(Citrus, guava, loquat, myrtle, olive, physalis, melon and watermelon) These tenderer fruits have long been grown in our kitchen garden greenhouses but not as widely as they deserve. True these are more demanding than the more common soft and tree fruits. They cannot be planted and effectively forgotten about other than picking and pruning. In practice most are best grown in containers so they can be moved under cover for winter. However these can repay your watering and attentions with valuable produce, and far finer quality than the same bought from a supermarket. The perennials need frost free conditions under glass or plastic to crop as they have late autumn and winter harvests, most need to be frost free anyway to survive at all. But these do not want great heat; only freedom from frost, and they all go outdoors in late spring to come in again in late autumn. This keeps the pests and diseases from getting too well established and keeps them from overheating in summer. Indeed even in winter a cool conservatory will often suit them better than a hot greenhouse. On the other hand the melon and watermelon are annual summer crops, love heat and complement the others by occupying any indoor space the perennials vacate when moved outdoor. (Some varieties can be grown outdoors; but only with a cloche or similar providing near as much warmth as being indoors anyway.)

Citrus are really worth their cost. Their fruits need no description. The flowers often bloom spectacularly and of course have that delicious scent (oranges give the most). Their bushes are slow growing especially when confined to tubs, becoming small trees only in old age. Their leaves are aromatic and evergreen though may fall if the plant is distressed. Citrus need moist slightly acidic, well aerated, compost with plentiful high nitrogen feeding, and occasional syringing or misting. They like to be shallow planted not buried and prefer slatted wooden or terracotta tubs to plastic ones (I drill side ventilation holes in mine). They like moist but not wet compost; more are lost to water-logging than to cold. Citrus can be grown from seed but are very slow to fruit- twenty three years for my Ortanique! Cuttings are faster but less vigorous and not all take easily. Prone to all sorts of pests citrus benefit from regular soft soap sprays when under cover (as this strips the wax off their leaves it should not be done outdoors nor in bright sun). Often far too many fruits set, so, crucially; need thinning. (Masses of miniaturised fruits caused by not thinning can still be marmaladed.) Tangerines or Satsumas are excellent and crop well, and in time for Christmas. Lemons are good value, especially with several varieties as then you almost always have fresh ones handy. Grapefruits are surprisingly easy but cannot carry many at a time. Limes are the most tender and more easily lost. Sour oranges for marmalade, and sweet oranges are less valuable, to me anyway, than say more lemons or tangerines, but still quite easy. Kumquats are not really citrus but very similar and are treated similarly, their fruits can be harder to get to set and rarely need thinning. Citrus fruits turn from green to orange as they ripen but if kept consistently hot they may stay greenish.

It is also worth growing Guavas as these can be treated much the same as citrus and go along with the same treatment well. They can be grown from seed from supermarket fruits and crop in only a few years. Guavas are not so fussy as to compost as citrus but need more water. Their leaves are large laurel like and matt and their flowers are small cream shaving brushes. Ripened on the bush guava fruits are far superior, different even to bought examples, and are melting, luscious and very highly perfumed. There are two different strains; apple shaped and pear shaped, I prefer the latter. There’s also the mountain, cherry or strawberry guava, Psidium cattleianum with a smaller more glossy leaf and smaller, dark red fruits, black even. These are very rich in vitamins and anthocyanins, and delicious. This is a most attractive conservatory crop plant. Both types of guava shed their bark which along with prunings makes a pungent smoke good for jerking meat.

Another plant best treated much like citrus though actually very hardy is the Japanese Loquat, Eryobotrya japonica. This has huge leathery leaves and can make a fair tree in a sheltered spot. But because it flowers late the fruits have to get through winter and rarely ripen outdoors in the UK. However moved in and out in a tub as with citrus it can crop well with masses of tart apricot like fruits. These are variable from seed, though most are grown that way, only cropping after ten to fifteen years. At the other end of the size of leaf scale are Myrtles which are sometimes grown as ornamental evergreens but again rarely crop well planted outdoors. Moved under cover for winter you get reliable crops of black berries which make the most delicious jam. (The creamy flowers strangely smell of garlic sausage.) The more tender Myrtus ugni is similar with even tastier dark maroon berries.

