8 Must Have Annuals for the Summer Border

Garden centre benches are full of annual plants right now and when aiming to fill baskets and pots, there’s a broad range to select from. However, if you’re looking for taller plants to combine with perennials in your mixed borders, you may have to seek them out at specialist nurseries or on line – you’ll find some cracking annuals suitable for planting amongst hardier plants to prolong colourful and often fragrant displays throughout summer and up to first frosts.

Annuals are the perfect option for filling a bare patch of ground once bulbs and winter/spring perennials are spent – and if planted out while they’re young and small, there’s little risk of disturbing the dormant growth below them. I’ve picked out eight such annuals that are still available to sow or order now – they’re ones that I’m growing, have grown or would like to grow having seen them successfully planted in other people’s gardens!

  1. Tithonia rotundifolia ‘Torch’

The Mexican sunflower, with its flamboyant velvety petals is a flowering bee magnet! An absolute grafter, it’s perfect for the novice gardener wanting to try growing their own plants as it is so easy to propagate from seed. Tithonia can be sown either in trays up to the end of April or directly into the soil in May -June for July – September summer flowering.

One of Monty Don‘s favourites for setting off purples and blues in a border, this vibrant half hardy annual reaches a height of 1.5 metres, isn’t fussy about soil type as long as it drains well, but does require a position in full sun to thrive. I sow a tray of this gorgeous plant every year – it always performs well.

2. Cosmos

Next up and it’s the fabulous cosmos – what can I say, in flower colour ranging from white, through pastels to rich magenta, no garden should be without it in summer. Cosmos also sports attractive bright green feathery foliage and looks great planted ‘en masse’, in small groups in a cottage border or as cut flowers in a vase.

Another easy germinator, cosmos can be grown under cover from seed, but is also available on line in plug form and is usually available in small pots in garden centres by June. With a height and spread of up to a metre, it thrives in well drained soil in a sunny spot. Worthy of note – it may benefit from staking and deadheading is a must to ensure a long flowering period from June to first frosts.

3. Ammi visnaga

I absolutely love to see billowing cow parsley in the wild, but there’s no way I’m going to introduce it into our garden! A fabulous alternative is ammi, the one pictured, growing at Trentham Gardens last year is visnaga. Sarah Raven adds this plant to her best annual flowers list having interplanted it ‘ with blue, violet and white larkspur with great success’.

At just over a metre in height, seed packs or seedlings are available on line. If using seed, for best results they should be sown in autumn directly where you want them to flower the following summer, but they can also be sown under cover in February/ March for same year blooming. Ammi is a thirsty plant, it prefers a sunny spot and will tolerate any soil type.

4. Nicotiana sylvestris

Although there’s plenty of choice when it comes to nicotiana, where height is desirable in a mixed border the elegant sylvestris is hard to beat. Monty Don waxes lyrical on this highly scented plant when he describes ‘the warm flush of tobacco-plant scent just as the sun is slipping below the tree line is as much a measure of summer as sweet peas, dry grass and tomatoes. The season could exist without these things, but it wouldn’t exist enough‘.

Nicotiana sylvestris can be sown either in trays up to the end of April or directly into the soil in May -June for July – September summer flowering. Online, you should be able to obtain ready germinated seedlings or small plug plants. Growing to an impressive 1.5 m, this plant thrives in partial shade and moist well draining soil.

5. Helianthus annus

Sunflowers must be the easiest plant to grow from seed and I’m sure most of us can recall sowing seeds in our infant school days, competing with classmates to see who could grow the tallest one. But they’ve got more than educational value and many cultivars make worthy additions to the summer mixed border. There’s a plethora of choice today, Sara Raven has a fabulous ‘Vintage’ mix available to grow from seed or as small plug plants and it is perfect in a border or a vase. Pictured is helianthus annus ‘Velvet Queen’, a 1.5 metre variety with lovely rust coloured saucer sized flower heads.

Sunflowers can be sown in pots in early spring or directly in the ground up to the end of May. They will need to be planted out in full sun with a generous helping of organic material and provided with plenty of water on a regular basis. Deadhead regularly for a long display and with taller cultivars, staking is advised.

6. Salvia viridis

Pictured in a wonderful border with lychnis coronaria and calendula ‘Goldcrest’ mix, salvia viridis is a versatile annual clary sage that both compliments and contrasts with a wide range of colours to enhance a mixed or annual border. Unusually, we’re not looking at flowers for colour with this plant, the pink/purple bracts are its attraction.

A shorter annual at approximately 50cm in height, seeds, seedlings and plugs are available in single colour or blends of pink white and purple. Seeds can be sown under cover in early spring or autumn or directly in May for same summer flowering. Clary grows best in full sun, but any well draining soil suits it for a May to September display.

7. Lathyrus odoratus

Perfect for tumbling over an obelisk in a mixed border, sweet peas in any colour combination are fragrant, delicate and very easy on the eye! Widely available as seedlings in garden centres or on line, seeds can be sown in autumn and overwintered for early displays, or in early spring.

Sarah Raven has a really useful advice sheet to ensure success with sweet peas; her tips include assisting germination by soaking the seeds prior to sowing, not allowing the seedlings to get pot bound in their root trainers or ‘they will never be quite the same again’ and ensuring they are planted out with plenty of organic material. To give them a good start in life, Sarah advises to ensure they’re tied into a frame at a very young stage, ‘never letting them flop around’ and to feed regularly for the first month with a tomato or comfrey preparation. Lastly but not least, promote repeat flowering by picking and dead heading continually, if you don’t flowers will be sparse and the plant will become leggy.

8. Antirrhinum ‘Royal Bride’

I’m not a fan of snapdragon mixed trays or seed packets, but as single colour cultivars, they’re very effective planted towards the front of a border. I particularly love ‘Royal Bride’ which grows to approximately 60cm in height and is snowy white.

These half hardy annuals can be obtained as seeds, seedlings or plug plants. Seeds should be sown under cover in early spring or in late summer for over-wintering – the latter may be troublesome in cold conditions and they would need protection. Flowering from June until first frosts, snapdragons require moist well drained neutral to alkaline soil in full sun. You should also dead head to a pair of leaves to ensure good repeat flowering.

Annual propagation for summer borders is so rewarding – happy growing!