Learn About Asclepias

How to Sow

How to Sow and Plant

Asclepias may be grown from seed sown early indoors and transplanted outside after frost, or sown directly in the garden in summer, or grown from potted plants.

Sowing Seed Indoors:

  • Sow seeds indoors 6-8 weeks before last spring frost date using a seed starting kit
  • Sow seeds 1/8-1/4 inch deep in seed-starting formula
  • Keep the soil moist at 70-75 degrees F
  • Seedlings emerge in 14-21 days
  • As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
  • Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
  • If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of true leaves before transplanting to the garden so they have enough room to develop strong roots
  • Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning.  This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Sowing Directly in the Garden:

  • In milder areas, sow directly in the garden after all danger of frost.
  • Remove weeds and work organic matter into the top 6-8 inches of soil; then level and smooth. 
  • Sow seeds evenly and cover with 1/4 inches of fine soil. 
  • Firm the soil lightly and keep it evenly moist. 
  • Seedlings will emerge in 14-21 days.
  • Thin to at least 12 inches apart when seedlings have three sets of leaves.

Planting in the Garden:

  • Select a location in full sun with good rich moist organic soil. Asclepias is sensitive to clay soils.  
  • Prepare the bed by turning the soil under to a depth of 6-12, inches removing any debris, and lightly raking as level as possible.
  • The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
  • Plant on a cloudy day or in late afternoon to reduce transplant shock.
  • Dig a hole for each plant large enough to amply accommodate the root ball.
  • Unpot the plant and gently loosen the root ball with your hands to encourage good root growth.  Be careful as asclepias is sensitive to transplanting.
  • Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
  • Use the plant tag as a location marker.
  • Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.

How to Grow

How to Grow

  • Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their germination. 
  • Mulches also help retain soil moisture and maintain even soil temperatures. For perennials, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time.  Always keep mulches off a plant’s stems to prevent possible rot.
  • Careful watering is essential in getting perennials off to a good start. Water thoroughly at least once a week to help new roots grow down deeply. Soil should be damp at about 1 inch below the soil surface. You can check this by sticking your finger in the soil. Water early in the morning to give all leaves enough time to dry.  One inch of rain or watering per week is recommended for most perennial plants. You can check to see if you need to add water by using a rain gauge.
  • Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary.  Good air movement is also important.
  • After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer such as Garden-tone, as higher rates may encourage root rots.
  • “Deadhead”, remove spent flower heads to encourage continuous flowering and prevent seed development.
  • Remove and discard foliage after a hard frost in fall. 
  • In colder regions, apply another layer of mulch (1-2 inches) after the ground freezes in fall. Evergreen boughs (from Christmas trees) provide additional protection. Remove this mulch in the spring.
  • Asclepias does not divide well as it has a tap root. To propagate, wait until the plant seeds itself (in this case do not remove spent flowers) and transplant seedlings when they are young.

Growing tips

Growing Tips

  • Many gardeners do not cut back perennial flower seed heads in the fall, but wait until early spring before the new foliage appears. This provides food for wildlife over the winter.
  • For flower arranging, cut when blooms are 2/3 open.
  • Note that butterfly weed is not the same as milkweed as it does not provide food for monarch butterfly larvae, but the flowers do attract the pollinating adult butterflies for nectar.

Common Pests and Problems

Common Disease Problems

Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves. Spots may appear along the leaf midrib.The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and keeping weeds under control. Contact your Cooperative Extension Service for fungicide recommendations.

Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Practice crop rotation and do not plant related crops in the same area for several years. Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.

Rust: A number of fungus diseases that rust colored spots on foliage, stalks and husks. Burpee Recommends: Make sure plants have good air circulation. Remove infected plants. Contact your Cooperative Extension Service for fungicide recommendations.

Verticillium wilt: First seen on leaves in late spring after fruit production has begun. Leaves turn brown along margins and between veins. Leaves will wilt and dry up as the disease progresses. Burpee Recommends: Remove infected plants. Do not plant in areas of infection.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.

Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.

Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.

Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.

FAQ

Asclepias FAQs

Is butterfly weed the same as milkweed? Both are the same genus Asclepias, so both are related. Both attract butterflies, but butterfly weed serves as a source of nectar for adult butterflies.

Caterpillars are eating my plants! Will they be alright? To grow a butterfly garden you will have to expect the caterpillars to eat the leaves or they won’t be able to mature into butterflies! Make sure you have different kinds of blooming plants in your flower garden and you will be less likely to have heavy damage. Asclepias is a herbaceous perennial and will die back in fall so it is likely that the plants will be fine.

Is asclepias a native plant? Is it deer resistant? Yes and yes: asclepias is native to most of the USA and eastern Canada, and does tend to be deer resistant.

I tried digging up my butterfly weed to move it and it died when I replanted it. What was wrong? Asclepias has a long taproot what is easily damaged when it is disturbed. Only transplant seedlings which do not have the tap root as developed yet when you want to move asclepias.

I think my asclepias died over the winter, why? If it is still early spring take heart that asclepias does tend to come up later than many perennials. Perhaps it just needs more time. Otherwise the plant may have a crown or root rot, especially if the location is not well drained.

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