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.)
If bee activity is low, flowers of this family remain unpollinated, and fruit is unable to form. When this happens 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. See examples below.

Cucumber flowers – Male on the Left, female on the right.








Zucchini flowers – Male on the left, female on the right.








handpollin To hand pollinate, take a clean, dry, soft-bristled paint brush and ‘tickle’ the centre of a male flower to collect pollen on the tips of the bristles, then gently transfer the pollen to the stigma at the top of the style in the centre of female flowers, making sure that it is well-covered with pollen. (Image shows hand pollination of female cucumber flower.)
Or, you can 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.

Squash, melon and cucumber problems

A problem I am frequently asked about is why do immature fruit of the Cucurbit family become soft or discoloured, and fail to mature. The squash or Cucurbit family includes chokoes, cucumbers, grammas, gourds, pumpkins, rockmelons, squash, watermelons, and zucchinis.
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, it does not have a disease, or a pollination problem. Your plant is deficient in calcium. Calcium deficiency also causes blossom end rot in tomatoes and capsicums.
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 are not enough of these nutrients to go around, growing tips will get priority. Calcium deficiency can occur in several different ways.
Most commonly, it occurs when soil is too acid (soil pH less than 6) and there are insufficient calcium ions in the soil. In soils with a suitable pH of 6 – 7.5, erratic watering can cause it, as plants are unable to absorb nutrients from dry soil, when needed.

To avoid blossom end rot, ensure that your cucurbit (or tomato/capsicum) bed has a suitable soil pH before planting out seedlings. See Changing soil pH. If your soil is quite acidic, and the problem has already occurred, you can raise soil pH slightly by dissolving a generous handful of dolomite (a mixture of calcium and magnesium) in a full watering can, and apply this around the root area (under mulch) 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, use agricultural lime instead. This treatment will take several weeks to work, so good bed preparation is worth the effort.
Where erratic watering is the problem, mulch around your plants to reduce fluctuations in soil moisture, and water plants thoroughly once or twice a week, rather than giving them a light watering every day. Pumpkin vines require a lot of water to produce a good crop.