Canada Yew – Taxus canadensis Yew Family (Taxaceae) Common Names: Canada Yew, American Yew, Ground Hemlock
The genus Taxus is comprised of a group of coniferous evergreen shrubs, some like the English Yew (Taxus baccata) and the Japanese Yew (Taxus cuspidata), along with other cultivars are frequently used as ornamentals in landscape design (10). The Canada Yew’s sprawling, loose growing structure has deterred landscapers from using it as a featured plant in landscape designs, but with care, can be used as a landscape shrub (10). The practice of planting Canada Yew as an ornamental shrub has also been tarnished by its known toxicity to humans, horses and cattle, making other types of plants more desirable (5).
Botanical Information Region of Origin - Newfoundland west to Manitoba, south to Pennsylvania, Ohio, Northern Illinois and Eastern Iowa (11). Canada Yew is native to Minnesota, predominantly located in the northeastern section of the state (1). It is the only member of the Taxaceae family in Minnesota, though there are exotic yews available in the nursery trade, some of which may escape cultivation, but none have been known to naturalize in Minnesota (1).
Figure 2: Canada Yew - North American Range Figure 3: Canada Yew - Minnesota Range
Figure 4: Short Growing, Wide Spreading Shrub
Growth Habit – The plant has no true central stem, the bark is smooth until maturity, then becoming scaly (7). Yew’s spreading branches can self-root when contacting the ground to produce spreading colonies (5).
Shrub Size – The shrub is slow growing, mature height ranging from 1 to 5 feet, with wide spreading branches reaching outwards approximately 8 feet (2). One shrub can form a small colony over time and many shrubs can form large colonies (11). In ideal conditions the shrubs lifespan can reach over 100 years (5). Leaves – Leaves (needles) resemble other types of conifers, single, flattened, with a minute sharp point at the tip (7). Size of leaves ranging from 3/8 to 1-inch long. The leaves are dark green on the upper surface, paler green on the lower surface, with a projecting green vein simulating a stripe. The needles appear as two rows on opposite sides of the branch, giving the branch structure a perceived flat look. The flat appearance is caused by a spiral pattern around the twig, were the needles on the top and bottom of the twig twist, giving the appearance of being flat (7). Seedlings resembles Balsam Fir (Abies balsamea), which also has flat needles, but a Balsam Fir’s needles are blunt-tipped, where Canada Yew needles are sharper pointed.
Figure 5: Photo of Branch Structure of Yew
Stems and Branches - Twigs are mostly alternating, green to yellowish in color when young, becoming brown to reddish-brown after the first year (7). As the bark ages it becomes thin and scaly. The shrub has no central stem, multiple branches protrude from the main base. Secondary branching is mostly wide spreading, rising at the tips or sometimes ascending. Branches form roots where they touch the ground, forming extending colonies.
Hardiness - Winter hardy to USDA Zone 2-4 (4).
Figure 6: Canada Yew Favors Understory Forest Locations
Taxus canadensis is largely found growing as an understory shrub among fir or spruce forests, but they also flourish within aged hardwood forests (11). It is a shade-tolerant shrub that survives best in stable environments, suited well for climates with annual rainfalls of 20 to 64-inches (5). Once common across its range, the species has been diminishing primarily due to predation by over-abundant deer populations (5). Soil conditions require the following:
Soil Type - Moist, sandy or leached loam soil (11).
pH Level – 5.0 – 7.5 (11)
Moisture – Moist, well-drained soil, does not tolerate water soaked soil (5).
Site Characteristics – Canada Yew prefers cool, rich, damp woods and wooded swamps (11). The plant grows well in partial shade under overhanging canopies, mainly in climax forests environments. Can be found on banks, bog margins and ravines accompanied by shaded conditions.
Modification to Site to Fit Plant - Planting of overstory shade trees to provide afternoon shade (11). Irrigate to keep soil moist, but maintaining proper drainage (10). Position in yard to provide morning sun and afternoon shade on North/Northeast side of house.
Monoecious - The Canada Yew is monoecious, meaning it has both male and female flowers on a single plant (11). In certain conditions yews have been recorded to be dioecious, or having female on one plant and male on another. The size of the shrub and the frequency of wildlife browsing can influence the plant’s sexual expression and flower production.
Imperfect Flower - This signifies that the Yew plant will have separate male and female flowers, unlike perfect flowers that house both male and female parts (7). A Yew’s flower and seed structure are cone-like and called a strobilus. Flower timing begins in the spring, approximately April through May, and occurs only once a year (11).
Figure 8: Red Fruiting Structure (Aril) of Canada Yew
Figure 7: Photos of Male Strobili (left) and female strobili (right) Gymnosperm - The Canada Yew is classified as a gymnosperm; a vascular plant that reproduces by means of an uncovered seed, or ovule (1). This differs from an angiosperm, or flowering plant, whose seed is confined by mature ovaries, or fruits. The seeds of many gymnosperms are developed within cones and are not visible until maturity. The Canada Yew is a self-fertilizing shrub, which can also reproduce by layering, forming a continuous population of genetically identical plants (5). The connections between genets usually rot, giving way to new plants.
