Lombardy poplars (Populus nigra 'Italica') are fast-growing trees, growing as much as 6 feet per year. This makes them a popular choice when people want "living wall" privacy screens or windbreaks in a hurry. Lombardy poplar trees are best known for their columnar form and unusual branching structure—the branches start close to the ground and grow upward, parallel to the trunk. The fall foliage is a yellow color, but these trees are not primarily grown for their autumn display value. The bark turns black and develops furrows as the tree ages. In past times, Lombardy poplars were used for visual interest and to line golf courses. George Washington planted them at Mount Vernon in hopes of having a fast-growing forest.
|Botanical Name||Populus nigra 'Italica'|
|Common Name||The cultivar is called "Lombardy poplar," the species plant "black poplar."|
|Plant Type||Broadleaf, deciduous tree|
|Mature Size||40 to 50 feet tall and 10 to 15 feet wide for the 'Italica' cultivar; species plant can become much bigger|
|Sun Exposure||Full sun|
|Soil Type||Sandy to loamy soil|
|Soil pH||6.6 to 7.5 (neutral)|
|Hardiness Zones||3 to 9|
|Native Area||Lombardy region of Northern Italy|
How to Grow Lombardy Poplar
You may find nurseries that sell only the male trees so you won't have cottony seeds blowing around. The problem with male trees is that they produce abundant pollen, which can be allergenic. As this tree has shallow, spreading roots, you should plant it away from pipes, septic tanks, lawns, gardens, sidewalks, streets, and foundations.
Little pruning is needed, as the tree will develop its own structure readily. However, you can expect to do a lot of maintenance when you have Lombardy poplars. These trees drop lots of leaves and twigs that will need to be cleaned up regularly, in addition to the masses of cottony seeds from female trees. The wood itself is weak and you can expect frequent limb breakage. You have to be careful when working around the trees because the bark is thin and easily damaged.
To serve as a privacy screen, Lombardy poplars are planted in a row and spaced about 8 feet apart. Follow this strategy to employ for a privacy planting that makes use of their fast growth rate while compensating for their tendency to decline rapidly:
- Plant a row of longer-lived screening plants (for instance, Colorado blue spruce trees or arborvitae trees) where you want your final "living wall" to reside.
- Then plant a temporary row of Lombardy poplars behind them (so as not to deprive the longer-lived plants of sunlight). The Lombardy poplars will soon be giving your outdoor space some privacy, while you wait for the longer-lived plants to reach maturity.
- To minimize the spread of the Lombardy poplars' roots, dig a planting trench for them and line its sides with a 40-mil, high-impact polyurethane barrier (as you would do to contain a running bamboo).
- Before the Lombardy poplar trees begin to deteriorate (and before their root systems become too well established), remove them, letting the longer-lived plants take over the job of screening out prying eyes.
Grow Lombardy poplars in full sun.
Lombardy poplars will do well in soil that is sandy, loamy, or very loamy. It should be well-drained.
This tree has medium water needs. About 1 inch of water every two weeks through rainfall or irrigation will suffice.
Temperature and Humidity
The Lombardy poplar can be grown in a wide variety of temperate climates, including those where the winter low temperature is far below zero. In hot and humid climates, this tree is even more susceptible to Cytospora canker.
Propagating Lombardy Poplar Trees
It's rare that you would want to propagate a Lombardy poplar, but if you are so inclined, it can be done by rooting a hardwood cutting:
In the late spring, take a 6-inch long cutting from a stem segment about 1/4 inch in diameter, making the cut about 1/8 inch below a pair of leaves. Pull off all the leaves on the lower half of the cutting, leaving 4 or 5 leaves at the top. Bury the bare end of the cutting into a 6-inch pot filled with a mixture of perlite and coarse sand. Water the pot and pack the mix tightly around the cutting.
Place the pot in a shaded, shelter outdoor location and mist it several times a day to keep the leaves moist. Water the pot whenever the potting mix feels dry.
After about two weeks, the cutting should be rooted; transplant it into a 6-inch pot and continue growing in a dappled shade location for two or three months until plentiful new growth is present. The sapling can be transplanted into a permanent garden location in the fall.
Common Pests/ Diseases
These trees are susceptible to borers, Cytospora canker, and bacterial wet wood, reducing their lifespan. Almost all of these trees develop stem canker disease by the time they are 15 years old. Long before they die, they may be disfigured by these pests and diseases, rendering them unattractive as landscape plants and necessitating their removal. A similar tree, the upright European aspen (Populus tremula 'Erecta'), is said to be more disease-resistant.
When it is time to remove Lombardy poplars, be thorough in removing as much of the root system as possible. Lombardy poplars send out suckers throughout their lives, even from their stumps after they have been cut down. Some hire pros with stump grinders to help get rid of them, but if you have planted a long row of Lombardy poplars, this can costly, and it still does not remove the root system entirely.
Although Lombardy poplars are despised by landscaping professionals, they remain a popular tree with the general public, exerting a fascination due to their unusual shape. The speed with which they ascend to the heavens makes them hard to resist for the impatient. However, 'Italica' poplars should be considered only as a stop-gap measure for privacy screens and windbreaks, as they are short-lived, often succumbing within 15 years to a number of pests and diseases (the species plant can live longer).