Kale is one of the most useful crops for a British vegetable patch because established plants can keep providing leaves long after tender summer vegetables have finished. The mistake is treating every kale seedling like a little salad plant. Mature curly and flat-leaved varieties can become substantial, top-heavy plants, and they need much more room than a tray of baby leaves.
You can sow kale where it will stay or move young plants from modules or a seedbed. This guide focuses on planting young kale into its final position, choosing spacing and protecting the crop at its most vulnerable stage.
Choose kale to suit your space
Curly kale, 'Cavolo Nero' and other flat-leaved types vary in height, spread and harvesting habit. A compact cultivar can work in a container. A large winter kale may reach well above surrounding crops and cast shade over a neighbouring row.
Check whether you intend to harvest young salad leaves or full-size leaves for cooking. Young leaf crops can be grown close together and cut relatively early. Plants intended to stand through autumn and winter need generous spacing so air and light reach the stems.
Buy sturdy, well-coloured seedlings or raise your own in modules. Small plants are easier to establish than tall specimens with circling roots and coarse, ageing leaves.
Work out when to plant outdoors
In the UK kale is commonly sown between spring and early summer, with seedlings planted out when they are strong enough to handle. The RHS indicates that plants raised in a seedbed are often ready to move six to eight weeks after sowing.
Seedlings started under cover need hardening off before facing wind, rain and stronger sun. Move them outside for increasing periods, protecting them from sharp weather until they adjust. Freshly transplanted plants are not as resilient as mature kale, even if the variety is hardy.
Planting in hot, dry conditions creates unnecessary stress. Aim for an overcast spell or plant late in the day, then water in well. Avoid working saturated soil, as trampling and digging can leave lasting compaction.
Prepare soil and plan the spacing
Choose fertile ground that drains freely but holds enough moisture for continued leaf production. Remove weeds and add well-rotted organic matter where the soil needs improvement. Kale is a brassica, so rotating it away from ground recently used for cabbages and broccoli can help reduce disease build-up.
The RHS gives around 30–60cm spacing for mature kale, depending on variety, with rows normally at least 45cm apart. Follow the packet or plant label. If you're growing baby salad leaves only, spacings can be as close as around 7.5cm.
Measure the bed before removing seedlings from their modules. A patch that comfortably holds twelve small plants today may only hold six mature kale plants by October. It is more productive to give fewer plants adequate light than let a crowded patch compete for everything.
Plant the seedlings a little deeper
Water the module tray first so the compost holds together. Make holes deep enough to accommodate each plant's rootball without folding the roots upwards.
Ease each seedling out by supporting the rootball rather than pulling the stem. Position it slightly deeper than it was in its nursery module, with the lowest leaves just above the soil. This helps anchor a plant that may later catch the wind with a large canopy of leaves.
Firm the soil gently around the roots and water each plant thoroughly. Avoid burying the growing tip in the centre of the foliage. If seedlings have become excessively stretched and weak, planting deeper may help support them but won't correct a prolonged shortage of light.
Stop pests reaching young plants
Newly planted kale is particularly appealing to slugs, snails, pigeons and caterpillars. Inspect for damage early. A few holes in outer leaves are usually manageable; losing the central growing point can set a small plant back much further.
Fine insect mesh can help exclude butterflies whose caterpillars chew brassica leaves. Erect it on hoops or supports so the mesh does not simply lie over foliage. Secure all edges and inspect the plants underneath, because mesh only works if pests were not already trapped inside.
Bird protection may be necessary too. Use properly tensioned, wildlife-safe netting or another suitable barrier rather than loose mesh that animals can enter. Check protection after strong winds and as the plants grow taller.
What to do during the first few weeks
Monitor soil moisture every few days, more often during hot weather or in containers. Water slowly around the base to encourage the rootball and surrounding ground to become evenly moist. Avoid leaving a pot submerged in standing water.
A recently moved seedling may pause briefly while its roots settle. Look for new leaves at the centre rather than judging establishment from the oldest outer foliage. Remove weeds while small so you are not disturbing the kale's roots later.
Once plants are growing steadily, a mulch can help retain moisture and suppress weeds. Keep bulky material away from the stems to avoid a damp mound against the crown.
Growing kale in large pots
Choose a large, stable pot with drainage holes, a suitable peat-free multipurpose compost and a bright position. A single mature plant in an adequately sized container is usually more manageable than several squeezed into a small trough.
Container kale needs closer attention to watering because its roots cannot search the surrounding garden soil. When plants are fully grown, windy weather can dry the compost even on days that aren't particularly hot.
If growing baby leaves, a broad container can accommodate closer sowings. Cut leaves while tender and allow suitable plants to regrow. That is a different growing plan from keeping tall winter kale in a pot for many months.
Harvest without exhausting the plant
Start harvesting when the leaves are a useful size and the plants are firmly established. Pick older outer leaves from the lower part of the stem, leaving the central growing point intact. This allows the plant to keep producing fresh leaves.
Large leaves can become tougher as they age. Regular modest picking makes more sense than stripping a plant to a bare stick after months of neglect. Inspect the underside of harvested leaves and wash well before cooking.
Cold weather can alter kale's flavour, but varieties respond differently. Harvesting through winter is possible with suitable hardy types; don't assume every container specimen will thrive in an exposed position through severe frost.
Why newly planted kale sometimes struggles
If plants disappear overnight, look for slugs or grazing birds before deciding the soil lacks nutrients. Ragged holes and missing tender centres are clues; yellowing across entire plants may have a different cause.
Purple-tinged or slow leaves in cold weather may reflect growth slowing as temperatures drop. A seedling that wilts in the afternoon may simply need water, but persistently soggy roots can also cause wilting. Check the root zone before you reach for the hose.
If leaves become riddled with small holes, inspect for flea beetles, especially in dry weather. A healthy, well-established kale plant has a better chance of tolerating some damage than a freshly moved seedling.
Plan the next crop while this one grows
Make a note of the variety, planting date and spacing. It makes next year's bed plan considerably easier and helps you tell whether a compact cultivar actually stayed compact in your conditions.
If kale was grown after an earlier crop, replenish the bed appropriately before planting. Consider a succession of sowings for baby leaves rather than planting all your seedlings on one day. For mature winter kale, a few strong, well-spaced plants can provide a long harvest.
The key is simple: handle the rootball carefully, plant at a sensible depth, water in and protect the young leaves. Give kale the space of a full-size brassica from the beginning and it usually asks much less of you later.