Selecting for Double-Flowered Blooms in Stock | StoX® Series

In addition to providing some really beautiful and unique colors, the StoX® series has also been bred specifically for selection for double flowering plants at the seedling stage. In this video, we’ll show you how to select your plants at the seedling stage to increase the number of double flowering plants you have in a planting.

How to Select Stock Plants for Double-Flowered Blooms

If left unselected stock plants will produce about 55% double flowering plants and 45% single flowering plants, once planted out and left to flower. For a series like the StoX® series, you can select for double flowering plants at the seedling stage based on visual differences in the color of the young seedlings. The differences between single and double flowering seedlings become most visible after a cold treatment. The leaves of the double flowering plants will be a light green, while the leaves of the single flowering plants will be dark green.

Step #1: Apply a Cold Treatment

To apply a cold treatment, after germination and the cotyledons emerge, hold the seedlings at about 41°F for 4 to 7 days, and then follow that with 1 to 2 days of temperatures at 60 to 65°F. This should be enough of a cool treatment to bring out that difference in color between the seedlings. And at that point, you should be able to select for double flowering plants.

To achieve this chilling environment needed for selection, we've utilized the naturally cool outdoor temperatures when available, depending on when we're sowing, or we've used our floral cooler when outdoor temperatures are too warm.

Step #2 Remove Seedlings with the Darker Green Leaf Color

To select the double flowering seedlings, you would go in and just remove all the seedlings with the darker green leaf color.

We've double-seeded this tray to give us more options for selection.

This is a little bit counterintuitive to how you might think about thinning seedlings, because typically the darker color green is associated with better vigor and overall better health. The lighter green can sometimes be an indication of chlorosis or a nutrient deficiency. With stock, these lighter green colored plants are perfectly healthy and should continue to grow on and produce a really nice double-flowering plant. But again, it can feel a little strange removing these nice, dark, green, healthy looking seedlings. But these are all of the single flowering plants that are typically less desirable for cut flower use.

Plan for Wasted Space in the Seedling Tray

This is one of the things that just a reality of this type of selection process where we are going to have a little bit of wasted space in these trays. There will be wasted space. If there's wasted space for single flowering plants, it will be at the seedling stage and just in the trays, rather than planting out this whole tray of a mix of single and double flowering seedlings and then having potentially wasted space much later on in the process in the field, after time and energy has been put into planting, and space has been taken up in a tunnel or a field by single flowering plants that maybe will not have as high of an economic return. So again, you'll probably see blank spaces in your tray. If you use this selection method. But hopefully it will be a much better trade off having the wasted space here than having wasted space later on in your field or tunnel planting. And again, ideally, you will have a high percentage of double flowering plants that will be more valuable than the single-flowering blooms.

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