Olives are a moot point. They’re quite hardy but have rarely cropped well, or at all, planted outdoors in the UK. They may soon do so with the advent of the newest cultivars specifically bred to crop in our colder climate. However, as with citrus, olives have long been ripened by taking them under cover in tubs each winter. This now makes more sense, even with new sorts, because of our increasingly unpredictable weather. Olives are evergreen trees ,very slow to grow, tough evergreens and not fussy though detesting water logging. Buy a new variety as from seed will take a lifetime. An olive will flower and ripen fruit for you but remember, as for grapes and wine, the skill will be more in their handling. Growing the fruit is less crucial than brining and pickling or pressing, in ensuring a tasty product.

Cape gooseberries, Physalis peruviana, these are commonly and wrongly grown as an annual, much as a tomato plant, and so have not become popular. So grown they ripen small crops late in the year, even under cover. However grown as perennial climbing shrubs in tubs and hard pruned alternate winters these can give bigger crops throughout more of each year. Indeed these are more productive and easier to handle in tubs treated much like citrus than when planted in the border under cover where they grow too rankly. Or like pelargoniums slips can be rooted in autumn, over-wintered to be grown on in spring. Not at all fussy as to compost this is a tough plant. Ideally by nipping out tips you can keep one bushy or it will turn into long vines that need tying to canes or wire. These bloom with pale yellow flowers then, much later, the fruits in their Chinese lantern paper cases mature finally falling off when fully ripe. These stay so clean in their papery envelopes they dry to small ‘raisins’. Cape gooseberries are very rich in vitamins as well as tasty. The annual Physalis pruinosa is much more productive more quickly, more compactly, but sadly is not as tasty. Physalis ixocarpa another relation, the Jamberry, is a similar ‘fruit in a papery husk’ but this time is bigger bursting the case, and more like a big green or purple tomato. Not so sweet this is best used as you would a salad or cooking tomato, and is essential in many salsa dishes. All the edible Physalis make nice jams and jellies.

Melons bear little resemblance to the perennial shrubby fruiting plants above. But as mentioned they do very conveniently grow in the space liberated when those perennials are moved out. Although there are varieties that will sometimes; bear edible fruits outdoors in warm spots in good years, melons are very much plants for growing under cover. The seed is best started in a propagator and kept warm both before and after planting out- ideally using a cloche or coldframe inside your greenhouse to double up. They like a rich warm moist compost so on top of compost heaps or hot beds gives the best results. Water carefully but liberally and feed regularly. Be careful not to let them get cold, or wet especially where the stem enters the compost as then they rot. Planting on top a mound helps keep that neck dry. You could nip out the shoot tips and pollinate four flowers on the same day as recommended if you want four equally sized melons. If you want one hugely impressive melon with maybe other small ones let the vine ramble and set it’s own flowers- the first setting usually suppresses others. Support fruits with stocking slings or nets or wooden cushions as they eat best when caught dropping off the vine. Melons get very sweet and may be too perfumed for some eaten sun warmed- chill them a bit in the fridge first, then allow only partial warming before serving. There’s a huge range of varieties, netted and aromatic, white, green, cream or orange fleshed; try several till you find your favourite.

Watermelons are very like melons to grow but prefer it even hotter, with a less rich, poorer, more sandy compost, more water and less feeding. You definitely want to encourage no more than one fruit per plant so it gets all the sap. The key is a really high soil temperature. And one way to make the soil warm enough for melons or watermelons other than growing on top a hot bed or with soil warming cable is by covering it with black plastic so the sun heats it up. On top of this place a cloche or cold frame at least a fortnight or more before the plant arrives so the soil can get warm enough. Alternative to a cloche, make a tent of clear plastic held on sticks or wires a foot or two above the black plastic sheet. A tent like this even works well outdoors, however under cover makes it double glazed and gives excellent results.