The Alpine House at RHS Wisley is my favourite place of all to look for the most amazing little flowers.
Many true alpines, which naturally grow at high altitudes, flower in spring and early summer and so I have been visiting every February until May for the last three years to admire little flowering bulbs such as fritillaries crocuses or perennial hepaticas. Their flowers are usually very small so it is best to photograph them armed with a macro lens such as Nikkor 105mm f/2.8g macro and Zeiss Macro Planar 100mm f/2. To get closer to the plants I used a bean bag as tripod was a bit cumbersome in a small greenhouse. I guess even a longer macro lens would be beneficial here - the flowers can be really minute. Magnified, they let us enter some truly enchanted territories. Patel and delicate is how I see them and so I try to paint them with my lenses.
Leucocoryne
Leucocoryne vittata
Oxalis versicolor
Ipheion uniflorum 'Charlotte Bishop'