1. When to Pick a Bottle Gourd: After Its Fine Hairs Are Gone
According to Japanese encyclopedic descriptions, the ideal time to pick a bottle gourd is when the fine hairs on the skin are gone and the fruit makes a high-pitched sound when flicked with a finger. [1] This detail is a key clue that even the smooth-looking fruit has hair when it is young. However, these sources do not explain exactly when or how the hair falls off.
Bottle gourds are often harvested to use the hard shell as a container. The inside of the fruit’s skin hardens as it matures. The general guideline is to harvest about 50 to 60 days after flowering, though this number changes depending on how the plant is grown. [2] After harvesting, the fruit is soaked in water to ferment and remove the inside, leaving only the hard shell for making water bottles or sake containers. [2] To understand the fruit’s hair, we must first look at the parts that become the fruit.
2. How a Bottle Gourd Starts Out: An Ovary Covered in White Hairs
Before it becomes a fruit, the part that develops into the gourd is called the ovary. A database of Thai vegetables notes that the ovary of the bottle gourd’s female flower is covered all over with white hairs that have glands at their tips. [3] The leaves are also said to have soft hairs. [3]
Plant descriptions from North America add more detail. They state that the underside of the leaves is covered with fluffy hairs, while the hairs on the stems are simple, meaning they do not branch or have glands. [4] So, while the mature fruit looks smooth, the ovary that develops into the fruit, as well as the leaves and stems, are all hairy. Interestingly, some other plants in the gourd family have hairs that make human skin itch just by touching them.
3. Why Zucchini Hairs Can Make Your Skin Itch
Zucchini is a type of squash, and a 2023 study reported that many zucchini varieties are covered in sharp, dense hairs on their above-ground parts. These hairs can cause itching on the skin of people who tend to the plants, pollinate them, or harvest them. [5] It is important to note that this finding is specific to zucchini and does not necessarily apply to all squash varieties.
The same study classified zucchini hairs into seven types based on their shape. Four types are non-glandular hairs (without glands), and three types are glandular hairs (with glands that secrete substances at the tip). [5] This shows that "hair" on plants is not just one simple structure; it varies in form and function.
4. What Plant Hairs Do: Protect Against Insects, Water Loss, and Sun
What do these hairs do for the plant? A review of plant biology suggests that hairs help protect against herbivores (animals that eat plants), reduce water loss, and shield the plant from ultraviolet rays. [6]
Research on tomatoes also suggests that hairs play a role in defending against insects. [7] Dense hairs might make it difficult for insects to walk on the leaves or chew them easily. However, the specific role of hairs on bottle gourd fruit is not clear from the sources reviewed here. To find out more, we can look at experiments on a close relative: squash.
5. Wild Squash Has More Leaf Hairs Than Cultivated Squash, Yet Beetles Still Ate It
A 2024 study compared wild squash (Cucurbita argyrosperma) with cultivated varieties. It found that the wild squash had more hairs on its leaves than the cultivated ones. [8] However, when researchers tested damage from a specific type of beetle (Diabrotica balteata), they did not see a big difference in how much the beetles ate, regardless of the amount of hair. [8]
Interestingly, in the cultivated varieties, the plants produced more hairs after being eaten by the beetles. [8] This suggests that hairs might not just be a passive shield but can increase in response to damage. However, this result comes from one specific beetle and one experiment. It does not prove that hairs never work as insect repellents. The results do not show whether hairs deter other insects.
6. Why Scientists Know Less About Fruit Hairs Than Leaf Hairs
In botany, the surface of gourd fruits is described by whether it has hairs or not. Bumps or prickles are considered separate features from hairs. [9] For example, cucumber fruit is covered in hairs made from skin cells. These include small glandular hairs that produce a white powder (mostly silicon dioxide) and much larger prickles. [10] However, we cannot assume that bottle gourds or squash have this same white powder.
A review article states that the structure and function of hairs on gourd fruits are less studied than the hairs on leaves and other parts. [6] This means that the sources reviewed here do not explain exactly when or how the fruit’s hairs change in bottle gourds and squash.
7. How to Observe the Hairs and Prickles on a Cucumber Yourself
If you want to explore this further, you can observe a cucumber from your kitchen with a magnifying glass. Look for small prickles at the tips of the bumpy protrusions, or check for a white powdery substance on the surface. This powder is said to be produced by the cucumber fruit. [10]
When touching the cucumber, do so lightly. Sketching or writing down what you see can help you compare it later.
Questions remain: When exactly do the fine hairs on a bottle gourd fruit disappear? And against which pests are the hairs of wild squash effective? The sources in this article do not provide complete answers to these two questions.