1. When Camellia Flower Buds Form and When the Flowers Bloom
Camellia flowers usually bloom from February to April. Some early varieties bloom in November, while late ones bloom in May, so there is a wide range in flowering times [3]. When are the buds for these winter flowers created? A clue comes from observation records by Susumu Ishizawa of Niigata University, focusing on plants in snowy regions. The subjects were the snow camellia and its relative, the Yuki-bata camellia. New shoots begin to form around the end of June, after the leaves on spring-grown branches have fully opened, and are mostly complete by August. Flower buds form at the base of these new shoots [1]. Another record states that buds separate and form around the end of July, when the current year’s branches have finished growing, and they gradually enlarge throughout summer. By late autumn, the plant overwinters with next year’s flowers and leaves already formed [2]. This indicates that bud formation progresses from late June to August, with differentiation occurring around the end of July. Since the observations were of snow camellia relatives, the common camellia likely follows a similar schedule, but the data directly shows the snow camellia group. In short, winter flowers are prepared in the summer. How do these flowers become fruit in a season with few insects?
2. Which Animals Carry Camellia Pollen When Insects Are Scarce in Winter
February to April, when camellias bloom, is a season when insects are not very active. The Japanese white-eye is introduced as a representative bird that visits these flowers to help with pollination [4]. Flowers that rely on birds for pollen transport are called "ornithophilous flowers." These flowers are said to attract insects and birds by having conspicuous colors and shapes, strong scents, and abundant nectar [4]. The large, sturdy structure and high nectar content of camellia flowers are suited to visits from birds. However, the source does not state that the Japanese white-eye is the only bird visiting camellia flowers. It only indicates that the white-eye is considered a representative pollen carrier. After pollen is transported, whether fruit forms may depend on which pollen arrives. Is there a difference in fruit formation between pollen from the same tree and pollen from another tree?
3. How Cross-Pollination and Self-Pollination Change Camellia Fruit and Oil Amounts
The Nagasaki Prefectural Agricultural Technology Development Center compared seed and oil formation by varying camellia pollination methods. The parent variety used for seed collection was Tamano-ura [5]. The fruit set rate (the percentage of flowers becoming fruit) was 5.0% for self-pollination, 47.5% for cross-pollination with pollen from another tree, and 71.0% for natural pollination. No fruit formed from the 40 flowers that received no pollen. The average number of seeds per fruit was 8.5 for cross-pollination, 4.3 for natural pollination, and 2.0 for self-pollination [5]. The expected oil yield per flower was 1.045 g for cross-pollination, 0.639 g for natural pollination, and 0.015 g for self-pollination. Dividing the cross-pollination yield (1.045 g) by the self-pollination yield (0.015 g) gives approximately 70 times (author’s calculation). Since a 1-yen coin weighs 1 g, this is the difference between a tree where one flower can yield the oil weight of one coin and a tree where it yields only one-seventieth of that. It is interesting that natural pollination had the highest fruit set rate but a lower expected oil yield than cross-pollination. The report states that the reason for the high natural pollination rate is unknown. Also, because this was a test of one variety over one year, the results cannot be directly applied to all camellias. How do fruits that successfully pollinate grow afterward?
4. Why Camellia Fruit Stops Growing by Late July While Seed Oil Increases in Autumn
In the same Nagasaki test, camellia fruit thickness was measured from April 20 to August 28. Fruit enlargement growth stopped by the end of July [5]. Late July coincides with the time when snow camellia buds differentiate, as seen in the previous section. At the same time, fruit growth ends, and next year’s flower buds begin to form. However, neither source states whether these two events are related. After the fruit matures, seed oil accumulates in autumn. A report from the Gotō Islands in Nagasaki Prefecture found that seed oil content is about 30% from September onwards; harvesting earlier reduces oil yield [6]. Mature fruits usually split into three, containing large seeds inside [3]. Judging the right time to harvest is difficult, and the splitting pattern of individual trees is not a reliable guide for determining the optimal time for an entire region. Therefore, research uses nearby wildflowers as indicators. For *Cayratia japonica* and *Ampelopsis glandulosa*, the optimal harvest time is when flowers are no longer seen around the collection site, though criteria differ by indicator plant. The 30% figure is from a 2015 survey on Fukue Island and is not a nationwide standard [6]. Where on the branches do fruits and buds form?
5. Why Camellia Flowers and Fruit Form at the Tips of Branches
Camellias produce flowers and fruit at the tips of branches that grew that year (current-year branches). Therefore, to increase fruit production, it is necessary to increase the surface area of the tree crown (the area of branch tips), according to the Nagasaki Prefectural Agricultural Technology Center [7]. This report compared isolated trees that did not mix with surrounding trees to trees in crowded forests. Seed production was an average of 790 g per isolated tree and 297 g per tree in a crowded forest. 790 divided by 297 is about 2.7 times, which the report summarizes as "more than twice" [7]. The study measured 4 isolated trees and 19 forest trees over four years. Because the number of trees measured was not large, the 2.7-times difference cannot be applied to other locations. Still, for trees where flowers and fruit form at branch tips, isolated trees with fewer neighbors and wider branch tips produced more fruit. Whether sunlight is involved is not clear from this report. Summer buds also form at the base of new shoots, so they are also near branch tips. At a single branch tip, fruit and buds grow at different times. So far, this has been about relatively warm regions like Nagasaki and Niigata. Do camellias bloom even in colder northern areas?
6. Why Camellias Bloom in May in Aomori's Tsubakiyama
Common camellias are abundant in southern and central Japan, becoming less common as one moves toward the Tohoku region. Tsubakiyama in Hiranai, Aomori Prefecture, is considered the northern limit of their distribution [8]. Tsubakiyama contains over 10,000 common camellias of various sizes and was designated a Natural Monument in 1922 (Taisho 11). They bloom from early to mid-May, opening red flowers [8]. Camellia flowering periods range from November for early types to May for late types [3]. While some regions like Kanagawa Prefecture begin blooming around February [4], communities like Tsubakiyama bloom in May. Even for the same common camellia, the flowering season shifts by several months depending on the region. Whether northern camellias follow the same mechanism from new shoot formation to flowering is a question for readers to investigate.
7. How to Observe Buds, Flowers, and Fruit at Camellia Branch Tips Near You
If there are camellias near your home or in a park, take a look at the branch tips. Do not enter private gardens without permission, and do not break branches; just look. Camellias are evergreen, so you can observe branch tips year-round. By noting in a journal which stage—bud, flower, or fruit—is on the same branch tip each month, you can see how the patterns of buds forming in summer and fruit growth stopping in late July apply to your own tree. Writing down what you see with the date allows you to review your notes six months later. Months with nothing on the branch tips are also part of the record. The original sources include Susumu Ishizawa’s records from the Niigata University Repository and three Nagasaki Prefecture results (pollination, oil, tree form), available in Japanese. They are listed in the source section. No materials were found here to determine if northern camellias form buds at the same time as southern ones. Next, look for data on Tsubakiyama’s bud formation in Aomori Prefecture records and compare it to the period recorded for snow camellias to understand the annual cycle of northern camellias.