02-11
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Plant Answer Line Question

Keywords: Acer palmatum, Transplanting

I need advice on moving a Japanese Maple tree. The tree is 10 feet tall, and has begun to grow unevenly because it was planted too close to a very large wisteria in front of our house. Ideally, we would only move it 8-10 feet, as there is a wide open space with lots of sunlight just east of its current home. I don't know how deep the Japanese Maple typically roots, or how difficult this may be, but any information you could provide would be very much appreciated.


According to the book Japanese Maples by J. D. Vertrees (Timber Press, 1987), Japanese maples do not have deep, tap-root structures, but are mainly a fibrous root network which stays in the upper level of the soil. As they mature, however, there will be roots going deeper, so if you are planning to move the tree, you will want to be sure to get as much of the root ball as possible. If the tree is not too old, it should be easier. Make sure to water the tree well and prepare the new site before you begin digging carefully.

The Royal Horticultural Society has general information on moving mature trees and shrubs which may be of use to you, keeping in mind that fall is a good time for you to move a tree here in the Northwest.

You can also contact a certified arborist for advice. For a referral, contact Plant Amnesty. You can also go directly to the local chapter of ISA, the International Society of Arboriculture.

Date 2017-07-18
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Plant Answer Line Question

Keywords: Leaves, Acer palmatum

I planted an Acer palmatum a year ago spring. It has healthy leaves in spring then they all curl and turn brown in summer: not a pretty sight. I feed and water regularly. It gets late-morning and afternoon sun. It doesn't get very hot, maybe in the 70s to low 80s on average in summer with an evening fog rolling in from San Francisco Bay. Any ideas?


Acer palmatum sometimes displays this foliage problem. According to Japanese Maples by J.D. Vertrees and Peter Gregory (Timber Press, 2009), root weevils can cause this type of damage. Also, Verticillium wilt as well as other fungi can cause leaves (and often branches) to die. Leaf scorch seems to me the most likely cause, and your fertilizer may be contributing to it: Vertrees says excess nitrogen in the soil can lead to leaf scorch, as can watering so that the leaves become wet in the hottest part of the day.

I recommend that you contact the Alameda County Master Gardeners for more information and a more specific diagnosis.

Date 2017-05-04
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Plant Answer Line Question

Keywords: Acer palmatum

Is there a Japanese maple of any variety which will withstand full sun without leaf scorching or color alteration?


I consulted Japanese Maples, 4th edition, by J.D. Vertrees and Peter Gregory (Timber Press, 2009), which has a guide to uses and characteristics of different cultivars. Below is a list of the ones whose preferred light conditions are listed as "sun," as opposed to "shade" or "any." However, that probably doesn't mean that they will withstand absolutely searing sun with a lot of reflected heat from pavement, etc. The authors say that green varieties and their cultivars take full sun very well, but may sunburn in late-summer heat. You can prevent this if the tree is planted where it will get afternoon shade, and if you are vigilant about watering. Avoid variegated forms, which will need semishade. Also, red-leaved cultivars require full sun if you are to obtain the best color from them.

  • Amagi shigure
  • Aoba jo
  • Aratama
  • Autumn Red
  • Beni hime
  • Beni yubi gohan
  • Bewley's Red
  • Bloodgood
  • Boskoop Glory
  • Chirimen nishiki
  • Crimson Carol
  • Deshojo
  • Dissectum Nigrum
  • Dr. Tilt
  • Eddisbury
  • Emperor 1
  • Fireglow
  • Garnet
  • Glowing Embers
  • Hagoromo
  • Kiri nishiki
  • Kogane nishiki
  • Margaret Bee
  • Masu murasaki
  • Matsugae
  • Oshu shidare
  • Otome zakura
  • Pendulum Julian
  • Pink Filigree
  • Red Filigree Lace
  • Red Flash
  • Samidare
  • Sekka yatsubusa
  • Shaina
  • Shigure zome
  • Shikage ori nishiki
  • Shojo
  • Shojo shidare
  • Stella Rossa
  • Summer Gold
  • Sunset
  • Taki-no-gawa
  • Tennyo-no-hoshi
  • Trompenburg
  • Vandermoss Red
  • Villa Taranto
  • Waterfall
  • Watnong
  • Yezo nishiki

Date 2017-05-26
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August 01 2017 12:36:01