Propagating conifer seeds
Before filling our Vitopod electric heated propagator with vegetable seeds for next season, we thought we would propagate some tree seeds. We chose Sequoia Sempervirens (coastal redwood).
Coastal redwoods are the tallest trees in the world reaching heights of 400 feet (120 metres) with root systems 200 feet (60 metres) long. They are a deciduous conifer native to a narrow strip of land which stretches 450 miles along the northern coast of California. The most impressive example of sequoia in the UK is at Cowdray Park, West Sussex.
Sequoia seeds are difficult to germinate which is one of the reasons for their endangered status. The seeds have a germination rate of around 35% (50% of our seeds germinated) and will remain dormant until the conditions are perfect for the seedlings to establish. They need a period of stratification to break their dormancy, this is done in 2 stages
- They are soaked for 24 hours in cold water
- The seeds are kept a constant temperature of 4oc for 30 days.
We started the stratification process on the 25th September and the seeds were sown on the 25th October in seed trays. The Vitopod heated propagator was set to 20oc and the vents were kept closed. A week after sowing 50% of the seeds sown had germinated and growing strongly, the humidity was gradually decreased by opening the vents. A week after germination the seedlings had developed sufficiently to be pricked out and transferred to individual 3 inch pots.
After the seedlings have germinated, they quickly develop a good root system so that they can support growth of up to 8 feet a year. Due to the speed at which the roots develop, the seedlings were pricked out soon after germination in order to prevent too much stress to the young plant (one seedling already had a root system 3.5cm in diameter). The seedlings are currently in the Vitopod heated propagator where they will overwinter before being planted in the ground.
These trees make excellent additions to any large garden, they should be planted in early spring after the last frosts. These seedlings however are ultimately destined to be trained as bonsai.