*2.2. Image Data Acquisition*

The images utilized in this research were captured between 3 April 2020 and 16 April 2020, in the First Asian Alpine Orchard in Shihe Township, Lingbao City, Henan Province (E 111◦4 2.6976 , N 34◦27 1.44 ), while the whole orchard was in the first flowering stage. The subjects were 115 red Fuji apples from 5-year-old trees in rows 4.2 m apart with 2.1 m between the plants. To simulate IoT devices to acquire images of apple trees, the investigator stood 2.5 to 3 m away from the tree's roots and used a mobile phone to capture photographs of the blooming stage of the apple trees.

The camera was operated from 10:00 am to 12:00 pm on the 13 days of shooting, and 115 images were obtained daily. A total of 1494 images of 3000 × 3000 pixels of apple trees under different weather conditions, including sunny, cloudy, and rainy days, were obtained in this study. Table 1 presents the precise weather information.

**Table 1.** Weather on various dates of shooting.


The flowering status of apple trees is divided into four stages: the first flowering stage, the middle flowering stage, the full flowering stage, and the last flowering stage, which correspond to the four growth statuses of apple flowers. The first stage of the apple flower is the bud (Figure 2a, red arrow), and they become half-open at the second stage (Figure 2a, green arrow and Figure 2b, green arrow) when the buds swell into white or light pink blooms that look like balloons. Once the petals have unfurled in the bud, the flower enters the fully open stage (Figure 2c, blue arrow), and the end-open stage is when the petals drop completely (Figure 2d, purple arrow). This experiment labeled 39,980 instances of the four flowering stages on 317 3000 × 3000 pixels images of Fuji apple trees using labelimg (Table 2), fulfilling the criterion that at least 3000 to 4000 instances of each class must be labeled in complicated agricultural contexts, as suggested in [27].

**Figure 2.** Flower images of apple tree at four flowering stages (300 × 300 pixels). (**a**) First flowering stage; (**b**) middle flowering stage; (**c**) full flowering stage; (**d**) last flowering stage.

**Table 2.** Unprocessed annotation data information.


Table 2 displays the raw annotation category information, including the number of annotations, the aspect ratio of various flowers, and the ratio of the area occupied in the image. The number of flower annotations in the first three growth stages was close, except for the last bloom. The aspect ratio is the ratio of the labeled flower length to the width, with the same category of flowers possessing a length-to-width pixel ratio near 1:1 and an average pixel size ratio among the different flower stages of 17:22:49:27. Therefore, the order of the size of the average area is fully open > half-open > end-open > bud. The fully open stage has the highest number of annotations and largest average area. However, its ratio in the image was less than 0.03 %, and the other three flowering stages made up less than 0.01 %, making accurate flower detection more challenging.

From the overall view of the annotation information, the image data utilized in the experiment and the annotated data were of high quality, which provided practical support for the training and validation of the model. This dataset has the following characteristics:

