A perfectly grown cucumber in a greenhouse should be straight and cylindrical with smooth skin reaching 18 or more inches in length. There are two cucumber types: ordinary and all-female. Each types has its varieties. Kyoto and Telegraph belong to Ordinary varieties.
At the same time, All-female type includes Birgit, Femspot, Pepinex 69 and Petita varieties. Ordinary varieties are demanding, so the air should be warm and moist. On the other hand, All-female varieties are easy to grow and are much more resistant to diseases.
Dealing with pests and diseases can be a headache when growing cucumber plants. Also, you need to be careful not to keep the compost soggy as it can result in wilting and dying of cucumber plants. If you are a newbie or experienced grower, you probably came across small and misshapen fruits.
So, why are greenhouse cucumbers short and fat?
Although inadequate watering, feeding and diseases affect the size and shape of fruits, generally, lack of pollination leads to short and fat cucumbers. When you cut a fruit and it doesn’t have seeds, female cucumber flower didn’t get pollinated resulting in small cucumbers.
Reason 1 – Watering
Fat yellow cucumbers that taste bitter are results of overwatering. If you cut them lengthwise, you will see a lot of seeds. Yellow cucumbers can also be over-ripe unless you are growing yellow cucumber varieties and are not aware of it.
As a general guidance for watering – provide an inch of rainwater during the course of a week, or slightly more if the temperatures are especially hot. Always water cucumber plants at the base keeping the leaves dry. I have an article on how to water plants in a greenhouse, please have a look at this.
In contrast, insufficient watering can lead to a formation of small cucumbers. The most important time for watering are first 2 to 3 weeks after planting out. Moreover, how much water plants receive directly affects flowering and fruit development.
Reason 2 – Feeding
Cucumber plants are heavy feeders. You need to add aged compost to the soil in spring and fall. However, you need to feed them more during growing season. Short cucumbers can result from poor feeding when blossoms were setting.
So, you need to feed cucumbers every 2 weeks once the first fruits have started to swell. You can use either Tomato Fertilizer, compost tea which is brewed compost with water or a 24-8-16 water soluble fertilizer. Just use a tablespoon of fertilizer with a gallon of water.
Reason 3 – Lack of Pollination
Ordinary varieties produce male flowers first and then female flowers on the same plant. It means that cucumbers are self-pollinating, so they don’t need to get pollen from another plant. However, they do rely on bees to transfer the pollen from male to female flowers.
Female flowers have tiny cucumbers at the base and the fruit comes from the bright yellow flower. When female flower lacks pollen, cucumber swells at the stem and fruit doesn’t grow to a full length. Moreover, blossom end can twist or curl producing cucumbers that are short and fat.
So, what are the causes of poor pollination? First, hot temperatures during flowering period can kill the pollen. Second, pesticides, which you use to control pests, can reduce population of bees. However, in a greenhouse growers usually hand-pollinate cucumber plants or grow All-female varieties.
Reason 4 – Diseases
Cucumber mosaic virus (CMV) can cause misshapen small fruits with dark green warts. The color of the fruit is either white or yellow with patches or spots of green. The signs can get worse with the increase of temperature in a greenhouse. Most of the time aphids spread CMV.
Unfortunately, there are other diseases that affect cucumber fruits. For example, fungal diseases like Anthracnose and Belly Rot which favor warm and humid conditions. These diseases cause lesions and spots on cucumber fruits.
