Cucumbers are immensely satisfying to grow but not always easy. Without wanting to appear negative I think it is best to deal with the problems first. After all, we know what they taste like. Cucumbers like warm, humid conditions and to be grown fast. It is often said that it is impossible to grow tomatoes and cucumbers in the same greenhouse and while this is not technically correct, cucumbers do prefer more shade and more humid growing conditions. One of the biggest problems with cucumbers is red spider mite. These tiny pests suck the sap from leaves causing them to become yellow at first and then bronze as the infestation becomes more severe and the webbing over the leaves begins. Cucumbers can be sensitive to chemical sprays and red spider mites are difficult to kill with pesticides anyway so red spider mites are a real issue. The best way to prevent and control them is to damp down the plants with water – regularly. I do not know if it is a fact or not but i find that spraying/sloshing the plants with seaweed fertiliser/tonic helps too and the nutrients can’t do any harm.
Powdery mildew is the next issue, forming white patches on the leaves and eventually covering the foliage. Some varieties are resistant but the answer is to prevent plants from drying out at the roots.
Which all sounds like lots of water is the key. But only when the plants are growing strongly. Young plants are very prone to rotting at the base if the soil is wet and cold. That is why, when planting, it is best to plant them at the same depth as in the seedling pot and then make a mound of compost around the stem, into which new roots will grow.
So, having got that off my chest, we need to look at the plants. Cucumbers are broadly divided into greenhouse and outdoor (ridge) cucumbers. The former are the most popular because the fruits are long and smooth. These are rather peculiar because the plants are parthenocarpic, meaning that the fruits form without pollination. That is why the fruits do not contain large, hard seeds, just like bananas which are also parthenocarpic. This is not as odd as it sounds and some courgettes are also parthenocarpic. In traditional kinds such as ‘Telegraph’ it means that a daily job is to get up every day, before the bees, and remove all the male flowers. If the female flowers are pollinated the fruits swell and become bitter and inedible. So breeders have produced all-female hybrids which do not produce male flowers and save a huge amount of work. However, if the plants are stressed, dry or starved, they will produce male flowers – so keep them growing fast and well. And it goes without saying that you should not grow F1 all-female cucumbers in the same greenhouse as ‘ordinary’ cucumbers.
Outdoor/ridge cucumbers and gherkins produce male and female flowers on the same plant and need to be pollinated. Most people dislike them because of the larger seed cavity and thick, often spiny skin but they do have a more intense flavour. They can be grown outside in sheltered areas and make decent crops when grown in pots on the patio.
You need to keep cucumber plants warm so delay sowing until it is warm enough not just to germinate the seeds but to keep them growing afterwards. Mid April is sensible in most cases. F1 hybrid seed is expensive so sow one seed, on its side, in each small pot. Keep the compost moist but never wet. Keep at 20-25c. Once the seedlings have one true leaf, they can be planted out. You can plant in the soil (where there may be an issue with soil fungi) or in pots of compost or two plants per growing bag. To avoid the risk of overwatering when the soil is cold, it is a good idea to pot them form the small seedling pot into a slightly larger pot before planting them in the final growing position.
Once growing away well, keep them moist and feed well. Once the plants start to swell a few fruits you need to increase the feeding or the plants will not make more fruits until the existing ones are harvested. It does pay to keep picking the cues. You can train the plants as you like, and they need some sort of support. It is usual to keep plants as a single stem and shorten the sideshoots to a few leaves as they grow but plants can also be pinched out when young to grow several stems. Ridge cues are usually allowed to do their own thing. If well fed, and if the fruits are picked regularly, cucumber plants can be very productive.
In addition to these there are crystal apple or lemon cucumbers. I won’t repeat myself so you can read about them here.