border England english flowers garden Great Britain herbaceous mauve nature perennial petals plant red stems summer cultivar daisy flower flowerhead grow head mop natural odd petal unusual yellow Aconitum blue monkshood plants Ranunculaceae spikes tall autumn blooms dahlias heads magenta norfolk perennials purple abundance abundant background carmine colour display many Monarda pink profusion texture everlasting fuchsia Lathyrus peas Sussex sweet diverse diversity flamboyant mixed variety various delphiniums light pale