Fruit/Seed Production - Male strobili are more numerous than female, they are oval to elliptical in shape, and the cone scales are yellowish in color (6). The strobili have a pollen sac that begins creamy in color, turning tan with maturity. The female strobili resemble a newly formed bud, and are less numerous than male. The egg-shaped scales are brown to greenish in color. Fruit is a cup-shaped, jelly-like cone named an aril. They are approximately 3/8” long in size, maturing to a bright red. The aril is open on the end, exposing a single seed. The seeds are hard, dark brown, oval to egg-shaped with a conical tip. Seed ranges from 4 to 5 mm in diameter. Aril’s red fruit is jelly-like and edible, but the seed is poisonous (6). Fruit can be found on the underside of newly formed twigs. The seeds are eaten by birds, which then move the seeds through their droppings to new sites (8).
Figure 9: Photo Shows Proper Cutting at Growth Node
Propagation Cuttings are the preferred method of propagation, cuttings can be rooted at any time of year, with successful rooted plants within a year (3). Best rooting occurs when the cut is made at growth node, making sure the cutting is of appropriate size for the desired growth container. Recommended growth media consists of two-parts peat moss to one-part vermiculite. Best rooting results are obtained when a hormonal stimulus, such as Seradex #3, is applied to the end of the cutting.
Figure 10: Inserted Cuttings Within Containers, Grit can be Applied to Retain Moisture
Insert cutting into growth medium to an approximate depth of 1 to 1.5 inches, removal of leaves is not necessary (3). A light grit can be applied to the top of the growth medium to help retain moisture during rooting process. Cuttings take approximately 2 years before truly ready for outdoor planting (3). Seeds can be planted, but require a two-year stratification/germination period before true growth (12).
How to plant - Plant in hole dug twice the size of root ball, making sure not to plant stem to deep (13). Water regularly, but not in excess (6). Plant early spring or late fall.
How to prune - This can be a high maintenance shrub that requires regular care and can be pruned at any time of year (6). To keep desired form and foliage thickness, pruning is necessary to eliminate suckers and uneven growth. Improper pruning can result in lower areas of the shrub becoming shaded, resulting in sparse leaves and or dying branches (7). Proper pruning keeps the plant narrower at the top compared to the base, allowing light to reach the lower areas of the shrub.
Figure 11: Canada Yew as an Ornamental Shrub
Landscape - Canada Yew is not known as an ornamental or landscape choice, but it can be used in the right site selection. The shrub works well as ground cover in shady sites, and also for wildlife planting as natural cover (9). Pruning is recommended to keep the foliage thicker, Canada Yew like to spread, causing the plant to thin out. Best grown in partial shade areas. It is not as versatile as other species of yew for ornamental purposes (11).
Wood - The Canada Yew is not a source for timber or wood products. The shrub has no true main stem, or significant wood structure for timber or wood product use (7).
Chemical - An anti-cancer chemical (Paclitaxel) was discovered in the bark of Pacific Yew (Taxus brevifolia) trees, the demand for this chemical was so high that it began depleting the supply of Pacific Yew (4). Shortages led researchers to investigate all yew species for possible sources of paclitaxel. Researchers discovered that Canada Yew are an excellent source of paclitaxel as well as two other taxanes contained in its foliage, bark, and roots. Canada Yew quickly became a major source, and a valuable resource for chemicals in the battle against breast cancer. Companies soon realized that acquiring Canada Yew in the wild was depleting natural ranges of the species, which prompted growers to experiment with farming of the shrub (3). Canada now has working nurseries and farms dedicated to growing and propagating Canada Yew for the harvest of taxanes from the plant.
Figure 12: Canada Yew Farm in Eastern Canada, Sections of the Shrub are Harvested for the Anti-Cancer Chemical Taxane.
Figure 13: Large Stands of Canada Yew Have Been Decimated by Intensive Browsing by Deer Populations
Wildlife – Leaves and twigs are important winter food for moose and whitetail deer, aril and seeds are eaten by various bird species (11). Birds aid the Canada Yew by dispersing the seeds for future plants. Deer populations have also created a problem for the Canada Yew. Over-grazing by deer has decimated many areas were the plant once flourished (5).
Historical – Yew are widely used by Native Americans for medicinal purposes (4). Many tribes use the needles or twigs for rheumatism, boiling them with other plant materials such as cherries into a liquid. Multiple tribes used the plant for other purposes such as blood clotting, pain relief, numbness, paralysis, fever, scurvy, arthritis and bowel ailments.
Figure 14: Scale Insect on Needles and Twig
Limitations Diseases/Pests - Armillaria root rot is a fungus that girdles the base of the shrub killing the cambium and is fatal to the shrub (8). Salt damage can result in browning of the needles and dying off of branches. The black vine weevil’s larvae feed on the roots and adults chew on needles, cause minimal damage. Scale insects feed on needles create colored bumps. The insect is not fatal to the plant, causing only minimal damage, but can be unsightly on ornamental plants. Yew’s have trouble with wet or water-logged soil, causing yellowing or possible death (8). Areas of consistent wind can cause yellowing of branch needles (2). Does not tolerate excessive heat such as corners or south facing structures.