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.

4 thoughts on “Squash, melon and cucumber problems

  1. This article has been helpful to Debra:
    I just wanted to let you know how grateful I am for some advice on your website. Last season I had my zucchinis and they struggled along with Downy Mildew the whole season. I used the milk solution you suggested and while I had some success I started losing zucchinis left right and centre. It started with a dwarfed end that was mushy the then the whole thing would turn to mush. I assumed they had a virus of some sort or the Downy Mildew was a really bad case so I pulled them out. I put my new ones in this year in different places in case the disease was still around, anyway they started doing the same thing. Then I found the information on your website saying about the dolomite and mixing it with water and applying it under the mulch – I can’t believe the difference. I pulled off all the ones that were on the plants and within a few days I have had a huge surge in lovely firm edible zucchini’s. My husband is very impressed that what I have done has worked.

    Thank you for your website and advice. I am finally getting my own copy of Easy Organic Gardening for Christmas and I think the local librarian will be extremely pleased as I kept borrowing and re-borrowing their copy. Cheers, Debra

  2. I have rockmelons growing in the vege patch and now some of the vines have produced 3 tiny melons…What should I use to fertilise the soil so that I can ensure the fruits will develop well? So far, I have been only feeding the vines Seasol (seaweed soln) once in a fortnight. Also, I did not test the soil pH before planting and am a bit concerned about what you said about calcium deficiency. Am I able to get a test kit somewhere? Do you know if Bunnings sell it?
    I water the soil around the stems early each morning as the weather here in Melbourne is rather warm at the morning…one day it was 37 and some of the melons really drooped under the scorching heat. So I am not sure about just giving them watering thoroughly twice a week. I also use a dripper for them which I refill once it goes dry. This is my first time growing melons.

    Audrey, all the squash family need a good supply of nutrients to provide a good crop, and seaweed is only a supplementary fertiliser. It can contain a lot of potassium and too much of this can block the availability of other nutrients. Soil pH is also very important for the squash family, and you can obtain a Manutec soil pH test kit from Bunnings or major nurseries. They are usually about $20 but Bunnings had them recently for around $15.
    Regarding watering, the key word is “thoroughly”. The soil needs to be damp to the depth of the roots. If the soil has been thoroughly dampened and then covered with a thick layer of mulch, a top up watering a couple of times
    a week will keep them growing strongly. Daily watering encourages roots to stay close to the soil surface and plants will wilt quickly on hot days. – Lyn

  3. Thankyou! My yellow zucchinis have just this problem going mushy on the end, a friend has the same problem, but neither of us knew why.

    I’m off to buy some dolomite.

    Nanette….Murwillumbah northen NSW

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