Your June seed sowing jobs

Flowers

Cornflowers

Cornflowers (Centaurea cyanus) are easy to grow and provide an abundance of summer blooms. Sow seeds direct into well-prepared soil in a sheltered, sunny spot at a depth of 12mm. Sown early this month, they should be flowering around mid- to late-summer. As well as creating beautiful bouquets, these hardy annuals are a magnet for pollinating insects, so they will benefit wildlife as well as looking fantastic in arrangements.

We love to combine the deep crimson button-blooms of Centaurea ‘Black Ball’ with the creamy-copper tones of Calendula ‘Sherbet Fizz’ for a dramatic display. Centaurea ‘Classic Magic’ is a wonderful mix of white, deep purple and smoky mauve flowerheads. It looks gorgeous on its own in a vase, or try pairing it with the white umbels of Bishop’s flower (Ammi majus) or wild carrot (Daucus carota). For a vibrant collection of blues and purples, try mixing the wild cornflower (C. cyanus) with Nigella ‘Midnight’ and Salvia viridis ‘Blue’.

• How to grow cornflowers

Zinnias

Zinnias can also be sown outside this month. Like cornflowers, they prefer a sheltered, sunny spot, and should be sown thinly at a depth of 3mm. Picking flowers regularly encourages plants to produce more blooms, which makes them perfect for arrangements. Zinnia ‘Lilliput Mixed’ is a spectacular selection of bright yellow, orange, purple and pink fully double flowers that last well in a vase. For a more subtle combination, try Z. elegans ‘Benary’s Giant White’ with Z. ‘Benary’s Giant Lime’ and Z. ‘Queen Lime Red’.

• 10 colourful zinnias to grow

Sweet Williams

Sweet Williams (Dianthus barbatus) are one of my favourite flowers to bring rich colour and scent to the garden in late spring and summer. This relation of garden pinks and carnations is a short-lived perennial, often grown as a biennial. Cultivars come in a range of colours from Dianthus (Nigrescens Group) ‘Sooty’ with its deep maroon flowers, through the vivid pinks, purples and reds of D. ‘Sweet’ and D. ‘Electron Mix’, to the unusual spiky green heads of D. ‘Green Trick’.

These sun-lovers prefer fertile, well-drained soil, and they make superb cut flowers, lasting well in a vase. Sow seeds outside at any point over the next few weeks, 1cm deep with rows 30cm apart in well-prepared soil raked to a fine tilth. Cover thinly with soil and keep well-watered in dry weather. Sown now, sweet Williams should flower from next May until late summer. Regular deadheading prolongs the flowering period.

Forget-me-nots

Pale tulips like ‘Apricot Beauty’ and ‘Purissima’ look beautiful underplanted with drifts of azure blue forget-me-nots (Myosotis sylvatica). Sown in-situ this month, forget-me-nots will readily self-seed once established, spreading through the borders with a mass of flowers appearing from April to June. Unwanted plants can be removed or replanted as necessary.

These versatile biennials thrive in moist, but well-drained soil in sun or partial shade, and make a great addition to spring container displays. As well as the traditional blue form, they are available in white and pink such as M. ‘Snowsylva’ and M. ‘Rosylva’. The wild form of water forget-me-not (Myosotis scorpioides) can also be sown outside in June. This perennial spreads along the edges of ponds and through bog gardens. One of the most wildlife-friendly pond plants, water forget-me-not attracts pollinating insects to its nectar-rich flowers, and provides a place for newts to lay eggs in the leaves.

Sow forget-me-not seeds thinly into well-prepared soil which has already been watered. Germination can take up to a month and plants should be thinned to 15cm apart when large enough to handle. Sown this month, plants should flower next spring.

• How to grow forget-me-nots

Thrifty tip

It is quick and easy to create new tomato plants for free in early June. When you remove side shoots from cordon tomatoes, simply pot up the shoots into gritty peat-free compost, water them and place in a warm spot. They should root within a week or so, and develop into healthy new plants. You can also place side shoots in a glass of water until they produce new roots, then carefully pot them up. Plants created from side shoots will start to fruit later than the original plants, helping to extend the cropping season.

Vegetables

Lettuce

Picking fresh homegrown lettuce is a summer delight, with plants easily and cheaply grown from seed. Sow outdoors into well-prepared, fertile, moisture-retentive soil in a drill 1cm deep, and keep well-watered throughout the growing period. Leave 30cm between rows, and thin seedlings to 20-30cm apart, depending on variety. Lettuces will be ready for picking between six weeks (for loose-leaves) and 10 weeks (for hearting lettuces).

