Diarmuid Gavin: Tender perennials take work to grow - but they're worth it
We love to grow colourful plants in our gardens through the summer months. Reliable hardy perennials, such as lupins, delphiniums and myriad others, have beautiful flowers that often last the entire summer and into autumn. These are just some of a huge range of colourful plants that can be kept in the ground all year round thanks to our temperate climate, and the lack of extremes of hot or cold, wet or dry which we enjoy.
Using tender perennials - which are more sensitive to cold and frosts - outdoors takes some work. Many, such as marguerites, pelargoniums, fuchsias and osteospermums, are instantly recognisable favourites.
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They flower year on year but need to be taken indoors for the winter. However, the rewards for the extra effort it takes to grow them can be magnificent.
The easiest method of using tender perennials is to plant them in pots, so you can place them outdoors on the patio or tuck them in between plants to fill gaps in your border. You can also plant them in the ground and dig them up in autumn or take cuttings.
Below I have listed some of my favourite tender perennials in the hope that they will inspire floral creativity in your gardens!
Brugmansia (pictured), or datura as they used to be called, are quite spectacular with their bold trumpet-shaped flowers, giving rise to their common name, angels' trumpets. The flowers come in white, red, yellow and orange, can be up to 8in in length, and are often deliciously night scented. They can be prone to red spider mite, a common pest of warm, dry greenhouses. This causes speckling on the leaves and sometimes the leaves dry up completely. Biological controls which involve releasing predatory spiders are very effective, or you can use organic sprays as well. Hard prune at the end of growing season and water sparingly over winter indoors. Take note: all parts of this plant are poisonous so please handle with care.
While there are many hardy varieties of fuchsia (pictured left), a lot of our favourite cultivars for hanging baskets and pots are half-hardy and will need to return indoors in winter. Cut back their growth by a third for their winter dormancy. In summer, they drip with gorgeous blossoms; pinch out tips when they are growing to make plant bushier and keep dead-heading these beauties all summer to keep the flowers coming. Regular liquid feed will help power the flower supply. 'Swingtime' is good trailing one for hanging baskets, with a big white frilly skirt. 'Blacky' has larger than usual blooms with lovely dark petals. I also like the delicate white ones like 'Annabel', enhanced with soft pink tints.
3. Marguerite daisies
These are one of the most cheerful plants - a bit like oversized lawn daisies. Now also available in zingy pinks and yellows, Marguerite daisies (argyranthemums) will brighten up bedding schemes or can look very elegant when trained as a standard with a spherical head of flowers. But don't throw them away at the end of summer! Overwinter indoors but if this is in a garage, the temperature mustn't go below 5˚C. They can get a bit leggy over time, so it's worth trimming them back at the end of summer. Alternatively take cuttings and maintain these at 7˚C.
Salvias vary greatly in their hardiness and all make great garden plants. Depending on your region, you may be able to get away with cutting them back in autumn and covering with a good layer of mulch. I wouldn't risk doing this with salvia discolor, the Andean silver-leafed sage, which is a particularly beautiful tender variety with a striking contrast between the almost black flowers against the pale, mint-green foliage.
I've lost some chocolate cosmos trying to overwinter it in the garden. It simply didn't survive the cold, wet winter, so my next one will definitely be coming indoors at the end of the growing season!
Tender perennials are good candidates for propagation via cuttings. Start taking softwood cuttings of pelargoniums, petunias, bidens and fuchsias now and during the summer, and towards the end of summer gather your semi-ripe cuttings of penstemon, salvias, and marguerites.