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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Acer circinatum, Fall foliage

I have a vine maple tree whose leaves turn a very plain, rather ugly brown in the fall. It gets full sun from about noon until sunset. From what I have read, its leaves should turn red, orange, and yellow. What can I do to trigger this? I am thinking of how Hydrangeas are different colors depending on the acidity of the soil. I would like a tree with attractive fall color. I have also read it likes moist places in the shade, and it has not had that environment in my yard. Could the amount of water it gets in the summer, or lack of water, be affecting this?


According to J. Harris in The Gardeners Guide to Growing Maples (2000, p. 119), "Autumn color is due to a chemical change in the leaves and a combination of the remains of the chlorophyll grains and a substance called anthocyanin. The color assumed by leaves depends on soil and air conditions and on the amount of moisture. If conditions are very dry in the autumn, then the color will not last for long. After a frost, colors appear more intense, but the frost can check activity. It will also not be so good in very wet conditions."

The National Arboretum provides a complete explanation of why autumn leaves turn color.

There is an excellent article in the Seattle Times (September 25, 2008) by former Washington Park Arboretum Collections Manager Randall Hitchin which also describes this process.

There are other possibilities why your vine maple is not producing good fall color:

1. It might be getting too much light. The natural habitat for the vine maple is under an overstory of large conifers (Japanese Maples, by J. Vertrees, 2001, p. 247). Afternoon sun is the most intense and could be stressing the tree. Harris (2000) notes that while tree-like species prefer open sites, woodland conditions and dappled shade are ideal environments for shrubby maples. (Harris., p. 118).

2. Other than light, the environment might be a little off. Vertrees (2000, p. 247) notes that with vine maples, intense color does not develop in environments where abundant moisture and fertility keep the trees from being under stress, i.e., they need stress to produce good color.

3. Trees of the same species will exhibit different fall colors depending on the growing environment and peculiarities of each individual tree. (As identical twins can be quite different). When selecting a tree for fall color, it is best to first view it in autumn -- then remember it will change somewhat when it is installed in a new home.

It is not likely that changing soil pH will have an effect. I have been disappointed in fall color a couple of times and finally replaced the trees -- after viewing them in full color in the nurseries.

Date 2017-06-08
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Plant Answer Line Question

Keywords: Cotinus obovatus, Cotinus coggygria, Fall foliage

I planted some beautiful Cotinus coggygria 'Grace' in practically full southern exposure in my yard, and their foliage has gradually turned from deep wine red to a pale olive green. Is my soil not acidic enough? Did I overwater? Or is it something else?


You are not alone in noticing this color change. I found the following discussion about Cotinus coggygria x Cotinus obovatus 'Grace' on a GardenWeb forum. Here is an excerpt:
"The true 'Royal Purple' smoke bush will not turn green. Some smoke bushes are grafted, most do not grow true from seed. You must order one from a true nursery or visit a specialty nursery to get a good Royal purple smoke bush. There are also many different purple smoke bushes who have different characteristics. 'Grace' is a hybrid cross between the green smoke bush and Velvet cloak (which is a gorgeous true purple smoke bush). 'Grace' has blue green leaves with red tinges around the leaves."

An article by David Wheeler in the British paper The Telegraph describes this variety of Cotinus:
"A hardy plant of exceptional beauty at several different times of the year, Cotinus 'Grace' has nothing of the leaden darkness so often criticised by those who dislike purple foliage. Less purple than red suffused with green, the leaves bring a bold note to the garden that can complement or offset other foliage colours.
'Grace' is a garden hybrid, one of five seedlings resulting from a deliberate cross between the American chittamwood (Cotinus obovatus) and a variety of the Venetian sumac (C. coggygria 'Velvet Cloak'). Raised by Peter Dummer, propagator at Hillier's nursery, in Winchester, in the late 1970s and named after his wife, it has won the Royal Horticultural Society's top awards. Like both parent plants, it exhibits long-lasting autumn colour, the prominently veined, broad oval leaves (up to 5in long) turning to a brilliant scarlet before falling in mid-October."

