Showy milkweed Asclepias speciosa. ( Terry Glase/Lady Bird Johnson Wildflower Center)

Milkweeds are not the most spectacular of flowering perennials, but they can look highly effective as fillers and textural foils in plant combinations. They are a must in any sunny herbaceous garden where the gardener wants to attract monarch butterflies.

Three or so species are typically found in home gardens, but others deserve to be grown as well. As a group, they have two things against them: They can be hard to find and there’s that word “weed” in their name.

They are wild plants, growing on disturbed land, and some species will spread if unchecked, but their “weed” label is for the most part a throwback to an age when native flora was undervalued and naturalistic gardens were generally unknown.

Some milkweeds will probably never be valued garden plants, but it is interesting that a dozen species are known to grow in the Mid-Atlantic.

Asclepias verticillata. (James Gagliardi/Smithsonian Gardens)

Here are ones of particular value to gardeners who want to support monarchs and other pollinators:

1. Butterfly milkweed (Asclepias tuberosa): This is grown for its clusters of orange flowers, which appear in late spring and early summer. They develop into showy seed pods that break open to reveal seeds with silken hairs. It grows three feet high and two feet across and prefers sun to partial shade. Avoid planting them in heavy wet soil.

2. Swamp milkweed (Asclepias incarnata ): This will take wet soil, as its name suggests, though it doesn’t need it to flourish. Plants bloom later than butterfly milkweed, and the flowers are a pale to deep rose pink. A variety named Ice Ballet has creamy white flowers. The plant will grow to four feet tall and two feet across.

3. Whorled milkweed (Asclepias verticillata ): This variety has fine leaves and small, white flower clusters that appear in early summer. It’s resistant to deer browsing but also toxic to livestock. It grows to three feet high by two feet across.

4. Common milkweed (Asclepias syriaca ): This is the coarsest of milkweeds and the one most considered a genuine weed by farmers for its ability to form invasive clumps by underground runners. This same quality makes it great for holding soil banks together. Colonies grow to six feet tall and just keep spreading. The flowers appear in June as dull purple balls.

5. Purple milkweed (Asclepias purpurascens ): This deserves more use but is hard to find because of poor seed germination rates. It forms handsome, spreading clumps five feet tall, but by late season it suffers from weevil damage.

6. Balloon plant (Asclepias or Gomphocarpus physocarpus ): This is a tropical, non-native annual milkweed grown as a garden curiosity, though monarchs feed on it. It is grown for its size — six feet tall by late summer — and its lime green, spiky seed pods.

7. Tropical milkweed (Asclepias curassavica ): Tropical milkweed, sometimes called blood flower, is not a native milkweed, nor is it hardy in the Mid-Atlantic. It may self-seed here. It grows to three feet tall and two feet across, with bright red-orange flower clusters. It is attractive, but has its ecological detractors.

Where to find milkweed

Obtaining milkweed for the garden can be challenging. Even if you have a friend with milkweed to spare (don’t collect from the wild), established plants are deep-rooted and won’t move well.

Seed may be stubborn to germinate and may need a period of cold treatment.

Another consideration: Plants at garden centers may have been treated with pesticides that could harm feeding caterpillars. Plants that have been sprayed with contact insecticides will produce fresh, untreated growth, but plants raised with systemic pesticides such as neonicotinoids will remain toxic to monarch larvae. Ask what pesticides have been used in growing the plants.

These specialty nurseries and native plant groups sell milkweed plants, typically the swamp milkweed, common milkweed and butterfly milkweed. Check hours and plant availability before setting out.

→Nature by Design

300 Calvert St., Alexandria. 703-683-4769.

→Hill House Farm and Nursery

631 Scrabble Rd., Castleton, Va. 540-937-1798.

→Earth Sangha

Franconia Park, entrance at the end of Cloud Drive, Springfield. 703-764-4830.

→Watermark Woods Native Plants

16764 Hamilton Station Rd., Hamilton, Va. 540-441-7443.

→Abernethy and Spencer

18035 Lincoln Rd., Lincoln, Va. 540-338-9118.

→Loudoun Wildlife Conservancy

The conservancy is holding a milkweed plant sale Sunday at 12:30 p.m. at Morvern Park, 17263 Southern Planter Lane, Leesburg. 703-777-2575.

→Chesapeake Natives

The nonprofit nursery will hold a sale (nectar plants and some common and butterfly milkweeds) Sunday 10 a.m. to 2 p.m. at Rosaryville State Park, 9640 Rosaryville Rd., Upper Marlboro. 202-262-9773.

→Monarch Watch

The organization sells 32-plug flats of milkweed, maybe too many for one garden but enough to share with others. 888-824-4464. www.monarch

→Herring Run Nursery

Plant sales are staged in the maintenance area of the Mount Pleasant Golf Course in north Baltimore, 6131 Hillen Rd., Baltimore. This weekend and next, 10 a.m. to 3 p.m. Four species available. 410-254-1577.  

— Adrian Higgins