Best milkweed for monarchs

The spring migration of the monarch butterfly has already begun and these butterflies will reach Kansas in the upcoming weeks. Many local gardeners are very interested in supporting monarch butterflies by planting milkweed.

Milkweed and monarchs truly have a unique and fascinating relationship. Milkweed is toxic to other insects due to the network of pressurized latex canals in the leaves that contain a lethal brew of poisonous cardenolides. But monarch caterpillars have learned to cut milkweed leaf veins to neuter these chemical defenses. The caterpillar will cut the mid-vein on the leaf before feeding to prevent the latex from leaking out. In addition, caterpillars also have the ability to sequester or store up these cardenolides for their own defense. The specific coloring of both caterpillar and butterflies indicate to other predators that they are toxic to consume.

It is estimated that an additional 1.8 billion stems of milkweed are needed to conserve our monarch butterflies and new research has helped us hone in on the best milkweed varieties to plant.

Which milkweeds recruit and support monarchs?

Recent research from the University of Kentucky tested eight types of milkweed and found that all eight were suitable for monarchs and supported similar larval growth.

The most attractive milkweed to egg-laying monarchs were three relatively tall varieties of milkweed that have broad leaves. These were swamp milkweed, common milkweed, and showy milkweed. Tall varieties of milkweed are more easily located and utilized by the butterflies and the broad leaves provide plenty of egg laying space.

In general the size and type of a butterfly garden will dictate which milkweed varieties are best to use.

Large gardens with open space

For gardens with plenty of space in here in Central Kansas, the best milkweeds to plant are common milkweed or showy milkweed. Monarchs use visual cues such as leaf shape to locate milkweed and these taller varieties with broad leaves are easier for the butterflies to find as they migrate. Both can spread by rhizomes and will form colonies over time.

Small gardens

The best milkweeds for smaller gardens include: butterfly weed, green milkweed, prairie (Sullivant’s) milkweed, and swamp milkweed. These varieties tend to be better at staying where they are planted rather than spreading aggressively.

Avoid tropical milkweed

Tropical milkweed (Asclepias curassavica) is a beautiful plant and easy to grow, but it is a problem in temperate regions where it does not die back as soon as other milkweed varieties. Milkweed dieback is a signal that monarchs use to migrate to overwintering grounds. Monarchs may be fooled into continuing to use this milkweed and may fail to migrate at the appropriate time. While not completely understood, tropical milkweed is also linked to monarchs abandoning their normal fall migration to Mexico. When a cold snap occurs, the monarch adults, eggs, and larvae remaining on tropical milkweed will not survive and this was directly observed by scientists in Oklahoma in 2019.

Use multiple milkweed species when possible

There is evidence, at least from field cage trials that monarchs may lay more total eggs when several milkweed species are available than when they are restricted to a single species. Planting several species of milkweed, including taller and shorter varieties is a good idea when developing monarch butterfly habitat.

Other great nectar and or host plants to include in butterfly gardens in Kansas

Newer varieties and hybrids tend to have reduced nectar supplies as they are often selected by plant breeders for other features. When possible choose standard varieties that are tried and true.

Perennials	Bloom Color	Bloom Time	Size
Aster (Aster)	Pink, blue, purple	Late summer – fall	12 – 36”
Bee balm (Monarda)	Pink, red	Early summer	24 – 36”
Black-eyed Susan (Rudbeckia)	Yellow	Mid – late summer	18 – 36”
Blazing star/gayfeather (Liatris)	Purple	Mid- summer	24 – 36”
Catmint (Nepeta)	Blue, pink	Summer	1 – 3’
Coneflower (Echinacea purpurea)	Purple, white	Mid- summer	24 – 36”
Coreopsis (Coreopsis)	Yellow	Early summer	12 – 24”
Goldenrod (Solidago)	Yellow	Late summer – fall	18 – 36”
Joe Pye weed (Eupatorium)	Pink, purple	Late summer – fall	3 – 6’
Milkweed (Asclepias)	Orange, yellow, red, pink	Summer – fall	24 – 48”
Phlox (Phlox paniculata)	Pink, purple, white	Mid- summer	24 – 36”
Pincushion flower (Scabiosa)	Pink, blue	Summer	12 – 18”
Sedum, tall varieties (Sedum)	Red, pink	Late summer – fall	18 – 24”
Sunflower	Yellow	mid-late summer	varies
Yarrow (Achillea)	Yellow, red, pink, white	Summer	12 – 24

Annuals	Color	Size
Globe amaranth (Gomphrena)	Purple, pink, red, white	10 – 18”
Heliotrope (Heliotropum arborescens)	Purple, blue	12 – 18”
Verbena (Verbena. bonariensis)	Purple	24”
Pentas (Pentas lanceolata)	Purple, pink, red, white	18 – 24”
Cosmos (Cosmos bipinnatus)	Pink, white	24 – 36”
French marigold (Tagetes patula)	Yellow, orange, white	10 – 24”
Lantana (Lantana camara)	Yellow, orange, white, pink	Sprawling 24 – 36”
Cosmos (Cosmos sulphurus)	Yellow, orange	24”
Zinnia (Zinnia elegans)	Multicolored	12-24′”

Shrubs	Bloom	Bloom time	Size
Lilac (Syringa)	Purple, blue, pink	Spring	4 – 12’
Mock orange (Philadelphus)	White	Spring	4 – 6’
Butterfly bush (Buddleia)	Purple, pink, red, white	Summer – fall	4 – 6’
Blue mist spirea (Caryopteris)	Blue or purple	Late summer – fall	2 – 3’
Buttonbush	white	Summer	6-12′
Spirea (Spirea)	White, red, pink	Spring – summer	2 – 6’

Herbs	Bloom	Bloom time	Size
Chives (Allium schoenoprasum)	White, lavender	Spring – summer	12 – 18”
Dill (Anethum graveolens)	White	Summer	2 – 3’
Lavender (Lavandula)	Blue, lavender	Summer	1 – 2’
Marjoram (Origanum majorana)	White, pink	Summer	8 – 18”
Oregano (Origanum vulgare)	Pink, white	Summer	18”
Sage (Salvia)	Pink, red	Summer	18 – 24”
Thyme (Thymus)	Pink	Summer	2 – 12”
Fennel (Foeniculum dulce)	Yellow	Summer	2 – 4’