Paulownia requires relatively specific site requirements to grow successfully. The annual rainfall should be at least 900 to 1000mm in warm temperate areas and 1200 to 1400mm in the subtropics. Summer rainfall is essential or irrigation will be required during the summer months. However, because of the costs involved irrigation will reduce the profitability of the plantation.

Soils must be well drained but still have a high water holding capacity and a pH of between 5-7. Paulownia cannot survive flooding, boggy or swampy sites. Paulownia can be grown on a range of soils from loams and sandy loams to well structured soils such as chocolate basalts and krasnozem soils. Paulownia will not grow well on podsolic soils with heavy clay subsoils.

Site preparation is similar to the establishment of other types of timber plantations and usually consists of deep ripping and either ploughing or mounding in preparation for planting. Weed control is essential before the establishment of the trees.

Paulownia plantations are generally hand planted with container grown stock. Selection of quality genetic material is most important. Planting is in spring. Initial planting densities can range from 300 to 600 stems per hectare at a spacing of between 4m ´ 4m to 6m ´ 6m respectively. A number of nurseries will supply trees, and a search of the Internet is a good starting place to source them.

Weed control is critical in the early years and should continue until canopy closure which is generally between the ages 3 to 5 years. Paulownia plantations are generally fertilised at planting with a follow up within the first year. Further fertiliser is needed at least until canopy closure.

Management of paulownia plantations can include coppicing, pruning and thinning.

Young trees (the first years growth) can be cut to ground level in spring to encourage coppicing if the stem is even marginally unsatisfactory. This results in straighter, better formed stems.

Paulownia trees are generally pruned (removal of lateral branches) to produce a knot free butt log. This is carried out in the second and third years to a height of between 4 to 6 metres. Pruning should not be to heavy so that the rate of growth is maintained. Pruning increases the wood quality and value of the timber.

Thinning can be required depending on the initial planting density and silvicultural strategy for the plantation. Diameter growth is influenced by stand density. If the stand density is high then thinning may be necessary to increase diameter growth on the remaining trees.

Marketing

The major commercial market for paulownia timber is in Japan where it is used to make a multitude of products including furniture, handcrafts, lumber, veneer, plywood and charcoal. The timber is light weight, relatively soft and has a ring porous structure similar to Australian Red Cedar. There may be some potential for its use in imitation red cedar furniture.

Paulownia is being promoted as a replacement to imported timbers. Research and development into the utilisation of paulownia is occurring in Australia. Potential markets include its use in light furniture, sliced veneer production and mouldings. These are markets where hoop pine, a native plantation grown timber is currently utilised.

A comment by end users in a study by Hopewell and Leggate (2000) stated "many established species are available in guaranteed continuity of supply, grade quality and at more competitive prices than those currently quoted for Paulownia".

The financial information available about Paulownia appears to be quite unrealistic. Often such financial analysis assumes that there is a strong linkage between the grower and the processor. This is quite often not the case. More often than not the grower does not process timber and would receive a royalty rate for the logs grown.

Royalty rates represent the net sale proceeds after harvesting, cartage, onsite roading and selling costs are taken into account (Cole-Clark, 1999).

Financial returns also assume that there is a strong market for the product. At present this is not the case although this could change over time as more paulownia becomes available.

There is a strong case for assuming that paulownia will compete with hoop pine in the market place as they produce similar products. One could assume that paulownia will receive a similar royalty rate to hoop pine. The current royalty rate for hoop pine is $80 per m³.

The productivity of hoop pine plantations averages 16m³ per hectare per year. The productivity of the first rotation Paulownia plantations in Australia is between 15m³ and 20m³ per hectare per year (Hopewell and Leggate, 2000). This will improve over time with improved breeding and silvicultural practice. Even so productivity is roughly similar.

The cost of establishing a Paulownia plantation can be very high when compared with the establishment of other types plantations. Jay (1998) states that costs may total approximately $15 000 per hectare when all costs are considered including the rent of the land. Cole-Clark (1999) states that the cost of establishing either eucalypt, softwood or cabinet timber plantations can vary between $1500 to $5000 per hectare although this does not include cost or rent of the land.

Growing paulownia is an intensive operation compared with other types of plantations. It requires growers to be prepared to look after their plantation intensively in the first few years. Growers should also have a good knowledge of the silviculture of the species so that potential returns can be maximised.

When establishing a paulownia plantation select your site carefully, acquire high quality planting stock, ensure that the planting is done correctly, maintain competition control for a least 3 years and follow the recommended coppicing, pruning and thinning procedures.

The benefits of growing a paulownia plantation compared with other types of plantations requires careful consideration.

Justin Black
February 2001