How to grow summer cabbages. Cabbage is a demanding plant both is the amount of nutrients it needs and the space it takes up in the garden. It really is easy to grow if you feed your soil properly to begin with and take precautions against some common pests. Fresh cabbage is delicious in a slaw or steamed with a little pepper and butter so well worth growing if you have the space. Our favourite Summer cabbage variety is 'Stonehead' which produces reliable crops of very firm and tasty heads.
Site and Soil
Summer Cabbage is classed as a heavy feeding plants so add plenty of garden compost and/or well rotted farmyard manure your soil before sowing or planting.
Summer Cabbage is best sown in a greenhouse or similar environment in March and April for planting out about 4 weeks later. Sow 1 seed per cell in a modular tray at about 2 cm deep in a good quality seed compost. Apply a gentle liquid seaweed fertilizer every week until ready to plant out.
Sowing in Modules.
Seeds can also be sown outdoors from April to early May. Sow 3 seeds 1.5 cm deep every 45cms. Thin out seedlings after 2-3 weeks to leave 1 plant every 75 cms. The spacing is 45 cm between plants and 45 cm between rows. Cover seed beds with fleece or enviromesh to protect against cabbage root fly at least until mid May when the risk will be reduced.
Leggy Seedlings - Seedlings grown indoors are at risk of becoming long and spindly or ‘leggy’. Leggy seedlings occur when the plant gets too much heat but not enough light. Seedlings growing early in the year can suffer because there aren’t sufficient light levels to compliment the heat provided by growing indoors.
Growing on a windowsill - Always use a south facing windowsill with plenty of light. Place a mirror or other reflective material behind the plant tray to reflect daylight coming in the window on the dark side of the plant.
Using a heat mat, heating cable or propagator - As soon as the seedlings have germinated remove from the heat source. If growing in a greenhouse or tunnel protect the young seedlings at night by covering with horticultural fleece. Fleece will protect plants from temperatures as low as -3.
Where 2 seeds have germinated in a single cell remove the weaker one by pinching out with your finger nail or cutting with a small scissors. Don’t pull them out to avoid damage to the neighbouring seedling.
Compost should be left moist rather than soaking. Avoid letting the seedlings dry to the point where the compost starts to pull away from the edge of the tray, it can be difficult to wet as the compost can form a crust on it’s surface.
Hardening off means getting your plants used to more hostile outdoor conditions. Leave the plants outdoors on mild days, progressing to every day and finally all night. A cloche cover or Cold Frame is perfect for this practice. If you have started your seeds on a windowsill you will need to leave them in an unheated room for a day or two before moving outside to the cloche
Cabbages like a fertile, well-drained, moisture-retentive soil. A firm soil is also desirable so where possible add well rotted manure or garden compost in the Autumn and allow to settle over the Winter.
Summer Cabbage should be planted 45 cm between plants and 45 cm between rows.
Water plants well before you begin. To plant a seedling make a hole in the soil about the size of the rootball with a dibber or trowel. Mix a slow release nitrogen rich feed like Seamungus poultry pellets around the planting hole and root zone.
Fill the planting hole with water several times before planting the seedling, this will help the plant to establish better. When planing you need to push the soil in around the roots firmly with your fingers to get good contact with the soil. Don’t firm down on the top of the soil as this can compact it and prevent moisture getting down to the plants roots.
You are better to transplant on a dull day or in the evening to prevent the plants wilting in hot, dry weather.
Pests and diseases
There are a number of brassica pests you need to look out for when planting Spring Cabbage. You can read more information about brassica pests and diseases here.
Cabbage root fly.
The best way to avoid cabbage root fly is to keep the flies out by covering your crops with a fine protection mesh like enviromesh. You must make sure the edges of the mesh are secure to prevent any intruders sneaking in by covering with soil or weighing down with bricks or stone.
Cabbage root flies lay their eggs around stems of seedlings where they hatch, burrow down and munch through the roots. You can also prevent this happening by placing cabbage collars around the base of the plants which the larvae can't get through.
You could also apply a natural nematode pest control which kills root fly maggots at the larval stage. A product like 'Supernemos' is excellent as it also attacks the larval stage of other pests like leatherjackets and wireworms.
Cabbage White Caterpillars.
Check periodically for small yellow eggs on the underside of the leaves and remove by brushing them off.
Cover the seedlings with fleece or micromesh to keep out cabbage white butterfly.
Nematodes. These are naturally occuring microscopic worm which attacks the larvae of the cabbage root fly. The nematodes are in your garden soil anyway you're just increasing the numbers. It is a non chemical product so is safe for use around pets and children. You will need to do a couple of applications but in my opinion it's well worth it as you'll also protect a whole host of other crops.
Remove any yellowing leaves at the base of the plant. Wash off whitefly with a strong jet of water.
More likely in established allotments or gardens than new or isolated gardens.
Clubroot likes acid conditions so adding lime (alkaline) to the soil before planting will help prevent the disease. To remove completely stop growing any brassica for at least 10 years.
Keep the soil clear of weeds using an oscillating hoe or similar. Hoeing is also beneficial as it invigorates the microbial life in the soil which makes more nutrients available to your plants.
Remove any yellow, discoloured leaves from the plant as they may harbour disease which will spread to your crop.
As Winter approaches earth up the cabbage stems by dragging soil up around the stems to prevent them rocking in the wind. Remember to keep an eye out for cabbage white butterfly eggs on your cabbage plants. Look under the leaves for the little yellow eggs and brush them off. It is much easier to cover your crops with micromesh (enviromesh) if you haven't done so already. Make sure no butterfly gets in while you're doing it! Hoe regularily to control weeds and to stimulate the growth of the plant. One of the best gardening tools you'll ever buy is the oscillating stirrup hoe. It's a very effective old fashioned tool that really works properly. Hoeing not only removes the weeds but it also breaks up the surface of the soil and creates a fine texture or 'tilth'. A good tilth lets air and moisture in to the roots of your plants thus increasing their vigour.
A liquid feed given at about 14 weeks from sowing which will increase the size of your harvest. Summer cabbage is a very demanding crop and a nutrient boost at this stage will make big difference to the size and quality of the cabbage you'll harvest in a few weeks.An excellent feed can be made from soaking seaweed and poultry manure pellets in water over a couple of days. Strain the liquid to allow it to be applied through a watering can without clogging the rose.
The best time to add a foliar feed is in the late evening or early morning. This is when the stomata (small openings on the leaf surface) are open. Essentially this is when the plant breaths in.
Summer cabbages can be harvested in August and September depending when you planted them, they are cut when you wish to use them and are not stored for any length of time.
Harvest your cabbage by cutting with a sharp knife close to ground level. Cut a deep cross in the remaining stump you will get a secondary crops of mini cabbages from the old stem.
Dig up the root after your secondary crop and preferably burn rather than compost to avoid encouraging club root.
Growing Cabbage video coming soon!