Cucumbers
There are a wide range of cucumber varieties that are best suited to salads, pickling and 'cocktail' varieties. East and West Asian as well as European salad cucumbers all serve different culinary purposes. These all range in flavour from tart, sour, mild, lemon or apple and the typical salad cucumber in supermarkets. The key here is to grow what you like and eat, so if you enjoy pickles, go for gherkins or for a preference of salads perhaps grow the European cumber varieties. If you want to try something different go for a crystal apple/lemon similar to a salad cucumber but with a citrus tang, or a Cucamelon, which are tiny with a tart flavour.
To have a go at growing cucumbers, sow from February to June at the latest. As cucumbers and melons are warm climate plants, seeds tend to only germinate when at a constant 15 degrees or more. If you struggle to do this, you can buy seedlings. Plant out from May for a nice crop from July - September. For warmer climates the growing season may be prolonged, however, for very cold areas it will be a shorter season. Cucumbers need the heat to grow and ripen along with lots support due to the thin vines and heavy fruit.
Good varieties to try are Marketmore, Crystal Lemon, Kyuri and Kirby. For something different why not try Socrates or Snake Melons.
Melons
When we think of melons, the delicious honeydew, cantaloupe or watermelon often come to mind but there are many more varieties with different textures and flavours. A couple of good examples would be the frog skin melon, with dappled green skin or the sweet and creamy Casaba varieties.
Melons are closely related to cucumbers so could be in the same category, however, as there are so many different types of cucumber and melon they have been separated. Just like cucumbers they require a warm - hot environment with rich soil and tend to only germinate when the seed is at a constant 15 degrees.
A greenhouse or a heated mat/propagator will be needed to germinate the seeds yourself or you can buy seedlings from most nurseries, garden centres and home/hardware stores. Unlike cucumbers melons should only be sown from April - June due to the heat they require. They can be harvested from July and August or into September for warmer climates such as the Mediterranean, southern United States, Australia etc.
Pumpkins
Pumpkins are really a type of squash, however, they have their own category due the huge popularity and seasonal significance. Pumpkins have a very similar growing range as summer squashes like courgettes. Sow from April onwards through to June transplanting out from May depending on your frosts.
If you want to sow direct do so from May. Pumpkins sown in March with a good start should be ready for eating from late June and July. You can continue to harvest pumpkins until the end of October. If you're new to pumpkins you might enjoy the sizable Connecticut Field or the littler Small Sugar varieties. If you have young kids or you really like pumpkins why not go for Atlantic Giant, which is much bigger.
Summer squashes
You will see some types such as courgettes (zucchini), marrows and the French/Italian round squashes year round in farmers markets or grocers. There are many other types you may not see commercially, such as Patty-pan, Loofa and either crookneck or straightneck summer squashes.
Most seed packets or grow guides will advise you sow from April to May. However, you can start courgettes off from mid-March with no issue as long as they are kept undercover and reasonably warm. To give plants the best start sow them in pots before transplanting out once they have their 'true leaves' (not the original two that sprout) and are over 10 cm (4 inches) tall. Your summer squashes should be harvest ready from July onwards.
Courgettes can be harvested from small to large, some people prefer the flavour of smaller ones so why not do both and compare your results?
Winter squashes
If the term winter squash is new to you it's likely you already know a few of the varieties including Butternut, Hubbard and Spaghetti squashes. There are many other varieties that are either highly priced or may not be sold in some areas, such as Banana and Kabocha or Carnival, which are brightly coloured. One of my favourites is Delicata, which has a sweet earthy taste a bit like a cross between a squash and a sweet potato or woodland mushroom.
Sow winter squashes from the last half of April until the end of May or perhaps into the first week of June. They should be ready for picking from late July until the end of October or early November. To give winter squashes their stereotypical hard skin, leave them for up to 10 days after picking in the sun for the squash to harden. This will help if you are storing them to use through the winter.
Like pumpkins and marrows winter squashes can be quite large and with a good portion of surface area on potentially wet soil it's a good idea to rest the bottom of the squash on an old tile or bark chippings etc. to keep away rot, mould and slugs from getting to it first.