There are a number of families that produce genera with similar-looking flowers, but different flowering seasons. The daisy family, for example, can field a team from late winter until late autumn, and in a number of colours, too. For example, a spring-flowering yellow daisy such as Euryops acraeus could be followed by Ursinia calenduliflora in summer, or a white Shasta daisy (Leucanthemum x superbum) in early summer could precede a white Michaelmas daisy such as Aster `Kristina' in autumn. The idea is less to replace like with like - the garden might become dull and samey if you did - than to perpetuate the atmosphere that each plant grouping engenders.
Some of the best plants to use for this kind of mimicry are the yellow- flowered ornamental peas. They are to be found placed in a number of genera - Colutea, Piptanthus, Genista, Cytisus, Lupinus and Thermopsis - but all have family members with the same clean, golden-yellow pea flowers, which go so well with both scarlet and caerulean-blue flowers, not to mention glaucous green foliage. Even more convenient, these genera generally enjoy the same con- ditions, namely, a light, free-draining soil in full sun.
On the rock garden in spring, Genista pilosa is an obvious choice for spring display; it makes a prostrate, thickly-set, shrub, with bright- yellow flowers, well set off by mid-green, lance-shaped leaves. Before it has finished flowering completely, the baton has been taken up by G lydia, more delicate in appearance, a little taller at 60cm, but with the same spread of 1 metre. (For a slightly different effect, you could substitute G sagittalis, which has masses of short, upright, winged green stems and spikes of dense, small flowers.)
In the mixed border, the shrubby Genista tinctoria (dyer's greenweed) has upright heads of yellow flowers on 60cm tall stems, at the same time as the perennial Thermopsis villosa, the aptly named "Carolina lupin", which has acid-yellow flowers from March to May. The combination of glaucous foliage and yellow flowers is a particularly happy one in thermopsis, prompting the obvious question why it is not grown more widely. Flowering for a long period into early summer is another shrub, Piptanthus nepalensis (often called the "evergreen laburnum"), with leaves composed of three blue-green leaflets, and fresh yellow flowers. This also grows well against a warm wall, and can be trained easily along wires.
For later flowering, I suggest one or two of the larger cytisus and genistas; they are highly suitable for cheering up a shrub border that has gone off since the end of June. Just finished is Genista tenera `Golden Showers', an aptly named arching shrub of grace and delicacy, up to 3 metres tall, with golden, fragrant flowers; still to come is the better-known, and even taller, Etna broom. To me it epitomises the late summer shrub border, although an equally good candidate is "bladder senna", Colutea arborescens, which has large flowers in racemes for weeks and weeks, and grey-green pinnate leaflets, and has the virtue of producing the most intriguing semi-transparent, inflated balloon pods. It grows well in towns, even on poor soils.
If you think that this idea takes too much planning, I suggest you choose Coronilla valentina glauca, a charming, if slightly floppy evergreen shrub, which, if put in a warm sheltered place, will flower practically all year. And, if your soil is poor and sandy, why not gorse, which has been known to flower 12 months through? It's all right, I'm only kidding.Reuse content