Growing Canada Yew in Plantations: Profitable or Not?

Canada yew is a low evergreen shrub that is native to eastern Canada. Over the past five years, demand for yew biomass in general has increased dramatically, because it contains chemicals called taxanes that are used to make important anti-cancer drugs.

One of these taxanes is paclitaxel, the active chemical in chemotherapy drugs such as Taxol®, which is used to treat breast, ovarian, and non-small cell lung cancers as well as Kaposi's syndrome, an AIDS-related cancer. In 2000, while still under patent, paclitaxel was the world's most valuable anti-cancer drug, with sales peaking at US $1.6 billion and current sales running at about US $1 billion per year. Worldwide demand for paclitaxel and newer second-generation taxane drugs such as Taxotere® and Abraxane® is rising by about 10% per year.

Most of the demand for taxanes is now met with biomass from English yew plantations in Europe, US, and Asia. In Canada, however, wild Canada yew is in demand, as its foliage, bark, twigs, and roots contain relatively high levels of taxanes, particularly paclitaxel. Unfortunately, Canada yew, the last significant source of wild yew biomass in the world, is not always harvested sustainably. Given the high taxane levels in Canada yew and concerns about wild harvesting, we asked the question: How can we best grow and harvest this shrub in plantations?

Research on Growing Canada Yew

In 2004, we began studying the feasibility of growing Canada yew as a value-added plantation crop, working with Bioxel Pharma of Laval, Quebec and the Thessalon First Nation BioCentre near Thessalon, Ontario. Our objectives were to determine best practices for growing yew in plantations and to find and propagate elite individual yew plants - those with superior growth rates and high paclitaxel content.

We established four plantations from wild yew rooted cuttings, and after four growing seasons, assessed the effects of plant spacing, mulch, fertilizer (nitrogen-phosphorous-potassium (NPK) applied annually), compost, mulch plus fertilizer, mulch plus compost, and no treatment on plant growth. We collected cuttings from 26 yew plants from throughout Ontario, propagated and grew them in the greenhouse, and then planted them to assess how well each grew and how much taxane each contained.

How Canada Yew Responded to the Treatments

Yew plants treated with mulch plus compost produced almost three times as much biomass as untreated plants, and those treated with fertilizer produced almost twice as much (Table 1). The mulch plus compost treatment was also the most expensive - nearly $10,000 per hectare. However, this project was small-scale; costs would likely be less for a larger-scale operation. The NPK fertilizer treatment produced the most cost-effective increase in yew growth at about $400 per hectare. Neither of these treatments increased growth enough to make plantation culture profitable for a whole-plant harvest system, which calls for harvesting the entire plant every three or four years and replacing it.

Table 1. Effect of plantation treatments on total Canada yew plant biomass after four growing seasons. Means (n=840 plants) followed by different letters are significantly different (p ≤0.05).

Elite Individuals are Superior

We found that both growth rate and taxane concentration were significant determinants of taxane production. Growing the top 10% of yew plants - those with superior growth and taxane concentrations - in a plantation would yield two to four times more taxanes per hectare than would a plantation of average yew plants.

Although the plantation treatments also affected the taxane concentrations of yew foliage (with mulch having the greatest positive effect), these effects were small compared with the effects of growth rate and taxane concentration differences.

Can Yew Plantation Culture Be Profitable?

Establishing a Canada yew plantation is costly (estimated at $60,000/ha). It would not be profitable using average Canada yew plants propagated from randomly collected wild populations. To reduce costs and increase profitability, we recommend the following:

• Since plant propagation accounts for about three quarters of yew plantation establishment costs, more research should be conducted to develop more efficient, cost-effective propagation methods.

• Screening for elite yew plants should be conducted to maximize yew taxane concentrations and growth rates and thus increase the value of yew biomass as well as production levels.

• Plantations should be harvested regularly to generate more biomass and income over time and to avoid reestablishment costs every three or four years.

Implementing these strategies will increase the likelihood that growing Canada yew will become a cost-effective option for Ontario farmers and nursery operators.

The authors thank the Northern Ontario Heritage Fund and FedNor for funding support. Additional support was supplied by Bioxel Pharma, Canadian Forest Service, Ontario Ministry of Natural Resources, and Thessalon First Nation. Our collaborators, Drs. Ron Smith and Stewart Cameron of the Canadian Forest Service, Atlantic Forestry Centre provided 10,000 yew plants, propagation and plantation design advice, and a planting crew.

Thomas L. Noland is a tree biochemistry research scientist with the Ministry of Natural Resources' Ontario Forest Research Institute in Sault Ste. Marie. Mamdouh Abou-Zaid is a natural products chemistry research scientist with the Canadian Forest Service-Great Lakes Forestry Centre, also in Sault Ste. Marie.