Eco way to protect my shaded roses from whitefly

I watched Monty Don this week planting fennel, ammi magus and asters to encourage the parastic wasps that feed on white fly. My roses are planted in a North facing garden in clay soil that is mostly shaded. Can anyone suggest what plant would grow there to encourage the wasp? (Encarsia formosa I think) Thank you all!
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Slightly off topic but garlic boiled with water and sprayed once cool has worked for me here, if it's good enough for the Rose Garden at Buckingham Palace, it's good enough for me
Oo stinky but sound! Thanks I'll have a go
Indeed
I get told off for making the kitchen stink!