Butterflies require both host plants on which to lay their eggs and provide food for the caterpillars plus nectar plants which feed the butterflies. Most of these plants require a sunny location.
Other elements to include are shrubs for protection; rotting meat, fruit or tree sap or animal droppings; larval food or host plants; wet mud and puddles. This list will get you started.
Trees, Shrubs, and Vines
Abelia
Apple
Blueberry
Butterfly Bush
Caryopteris
Climbing Roses
Currant
Honeysuckle
Lilac
Mahonia
Maple
Mock Orange
Potentilla
Privet
Rhododendron
Spiraea
Sumac
Trumpet Vine
Tulip Tree
Viburnum
Willow
Annuals and Perennials
Agastache
Allium
Alyssum
Aster
Astilbe
Baptisia
Bee Balm
Begonia
Black-eyed Susan
Borage
Candytuft
Catmint
Catnip
Centaurea
Chives
Chrysanthemum
Columbine
Coreopsis
Cosmos
Daylily
Delphinium
Dianthus
Dill
Foxglove
Gaillardia
Goldenrod
Helenium
Heliopsis
Heliotrope
Impatiens
Joe-Pye Weed
Jupiter’s Beard
Lavender
Liatris
Lobelia
Lupine
Mallow
Milkweed
Myosotis
Oregano
Parsley
Penstemon
Phlox
Pineapple Sage
Primrose
Purple Coneflower
Ranunculus
Rock Cress
Rudbeckia
Russian Sage
Sage
Salvia
Scabiosa
Sedum
Shasta Daisy
Sweet Pea
Sweet Violet
Thistle
Thrift
Verbena
Veronica
Viola
Wallflower
Yarrow
Zinnia