As we approach the time when we can guarantee that there will be no more frost, I thought that I should like to share with you some of my favourite exotic plants, some are hardy, most are not but all add that extra 'oomph' to any planting scheme.

I shall expound on some of the perennials that I would not wish to garden without, seed grown varieties can wait for another day.

Abutilons first. We have had the variety 'Patrick Synge' growing on a south-facing house wall for the past seven years, a showy variety with medium sized, gorgeous orange flowers from a red calyx. It makes a plant around 3 metres (12 feet) tall and I think that after our current cold winters, we can safely say that it is hardy.

It is a cross between the hardy A. Megapotamicum and a large flowered tender variety and takes on the best qualities of both parents. Abutilons are always worth trying in a sheltered position. When they become too large and unwieldy, take a cutting or two and back your luck - sometimes Dame Nature will surprise you!

The garden here would not be what it is without our vast collection of succulents, especially Aeoniums, most famously A. Zwartkop which translates as 'Black Head'. These we bed out in large quantities for the summer, grouped together they make quite a spectacle but, they are definitely not hardy. On several occasions I have left one or two out throughout the winter but alas, they are either reduced to a rather smelly mush or they look so disgusting that no one would wish to look at them at all!

While on the subject of succulents, there is one that has proved itself to be hardier that we could have hoped for. Aloe striatula began life with me as an indoor pot plant. I was going to throw it out because it had become rather old and decrepit when Graham said he would plant it in the Desert. That was some eight years ago and although it has taken quite a hit from frosts recently, it is still there. The year before last it suffered badly when all of its top growth was killed by sharp, prolonged frosts. However, from the rootstock below ground new growth emerged, hopefully this will prosper once more.

Amicia zygomeris is, like its name, a strange plant that fascinates and I think will continue to do so. I have yet to get it through a winter although in truth I have only been growing it for three years and recent winters have been cruel. Last year I planted three plants in the Diamond Jubilee Garden Walled Garden and gave them a substantial winter mulch as protection from frost, only time will tell if I have been successful in my ministrations.

This is a drought-resistant shrub that hails from Mexico with rather lovely bluish pinnate foliage, producing yellow pea-like flowers in late summer but the oddest thing about it is the strange, purple-flushed, plump stipules at its leaf nodes. Children of all ages will love popping them!

Arundo donax var. versicolor has been hardy here for years, although the books would have us believe otherwise. This is a stunningly variegated version of the giant reed grass. I find that to get the very best variegation, the plant must be seen before buying as there are some poorly variegated varieties in commerce, the best have lots of white in their variegation which together with the pale grey-green on the leaves looks stunning. It is a tall plant that will make 2.5 metres, (8 feet) in a single season, the best time to buy is in spring just as the foliage is emerging.

Bassia scoparia probably won't mean much to gardeners today but if I say 'Summer Cypress' or 'Burning Bush' maybe people will remember this as a plant that used to be widely grown as a 'dot' plant for summer bedding. Why not use it in groups where you can appreciate its fine and bright green foliage like that of a miniature conifer which flares up into crimson shades in the autumn?

Begonias have the reputation of being vulgar and so many of them are but there are exceptions. Begonia 'Dragon's Wing' is one such in my opinion; this can be had in pink or white and is like a giant form of Begonia semperflorens, it has the same bright-green shiny foliage that looks almost good enough to eat and grows to around 50 cms X 45 cms, (20 inches by 18 inches). The most useful thing about these begonias is that they will thrive beneath taller growing plants and they love growing in shady spots bringing colour and liveliness to what could otherwise be dull areas of the garden.

Cannas of all kinds are useful, as are bananas for their luscious foliage but we must watch out for cannas today being infected by a virus that causes striations on their leaves. This is seldom fatal but it does weaken the plant, it is recommended that infected plants be destroyed, but…!

My personal favourite has to be Canna 'Phaison', sometimes known as 'Tropicana' or 'Durban'. This has boldly striped leaves in shades of brown, purple and a rich cherry red. Canna 'Striata' runs this a close second with green and yellow variegated leaves too, both varieties flower but this is inconsequential for their foliage is the best reason for growing them.

Dahlias have, and quite rightly so, become very popular in recent years but, I do wish that gardeners would think more about allowing them to have companion plants growing in their midst. Verbena bonariensis is an obvious partner with lemon yellow, pale pink or red dahlias. You could also consider growing some eucalyptus from seed which is very easy, and to interplant dahlias with these seedlings so that their glaucous young growths complement flowers of any hue. You could also try some climbers as well like Morning Glories or the delightful Ipomoea lobata with cream and red flowers shaped like small bunches of bananas.

I thought that it would be easy to whip through this list of plants but, here we are on the letter D and I have run out of space so there will be more next week.