When people want a privacy screen, they usually don't want to wait five or ten years for it to fill in. Fortunately, there are quite a few options for extremely fast-growing evergreen shrubs that can form an almost instant visual barrier. Exactly how fast they fill in is determined in part by how close you space them, and of course by how big they are when you buy them. But even if you start with small specimens, the five plants below will form green wall within two to three years.
Leyland Cypress (Cupressus leylandii)
Capable of growing three to four feet per year, Leyland cypress is one of the top hedge plants in North America. They have a narrow, upright shape and a very uniform appearance. Their main drawback is size—Leyland cypresses eventually reach 50 feet or more, making them a great choice for a tall screen in a large yard, but vastly oversized for small spaces. They can be topped periodically to control their size, but they are healthier when allowed to grow to their full proportions. Leyland cypresses are also disease prone, but if their basic requirements are met—full sun, good drainage, modest irrigation and correct spacing—they usually remain healthy. USDA zones 6 to 9.
'Green Giant' Arborvitae (Thuja occidentalis)
`Green Giant' is similar to Leyland cypress in appearance and in most other respects, but it is more shade tolerant and less prone to disease. It can also grow to 50 feet, but it is more tolerant of severe pruning compared to Leyland cypress, allowing it to be kept to 20 feet or less without compromising its health. 'Green Giant' doesn't grow quite as fast as Leyland cypress, but it still puts out two or three feet of growth each year. USDA zones 5 to 8.
Japanese Mock Orange (Pittosporum tenuifolium)
Leyland cypress and Green Giant arborvitae are both coniferous shrubs with scaly, needle-like leaves. Though they have a tidy appearance they don't offer much in the way of visual interest. For something more unique, consider pittosporum, an evergreen broadleaf shrub with white flowers and glossy, wavy-edged leaves that are set off by the dark color of the stems. Pittosporums offer much more diversity in size, as well, with varieties ranging from head high to 25 feet tall to choose from. They tolerate either sun or shade, which is another big advantage. The main disadvantage with pittosporums is their lack of cold tolerance. USDA zones 9 to 10.
Tree Mallow (Lavatera maritima)
For a real show-stopping screen, consider tree mallow, a fast-growing evergreen shrub with large pink and purple hibiscus-like blossoms in late summer. Tree mallows have five-pointed leaves (like a maple tree) with gray-green hue. They grow in a rounded shape to about six feet tall and wide, unlike most fast-growing shrubs which have a narrow upright profile. USDA zones 6 to 10.
Bamboo (Multiple genera)
Though it is technically a large grass rather than a shrub, no list of fast-growing screen plants is complete without bamboo. There are dozens of varieties to choose from, ranging from head high dwarfs to 60-foot jungle behemoths. Most types of bamboo tolerate both sun and shade. The key with bamboo is to know whether you're planting a 'running' variety or a 'clumping' variety, which should be indicated on the label. The former are those that give bamboo a reputation for being invasive, and should only be planted in a planter (or with an underground rhizome barrier), while the latter are safe to plant directly in the ground. Hardiness varies by species, but there are bamboo varieties available for USDA zones 5 and up.