Nursery practices --
Controlling photoperiod

To meet specific delivery dates and desired size on summer- and fall-shipped crops, stock may be induced to set bud early. This can be achieved by shortening the photoperiod (daylength) using black out. The seedlings sense this as the onset of fall, cease vegetative growth, harden tissues and develop buds.

For summer delivery crops, blackout treatments usually begin three to four weeks prior to shipment. If the time between budset induction and planting is more than five weeks, stock may reflush, perhaps requiring a repeat of the process and a delay in planting.

Seedlings scheduled for summer or fall shipment should be inspected for succulence. Succulent stock is very sensitive to handling stress and planting shock and should remain in the nursery until sufficiently hardened.

© 1999 B.C. Ministry of Forests,
Nursery & Seed Operations Branch

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