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Plant Answer Line Question

Keywords: Magnolia grandiflora, Trees

I was reading an article in the local paper that mentioned Magnolia grandiflora 'Alta' and was hoping that you could tell me more about and its hardiness in the Pacific Northwest and what its mature dimensions would be.


Magnolia grandiflora 'Alta' is a trademarked Monrovia introduction. According to their website, it is "very slow growing to 20 ft. tall, 9 ft. wide in 10 years." Since this is a relatively recent introduction, there is not going to be much information about its hardiness in our area until more gardeners have grown it and shared their experiences. The longevity of the species Magnolia grandiflora and its cultivars can only be estimated (between 50-150 years, according to SelecTree.) Trees grown in urban settings are often affected by root disturbance, pollution, and the like, so their lives may be somewhat toward the short end of the expectancy range.

The local website of Great Plant Picks lists two different cultivars of Magnolia grandiflora, which may give you some idea of how well they do in our area. Here is an excerpt:

"Provide southern magnolias with good drainage and full to partial sun. They thrive in hot spots, where the extra heat encourages better flowering. These flowering evergreens prefer well-drained, sandy soil, but they tolerate average garden soil. Best growth and flowering requires occasional summer watering, but once established, southern magnolias withstand considerable drought. Garden gently under magnolias, for they have fleshy roots that can easily be damaged. The best approach for companions plants is to tuck in natural spreaders and let them flourish untouched."

From my observations, they do not do well in the occasional winters when we have heavy snowfall, as their evergreen leaf-laden branches are prone to breaking under the weight of snow. Otherwise, they seem to survive here.

Date 2018-09-26
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Plant Answer Line Question

Keywords: Trees, Transplanting

Can you direct me to information available on the transplant tolerances of different tree species?


There is general information on transplanting trees and shrubs from Morton Arboretum.

There is a table on "Ease of Transplanting" from Principles and Practice of Planting Trees and Shrubs by Watson and Himelick (Int'l Society of Arboriculture, 1997). It is the longest list of any I have found that covers this topic.

Date 2019-04-06
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Plant Answer Line Question

Keywords: Plant phenology, Leaves, 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. See the following article, "Turning Over New Leaves" by Richard Primack in the Arnold Arboretum newsletter. Primack (of Boston University) is the author of many articles on this topic. Primack and Caroline Polgar co-authored "Leaf-out phenology of temperate woody plants: from trees to ecosystems" (New Phytologist, Volume 191, Issue 4, pages 926-941, September 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.

Date 2019-04-27
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Garden Tip

Keywords: Tree identification, Trees--Diseases and pests, Trees--Care and maintenance, Trees

Silvics of North America Online by United States Department of Agriculture Forest Service, 1990.

Property owners with woodlots and tree lovers alike will find the Silvics of North America an informative and authoritative reference source on trees. Two hundred, mostly North American native trees are described including native habitat, associated trees and shrubs, propagation details, growth rate, and information on the major pests that may damage the tree. Many entries have information on the root development, which can be helpful in learning if a chosen tree will tolerate construction, or be appropriate for planting over water utilities.

Date: 2007-07-12
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Witness tree   by Lynda Mapes, 2017

Reviewed by: Brian Thompson on 2017-10-01

How would it be to spend a whole year observing a forest, the changing seasons and all the beings – plants and animals – that lived there. This is exactly what Lynda Mapes, a science reporter for “The Seattle Times,” decided to find out. She lived on the edge of the Harvard Forest, a 3,000 acre managed research forest in Petersham, Massachusetts, over 60 miles west of the main Harvard campus. “The Witness Tree” is the story of this undertaking.

To focus her attention, she concentrates on one tree, a northern red oak (Quercus rubra), of early middle age for this species. She examines this tree in every conceivable way, and with the help of experts from many professional and avocational perspectives. She also considers the humans that interact with the tree and the forest, including the cultural history of the area, and its impact on the natural history.

Throughout there is an ongoing consideration of climate and other changes in the forest. Both from the long view over millennia, and the more recent changes, such as the increase of the hemlock woolly adelgid (Adelges tsugae), and near demise of such forest stalwarts as the American elm (Ulmus americana) and the American chestnut (Castanea dentata). Some of this is told from the supposed perspective of her beloved hundred-plus-year-old red oak.

Mapes stayed in New England during the winter of 2014-2015, one of the coldest and snowiest on record. She writes, “While I froze in the Northeast, my husband at home in Seattle was cutting the grass and watching flowers burst forth in the warmest winter on record.” Contrasts like this, and the author’s gentle role in teasing them out of the world around her, makes this a very satisfying book.

Excerpted from the Fall 2017 Arboretum Bulletin.

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