Managing Ornamental Cabbage Seedlings

Ornamental cabbage: beautiful in a fall bouquet but a pain to plant. In this part of the country (Zone 5b), we usually sow in late June or early July, when the greenhouse is so hot that seedlings shoot up like rockets and are impossible to harden off before transfer to the field. The result is a wilted, stressed plant that begins its life in the field with a crooked stem. In addition, the problem is made worse by using 72-cell planting trays and then transplanting the large seedlings to a high density in the field, where we want to keep the plants small. We have been trying some alternatives that lessen the stress, and provide us with “well-adjusted” seedlings.

In this trial, conducted in 2015, we compared direct-seeding with raising seedlings in small cells in the greenhouse, but getting these into the field before they started to stretch. In the greenhouse the seeds were sown either singly in 288-cell trays, or 2 seeds per cell in 98-cell trays. In the field the seeds were sown at a 6 x 6 in. spacing, 5 rows in a 40-inch bed, and thinned down to 2 seedlings per hole. Two varieties were compared in the treatments: ‘Lucir Rose’ and ‘Crane Bicolor’. All seeds were sown on June 24, and the transplants put in the field on July 13. Hortonova netting laid on the ground provided a handy template for the spacing, and was raised during the season to provide plant support.

The results were very satisfying: we got a nearly perfect stand with the direct seeding, and the greenhouse-sown seedlings were transplanted before they became large and floppy. By the time of the early October harvest, there was no difference in stem length or the number of stems among the three treatments (see table). 

The diameter of the colored area at the top of the plant, termed flower, was also the same among treatments, although ‘Crane’ was slower to color in our relatively warm fall than ‘Lucir’. ‘Crane’ also was significantly taller at harvest.

So what’s next? It would be interesting to try direct-seeding with a mechanical seeder, or pinching the seedlings before they stretch. Give them a try!

Acknowledgements: Many thanks to Priscilla Thompson and Emily Burrister who did most of the work, and to the Harris Seed Company who supplied the cabbage seed.

TreatmentsVarietiesStem length, cmStems/ft‘Flower’ dia., cm
Direct seededLucir686.88.7
 Crane836.04.2
Small cellLucir606.28.0
 Crane785.84.4
Large cellLucir636.68.2
 Crane826.04.2

Photo: Near-perfect ornamental cabbage, both direct-seeded and transplanted from the greenhouse.

Chris Wien

Professor

Chris Wien is recently retired Professor of Horticulture at Cornell University. Contact him at [email protected]