Top view images of kale (Brassica oleracea)

Top view images of two Brassica oleracea varieties: B. oleracea var. acephala ‘Nero di Toscana’ - black palm kale (S1) and B. oleracea var. sabellica - curly kale (S2). Dataset contains 6400 images, 3200 per variety. Pictures were taken for 20 consecutive days (D). "b" after D marks the plants grown in the second stage (details below).

Detailed information:

The two varieties were grown in 8cm x 8cm pots inside the greenhouse of Wageningen University & Research. The pots were filled with a finely sieved peat compost. To ensure their germination, two seeds were seeded in each pot, a thin layer of compost being sieved on top of the seeds. The pots were then sprayed with water. Five days after seeding, a nutrient solution was applied. Thus, the substrate was saturated with ½ Hoagland solution to promote plants’ growth. Six days after seeding, the sprouts were transplanted to the pots where neither of the two seeds germinated. All additional sprouts were removed to establish the final growth stage of one plant per pot. The substrate was kept moist throughout the growing period by watering the pots daily or every two days, depending on the environmental conditions. These conditions were characterized by an average day temperature of 26°C.

The kale plants were grown in two stages, each stage containing half the plants and lasting for 28 days: June 16th - July 14th and July 10th - August 7th. In total, a number of 160 plants were grown per variety, summing up to 320 plants. Eight days after seeding, the plants reached the necessary growth stage to begin the dataset acquisition phase. Thus, all plants were photographed individually for 20 consecutive days, resulting in a 6400 image dataset.

The equipment used for taking the pictures consisted of a OnePlus 6T mobile camera and a phone holder. Top view pictures were taken by mounting the holder on a table, then stabilizing the phone on the holder at a 90° angle facing down. Furthermore, a centimeter ruler was placed in the bottom left corner of the picture frame.