June is the month to watch out for the Large Skipper butterfly on Sweet William, Virginian Stock or Candytuft.
I have recorded Large White and Small White, Meadow Brown and Speckled Wood, Painted Lady, Red Admiral and Small Tortoiseshell in the garden this month.
You might also see Green-veined White or Orange Tip, Holly Blue or Common Blue, Small Copper, Comma or Peacock.
The Alliums and Chives with Hesperis matronalis were flowering at the end of May 2004 in my back garden and have attracted butterflies in June in past years. My Thyme plants in the front garden were also a mass of flowers.
Sweet Williams were just coming into flower at the start of June.
A number of shrubs, both large and small, are worth watching: Lavender, Hebe, Escallonia, Cotoneaster, Ceanothus and Buddleia alternifolia. All of them have had butterflies feeding on their flowers in June.
My Verbena bonariensis will start to flower this month.
If you have sown Virginian Stock or Candytuft seeds, then watch those plants when they begin flowering. I have recorded butterflies on all those plants during June.
However, there are other butterfly attractors that are in flower like Pot Marigold & Red Valerian and some that are in bud like Field Scabious.
It should also be safe to buy and plant out summer bedding like French Marigolds.
I've also produced an overview of the butterfly year and there's a list of butterflies flying each month on my calendar page.