- Start seeds inside 2 months before the last frost; cold stratification in the refrigerator is essential.
- Seeds should be started in a cup of water. Make use of a seed mat that has been heated. There is no need for cold stratification.
How fast does Asclepias tuberosa grow?
Milkweed, also known as asclepias, is native to North America, and one of them, Asclepias tuberosa, has been named Perennial Plant of the Year by the Perennial Plant Association this year. This plant, sometimes known as butterfly weed or butterfly milkweed, has bright orange flowers that attract a variety of butterflies and bees with nectar and pollen. Butterfly weed’s leaf isn’t a favorite meal of monarch caterpillars, but it can help them survive. This drought-tolerant plant prefers a dry, sunny environment and is hardy in Zones 3 to 9.
Upright stems with clusters of bright orange flowers contrast attractively with the shiny green leaves of butterfly weed. Unlike other members of the genus, the stem sap is not milky. This milkweed is not invasive since it does not spread by runners like common milkweed (Asclepias syriaca). Although deer are not attracted to butterfly weed, aphids can be an issue in gardens and greenhouses.
This plant is expected to be in great demand in the next years. Butterfly weed blooms readily the first year after seeding, but there are a few crucial elements to remember if you want to grow it professionally.
This species displays some of the most extreme photoperiod reactions we’ve ever seen. It’s an obligatory long-day plant, which means it has to flower during long days. When grown at an average of 68° F, plants develop quickly under photoperiods of 14 hours or more, and begin flowering about eight to nine weeks after transplant. Plants that are exposed to photoperiods of 12 hours or less, on the other hand, die dormant after a few days (Figure 1, pictured above). Leaves droop, shoot growth appears to stop, and existing flower buds may suffocate (Figure 2). Unfortunately, simply reverting to longer days will not return the plants to active growth. A nine-week or longer cold treatment is required to break this dormancy; in our testing, all dormant plants treated to 41° F for 15 weeks bloomed.
It is critical to provide long days to plants in order to keep them actively growing. We propose at least 16 hours of daylight or four hours of night disruption illumination. A minimum intensity of 2 molm2s1 should be delivered by photoperiodic illumination. Use incandescent lights or LED bulbs intended to control blooming that emit both red and far-red radiation. Maintain these extended photoperiods for plants until natural daylengths reach at least 14 hours.
Butterfly weed has a huge tap root, making transplanting or dividing established plants difficult. It’s critical to utilize a well-drained medium in container production, so consider adding more perlite to a standard peat+perlite mix. During production and cold treatments, be careful not to over-water. The taproot attracts fungus gnat larvae, so keep an eye on the roots if your plants aren’t doing well.
Butterfly weed can grow up to 3 feet tall in the wild, but in container production, our plants were only 12 to 18 inches tall when they first bloomed. Sprays of daminozide (e.g., B-Nine, Dazide), paclobutrazol (e.g., Piccolo, Bonzi), and uniconazole (e.g., Piccolo, Bonzi) are apparently helpful for height management (e.g., Sumagic, Concise). To help fill out containers, use many plugs per pot or squeeze seedlings soon after transplant.
Do milkweeds grow back every year?
Plant milkweeds that are natural to your area whenever possible. Perennials, or plants that come back year after year, are native milkweeds. Their aerial portions (flower, leaves, and stem) die back in the winter, but their rootstock survives.
How do you plant Asclepias bulbs?
When given ample of sunlight, asclepias are remarkably easy to cultivate. They’ll grow in a variety of soil types, including poor, dry, sandy, or gravelly, as long as they get enough sun! These plants prefer a neutral to slightly acidic pH, but there’s no need to be concerned when it comes to these beauties.
When to Plant
Plant your starter plants in the spring or fall for the finest flowering results. While they may not bloom the first year, you may expect brilliant blossoms in succeeding seasons from early summer to early fall.
How to Plant
- 12 to 18″ apart, dig holes large enough to accept the roots without bending or breaking them.
- As you tuck the plant down, work the soil around the roots, leaving no more than 1″ of soil covering the crown.
How to Grow
- Water your Asclepias frequently during active growth to keep the soil moist, then less frequently once they’ve established themselves.
- Once the foliage and stalks begin to wither and die back, cut them back to ground level.
- If you live in a very frigid climate, mulch around the plant and remove it when the weather warms up in the spring.
Asclepias Tips & Tricks
- Keep in mind that the planting hole should be twice the width of the starter plant and deep enough to accommodate the entire root system.
- Transplant only if absolutely essential, as these plants prefer to be left alone and transplantation is difficult due to their long, strong roots. If you have to dig the plant up, be sure to dig deep because certain Asclepias cultivars have lengthy taproots.
- Expect a swarm of butterflies, bees, and other joyful pollinators to flock to the flowers.
- Fertilize your Butterfly Weed sparingly because it may harm the plants.
Should I cut back my milkweed?
During the fall and winter months, trim the milkweed stems to about 6 inches in height to dissuade monarchs from establishing winter-breeding colonies. Cutting back the milkweed will also aid in the removal of any OE spores that may be present. As the leaves re-sprout, re-cut the milkweed every several weeks. Because tropical milkweed dies back naturally when it freezes, it may offer fewer problems in the northern monarch breeding region.
These instructions do not apply in south Florida (south of Orlando), where a distinct, non-migratory monarch population has existed for many years. In this location, however, native milkweed planting is still recommended.
How do you make milkweed grow faster?
Milkweed does not always start growing in northern gardens in time for butterflies to benefit fully. There, you can start milkweed seeds indoors so that they are ready to sow once the soil has warmed up.
Before sprouting, milkweed plants benefit from vernalization, a chilly treatment. They get this when they’re planted outside, but you can speed up the process by stratifying the seeds. Place seeds in a damp soil container, cover with plastic wrap, and store in the refrigerator for at least three weeks. If desired, plant in containers and place under a grow lamp inside six weeks before soil conditions outside have warmed. Mist the soil to keep it moist, but seeds that sit in soggy soil may rot.
Transplant the seedlings to their permanent, sunny home outside when they have two sets of leaves. If planting in a row, space plants about 2 feet (61 cm) apart. The milkweed plant has a lengthy taproot and dislikes being moved after being planted outside. Mulch can aid in water conservation.
Milkweed plants can be used in mixed borders, meadows, and natural settings. To provide more pollen to our flying companions, put milkweed plants with tubular-shaped, shorter flowers in front of them.
Why are there no caterpillars on my milkweed?
This could be due to a variety of factors. If your missing caterpillars are 5th instar caterpillars, they most likely went away from your milkweeds to develop their chrysalis (they typically do not pupate on milkweed plants). A monarch predator is a more plausible suspect if earlier instars or eggs are missing. On our website, you may learn more about natural enemies. Monarch eggs reach adulthood in less than 10% of cases (and in other cases as low as 2% in some tests).
Where does Asclepias tuberosa grow?
USDA hardiness zones 3a-9b (lows of -40 °C or -40 °F) Perennial Most of the continental United States and eastern Canada are home to this species. Plant in direct sunlight.