Zucchini (Cucurbita pepo var. melopepo), also known as courgette or marrow, belongs to the Cucurbitaceae plant family, which includes pumpkins, melons, spaghetti squash and cucumbers. There are a number of different varieties, including those with yellow or pale green skins, and ones with a round shape. They are a warm-season crop and need a sunny in the garden (or in a large pot), with organic matter dug into the soil before planting. It is best to plant seeds directly into the ground in from early spring to early summer, preferably into a small 'mound' of soil, to ensure the good drainage that they demand. It is, however, possible to sow individual seeds into small pots and plant them out carefully (without disturbing the roots) when they are strong enough - this is useful if early crops are wanted and heat can be provided indoors for the pots to aid germination when the weather is still cold outdoors. The plants need to be spaced well apart to allow them plenty of room. Feed and water regularly, and apply a surface mulch over the soil around them, to maintain moisture.
The plants grow very quickly. The white-flecked, deeply lobed foliage is large and actually quite decorative. Large, brilliant yellow flowers with the texture of crepe paper soon begin to appear. Male flowers have a long slender stem, and the female ones can be identified by the cute miniature zucchini at their base. It seems as if natural pollinators simply cannot be relied upon to play their role, possibly because the flowers only seem to stay open for a few hours in the morning, so it is necessary to intervene and transfer the pollen from the stamen on the male flower to the stigma of the female flower, with a paintbrush or by dabbing directly, holding onto the base of the male flower. The fruit will begin to grow seemingly almost straightaway!
The first crops should be ready about six to eight weeks after planting; regular harvesting will encourage higher yields. They are at their most tasty if picked when fairly small. It's best to cut the zucchinis off rather than breaking them, which can damage the plant. It is apparently possible to plant a second crop in February to get further crops into autumn.
If you are overwhelmed with too many of them developing at once, you can refrain from pollinating for a few days (or eat the flowers)! I found it useful to grow three plants so that amongst them there would always be some male and female flowers opening on any given day. However, zucchini can cover some area as they grow: it's a good idea to choose more compact 'bush' varieties if possible, especially for growing in pots, rather than the rambling sorts. With the more sprawling types, it can be useful to pinch the leading shoot out when the runner is about 45 cm long, to induce branching.
The only problem I encountered with my plants was powdery mildew, which occurred during a period of cool, rainy, humid weather. I removed the worst-affected leaves and sprayed with an organic fungicide (based on potassium bicarbonate), which fixed the issue. Making sure the soil is kept moist is also a way to avoid powdery mildew.
Zucchinis can be eaten cooked or raw. They can be sauteed, stir-fried, stuffed, baked, char-grilled or spiralised into low-carb 'noodles', and they can be used in fritters, frittatas, risottos, pizzas, omelettes, pickles, cakes, muffins, bread, soups and salads. The flowers are also edible and can be added to salads or stuffed with cheese and baked or fried! There are many health benefits to a zucchini, including their being moderately rich in various vitamins and minerals (particularly vitamins A and C, noting that the vitamin C level is reduced and the vitamin A level is increased when the zucchini is cooked). Zucchini is also said to be rich in antioxidants, located mainly in the skin, which can augment eye health as well as conferring possible other benefits to the heart and bones. It contains soluble and insoluble fibre, helpful for digestion (as is the high water content!), and it is low in calories.
Note that zucchinis may occasionally contain a group of natural toxins known as cucurbitacins. These toxins give zucchini a bitter taste and can cause stomach upsets, but this phenomenon is rarely found in commercially grown zucchinis. It is advisable not to save seeds from your zucchinis for future growing, as they may revert to the wilder, bitter forms.