Fraxinus americana ‘Autumn Purple’
Figure 1. Young ‘Autumn Purple’ White Ash.
‘Autumn Purple’ White Ash1
Edward F. Gilman and Dennis G. Watson2
‘Autumn Purple’ White Ash is a male tree
introduced in 1956, growing 40 to 50 feet tall and
perhaps 35 to 50 feet wide, and is a cultivar of the
species which is native to moist locations (Fig. 1).
The tree grows rapidly and is almost pyramidal with a
round top when young, but gradually slows down and
develops an oval shape. ‘Autumn Purple’ White Ash
prefers a sunny exposure where it will develop its
consistently-outstanding deep red, maroon or purple
fall color, whereas the species develops yellow or no
fall color. Fall color often comes earlier than on other
trees. I can not think of another tree with better, longlasting
Scientific name: Fraxinus americana ‘Autumn
Common name(s): ‘Autumn Purple’ White Ash
USDA hardiness zones: 3B through 9A (Fig. 2)
Origin: native to North America
Uses: wide tree lawns (>6 feet wide); recommended
for buffer strips around parking lots or for median strip
plantings in the highway; shade tree; residential street
tree; no proven urban tolerance
Availability: generally available in many areas within
its hardiness range
Height: 40 to 60 feet
Spread: 35 to 50 feet
Crown uniformity: symmetrical canopy with a
regular (or smooth) outline, and individuals have more
Crown shape: oval; round
Crown density: moderate
Growth rate: fast
Leaf arrangement: opposite/subopposite (Fig. 3)
Leaf type: odd pinnately compound
Leaflet margin: entire; serrulate
Leaflet shape: lanceolate; ovate
Leaflet venation: pinnate
Leaf type and persistence: deciduous
Leaflet blade length: 2 to 4 inches
Leaf color: green
Fall color: purple
Fall characteristic: showy
Flower color: green
Flower characteristics: inconspicuous and not
showy; spring flowering
There is no fruit on this tree.
Trunk and Branches
Trunk/bark/branches: grow mostly upright and will
not droop; not particularly showy; should be grown
with a single leader; no thorns
Pruning requirement: needs little pruning to develop
a strong structure
Current year twig color: brown; gray
Current year twig thickness: thick
Wood specific gravity: 0.60
Light requirement: tree grows in part shade/part sun;
tree grows in full sun
Soil tolerances: clay; loam; sand; acidic;
occasionally wet; alkaline; well-drained
Drought tolerance: moderate
Fraxinus americana ‘Autumn Purple’ — ‘Autumn Purple’ White Ash Page 3
Figure 3. Foliage of ‘Autumn Purple’ White Ash.
Roots: surface roots can lift sidewalks or interfere
Winter interest: no special winter interest
Outstanding tree: not particularly outstanding
Invasive potential: little, if any, potential at this time
Verticillium wilt susceptibility: susceptible
Pest resistance: very sensitive to one or more pests
or diseases which can affect tree health or aesthetics
USE AND MANAGEMENT
This is a good tree for large open areas with
plenty of open soil space and makes a good shade tree
for homesites if shade is needed on the roof. It is
somewhat adapted for use as a street tree with plenty
of soil space but extensive use may be unwise because
of potential insect and disease problems as the tree
gets older and because of its sensitivity to extreme
drought. Ash decline is one of its major problems and
is probably caused by a complex of conditions,
including a mycoplasma-like organism. It has taken
out many trees in some locations. However, one
advantage of ‘Autumn Purple’ is the lack of seeds.
Seeds are a constant nuisance on the species and can
limit the species’ usefulness as a street tree.
Ash which have not been properly pruned can
break apart in wind storms, but White Ash has better
branch structure than seedling Green Ash. ‘Autumn
Purple’ reportedly has better structure than the species
with many closely-spaced branches. Be sure to space
major branches along the trunk and remove those
which are vigorously growing upright with narrow
branch crotches. Ash also has a tendency to produce
vigorous main scaffold branches opposite each other
on the trunk. Remove one so there is only one at each
position on the trunk. Some problems with graft
incompatibility have occurred with cultivars of White
Ash causing tree failure and breakage as the tree
grows. Select trees propagated on their own roots and
avoid those grafted or budded to Green Ash.
Grow Ash in the full sun or partial shade
preferably in a moist site although the tree does
withstand some drought. Growth will be best in
slightly acidic, neutral or slightly basic soil pH.
Borers can kill trees. The most common borers
infesting Ash are Ash borer, lilac borer and
carpenterworm. They can infest and ruin even
vigorously growing trees but are most common on
recently transplanted and trees stressed from other
problems. Ash borer bores into the trunk at or near
the soil line causing tree dieback. Lilac borer causes
swellings on the trunk and limbs where the insect
enters the tree. The carpenterworm larvae bore into
the heartwood but come to the outside of the tree to
push out frass and sawdust. Heavily infested trees can
be severely weakened. Keep trees as healthy as
possible by fertilizing regularly and watering during
Aphids are often seen but are usually not serious.
In late summer, fall webworm covers branches
with webbing. The nests in branches close to the
ground can be pruned out when first noticed.
Fraxinus americana ‘Autumn Purple’ — ‘Autumn Purple’ White Ash Page 4
The Ash flower-gall looks like a disease but is
actually a mite problem. The mites feed on the
flowers causing abnormal growth. The galls dry out
and persist on the tree into winter.
The most serious problem is Ash decline or
dieback which has a variety of causes, some poorly
understood. The rest of the diseases listed below are
usually not serious.
A rust disease causes distorted leaves and swollen
twigs. Small, yellow, cup-like structures, producing
yellow spores, appear on the infected areas. Controls
are usually not needed.
A number of fungi cause leaf spots on Ash. The
disease is worse in wet years and is partially controlled
by gathering and disposing of diseased, fallen leaves.
Anthracnose is also called leaf scorch and leaf
spot. Infected parts of the leaves turn brown,
especially along the margins. Infected leaves fall
prematurely. Rake up and destroy infected leaves.
Chemical controls are not practical or economical on
most large trees.
Canker diseases cause branch dieback and death of
the tree when the trunk is infected. Try to keep trees
healthy with regular fertilization.
Powdery mildew makes a white coating on the
Ash ring spot virus causes chlorotic yellow or
reddish spots or rings on the leaves. Infected trees
may be stunted and dieback but this usually does not
Verticillium wilt causes branches of infected trees
to wilt and die, eventually the entire tree may die.
Keep trees healthy and fertilize infected trees with
high nitrogen fertilizer to suppress disease symptoms.