Japanese elm tree named `Discovery`

A new cultivar of Japanese elm tree (ie., Ulmus davidiana Japonica) is provided that exhibits excellent form and resistance to Dutch elm disease. Unlike other Japanese elm trees the growth habit is clean, symmetrical, upright, and vase-shaped. The foliage is obovate to oval in configuration and is slightly smaller than is typical for the species. Good cold hardiness and resistance to elm leaf beetles are exhibited. The new cultivar is particularly suited for growing as an attractive landscape shade tree.

SUMMARY OF THE INVENTION 
The original Japanese elm tree of the new cultivar was selected during 1985 
from among approximately 500 seedlings of Ulmus davidiana Japonica that 
were being grown for testing and evaluation at Treherne, Manitoba, Canada. 
The seeds used to create the test planting were harvested from 
open-pollinated trees of the same species growing at the Agriculture 
Canada, Morden Research Station, Morden, Manitoba, Canada. The trees from 
which the seeds were harvested are believed to have been derived during 
the late 1930s from a Northern Manchurian source. A single plant of the 
new cultivar was discovered and was observed to possess the outstanding 
horticultural characteristics as described hereafter. This plant initially 
was designated No. 8502. 
Following asexual propagation the new cultivar of the present invention has 
been further tested and evaluated at Prairie Shade Nursery, Portage la 
Prairie, Manitoba, Canada; Jeffries Nurseries Ltd., Portage la Prairie, 
Manitoba, Canada; the University of Toronto, Toronto, Ontario, Canada; 
North Dakota State University, Fargo, N. Dak., U.S.A.; and at Bailey 
Nurseries Inc., St. Paul, Minn., U.S.A. 
It has been found that the new plant of Ulmus davidiana Japonica of the 
present invention exhibits the following combination of characteristics: 
(a) exhibits an attractive symmetrical upright vase-shaped growth habit, 
(b) forms foliage that is obovate to oval in configuration and is slightly 
smaller than is typical for the species, 
(c) exhibits good cold hardiness, and 
(d) is highly resistant to Dutch elm disease. 
The excellent tree form and resistance to Dutch elm disease of the new 
cultivar are particularly noteworthy. The clean appearance of the tree is 
maintained throughout the growing season. The vigor of the plant has been 
observed to be slightly less than that of the species and is believed to 
contribute to making the new cultivar slightly hardier than a typical tree 
of the species. The symmetrical upright vase-shaped growth habit generally 
is manifest throughout the tree beginning at the initial lateral branch 
and extending to the top of the crown (as illustrated). The seeds of the 
new cultivar generally are typical of the species. The new cultivar also 
has been found to exhibit resistance to elm leaf beetles. It is 
anticipated that specimens of the new cultivar will assume a height and 
spread of approximately 35 to 40 feet when fully mature. However, no plant 
of the new cultivar has reached such full state of maturity to date. 
When the new cultivar is compared to the `Freedom` cultivar (non-patented 
in the United States), it is found that the new cultivar exhibits a 
symmetrical upright vase-shaped growth habit while trees of the `Freedom` 
cultivar form an open crown with codominant lateral branching, the new 
cultivar exhibits smaller less serrated leaves than those of the `Freedom` 
cultivar, and the new cultivar exhibits yellow fall foliage coloration in 
the absence of a reddish-purple tinge that commonly is observed on the 
leaves of the `Freedom` cultivar. The good Dutch elm disease resistance of 
the new cultivar is believed to be substantially identical to that of the 
`Freedom` cultivar. The `Freedom` cultivar is understood to have been 
earlier derived from same general germplasm pool as the new cultivar of 
the present invention. 
The new cultivar of the present invention well meets the needs of the 
horticultural industry. It can be grown to advantage as an attractive 
landscape shade tree that can be maintained with relative ease. 
The characteristics of the new cultivar have been shown to be homogeneous 
and stable under a number of different environments as indicated above. 
Beginning in 1988 at Portage la Prairie, Manitoba, Canada, the 
characteristics of the new variety have been shown to be fully 
transmissible by asexual propagation using whip and tongue grafting and by 
micropropagation via tissue culture. 
The new plant of the present invention has been named the `Discovery` 
cultivar.

DETAILED DESCRIPTION 
The chart used in the identification of colors is that of The Royal 
Horticultural Society (R.H.S. Colour Chart). Common color terms are to be 
accorded their ordinary dictionary significance. The description is based 
on the observation of a test planting of the new variety while being grown 
at Portage la Prairie, Manitoba, Canada. 
Botanical classification: Ulmus davidiana Japonica, cv. `Discovery`. 
Plant: 
Growth habit.--Symmetrical, upright, vase-shaped which generally is 
exhibited from the initial lateral branch to the top of the crown. A major 
difference between the new `Discovery` cultivar and other Japanese elm 
cultivars is the generally symmetrical growth habit and the generally 
upright disposition of the branches. A typical crotch angle is 
approximately 40 degrees. This can be compared to the open crown with 
codominant lateral branching of the `Freedom` cultivar. 
Size.--The tree at full maturity is believed to be capable of assuming a 
height and width of approximately 35 to 40 feet. 
Bark.--Typical of the species. 
Seed.--See FIG. 4. Smaller than that of the American elm and typical of the 
species. 
Foliage: 
Shape.--Simple, obovate to oval with an acuminate apex and a base that is 
often nearly equilateral. 
Serration.--Coarsely double serrate (as illustrated), but commonly less 
serrate than the `Freedom` cultivar. 
Size.--The leaves commonly are approximately 15 percent smaller than those 
of the `Freedom` cultivar. Typical leaves of the `Discovery` cultivar 
commonly average 7.4 cm. in length and approximately 5.3 cm. in width. 
This can be compared to an average typical length of approximately 8.9 cm. 
and an average typical width of approximately 6.4 cm. for the `Freedom` 
cultivar. 
Color.--Medium green, yellow-green group 147A on the upper surface, and 
yellow-green group 147C on the under surface. During the autumn the leaves 
assume a yellow coloration. See FIG. 3 where some of the yellow autumn 
coloration is beginning to appear. The yellow autumn leaf coloration lacks 
the red-purple tinge that commonly is present on the leaves of the 
`Freedom` cultivar during the fall. 
Development: 
Vegetation.--Slightly less vigor than the species which is believed to 
contribute to slightly more hardiness than that of previously available 
plants of the species. It has been found that a one year-old tree of the 
new `Discovery` cultivar commonly produces a terminal growth of 
approximately 43.1 cm. This can be compared to an average terminal growth 
of approximately 48 cm. for the species. 
Disease resistance.--High resistance to Dutch elm disease that is believed 
to be comparable to that of the `Freedom` cultivar. Such disease 
resistance is maintained from the juvenile stage through maturity. More 
specifically, cultured stains of the most aggressive known forms of Dutch 
elm disease obtained from the University of Toronto were inoculated into 
trees of the new cultivar being grown at Portage la Prairie, Manitoba, 
Canada, on successive years during 1993 and 1994. As a result of such 
inoculation it was observed that a small amount of foliage tip die-back 
took place. Further study and analysis of the leaf tips has indicated that 
this condition of the tree likely was caused by natural toxins that were 
generated within the tree while combating the inoculations of fungus. 
Hardiness.--Very good and is believed to slightly exceed that of the 
species. Is hardy in Zone 3 of the USDA Plant Hardiness Zone Map.