When time is at a premium, focus on flowers that can look after themselves, whatever the weather, the goal being to grow those that thrive in either wet or baking summers.
I've got a large and varied garden and simply don't have time to mollycoddle everything - I need a lot of toughies as well as the more demanding specimens.
There's nothing new about gardeners being time-poor. In the middle ages, gardeners put their energy into growing veg and herbs, filling in the gaps with anything that grew easily, such as primulas and violas. When the cottage garden emerged in the 19th century, workers focused a little more on pretty plants, but at the end of a gruelling day they can't have had much time and energy for fiddly, time-consuming plants.
There are plenty of species that, to a greater or lesser extent, put on a good show, in sun or shade, with wet, dry or virtually no soil. They produce fine flowers and good clumps of attractive foliage.
Be warned, though. If you choose a plant that survives almost regardless of its surroundings, you'll need to keep a wary eye on it. When describing Alchemilla mollis, garden historian David Stuart commented that it's "hard to have enough of it, till you find you've nothing else". With a generous mass of fine, scallop-shaped pale green leaves supporting sprays of tiny yellow flowers, lady's mantle provides perfect ground cover. It appreciates soil but doesn't need much of it, growing in a gritty path or a ditch.
Like alchemilla, Vinca major - periwinkle - makes excellent ground cover. It does especially well in shadier spots, but tolerates sun or wet, if not soggy, soil. I do like its golden-edged green leaves and long-lasting deep-blue, five-lobed flowers. Lysimachia punctata - loosestrife - is another fine ground spreader that does equally well in full sun or shade. With tall, elegant stems crammed with yellow-cupped flowers, it's a fine specimen plant for any border. In fact, all lysimachias are trouble-free - but they are prone to spread.
Whether you go for tough ground-smothering plants or more controllable seed dispersers, such as aquilegias, be sure to factor in a good succession of flowering times. Little beats the almost fragile beauty of aquilegias, with their endless colour variations - perfect for early summer. If they start to dominate a border or produce any colours you don't much fancy, simply remove them. One splendid cultivar is Aquilegia caerulea. You could never have enough of this exquisite plant, with its pale blue sepals and white petals.
Astrantia major is another early summer beauty that, when deadheaded, provides a second flush in August. With fine, papery bracts, its flowers on tall multi-stemmed stalks take some beating. A rival to astrantia is perhaps hemerocallis, the day lily. Although each wonderful trumpet-shaped flower is short-lived, each plant keeps flowering for much of July and August.
A plant's foliage is perhaps more important than its all-too-brief flower. Geranium macrorrhizum has deep pink, pale pink or white flowers and its attractively scalloped leaves are nearly evergreen, providing a lasting backdrop. In autumn the leaves turn a wonderful range of wine red, so provide a bonus. Polemonium caeruleum, Jacob's Ladder, makes an interesting addition to any border. As with polemonium, foliage is a major attraction for Meconopsis cambrica, Welsh poppy. And, like polemonium, meconopsis seeds generously.