Roadside daylilies are the species that is invasive, so we'd recommend not trying any more of those. Hybrid daylily cultivars tend to be fine, though of limited benefit to butterflies as very few visit their flowers, and none use the foliage for caterpillar food. Black-eyed Susans tend to be fairly drought-tolerant, so we're surprised that they struggle. Any new planting, even of species known for good drought tolerance, should be watered as needed for the first 1-2 years it's in the ground in order to get established, so perhaps some young plants didn't persist well if they weren't irrigated enough. The fact that this summer (and even some of last year) was in a state of drought likely didn't help.

Do deer visit that part of the yard to browse? If so, that might considerably narrow-down a list of candidates to plant, unless they can be protected with fencing. Otherwise, we'll assume that deer are not an issue. Rabbits can be problematic, but we have fewer resources for rabbit-resistant plants to consult, and often they avoid a similar palette of plants that deer do.

Does the soil seem to drain well after heavy rain? Slopes may seem to be exceptionally well-drained, but that's not always the case depending on soil type, how it was moved and compacted during construction of the neighborhood, and if there are pockets of stone or other obstructions to drainage belowground.

It sounds like the site has full sun in summer? (Full sun is 6-8 or more hours of direct light.) For the list below, we'll assume that is the case.

Including host plants (those the adult butterfly lays eggs on for the caterpillars to eat) will help to attract butterflies and keep them in the area to reproduce. Some host plants for butterflies are not necessarily showy, and some are decent-sized trees and shrubs, but we'll include a few of the more compact options if you want to try them. It can take time for a local butterfly population to find them and start using them, so don't be discouraged if you don't see anything chewing on them for a year or two. Rarely are host plants those that the same adult butterflies will also visit for nectar, but sometimes there is overlap.

Below are some ideas for species to consider trying, with some being more aggressive than others in their growth habit. Botanical names are in parentheses, and use can use those to look up a plant's appearance and attributes. Those that attract butterflies also often attract other pollinators like bees (and sometimes hummingbirds). Use a variety of bloom times and flower shapes (flat clusters, upright spikes, daisy-like, etc.) to draw the widest range of butterflies throughout the season. A mixed-species planting will also add more seasonal aesthetic interest, plus be more resilient in the face of weather challenges or a future pest or disease issue. More information about pollinator gardens and links to garden design ideas can be found on the linked page.

As a generalization, many plants whose flowers tend to be popular with pollinators belong to the aster and mint plant families.

Nectar sources:

• Common Milkweed (Asclepias syriaca)
  native; can spread aggressively, so give it space to form a clump several feet across
• Butterfly Weed (Asclepias tuberosa)
  native; much more dainty than its relative above, and does not spread; tap-rooted, so avoid moving them once planted
• Hyssop (Agastache foeniculum)
  North American native, but not locally native; can spread into a clump two or so feet across, but might not if it doesn't have enough moisture; long-blooming
• Button Eryngo (Eryngium yuccifolium)
  native; Yucca-like foliage with interesting greenish-white flowers (not colorful, but still adds variety and structure to the mixed-flower garden)
• Joe-Pye Weed (Eupatorium, some renamed Eutrochium, several species)
  several species are native; other than a couple dwarf cultivars, most grow tall, so are best used as a backdrop where they won't block a view
• Ironweed (Vernonia noveboracensis, plus other species and hybrids)
  noveboracensis is locally native, and others are native in North America; grows tall, so good to have as a backdrop where it won't block a view; some varieties are shorter and mix well with other low or mid-size perennials
• Purple Coneflower (Echinacea purpurea, Echinacea tennesseensis, and a few other species)
  North American natives, but not in Maryland; avoid hybrids and cultivars with extra petals since they don't provide as much, if any, benefit to pollinators
• Brazilian Verbena (Verbena bonariensis)
  non-native, and can seed around a bit (the original plant may act like an annual and die off each winter, but seedlings generally repopulate the area on their own), but it's not invasive; long bloom period
• Narrow-leaved Mountain-mint (Pycnanthemum tenuifolium)
  native; all Pycnanthemums are pretty popular with pollinators, but not all have the same degree of drought tolerance...this one seems to be better than average, and there may be others in the group to try also
• Asters (many species, in several different genera)
  many native, though not all are equally drought-tolerant
• Catmint (Nepeta)
  non-native; long-blooming
• New Jersey Tea (Ceanothus americanus)
  native shrub; sometimes hard to find at garden centers

Host plants:

• Common Milkweed and Butterfly Weed (Monarch butterflies use other Milkweeds too, but these two are the most drought-tolerant local natives)
• Asters
• Field Pussytoes (Antennaria neglecta)
  native; creeping groundcover 
• Eastern Redcedar (Juniperus virginiana)
  native; there are shrubby, dwarf cultivars that can also add winter interest and foliage color (they're typically blue-gray)
• carrot-family herbs (parsley, dill, fennel)
  non-native, but probably more reliably in hot dry sun than the native host plant alternative Golden Alexanders (Zizia aurea)

Miri