Growth habits

Arborvitae are evergreen shrubs or trees. Left uncontrolled what most people think of as a shrub, can grow into a medium-sized tree. Some varieties of arborvitae can grow to a maximum height of 40' to 60' with a 12' to 15' spread. The plant has a medium growth rate.

Popular varieties are neat, symmetrical, even geometrical plants which grow into shapes such as globes, cones, or cylinders. They have scalelike leaves in flat sprays with blunt tips. The juvenile foliage is feathery, with small, needlelike leaves. Cones are small. Foliage in better-known varieties is often yellow green or bright golden yellow.

If planted in an area where they can get full sun most of the day the plants will reward you with dense foliage. Arborvitae will also tolerate shade but the plants may thin out and have a more open appearance.

Although the outer vegetation stays green all year, normal senescence takes place in the fall and is more noticeable then. Senescence is the process that causes the inner leaves to brown and dry. It is a natural occurrence, similar to a dog shedding, and shouldn't cause you concern.

Flowers
Arborvitae are monoecious…they have separate sexes on the same plant. The male flowers are yellow and drop off in the spring. Female flowers are greenish and they are the ones that produce cones. Sometimes you will find plants with lots of cones. It could be that the plant just has an overabundance of female flowers or sometimes it is a sign of plant stress.