This post has been updated. See Squash family not forming fruit?
The squash or Cucurbit family that includes chokoes, cucumbers, grammas, gourds, pumpkins, rockmelons, squash, watermelons, and zucchinis, produce both male and female flowers on the same plant, and rely on insects, such as bees, to pollinate the female flowers and produce fruit.
Although we eat many of this family as vegetables, in gardening terms, their produce is fruit.
With large areas of Australia experiencing prolonged overcast weather, and other areas experiencing smoke from bush fires, bee activity tends to be reduced and cucurbits may not be cropping. In circumstances like these, you may have to hand pollinate your plants to reap the benefits of your hard work. This is quite a simple procedure.
First identify the the female flowers on your vine or bush. At the base of each female flower you will find a miniature version of the mature fruit of that particular species. For example, cucumber vines produce what looks like a tiny gherkin at the base of each female flower while watermelon produce a watermelon miniature, often complete with stripes. The bases of male flowers, on the other hand,
join directly onto a vine stem.
Remove a male flower from the vine, and carefully peel back the petals so that the pollen bearing part in completely exposed. Then dab the centre of the male flower into the centre of a female flower. Repeat this process, replacing the male flower as pollen is removed. Then stand back, and allow nature to take its course.
If you can only find male flowers on your cucurbit vine, the problem takes a little longer to overcome. Pinch off the end of each long runner. This will stimulate the plant to produce side shoots called laterals. Some members of this family tend to produce female flowers on laterals. Once female flowers form, proceed with hand pollination if there are not many bees around.
If your cucurbit plant is producing small fruit that yellow and fall off before maturity, or turn mushy at the end furthest from the stem, you have a different problem altogether. Either you do not have enough calcium in your soil, or watering has been erratic and calcium has not been available when needed. Like us, plants need a good balance of calcium and magnesium to form a strong structure. Calcium and magnesium are required for growing tips of plants as well as fruit production and, if there is not enough of these nutrients to go around, growing tips will get priority. Dissolve a generous handful of dolomite (a mixture of calcium and magnesium) in a full watering can, and apply this around the root area of each plant – one full watering can per plant, or two around large vines such as pumpkin and watermelon. If you know that your soil has plenty of magnesium, you can use agricultural lime instead. §