P -- good source of pollen
N-- good source of nectar
* -- excellent for bees

Hamamelis P Hamamelis, commonly known as witch hazel, produces delicate blooms with intoxicating scent in the depths of winter
Hebe *N Veronica, huge range of half-hardy shrubs and woody perenials.
Hedera *NP Ivy. Important source of nectar and pollen in late autumn. Birds love the berries and nesting places.
Helianthus NP
Helleborus NP begin to flower as shrubs such as Camellia open, and as the spring bulbs like snowdrops
Hydrangea NP
Hypericum *P Rose of Sharon or St. John's Wort. Easy shrub with large cup-shaped golden yellow flowers carried in profusion June to September.

 

Iberis NP commonly known as candytufts. Used in Homeopathy for nervousness and muscle soreness
Ilex NP Commonly known as Holly
Impatiens *NP Busy Lizzie and Balsam. Lovely flowers in a large range of bold colours, June to September

 

Kniphophia *NP Red Hot Poker, Hardy perennial with spectacular firey 'torches' of flowers June to October.