Once stratified the seeds are sown into plastic pots during early January. Up to 12 seeds from the same cross are sown into a 16 cm diameter pot. Smaller pots are used with < 5 seeds. Pots are filled with an equal parts mixture of multi-purpose and loam-based seed composts. Seeds are pressed into the surface, edge up, with the end from which the radicle emerges down-most. They are covered with 1 cm of compost before firming the surface by hand.

Labelled pots are lightly watered and placed in cold frames. Once the seedlings emerge (3-7 weeks later), the pots are watered weekly, depending on the weather. Our germination rates are listed on the seed storage & germination page of this site. Seed-coats trapping cotyledons and preventing their unfolding for more than a few days are removed with tweezers. Emergence rates using this approach were 81% in 2017, 80% in 2018, 87% in 2019, but only 54% in 2020. 

Seedlings are transplanted at the two or three true leaf stage into individual cylindrical 1 litre plastic, or polythene sleeve, pots filled with an equal parts mixture of multi-purpose and John Innes No. 2 compost. Each pot is double labelled with year of cross/cross number/seedling number (e.g. 2019-8-1) and placed in a cold frame. The cold frames are opened during sunny weather and closed at night. Towards the end of May or early June, seedlings are transplanted into individual 5 litre pots, filled with an equal parts mixture of multi-purpose compost and good topsoil, incorporating controlled release (9 month) fertiliser granules. Seedlings are supported with 24” plant sticks and later with 4 ft bamboo canes. The pots are transferred into their permanent positions in nursery beds, half sunk into ground and mulched with turf and rough compost. The distance between adjacent seedlings in these rows is about 9 inches, equivalent to the diameter of the pot.

Seedlings are grown on their own roots in these 5 litre pots throughout the juvenile phase of development. We encourage them to pass through this phase as quickly as possible and then to flower. This is best achieved by maximising growth of the main leader, in order to increase the production of leaf nodes. Consequently, we don’t prune the seedlings during their first winter, leaving the main leader intact, except when pests or diseases cause die-back of the tip. 

Our seedling management throughout the juvenile phase aims to maximise the extension growth of the single main leader, together with the number of internodes this shoot produces. We apply a top-dressing of controlled release (9 month) fertiliser in February. This is sufficient for the whole year’s growth. We also top up soil levels on a regular basis. The pots are watered during dry periods in the summer, although the requirement for watering is reduced by sinking them into the ground. 

In view of the close spacing of seedlings, we aim to develop a ‘columnar’ growth form. Consequently, from year one onwards, we summer-prune any lateral shoots formed back to 3 leaves above the basal cluster. However, from year two onwards we leave a few laterals intact in case the seedling is tip-bearing rather than spur-bearing with respect to flowering. Winter pruning is confined to tipping back longer laterals to between 3-5 leaf buds, leaving the leading shoot unpruned, until the seedling flowers. Towards the end of the second year the supporting 4 ft bamboo canes are replaced by 7 or 8 ft canes inserted into the soil immediately adjacent to the 5 liter pots.Tied with string, these canes support the seedlings throughout the remaining years of juvenile growth.