Yews are interesting plants for several reasons. Not only have they been cultivated for thousands of years, they are among the oldest living trees. There are specimens are as much as 3000+ years old. Yews are dioecious, meaning they have separate male and female plants. The female plants may (if there is a male plant nearby) have red berries. All parts of the plant including the bark, the leaves and the seeds, whether fresh or dried, are very poisonous to people and pets. Strangely enough, the flesh of the fruit is not poisonous, though the seed inside the flesh is. Even more frustrating, deer seem to enjoy nibbling on yews and seem unaffected. Birds often eat the fruits unharmed, since the seed passes through them intact. Taxol, a drug that is promising in the treatment/prevention of breast cancer, was originally derived from the bark of the Pacific yew, Taxus brevifolia. There are many types of yews, but very few of them are suitable for our climate.
Surprisingly, they aren't really affected as much by the severe cold as they are by the snow. When the winter sun reflects off the snow onto a yew, the dark green foliage quickly absorbs the heat. Then the sun goes behind the clouds or sets and the warm foliage is suddenly frozen again. On yews, this results in severe browning of needles and even death of some of the twigs. The best option in our area is to grow specific winter-burn resistant varieties. After decades of growing and planting yews in our climate, Bachman's has settled on two reliable varieties: Taunton spreading yew and Japanese upright yew. And even though they are the most resistant to winter burn, we still recommend that you avoid planting them where they will receive direct afternoon winter sun. When they are planted in that situation, you can shade them to minimize damage by either wrapping them loosely with an open-weave burlap or constructing a shade barrier with burlap.
When planting yews, it is important to be very careful about drainage. Yews will not tolerate poor drainage. Bachman's Planting Guidelines can be followed to successfully plant yews but if there is any question about whether or not the soil is well drained, they should be planted with their crowns an inch or two higher than the surrounding soil level. Drainage can be tested by digging a hole a foot deep and a foot wide. Fill it with water, let it drain, then fill it again. If it drains the second time within a few hours, the soil is adequately drained. If the hole is still holding water 4+ hours later, the soil is not well drained. And if it is still holding water the next day, you have a definite problem. It is almost impossible to change the drainage of soil by adding soil amendments unless you are working with a very large area. Simply amending the soil in the area where you intend to plant may just result in a large "bathtub" that holds even more moisture. It really is better to match the plant to the soil type. Japanese upright yews prefer slightly acid soil but will also tolerate slightly alkaline soils. Check the pH every year or so and adjust it if the pH exceeds 7.5. Taunton yews should have neutral to slightly acid soil.
Yews are generally very hardy, healthy plants but you should watch for a few possible problems. They will occasionally be bothered by scale (sucking insects). Scale will look like small hard shells along the stem. The only other potential problem is Phytophthora root rot, a fungal disease encouraged by wet or poorly drained soil. If you have a problem with a yew, make note of the symptoms, take a sample or picture and bring it in to Bachman's for one of the horticulturists to look at it. Left unpruned, yews have a very graceful habit. The branches have a natural arch to them, giving the plant an overall soft appearance. If you prefer a more formal look, yews can be trimmed. Trim them in the early summer as the new growth fades from bright green to dark green. Yews often put out a second flush of growth in mid-season. To keep their neat appearance, they can also be pruned again in mid-August. With the exception of yews, evergreens should never be pruned back hard into bare wood. While we wouldn't advise any drastic pruning, yews are better about filling in a bare area than any other evergreen. Keep in mind whenever you prune, that yews are very slow growing.
Japanese Upright Yew Taxus cuspidata 'Capitata' This is the only upright yew that does well in our climate. Its habit is pyramidal, broader at the base and tapering to the top. Left natural, this plant will outgrow a one story house. Its size can be limited by judicious pruning, but it may still outgrow a foundation setting. Japanese upright yews are hardy to Zone 4.
Taunton Yew Taxus x media 'Tauntonii' The best variety for our climate, Taunton yews are resistant to winter burn. Tauntons will grow about 3-4 feet wide and 3-4 feet tall. Left unpruned, they have a loose, flat-topped shape. Young shoots have olive green twigs. Taunton yews are hardy to Zone 4.
Additional Bachman's Information
The Right Evergreen for the Site
Needledrop in Evergreens
Protecting Trees and Shrubs in Winter
Quality Container-Grown and B&B Evergreens
Watering Tools and Hoses
Gardening Tools and Gloves
Elemental Sulfur and Iron Sulfate