Source: The University of Massachusetts Extension's Drought Information Site.

Deciduous trees:
Acer griseum (paperbark maple)
Carpinus caroliniana (American hornbeam)
Cornus kousa (Kousa dogwood)
Cotinus obovatus (American smoketree)
Crataegus phaenopyrum (Washington hawthorn)
Ginkgo biloba (maidenhair tree)
Halesia tetraptera (Carolina silverbell)
Koelreuteria paniculata (goldenrain tree)
Liquidamber styraciflua (American sweetgum)
Magnolia x loebneri (Loebner hybrid magnolia)
Malus species (crabapples)
Platanus x acerifolia (London planetree)
Quercus species (oaks)
Sophora japonica (Japanese pagoda tree)
Tilia species (lindens)
Ulmus parvifolia (lacebark elm)
Zelkova serrata (Japanese zelkova)

Shrubs:
Aesculus parviflora (bottlebrush buckeye)
Arctostaphylos uva-ursi (common bearberry)
Aronia species (chokeberries)
Buddleja davidii (butterfly bush)
Calluna species (Scots heathers)
Chaenomeles x superba (Japanese flowering quince)
Clethra alnifolia (sweet pepper bush)
Comptonia peregrina (sweet fern)
Cornus mas (Cornelian cherry)
Cotinus coggygria (smoke tree)
Cotoneaster species (cotoneasters)
Erica species (heaths)
Exochorda racemosa (pearlbush)
Forsythia species (forsythias)
Hydrangea paniculata (panicled hydrangea)
Hypericum prolificum (shrubby St. John's wort)
Itea virginica (Virginia sweetspire)
Myrica pensylvanica (bayberry)
Philadelphus coronaries (mock orange)
Potentilla fruticosa (shrubby cinquefoil)
Rhus species, especially R. aromatica (fragrant sumac), R. copallina (dwarf sumac), and R. typhina (staghorn sumac)
Rosa rugosa (rugose rose)
R. virginiana (Virginia rose)
Spiraea species (spireas)
Syringa species (lilacs)
Vaccinium angustifolium (lowbush blueberry)
Viburnum dentatum (arrowwood)

Evergreens:
Abies concolor (white fir)
Cedrus libani subspecies atlantica (Atlas cedar)
Cephalotaxus harringtonia (Japanese plum yew)
Chamaecyparis pisifera (Sawara cypress)
Juniperus species (junipers)
Ilex crenata (Japanese holly)
I. glabra (inkberry)
I. x meserveae (Meserve holly)
I. opaca (American holly)
Picea species (spruces)
Pinus species (pines)
Taxus species (yews)
Thuja occidentalis (eastern arborvitae)

Vines:
Aristolochia macrophylla (Dutchman's pipe)
Campsis radicans (trumpet creeper)
Clematis Montana (anemone clematis)
Lonicera sempervirens (trumpet honeysuckle)
Parthenocissus quinquefolia (Virginia creeper)
Wisteria frutescens (American wisteria)

Perennials:
Asclepias tuberosa (butterfly weed)
Agastache foeniculum (anise hyssop)
Amsonia species (bluestars)
Artemisia species (wormwoods)
Aster species (asters)
Baptisia australis (false blue indigo)
Coreopsis species (tickseeds)
Dianthus species (pinks)
Echinacea purpurea (purple cone flower)
Echinops ritro (globe thistle)
Eryngium species (sea hollies)
Euphorbia species (spurges)
Gaillardia species (blanket flower)
Geranium macchorhizum (bigroot geranium)
Helleborus species (hellebores)
Hemerocallis species (daylilies)
Hibiscus moscheutos (common rose mallow)
Hosta species (plantain lilies)
Iris sibirica (Siberian iris)
Lavandula angustifolia (English lavender)
Liatris species (gay feathers)
Nepeta species (catmints)
Paeonia species (peonies)
Perovskia atriplicifolia (Russian sage)
Phlox species (phloxes)
Rudbeckia species (cone flowers)
Salvia species (sages)
Sedum species (sedums)
Stachys byzantina (lamb's ears)
Stokesia laevis (Stokes' aster)
Thymus species (thymes)
Verbascum species (mulleins)
Yucca species (yuccas)

Annuals:
Begonia Semperflorens-Cultorum hybrids (wax begonias)
Calendula officinalis (pot marigold)
Canna x generalis (canna lily)
Capsicum species (ornamental peppers)
Celosia argentea var. cristata (common cockscomb)
Cleome species (cosmos)
Gazania rigens (treasure flower)
Helianthus species (sunflowers)
Limonium species (statice)
Nicotiana alata (flowering tobacco)
Pelargonium x hortatum (geranium)
Petunia x hybrida (petunia)
Portulaca grandiflora (moss rose)
Rudbeckia hirta (black-eyed Susan)
Senecio cineraria (dusty miller)
Tagetes species (marigolds)
Verbena species (vervains)

Ornamental grasses:
Calamagrostis x acutiflora (feather reed grass)
Festuca glauca (blue fescue)
Panicum virgatum (switch grass)
Schizachyrium scoparium (little bluestem)