Posted: 14/06/2015 at 21:06
I think maybe something like a cardoon would fit well if you wnat something herbaceous but architectural - http://www.finegardening.com/cardoon-cynara-cardunculus
or you could try something like a cherry tree - Prunus ilicifolia ssp. lyonii likes alkaline soil and will produce edible cherries.
If you want a shrub, look at ceanothus griseus Yankee Point which has small glossy leaves and a cloud of deep blue flowers or cornus alba sibirica which will give you bright red stems in winter, white flowers in early summer and good autumn foliage. You could also go very formal and plant a yew and cut it to shape - square column, round pillar, pyramid, cone or whatever you fancy as it grows.