You can argue that Salix alba is one of the most important trees in human history due to its medicinal contributions. White willow has provided the world with the chemicals needed to make aspirin and other pharmaceutical products. Today, though the tree is beautiful, the straight species of Salix alba is usually avoided for horticultural uses in favor of one of its cultivars. Because of this, it is often hard to find wild-type white willow trees available in the nursery trade. If you plan to include the species in your garden design, you should only consider looking at the species cultivars. With that caveat in mind, the species cultivars make lovely additions to wet areas and spaces that may be on the damp side, such as the edge of a rain garden.
|Common Name||White Willow|
|Botanical Name||Salix alba|
|Plant Type||Deciduous tree|
|Mature Size||50-80 ft. tall, 40-70 ft. wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Medium to wet, well-drained|
|Soil pH||5.5 to 8.0|
|Flower Color||Yellow (male), Green (female)|
|Hardiness Zones||USDA 2-8|
|Native Area||Europe, northern Africa to central Asia|
White Willow Care
Caring for your tree and maintaining the area around your white willow is labor-intensive, which is one reason the tree is often avoided. The species suffers from numerous issues that keep S. alba owners on the lookout for signs and symptoms that their tree is has a problem or could be causing damage to their infrastructure. This tree's shallow, pervasive roots make it especially unwise to plant it near structures, pipes, cesspools, or sidewalks. Considering the the leaf and flower debris that makes the white willow untidy, and the weak damage-prone wood that tends to break under the slightest wind and ice stress, you may find yourself maintaining the tree more often than enjoying its beauty. It is also has a relatively short lifespan of only 20 years before it starts to fall into disarray.
If you already have a white willow, you can learn to care for your tree below, but if you decide on a new tree, you will be better served finding a native tree with the same characteristics or one of the cultivars.
Choosing a place in your landscape with ample sun is important for the health of your tree. White willows do not do well in shade. You will want to provide it with at least partial sun at the minimum, but your willow will live its best life in a bright sunny spot where it can soak up plenty of light.
What kind of soil you plant your willow in, or the soil your willow already is in, is going to play an important part in your tree's health. The perfect soil should be somewhat rich and able to hold on to a good bit of moisture while being well-draining. Its moisture carrying ability is better than its ability to survive drought—the white willow loves its moisture and can hold up against flooding but will not survive soil that dries out.
Soil pH is not too much of a concern unless your soil is especially acidic. The white willow can tolerate a pretty vast range of conditions when it comes to pH.
Water may be the most important element in keeping your white willow happy and healthy. Salix alba as a species needs plenty of water to thrive and survive. The normal advice of assuring water is plentiful while your tree is establishing itself then letting it fend for itself only applies here if your tree is placed in the best position. It would help if you placed it in a location that gets a lot of water naturally. Placing a white willow alongside a rain garden is a wonderful idea for just this reason. The most important thing to realize is that white willows can tolerate being overwatered once established, but they will not stay healthy long in drought conditions. If no water is present, the tree's roots will seek a water source, and if your pipes or sewer are available, you will have some issues.
Temperature and Humidity
The white willow favors a temperate climate, with a cooler being preferable to warm. You will notice that your willow will be one of the latest trees to drop its leaves and one of the first that leaves emerge in the spring. Salix alba's range is USDA 3 through 8; anywhere out of this Goldilocks zone, the tree will not survive.
Giving your white willow supplemental fertilizer is not a good idea. The wood of this particular species is already known to be weak and brittle and any fertilizer that may speed up branch growth and produce wood that is further weakened by hastened growth will only make this issue worse. If your tree seems to be suffering, test the soil then, and only then if a deficiency is found apply fertilizer as needed. Most likely the issue will be something else, and fertilizing will not be called for.
Types of White Willows
As mentioned above, using straight species S. alba is discouraged in residential landscaping because of its many issues and risk to the property. These cultivars are often used when S. alba is a must-have. Keep in mind is that the risks that come with the straight species are not eliminated, just lessened, and an alternative is often better for the garden and the local ecology.
- Salix alba 'Vitellina': a cultivar grown in gardens for its shoots, which are golden-yellow for one to two years before turning brown. It is particularly decorative in winter
- Salix alba 'Tritis': a cultivar with a slightly smaller width, rounded crown, major upright branches from which hang slender, pendulous golden branchlets which may reach the ground
- Salix alba 'Caerulea': the cricket-bat willow is distinguished mainly by its growth form, fast-growing with a single straight stem, and slightly larger leaves with a more blue-green color
- Salix alba 'Belders': a male cultivar with a straight to or gracefully bent trunk and a narrow oval crown often used for pollarding
Pruning a white willow is a practice in prudence. It has a beautiful form that is slightly drooping, though less than Salix babylonica (Weeping willow), that you want to maintain, but the main issue will be trimming weak, damaged, and dead branches. Trimming is easy when the tree is young; it should be done annually in the fall after the leaves have dropped. This species can have more than one leader, so prune as desired, lifting the canopy from the inside, allowing the outside to droop. Plan to make your cuts by walking around under the tree and ignoring the outer edge, which will form the a drooping habit. The only pruning you will do on the outer edge will be the cuts for maintenance, removing dead wood, branches that intersect with other branches, and damaged branches. As the tree becomes too large for you to prune from the ground with hand tools safely, it will be time to call in a certified arborist to do the work for you.
Though it is highly discouraged that the white willow is planted and propagated as straight species in a garden, it is possible through cuttings. The easiest method is by taking softwood cuttings in late spring or early summer. To take softwood cuttings, you will need to do the following:
- Cut four inches of new shoots above a bud on the parent plant early in the morning.
- Place the cuttings material in a clean plastic bag.
- Use a sharp knife and trim below a leaf node to make your cutting.
- Remove the lowest leaves and dip the base of the cutting in a rooting hormone.
- Insert the base of the cutting in a pot filled with soilless mix with the top two leaves just above the surface. Water the mix
- Place your pot with the cutting in a propagation box, or cover with a plastic bag and mist twice-weekly—place in indirect light.
- Remember to keep the soil moist going forward until roots form.
- Harden off your newly rooted willows (2-4 weeks).
Common Pests and Plant Diseases
White willows are susceptible to various diseases and insect problems. Most insects are just nuisances and do not cause any real issues. The most common pests you will see are aphids, scale, borers, and lace bugs. These do not cause any real risk, and you carefully consider chemical solutions as a solution as your tree is an important host to some butterfly species.
Anthracnose, crown gall, black canker, and blight, all diseases that affect the white willow, can cause issues if left lingering. But fortunately, these can all be prevented with proper maintenance and sanitary methods of tool upkeep when pruning your trees. Be sure to clean your pruning shears, saws, and lopers with alcohol or a bleach solution between different trees and properly dispose of all yard waste.