How to Plant Cucumbers: Spacing, Soil and Putting Up Supports

Buy a young plant, not a big one

Choose a cucumber with three or four true leaves and its seed leaves still green rather than yellowing. A plant with five or more true leaves, with white roots circling the bottom of the pot, is slow to put out new roots after planting and tends to stall as soon as it sets its first fruit.

Grafted plants resist fusarium wilt and sudden collapse, which matters if you grow cucumbers in the same bed year after year. They cost more than seed-raised plants, but on ground that has carried cucumbers or squash recently, or where a plant wilted and died last summer, grafted is the safer choice.

1. What a good plant looks like Seed leaves still attached, short gaps between the leaf joints, and a thick stem. A plant that has dropped its seed leaves has been in the pot too long and will visibly lag after planting.
2. Grafted or on its own roots On new ground, or a bed that has only grown cucumbers once or twice, seed-raised is fine. Where you have grown cucumbers, courgettes or squash repeatedly, or lost a plant to wilt, choose grafted.
3. Holding plants before you plant If you cannot plant the same day, stand them outside in full sun and water morning and evening. A day in a dim room is enough to make them stretch and flop after planting.

Very dark, thick leaves mean the plant has been pushed with fertilizer. Those plants tend to sit tight and sulk after planting, so pass them over.

Prepare the bed a fortnight ahead

Cucumber roots run sideways in the top eight inches (20 cm) of soil. Deep digging matters less than keeping that shallow layer open, moisture retentive and free draining at the same time, which is exactly what a generous dose of compost does.

1. Lime two weeks ahead If your soil is acidic, lime and dig it in two weeks before planting. Cucumbers want a pH of about 6.0 to 6.5, and root growth slows below that.
2. Compost and base fertilizer a week ahead Work in well-rotted compost at roughly four to eight pounds per square yard, plus a balanced fertilizer. Be generous with the compost.
3. Make the bed about a yard wide A yard (one meter) takes a single row, five feet takes a double row. Raise it four to six inches, and up to eight inches on heavy ground.
4. Lay black plastic mulch Put it down at least a week before planting to warm the soil. It also stops soil splashing onto the leaves, which delays the first outbreak of downy mildew.

Fresh, unrotted manure applied just before planting generates heat and gas that burns the roots. If you are short of time, use less at planting and make it up with liquid feed later.

Plant by soil temperature, not air temperature

Cucumber roots only start working once the soil is above about 60F (15C). Even with warm afternoons, cold soil in the morning means the roots cannot draw water, and you get plants that wilt in the day and never recover. Laying black plastic a week or two ahead makes a real difference.

In a year when late frost is still possible, waiting a week gets you picking sooner in the end. Plants set out too early simply stop.

Spacing and the planting hole

How far apart you space cucumbers decides how long the lower leaves stay wet after rain, and that in turn decides when mildew arrives. It is the cheapest disease control you have.

1. Space 18 to 24 inches apart Allow 18 inches (45 cm) for a single trained stem and 24 inches (60 cm) if you will let side shoots spread. Any closer and the lower leaves crowd, bringing powdery and downy mildew forward sharply.
2. Fill the hole with water first Dig the hole, pour water in, let it drain, then set the plant. Watering over the top afterwards does not wet the middle of the rootball and the plant is slow to take.
3. Plant shallow Set the plant so the shoulder of the rootball sits slightly proud of the soil. On a grafted plant, never bury the graft union: the scion will root and you lose all the disease resistance you paid for.

Put the supports up on planting day

About a fortnight after planting a cucumber starts running. Try to put supports in later and you damage the roots and snap the tendrils that have already taken hold. Build the frame before the plants go in, or at the very latest on the same day.

Use posts at least seven feet (2.1 m) long in an A-frame, run a rail along the top, and tie the crossings firmly. Cucumber leaves are large, and a plant carrying fruit presents its greatest sail area exactly when summer storms arrive. Build a frame that will not fall over rather than bracing it later.

1. Use netting with a wide mesh A mesh of seven to nine inches (18 to 24 cm) lets your hand through. Fine netting tangles the tendrils, makes training impossible, and you damage fruit every time you pick.
2. Tension the net properly Slack netting swings in the wind and the leaves and fruit rub against it and scar. Pull it tight top, bottom and both sides so it barely moves when you push it.

The first week after planting

Until the plant takes hold, water thoroughly over a circle about a foot (30 cm) across at the base. Do not feed yet. Feeding now keeps the roots in the top layer of soil, and that plant will not cope with a dry spell later in summer.

Once the vine is a foot long, tie it loosely to the support with soft twine rather than leaving it to the tendrils. Keep the tie loose, in a figure of eight. Setting the direction now makes all the later training far easier.

1. Days one to three Water at the base daily and check that anything wilting at midday has recovered by evening. In a hot spell, drape row cover over the plants to take the edge off the sun.
2. Days four to seven New leaves moving means the plant has taken. Start stretching the interval between waterings a little to draw the roots down. Still no feed.
3. Do not let the rootball dry A shallowly planted rootball dries fast, and wetting the surface of the bed does not reach it. Pour water directly at the base and let it soak in.

On a windy plot, a collar of row cover on the windward side for the first week or two stops the leaves being shredded.

Growing from seed and direct sowing

Cucumbers take only about 30 days from germination to planting out, which is a short raising period. If you need several plants, seed is cheaper and gives you a much wider choice of variety. Germination needs soil at 77 to 86F (25 to 30C), so in spring that means bottom heat or sowing later.

1. Sowing in pots Sow three seeds in a three and a half inch (9 cm) pot and cover with half an inch of compost. Thin to one after the first true leaf, and plant out at three or four true leaves, about 30 days from sowing.
2. Temperature while raising Hold about 77F (25C) until germination, then days in the 68 to 77F (20 to 25C) range and nights no lower than 59F (15C). If plants stretch, drop the night temperature.
3. Direct sowing Make the bed and lay the mulch, wait five or six days for the soil to warm, then sow three seeds per station. A scatter of chopped straw stops the surface capping and drying.
4. Thinning direct sown plants Seedlings appear in four or five days. Thin to one at three or four true leaves, cutting at soil level with scissors rather than pulling, which disturbs the roots of the one you are keeping.

Direct sown plants never suffer transplant check, so they root deeper and stand up to midsummer drought better. If you can sow at the right time, it is the stronger option.