Whereas the majority of the flowering shrubs appear at their best in late spring, our flower borders reach a later climax in July and we can, with a bit of organization, extend this season at both ends. June flowers must be chosen so as not to leave nasty scars of dereliction later on. Such in particular are flamboyant lupins, flag irises,and peonies.
Lupins always look dreadful after flowering, whether you cut them back — subsequent foliage is invariably mildewed — or whether you merely remove their seeding spikes. You may care to try the technique I adopt of treating them as. Sow seed each spring, line out the for the summer, plant them where they are to flower in the autumn and discard the plants after flowering, at the end of June. They can be replaced with late-struck dahlia or with annual seedlings sown in May and brought on in pots or boxes.
Delphiniums can be treated in the same way. From an April sowing they usually flower well in September-October and then again in June, after which bid them farewell. Peonies loathe disturbance but you can grow a late-flowering clematis or an everlasting pea (Lathyrus) behind them, and train its shoots to thread their way through the peony clumps and over their supports.
The rhizomes of the iris require a good baking in the sun, so irises should never be masked and it is better to set a bed aside for them alone ; somewhere that can be enjoyed in its season yet ignored when the irises turn shabby.
However keen you may be on growing a wide range of plants, it is very important to do some massing for effect. Otherwise, your border will be spotty and, in the aggregate, confused. Oriental poppies provide a marvellous splash in late May and June and they need never become a liability. Without detriment to the plants you can cut them to the ground the moment they look tired and interplant them withor cannas.
Phloxes are a powerful border element from early July onwards, with the bulk of them peaking in early August. They are a mainstay among border perennials for those who garden in a cool, wet climate (terrific in Scotland) or on heavy soils. If the spent flower heads of the earlier flowering kinds are removed, the plants will often carry a second crop in September. This is more likely to happen in the south, where the warmer climate allows time for bonus flowerings. Dead-heading will similarly extend your border’s season when applied to many other perennial flowers like Campanula lactiflora. Helenium `Moorheim Beauty’, Salvia nemorosa (Salvia superba).
Some of the best rent-payers are plants with a tremendously long flowering season that need little or no encouragement. Many of the cranesbills are outstanding in this way, especially the chalky pink Geranium endressii, excellent in sun or shade; the cheerful magenta ‘Russell Prichard’, which flowers from May till autumn, spreads into great pools over paving or climbs into its neighbours if taller than itself; and Geranium wallichianum ‘Buxton’s Blue’, which has the same sort of habits but starts two months later.
In a small border, always beware of plants with a brilliant but short season that quickly become passengers. Such is the early, July-flowering Lychnis chalcedonica, and yet I rate its domed heads of brilliant scarlet flowers highly. Also, the beautiful azalea-like flowers of the Peruvian lily. Alstroemeria ligtu hybrids, in shades of pink, apricot and crimson, but just a mess from late July onwards. One solution is to plant a late developer in front of them that will grow up and conceal them when, but only when, they have gone over. One of the most obliging is the 2m (6ft) Verbena a bonariensis, with heads packed with tiny purple flowers. Its season starts in late July and carries on till October. Although it grows so tall I always have some at the front of my border because it is so stemmy that you can see through it if you want to, and really a border that is carefully graded by height is a bit of a bore, like someone who is overtidy in the house.
I have written only of, so far, but my own borders are mixed and include, for variety of habit and length of season, bulbs (starting with snowdrops), , tender bedding plants and, most importantly, shrubs. These last contribute bulk and solidity with a greater air of permanence than is in the nature of herbaceous plants. It is also a good place for shrub roses, those having a double season being especially valued.
The organization of a mixed border requires thought and quite a lot of work; but this is interesting in itself, and nothing is more satisfying than to achieve a result that arouses admiration from friends and visitors whose appreciation you value. The best results always have an appearance of ease and relaxation. That is the art of being professional and is something the amateur can well develop, given enthusiasm, energy and an eye for what looks right.