A page from Woodlanders Nursery catalog suggests the green phase is normal:
"Reddish new foliage turns blue-green and finally good orange, red, and yellow in fall. Plant in a sunny location with well-drained soil."

The Brenton Arboretum in Dallas Center, Iowa describes the leaf color change similarly:
'Grace' - Hybrid between C. coggygria and C. obovatus; large pink panicles; leaves 4 to 6" long, light red when young,turning blue-green in summer and red, orange or yellow in autumn; height estimated 20'; zone 5.

It sounds to me as if the leaves go through several changes, and your patience will probably be rewarded with the expected fall color in time.

Date 2017-08-15
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Plant Answer Line Question

Keywords: Leaf marcescence, Leaf abscission, Quercus, Fall foliage

I have a large lawn with a southern exposure, and fairly good drainage. I would like to plant 1-3 large shade trees. I have been considering northern red oaks for the location, as they seem to grow well in this climate, should provide good shade, and they have nice fall color. However, I don't like oaks which keep their dead leaves through the winter (as Scarlet oaks do). I find the dead leaves unsightly and messy, and I will not want the shade in the winter. Do red oaks also keep their dead leaves on their branches in this manner? If so, have you another recommendation, other than maples?


According to the Sunset Western Garden Book, pin oak (Quercus palustris) keeps its brown leaves through the winter, but Northern red oak (Quercus rubra) loses them in fall. The retention of leaves in fall (meaning that they delay dropping them until spring) is a phenomenon called marcescence. At times young trees of other oak species, even Quercus rubra, can keep their leaves all winter, particularly if it is an unusual winter. You might consider Katsura tree (Cercidiphyllum japonicum) or sweet gum (Liquidambar styraciflua) for fall color with more reliable leaf drop.

Date 2018-03-14
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Plant Answer Line Question

Keywords: Pyrus, Fall foliage

Which semi-dwarf pear tree should I plant to get good fall color? I want to eat the fruit and have beautiful yellow to red fall leaves in my landscape.


Not many of our resources on pears describe the color of the fall foliage, as they tend to focus on the taste and appearance of the fruit. However, I did consult Lee Reich's Landscaping with Fruit (Storey Publishing, 2009), and on page 146 he features "seasons of visual interest." Here is what the author has to say:
"Come autumn, leaves of many pear varieties, including many Asian varieties and such Europeans as 'Colmar d'Ete,' 'Durandeau,' and 'Triomphe de Vienne,' take on very attractive coloration. Ripening pears among the leaves, especially yellow varieties, also contribute to the show."

I suspect that the varieties mentioned above are heritage varieties that may be challenging to find. You might find these links of interest:

By doing an internet search, I came across a reference in a book entitled Growing Shrubs and Small Trees in Cold Climates by Debbie Lonnee et al. On page 233, the authors mention that the variety 'Golden Spice' has "nice fall color." The 'Luscious' variety is said to "turn a nice red in fall." This book confirms what I have read elsewhere, which is that ornamental pear trees are better known for their fall color.

Another approach would be to talk to pear vendors at farmers markets or talk directly to fruit farmers in your area, and ask if there are particular varieties which are notable for their autumn foliage.

An additional consideration is choosing pears which are late-ripening. If you want the fall color to coincide with the pears, you should probably choose a late-ripening variety. Pears are harvested before they are fully ripe, so later varieties will give you a better chance of night temperatures being sufficiently cool for leaves to begin changing color. Oregon State University's publication, "Picking and Ripening Apples and Pears," by R. L. Stebbins et al., has additional details on different pear varieties.

Date 2017-04-22
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Garden Tip

Keywords: Fall foliage

Ever wonder when you might expect to find a great display of fall foliage, either in your own area or another part of the country? The United States Forest Service has a toll-free Fall Color Hotline you may call: 1-800-354-4595. The site also lists spots of particular beauty for fall viewing.

Date: 2009-08-19
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May 22 2018 15:48:30