Clean the exterior of the greenhouse by washing the panes of glass with warm water and a sponge. Higher parts of the greenhouse can be reached by attaching a sponge to the end of a broom handle or a bamboo cane. Old plastic labels or a gentle jet wash attachment on the end of a hose are ideal for getting in under the window panel joints to remove the build-up of dirt underneath. Clean on a moderately windy day and let the breezes dry out the greenhouse as it's washed. Once the panes of glass are dry, insulate the greenhouse with bubblewrap to protect any plants you are overwintering, and to encourage the greenhouse to heat up more rapidly in the spring.
Check the panels for any broken or cracked glass. They should be replaced. If you are planning on doing the job yourself, then you should wear gloves and goggles. Wooden frames can be painted using a wood preservative, making sure that none of the solution touches the plants.

Growing bags

Despite only measuring 35cm x 95cm (13in x 37in), growing bags have enough space for three vegetable plants that will provide you with enough food for several meals over the summer. Plant two to three plants in each bag during spring.
Bags were traditionally used under glass and were introduced as an alternative to planting directly into greenhouse soil. Not having permanent borders meant the space could be used more efficiently throughout the year and plants would not become infected by soil-borne diseases. Today, they are still ideal for growing plants in the greenhouse, but are also perfect in a sunny spot outdoors.
Growing bags are ideal for plants that don't have deep roots, such as tomatoes, cucumbers, sweet peppers, chilli peppers, aubergines and courgettes. Plant two to three plants in each bag during spring. Alternatively, cut a long panel in the top of the bag and sow salads in rows. Endive, lettuce, basil and rocket can be sown from spring to late summer.
If growing salads, prepare the bag as before and cut out a long panel on top of the bag. Plant or sow in rows across the width of the bag.

Currants

Bare rooted currant varieties are widely available for planting between October and March, while container grown currants can be planted all year round, as long as the soil is not frozen or waterlogged. If possible, buy a two year old plant – once planted it will remain productive for almost 20 years.
Grow currants in well drained soil, which has been enriched by adding plenty of well-rotted manure. Choose a slightly sheltered spot, and although plants prefer full sun, they will tolerate dappled shade.
Dig a hole that is wide enough for the roots to be spread out and deep enough, so the soil mark on the stem is level with the surface of the soil. Place the bush in the centre of the hole and gradually fill with soil, firming it as you fill. Water and finish by spreading a layer of well-rotted manure over the root area of each plant. If you are planting a number of red and white currant varieties, leave 1.5m between plants and 1.8m between rows.
Red and white currants should be trained as an open centred, goblet-shaped bush - this allows light and air to flow freely around the branches, and makes picking easier. After planting, pull off any suckers growing from beneath ground level and cut back to the stem, any branches less than 10cm above the soil – this will give the bush a short leg. Prune all other branches to a third of their original length, cutting to an outward facing bud. In subsequent years, allow branches to grow in the main framework until your bush fills its allotted space. Then, prune back the upright growing leading shoots to half their length, cutting to an upright bud. At the end of June, prune back side shoots to half their length and then to two or three buds in winter.

Leeks prefer a sunny, sheltered site with well-drained soil. As they will sit in the soil for a long time, they are ideal crop for the allotment, although many have fantastic foliage that makes them an ideal vegetable to grow in flower borders or an ornamental potager.
If possible, prepare the soil for planting in the winter. Dig the site well, removing weeds and working in plenty of well-rotted manure to improve its ability to retain water. Leeks can be planted in heavy soil, but improve the drainage by mixing in some horticultural sand. This is a hungry crop – spread a general balanced fertiliser over the soil a week or so before sowing and rake in. A rate of 60g per square metre is ideal.
The easiest method is to sow seed directly into the soil between March and April. Alternatively, you could cheat and buy ready-grown seedlings, many nurseries offer a good range. By careful choice of varieties you could have an ample supply of leeks to harvest from mid-summer until the following spring.
On the allotment seeds are best sown in rows, 30cm apart. Mark a straight line and use the corner of a rake to make a shallow groove in the soil, about 1cm deep. Sow seed thinly along the trench, cover with soil, water and label. When seedlings have three leaves each, about four to five weeks later, thin to leave plants every 15cm – the seedlings you remove could be used to plug gaps elsewhere.

