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Plant Answer Line Question

Keywords: fastigiate trees and shrubs, Cornus kousa, Trees in cities

Can you recommend some narrow or fastigiate trees for the space between our house and the house next door? The space is about 14 feet wide. Will Cornus kousa 'National' work?


From what the experts say, Cornus kousa grows 20-30 feet high and wide in cultivation. They can grow to twice that size in the wild.

I found this and other information that might help you in the sources below:
1. Trees and Shrubs for Pacific Northwest Gardens, by J. Grant, 1990, p. 71
2. Trees & Shrubs Hardy in the British Isles, by W.J. Bean, 1976, p. 703
3. Manual of Woody Landscape Plants, by M. Dirr, 1998, p. 260
4. North American Landscape Trees, by A. Lee Jacobson, 1996, pp. xiii, 144

The Seattle City Arborist's Office recommends the following narrow trees:
1. Magnolia grandiflora 'Little Gem' - 15 ft. high, 10 ft. wide. White flowers, evergreen.
2. Malus 'Adirondack' - 18 ft. high, 10 ft. wide. White flowers, red fruit, excellent scab resistance.
3. Malus 'Red Barron' - 18 ft. high, 8 ft. wide. Red flowers, red fruit, yellow fall color.
4. Malus 'Golden Raindrops' - 18 ft. high, 13 ft. wide. White flowers, yellow fall color, abundant yellow fruit.
5. Prunus serrulata 'Amanogawa' - 20 ft. tall, 6 ft. wide. Pale pink double flowers, bronze fall color.

Here are additional sources:

Date 2018-04-05
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Plant Answer Line Question

Keywords: fastigiate trees and shrubs, Woody plant cuttings, Hedges

I have an interest in propagating woody plants such as columnar, or more fastigiate types of holly, barberry and others for establishing barrier hedges here in Oregon. Is there any merit to the suggestion that only vertical cuttings be selected from the parent plant, as opposed to selecting other material from lower down, or that which has a less skyward orientation?


I consulted Michael Dirr's Reference Manual of Woody Plant Propagation (Varsity Press, 2006). What he says about Taxus (yew, not a plant you mentioned, but one which has some upright cultivars) is that "Taxus cuttings are highly topophytic and maintain the growth habit they exhibited on the parent plant." In this case, that would suggest to me that if you wish to encourage a plant with mostly vertical form, then a vertical cutting would be useful *if* that genus of plant has cuttings which echo the shape they had on the original plant.

I don't see any obvious indications that all species of Berberis (barberry) or Ilex (holly) have this characteristic. Ginkgo does, and so a cutting from a horizontally-growing parent plant will retain that growth habit. (See Peter Del Tredici's article on ginkgo trees from Arnoldia, Summer 1991 issue.)

In order to obtain a comprehensive knowledge of which plants exhibit topophysis and which do not, you would need to consult a plant physiologist, or spend a fair amount of time consulting books such as Dirr's mentioned above. Hartmann & Kester's Plant Propagation (8th ed., 2011) says that "plants of certain species produced by cuttings taken from upright shoots (orthotropic) will produce plants in which the shoots grow vertically. Plants produced from cuttings taken from lateral shoots (plagiotropic) will grow horizontally, as occurs with Podocarpus." Alas, this book does not provide a thorough list of plants which do this. The few examples given include: Taxus cuspidata, Norfolk Island pine, Podocarpus, and coffee.

You could always err on the side of caution, and only select upright cuttings. However, in some plants, cuttings from lateral shoots have better rooting rates (such as Rhododendron).

An aside: some species of holly (especially English holly, Ilex aquifolium), and some species of Berberis are considered invasive or noxious in some parts of the U.S. Check your county noxious weed lists before propagating them.

Date 2018-03-14
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May 23 2018 14:32:42