I have had a problem for a few years now. In my garden, there's a rock garden which was built before we came to this house. It's very authentic. Anyway, there are three levels and not much soil in it (due to some large rocks) and most importantly, a big pine tree on the top. So it's quite a shady area down under.

My plan used to be planting astilbe and hostas under the pine tree. They grew poorly and never took off. It's actually a dry shade, so they suffered a lot. Their leaves turned brown in summer despite watering, there's been five years and none of them grew. There's been much root competition and probably very little soil. There is a lonicera brownii growing by the wall and it just hasn't grown much in more than 5 years! I have some spring bulbs planted too - narcissus, eranthis, corydalis solida, scilla, convallaria, crocuses, chionodoxa, puschkinia, brodiaea and galanthus. There are also some cyclamen, anemone lipsiensis, anemone nemorosa 'Royal Blue' and hepatica.

On the lover levels, there are campanulas (portenschlagiana, poscharskyana, pulloides G.F. Wilson, cochleariifolia, cochleariifolia blaue taube), which I rely on mostly. Then there are some erodiums (Bishops Pink, Bishops White), two geranium cinereum (the most slow growing of them all), two geranium Jolly Jewel, sysirinchium, sedum kamtschaticum and cauticola.

This year I planted solomons seal, corydalis Craigton Blue, lamprocapnos, doronicum, oxalis obtusa, hirta and adenophylla which went summer dormant.

But the problem persists: under the pine tree only hostas, tiarella, pulmonaria and epimedium would grow. I know geranium macrorrhizum, heuchera, vinca, lamium and liriope would do it but they are planted somewhere else. I'm also growing corydalis lutea and corydalis ochroleuca from seed. So this year I bought some seeds of spigelia marilandica and germinated them successfully. There are many growing now and I really hope they'll get established. I also bought a hardy begonia (begonia grandis). Has anyone had any experience growing these two? Do they cope well with root competition? Do they tolerate drought? At least more than astilbe? It's been hard to give up on astilbes but they are just too fussy and sensitive for this situation.