Herbs
Spearmint, Mentha spicata; mint will thrive in most soils, to the extent that it can easily become a nuisance. To avoid this, try growing it in a container on the patio. Use the leaves to flavour new potatoes and peas.
Rosemary, Rosmarinus officinalis; this pretty herb produces blue flowers and has highly-scented, needle-like leaves. Plant in a sunny, sheltered area of the garden.
Thyme, Thymus vulgaris; grow thyme in a well-drained, sunny area of your garden. The leaves of this evergreen herb can be picked throughout the year. Their distinctive taste goes well with a variety of dishes.
Chives, Allium schoenoprasum; grow in moist soil and full sun. For a regular supply of delicious leaves for your salads cut off the flowers before they open.
Lavender, Lavandula; a pretty herb that produces beautiful scented flowers during the summer months. Cut and dry some to make pot-pourri.
Sage, Salvia officinalis; this strong-flavoured herb has grey-green leaves and spikes of blue flowers. Grow in a sunny area of the garden.
Oregano, Origanum vulgarea; planted in a sunny area of the garden, marjoram will grow as vigorously as mint. Children may recognise its taste as it's often used in pizza and pasta.
Coriander, Coriandrum sativum; this popular herb, frequently used in Indian cookery and salads, favours a sunny, sheltered area of the garden. Both leaves and seeds can be used for flavouring.
Sweet bay, Laurus nobilis; this evergreen shrub or small tree likes a sheltered position in the garden. Its leaves are the key ingredient for bouquet garni and are great in stews.
Tarragon, Artemisia dracunculus; grown in a sheltered spot, tarragon can spread at the same rate as mint but is not totally hardy, so cover with straw as winter approaches.

Chicory
There are three types of chicory: red chicory, which is sometimes known as raddichio and is often seen in mixed salad packs in supermarkets; sugarloaf varieties, which resemble lettuces and forcing chicory – this isn’t grown in the normal way. It is deprived of light, or forced, in winter to make edible white growths called chicons.
Chicory will thrive in a sunny spot with well-drained soil. It can be grown in short rows on the vegetable patch or allotment, and is also ideal for raised beds and large pots.
If you can, prepare soil for spring sowing by digging in the winter, adding plenty of well-rotted manure. Remove weeds, any very large stones and rake to leave a level finish. A week before sowing sprinkle a general purpose fertiliser (of approximately 30g per square metre) over the area and rake into the surface.
Sow seeds in July or August, for plants ready to be picked from October to December. To sow in rows, stretch a length of string between two canes to make a straight line and make a shallow trench, about 1cm deep, with a garden cane. Sow seeds thinly, then cover, water and label.
Alternatively, fill a large 45cm (18in) diameter pot with compost, level and tap to settle – aim to leave a 2cm (1in) gap between the surface of the compost and the rim of the pot. Sow seeds thinly across the surface and cover with a 1cm (0.5in) layer of vermiculite. Water and stand in a cold frame, or in a slightly shaded space in the garden.

Plant sweetcorn in the spring and by late summer you’ll be picking lots of fresh cobs, which are far tastier and more succulent than any you can buy in the shop.
Sweetcorn is wind pollinated and best planted in large blocks, where the male flowers at the top of the plant have more opportunity to shed their pollen on the female tassels (where the cobs will form) below. Each plant will produce one or two cobs, so work
Sweetcorn likes free-draining, moisture retentive soil. If you can, prepare the bed the previous autumn before planting, adding plenty of well-rotted manure to the soil. Don’t worry if you never had time, beds can still be made in the spring. First remove weeds and dig over the site with a spade, removing any particularly large stones. Level roughly and then work over the area with a rake to leave a fine finish. out how many cobs you are likely to need (you can freeze them) and provide enough space to achieve this.
Ready-grown plants will establish quickly and provide cobs earlier than sowing seed directly into the soil. In April, fill a 7.5cm pot with compost, make a 2.5cm deep hole in the top with dibber (a pencil will do if you don’t have one) and drop two seeds in. Cover, water and put on a windowsill to germinate. When seedlings are about 2cm tall discard the weakest one and put plants in a shady place outdoors to toughen up before planting out.