Extending the planting season of exotic plantation species — Fact sheet

This fact sheet by Scion provides information to help nurseries and in-forest establishment teams deal with disruptions to planting. It has tips to extend the planting season, and to help seedlings survive when planting outside normal planting times.

Nursery and planting disruptions during COVID-19

During COVID-19 lockdowns, nursery disruptions included lack of available stock (for example seedlings, cuttings, plugs), and the inability to continue production.

The main disruptions to planting were an inability to do pre-planting spraying and site preparation. Stock changes also caused disruptions.

Ways to extend the planting season

Growing seedlings in containers

There are many benefits of growing seedlings in containers.

  • They help extend the planting season.
  • They help plantings survive, especially on poor sites.
  • They’re generally easier to handle and transport.
  • Seedlings are less likely to be damaged.
  • Having intact root plugs (the clump of dirt packed around the root ball of a plant) when transplanting from container to the ground reduces transplant shock, and can help seedlings establish better.

You can find container recommendations for several exotic and native species in the report.

Holding nursery stock

For holding nursery stock, a range of nursery practices are recommended:

  • topping (trimming the top of a plant to stop vertical growth)
  • wrenching (delaying root growth) in bare root crops
  • ground planting (after one year in the container - to help prevent root damage)
  • repotting
  • cool storage – seedlings can be kept in cool storage for up to 4 weeks
  • climate control
  • effective nutrient and water management – the timing of this proved to be the best way to prevent excessive growth in the nursery. It also helps prepare crops for lifting, storing and planting.

At the planting site

You can also help keep seedlings alive by:

  • moving them to the planting site using refrigerated transport
  • making regular deliveries with no more than 2 days of stock delivered to site
  • using larger planting crews to speed up planting.
EF canopy cover jpg
Don’t chill radiata pine seedlings for more than a few weeks. Plants are solar-powered and will slowly run out of energy without light.

Increasing survival rates

When establishing bare root crops in a dry spring, seedling roots can be dipped in a hydrogel slurry. This helps the seedlings hold water and increases survival rates. Root dipping can:

  • increase root moisture by about 50%
  • increase crop survival by 13%
  • increase growth by 10% compared with untreated plants (which had a 33% mortality rate)
  • add benefits from micronutrients at the time of planting.

The extra planning and hydrogel costs are offset by savings from having to replace fewer plants.


It is possible to extend the planting season and make it successful by doing a few things:

  • planting in containers
  • using nursery practices like cool storage and nutrient and water management
  • holding stock by slowing growth with topping, wrenching and repotting
  • having small regular deliveries of seedlings made to site using refrigerated transport
  • for bare root crops, dipping seedlings roots in a hydrogel slurry to increase survival rates.

One Billion Trees Programme research

This fact sheet was produced by Scion Research. It is based on 7 technical reports produced under the Managing delays in planting research commissioned by the One Billion Trees programme.

Read about other One Billion Trees science projects on the Ministry for Primary Industries’ website.