In spring, heart-shaped, glossy-green leaves unfurl to 3-4 inches long.

Alders remain an underappreciated and underused group of trees and shrubs despite their potential uses in the landscape. Native to various parts of the globe, alders need greater promotion not only in the United States but for afar as well.

The Italian alder, Alnus cordata, although commercially available, is often overlooked by growers and landscapers, who perhaps mistakenly believing it to be more culturally demanding than it really is.

In spring, heart-shaped, glossy-green leaves unfurl to 3-4 inches long. The foliage remains exceedingly pest- and disease-free throughout the growing season. If I were to judge this particular alder just on its leaves alone, it may not rank at the top of my alder list. Because other Alnus species have interestingly notched leaves and other variations that give the foliage more character, Italian alder needs additional traits to justify its use as a landscape tree.

It passes this test with flying colors. As with any plant, it is important to value a species based on all of the aesthetic and utilitarian merits it has collectively. Getting back to foliage, Italian alder can have yellow fall color but the event is rarely striking and thus can only be considered a secondary and unreliable characteristic.

Fun fruits

Italian alder, as well as related species, have unusual flowers and fruiting structures. Male and female flowers are separate but both are present on the tree making the species monoecious. Yellowish-green, clustered and individually 2-3 inches long, the drooping male flowers (catkins) appear late February to March and persist lending ornamental appeal to the tree when observed at close range.

Additionally, the female fruit expands into a miniature pineconelike structure (strobile) and likewise often persists even into winter. These strobilius mature to more than 1 inch long and about half as wide, are often profusely arranged on older trees and significantly add to the ornamental appeal of the species. The reproductive parts of alder species are fascinating, attractive and are often overlooked as adding ornamental value.

As alluded to earlier, fall color is often disappointing. However, with the persistent strobilius and attractive brown bark, there is fall and winter interest to the tree. With higher temperatures, catkins emerge with the cycle starting up once again.

Tough cookie

Italian alder needs to be mainstreamed in the nursery and landscape professions. Like many other alders, it is much tougher and more versatile than often perceived. Expect this tree to grow well in normal moisture levels as well as in poorly drained areas, by ponds, in depressed sites, etc.

It does well in the aforementioned wet spots, but high moisture is not mandatory for its success.

Upon establishment, A. cordata is reasonably drought resistant and will only slightly scorch or lose leaves in extreme or prolonged dry periods. Although it will never be a xeriscape candidate, it is rugged within reason.

Chlorosis can be a problem in excessively high pH areas but otherwise the tree is happy in a myriad of soil types. Over time, Italian alder can exceed 30-35 feet, so locate it for the purpose of being a shade tree. I consider its growth rate moderate at best, so quite some time may pass before having a large pyramidal-shaped tree, especially in nonirrigated landscapes.

Propagate the tree by seed providing stratification of 90 days at 34F-36F. Alders can also be asexually propagated by softwood cuttings under mist. There is perhaps room to improve the species by finding more compact plants.

'Sipkes' is a selection made in Europe quite some time ago for its superior growth habit. However, I have no experience with this cultivar. As for the species, liners or seed may be purchased from Lawyer Nursery in Plains, Mont.

-- Mike Schnelle
Oklahoma State University, Stillwater

SPECIFICS:
Name: Alnus cordata
Common name: Italian alder.
Description: Pyramidal shade tree reaching 30-35 feet tall, higher with age. Yellow fall color isn't impressive, but fruit and attractive bark give great winter interest.
Hardiness: USDA Hardiness Zone 5.
Landscape uses: Suitable where medium-sized shade trees are needed. Also useful as a street tree.
For more: Lawyer Nursery, 950 Highway 200 W., Plains, MT 59859; (800) 551-9875; fax (406) 826-5700; www.lawyernsy.com.

Send this article to a friend

Enter your e-mail address:


Enter your friend's e-mail address:


Click the image below to send:

© 2001 Branch-Smith Publishing