Farm Forestry New Zealand

Poplars are commonly sold as bare stakes and poles, and sometimes as rooted cuttings. Stakes and rooted cuttings are much cheaper than poles and rooted cuttings in particular have a more reliable strike rate in areas with dry summers or on exposed hillsides.

Poplar poles are generally planted into pasture which requires no site preparation. Poplar stakes and rooted cuttings may require some vegetation control so that grasses and weeds are not competing for soil nutrients and moisture.

Planting

Most regional councils operate nurseries. The Hawkes Bay Regional Council offered stakes and poles in 2019 at prices of: 1 Metre, $2.20; 2 Metre $5.40; 3 Metre $10.00. Protectors were 1.1m Netlon $3.40; 1.7m Netlon $4.60; 1.7m Dynex pole protector $7.20. Delivery was extra.

The best time to plant poplar is from late June to early August. Plant across the lower half of exposed windy slopes, and plant only the sheltered, moist sites on the upper part of slopes.

All poles, stakes and cuttings planted in paddocks must be protected from stock. Cattle should be kept out for at least one and preferably two or three years. Do not plant poles where there are goats or deer.

Avoid any ridge tops exposed to prevailing winds. When planting on very steep slopes plant the poles away from steep banks with thin soils, and angled out from the vertical. This will prevent stock on the uphill side from eating the growing tips.

Planting techniques are described in this fact sheet How to care for poplar and willow poles.

Planting techniques are shown in the following short videos:

• Planting Poplars & Willows: Choosing the Best Poles
• Planting Poplars & Willows: Successful Planting
• Managing Poplars & Willows: Re-Ramming Recently Planted Poles

Spacing

When planting poles for soil conservation, space poles at between 25 and 100 stems per hectare (sph). Steep slopes require closer planting as described in this short video: Planting Poplars & Willows: Successful Planting.

When growing for timber, plant poplar as rooted cuttings at up to 1,000 sph. Trees may later be thinned down to a final spacing of 250-300 sph, similar to a radiata regime.

Releasing

Spray or clear weeds around stakes and rooted cuttings during the first summer, if necessary more than once. Be careful not to spray the poplars themselves. Glyphosate is the safest, and can be sprayed on wet sites, but must not come into contact with green stems. As they grow poplars are unlikely to shade out weeds, so problem weeds such as gorse and blackberry should be sprayed out before planting.

Grazing/Browsing

All poles, stakes and cuttings planted in paddocks must be protected from stock, usually with sleeves to prevent rubbing. Cattle should be kept out for at least one and preferably two or three years. Do not plant poles where there are goats or deer.

Kawa is not very palatable to possums but these should be controlled so they do not break out leaders and branches. Young kawa wands may be palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them.

Pests and diseases

Kawa is rust resistance in most situations. Insect damage is generally of little importance and usually fungal diseases are not fatal.

See Poplar pests and diseases »

Poplars are enormously versatile. They readily coppice (i.e. the stumps resprout after harvesting), and so may be regularly harvested for biofuels or for taking up nutrients in riparian strips. Their leaves and small branches are palatable, so the trees may be pollarded for fodder. They have extensive root mats that interlock to bind erodible soils. Grown to maturity they produce quality timber.

Pollarding

Grown for supplementary feed, pollarded trees may be cropped on a 3-4 year cycle once they are more than 5 years old. Pollarding is described in this Poplar fodder trial. Another study, Poplar and willow as supplementary fodder sources suggests that the nutritional value of intact poplar leaves in summer and autumn is usually similar to that of pasture during the same period, particularly during drought, and they are rich in trace elements such as zinc.

Pruning

The leaves are palatable to livestock and prunings may be a useful feed source during drought, so pruning should be scheduled for summer. Form prune poplar late in summer to encourage one dominant leader, and if grown for timber, prune the trees every couple of years to prevent lower branches from getting too big. Guidelines are here »

This video may also be useful: Managing Poplars & Willows: High-Pruning Poplars »

Thinning

On highly unstable sites trees should not be thinned at all. Otherwise to maintain grass growth it is generally safe to fell every second tree to a final spacing of 20 to 24 metres on slopes, and 10 to 12 metres on stream banks, between years 10 and 15. Grown at higher stockings for timber, poplars may be thinned on the same schedule as radiata pine, i.e. to around 600 stems per hectare at ages 4-5 and to around 250-300 stems per hectare at ages 9-10.

When to harvest

Poplars grown for erosion control can be harvested for timber if they are cut and replanted in rotation to maintain soil protection. One suggestion is to log selectively, taking every fourth tree every 10 years and letting the others grow on so that the total root system stays intact.

Poplars grow quickly and on good sites can produce useful timber in 15 years. For high grade peeler logs and saw logs they should be grown on for another 10 to 20 years.

If the poplars have been pollarded for supplementary feed and remain productive, they may be grown to almost any age.

Mature poplars can provide high quality veneers, appearance grade timbers and useful farm timbers. See Tree Grower article Wood properties and use of poplar and willow.

Markets and demand

Poplar logs currently have limited commercial markets but can attract good prices as shown in this poplar logging case study and in Growing poplars for timber in Northland.

A study of Kawa poplar timber grown in Northland reported excellent structural properties and tested a range of high-value applications for the sawn timber, demonstrating significant opportunities for commercial timber production.

Kawa grows rapidly at rates of 1 to 2.5 m a year depending on rainfall and soil fertility. After age 25 the trees keep growing but may be regarded as mature, reaching heights of 30 to 35 metres.

This paper offers some advice on monitoring growth.

Timber return on investment

In New Zealand poplar is primarily grown for erosion control, but even so it can be managed and harvested for timber. On good sites it grows faster than radiata pine, it can reach a marketable size in 20 years or less, and it can attract better prices than radiata pine as export logs. It is one of the few timber species which can support grazable pasture throughout its rotation. 

Plant & Food Research publication Trees for the farm: A decision support tool for farmers suggests the typical costs (in 2015) of establishing, managing and harvesting poplar grown for erosion control at a stocking of 60 stems per ha and harvested at age 20 would be around $6,000 per ha spread over the period. 

Return on investment will depend on what you are growing the trees for, the price of planting stock, how you manage the trees and when you harvest.

See Emissions trading »

• Poplar- Information resources
• Report: Kawa poplar timber - properties and market opportunities
• Sawn timber and structural products from ‘Kawa’ poplar (Populus deltoides Marshall x P. yunnanensis Dode) grown in Northland, New Zealand
  New Zealand Journal of Forestry Science 53 (2022)
• The authoritative source of information on poplars and who grows them is the Poplar and Willow Research Trust.