How to Grow Cucumbers from seed
Like many other veg, cucumbers you grow yourself have much more flavour than those from a supermarket. And that is the first reason to grow them. Another reason is that they are versatile and you can grow them inside or outside, in the ground, in pots or in grow bags so they work whatever your space.
Cucumber Flowers - Male vs Female
One of the main cucumber growing problems is the flowers falling off without producing any cucumbers. So to grow them successfully you need to understand flowering. Cucumbers produce separate male and female flowers on the same plant. Which variety you choose seems to be the real crux of cucumber growing and governs what you have to do to grow them successfully. Excuse me if I get a little technical for the next few paragraphs but the ins and outs of male and female flowers needs a little explanation.
If you aren't interested in this and just want to get your cucumbers in the ground then just check what your seed packet says in terms of flower removal and skip to the How to Sow Cucumbers section!
If not, here goes... There are two sorts of cucumbers - monoecious and gynoecious and both of these can be parthenocarpic i.e. they can produce fruit without pollination.
The traditional Cucumber variety- monoecious
Traditional varieties have both male and female flowers in a ratio of about 10 male to 1 female. The male flowers usually appear first followed by the female. This leads some to believe that their plant will not produce female flowers but if you hold your nerve you will be rewarded. If you have a variety that needs pollination then there is no need to remove the male flowers. Their pollen will hopefully be transferred, usually by bees, or wind, to the female flowers to pollinate them. After which your cucumbers will appear.
If you have a parthenocarpic variety (no pollination needed) then these take a bit of care as you have to pick the male flowers off. Otherwise they will pollinate the female flowers and the fruit will be bitter. (see below for more on bitterness) To identify the sex of the flower, look behind it and see if there is a cucumber growing. This is a female flower. Leave these. If there is no swelling behind the flower then this is a male and the flower must be picked off depending on your variety.
The Modern Cucumber variety - Gynoecious
These are simple to grow as the flowers will be predominantly female. With Parthenocarpic varieties they will produce fruit without pollination and will be seedless. Take care as, even though they don't need to be pollinated, they still can be from nearby plants. So you may want to grow in a greenhouse or cover them to avoid getting bitter cucumbers. These are the ones to look for if you want to grow cucumbers indoors - some seed packets class these as "indoor cucumbers".
With the Gynoecious variety pollination is still needed so some traditional varieties will also need to be sown alongside. Plant your own or check with neighbouring plot holders! These 'modern' cucumbers are shorter than traditional ones but you do get more of them. The fruiting period is shorter too so you are more likely to have a glut of cucumbers. A traditional variety will give you a longer steady flow over the summer.
The key to success is to make sure you understand which sort you have from the information on the seed packet. Follow the instructions and you will be fine.
How to Sow Cucumbers
Sow cucumber seeds 1" (2.5cm) deep into 3" (7.5cm) pots from late Feb to March if you are growing cucumbers in a heated greenhouse or similar environment. Or late March if you are growing in an unheated greenhouse, a cold frame or just outdoors.
Cucumbers are good growers so you will need to re-pot them before they are ready to go outside. In late May put them outside for a few days in their pots to hardened them off. If you have left it too late to grow cucumbers from seed then all is not lost, you can still buy small cucumber plants from the garden centre.
How to Plant Cucumbers Outside
Prepare the bed. Dig in some rotted organic matter, such as a sack of garden compost, and rake in 100g per square metre (3½oz per square yard) of general purpose fertiliser.
Transplant the plants into their final position 18" (45cm) apart in June. To give them a head start and the warmth they need to boost growing, keep them covered once outside. Bell cloches or an Easy Poly Tunnel are both ideal for this. These will also keep the pests away - watch out particularly for slugs!
Growing Cucumbers vertically
Cucumbers grow best when they have a frame work to elevate them above the soil where they fall prey to slugs and snails. So once planted train the main stem up a vertical wire or cane. If you are growing cucumbers in a greenhouse then
As they grow, pinch out the growing tips when they have 6 or 7 leaves so that the plants can put all of their energy into producing quality cucumbers. Pinch out:-
- the main shoot when it reaches the roof of your greenhouse or the top of your cane.
- the sideshoots two leaves beyond a female flower
- the tips of flowerless side-shoots once they reach 2' (60cm) long.
Cucumbers are 96% water so make sure you give them plenty of water too as they are a thirsty plant. Make sure you water round the plant not onto it. If in the greenhouse, keep the humidity high by watering the floor too. Once planted out, feed every 10-14 days with a balanced liquid fertiliser.
When to Harvest Cucumbers
Harvest will be 50 to 70 days after sowing. Cut the fruits when they are about 6" - 8" (15-20cm) long using a sharp knife. They will last 2 to 3 weeks if stored well.
Common Cucumber Growing Issues
If you want to know why some cucumbers are bitter then there are a few possible reasons some of which can be avoided with proper care.
How to Avoid Bitter Cucumbers
- For varieties that do not require pollination, remove male flowers or keep the plants indoors out of reach of pollinators to avoid accidental pollination. A question I have been asked is why those varieties that do require pollination do not suffer in the same way. The answer is that for some reason, most likely genetics, the varieties that require pollination simply don't produce the cucurbitacin chemicals that would make them bitter.
- Give the plant proper care as stress often causes bitterness. Stress comes when the plant is too hot, receives uneven watering, or is subject to extreme temperature fluctuations. So use shade netting, open greenhouse vents and water regularly.
- The other issue - and one you can't do much about - is heredity. There is a recessive trait that can cause a plant to produce bitter fruit from the start. You may plant seeds from the same packet and treat them all the same, only to discover one of the plants produces bitter. If this is the case the only option is to scrap that particular plant and sow again.
All male cucumber flowers
If you don't see cucumbers swelling behind your flowers and then they fall off, then they were male flowers. When the plant is stressed for example by lack of water or high plant density it may react by only producing male flowers. High temperatures like we saw in 2020 can also do this to plants. Other stresses, such as damage from insects or blowing soil or low light can result in fewer female flowers. To avoid this try to reduce the stress the plants are under by watering regularly and well. Ensure there is adequate space between your plants and some shade if the weather is particularly hot.
Cucumber Pests & Diseases
Slugs are the main problem when growing cucumbers outside. Try a beer trap to keep them away.
Cucumber mosaic virus is passed by aphids, so it is very important to control greenfly. The virus stunts the plants and leaves show distinctive yellow mosaic patterns. Flowering is reduced or non-existent, while any fruit that do appear are small, pitted, hard and inedible. Destroy Infected plants and wash your hands after touching them so you don't spread the virus.
Mildew is a serious problem to varieties that are not resistant. It shows as a white powdery deposit over the leaf surface and leaves become stunted and shrivel up. Treat by keeping the soil moist and consider a cooler location for your next planting.
Red Spider mite can also be a problem if your cucumbers are in the greenhouse - find out more here
How to Choose the right Rootrainer (and why they work)
Rootrainers are planting cells that give much less root disturbance making them perfcect for filling your vegetable garden or flower borders. Part...Read More
How to Plant Sweet Peas in Winter
Sweet peas are gorgeous fragrant climbing plants that are great as cut flowers and a treat for the pollinators on your plot. They grow well in the...Read More
A Guide to Winter Pruning for Fruit Bushes & Trees
Winter pruning serves several crucial purposes. It helps maintain the shape and size of your plants, encourages robust sp...Read More