‘Romaine Ballon’ is a delicious cos variety, best sown in small batches every two or three weeks. This bolt-resistant variety produces large heads with sweet and crunchy salad or braising leaves. For loose-leaf lettuces, try ‘Lollo Rossa’ with its frilled red leaves that look as attractive in the garden as on the plate. It is great as a cut-and-come-again crop or can be harvested in its entirety. ‘Tom Thumb’ is a butterhead lettuce with small green heads that can be picked around 10-12 weeks from sowing. It is ideal to grow in container.

• How to successional sow lettuce seeds

Spring onions

Spring onions are one of the easiest vegetables to grow in containers or raised beds, with crops ready to harvest within eight weeks. We love to grow red salad onions, such as quick-maturing ‘Apache’ and versatile ‘North Holland Blood Red’, which can also be grown as a bulb onion, as well as traditional white spring onions. ‘Guardsman’ is a mild-flavoured spring onion with strong, straight stems, and ‘White Lisbon’ is a popular variety, ideal for containers. Seeds are also available in mixes of both red and white types.

Spring onions can be sown outdoors this month in small batches to provide continuous harvests throughout summer and into autumn. Sow seeds thinly at a depth of 1-2cm in a sunny spot, in fertile, well-drained soil. Rows should be spaced 10-15cm apart. Water spring onions in hot periods or when soil becomes dry, paying particular attention to plants in containers. Spring onions are toxic to pets if eaten.

• How to grow spring onions

Runner beans

Runner beans are prolific croppers, particularly in cooler, wetter summers, and their attractive flowers (a range of white, red, salmon and bicoloured) brighten up the vegetable patch. Plants sown in mid- to late spring can be transplanted into the garden now, and seeds can be sown outside this month too. Choose a warm sheltered spot and provide sturdy support with canes in a wigwam. Sow two seeds 5cm deep at the base of each cane. If both germinate, remove the smaller seedling and tie the new shoots of the remaining plant to the cane to help them begin to climb.

‘Snowstorm’ and ‘White Lady’ have pure white flowers that are less prone to being eaten by birds than red flowers and both produce delicious beans. With her unusual salmon-pink blooms, ‘Sunset’ is a delicious heritage bean, and ‘Black Knight’ combines red flowers with eye-catching pods that mature to a deep purple. ‘Painted Lady’ is an excellent bicoloured variety with red and white flowers, and ‘Tenderstar’ has red and pink flowers that develop, as the name suggests, into stringless pods with a soft texture. If you don’t have much space, try compact varieties like ‘Hestia’ or ‘Jackpot’ which only grow to 45-50cm in height and produce bumper harvests in containers. Beans and pods must be cooked before eating.

• Five of the best runner beans to grow
• How to grow vegetables in pots

Carrots

We always look forward to unearthing the first carrots of the season, and with so many choices there are always new varieties to try out. Classic orange carrots such as ‘Norfolk’ and ‘Autumn King 2’ are a must, but it’s fun to experiment with different colours too. The long, sweet roots of ‘Yellowstone’ brighten up any meal, and ‘Purple Haze’, another of our favourites, has deep purple skins with a surprise orange centre when sliced. For a paintbox of carroty colours, ‘Rainbow Mix’ is a striking combination of red, orange, yellow and purple roots, all with subtly different flavours.

Early carrots like ‘Adelaide’ and ‘Early Nantes’ sown in spring should be ready to harvest this month, and maincrop carrots can be sown outside now for harvests later in the season. Sow seeds in a 1cm deep drill in well-prepared soil, making sure as many stones are removed as possible to avoid roots forking. Sow sparingly to avoid the need to thin seedlings which risks attracting carrot root fly. You can also protect carrots by erecting a barrier more than 50cm high which will prevent the flies accessing the plot. Some varieties like ‘Flyaway’ and ‘Maestro’ are more resistant, so these are good to try if carrot root fly is a problem in your garden.

• How to grow carrots

Growing Greener

To provide continuous cropping and avoid gluts, sow vegetables like lettuce, beetroot and spinach successionally over the next few weeks. Small sowings can be made every 10-14 days, but timings vary depending on the type of crop and how quickly it matures as weather conditions change.

You don’t need a vegetable plot or raised beds for successional sowing – you can sow little and often in pots too. Radishes, salad leaves, rocket and round carrots such as ‘Rondo’ and ‘Paris Market 5’ are particularly suited to container growing.

• Get the best from veg in pots

What else to sow in June

• Vegetables: radish, beetroot, French beans, summer squash, pak choi, Florence fennel
• Flowers: honesty, foxglove