Like most plants of the Asclepias quadrifolia genus, four-leaf milkweed is toxic. The stem and leaves of four-leaf milkweed contain a thick, milky juice. The plant produces showy flowers, and it attracts various insects that feed on the foliage. The monarch butterfly needs four-leaf milkweed in order to survive.
I. Appearance and Characteristics
Asclepias quadrifolia, commonly called four-leaved milkweed or fourleaf milkweed, is a species of milkweed in the Apocynaceae (dogbane) family. It is sometimes referred to as whorled milkweed, but it should not be confused with Asclepias verticillata. A. quadrifolia occurs in the eastern United States and Canada.
Fourleaf milkweed is a perennial herb with an upright stem growing from a fleshy rhizome. The stem has a milky sap. The plant is small and slender compared to other milkweeds at only 50 centimeters (20 in) tall. Leaves are usually elliptical to ovate and 2.5–12.0 centimeters (1.0–4.7 in) long and 1–6 centimeters (0.4–2.4 in) wide. Leaves are opposite and appear in 3 to 4 sets on the stem, with one of the higher sets having 4 leaves arranged in a whorl (giving the plant its common name) and the other sets consisting of only 2 leaves.
Pale pink to white flowers are borne in 1 to 3 rounded, usually pendulous clusters, or umbels from the leaf axils and terminus. Flowers bloom from May to July. Insects that take nectar from the plant include bumblebees and other bees, wasps, ants, flies, and butterflies. The caterpillars of the monarch butterfly feed on the foliage.
The fruit is a follicle or pod that is very slender, 8.1–14.2 centimeters (3.2–5.6 in) long and 0.6–0.8 centimeters (.25–.3 in) thick, lacking tubercles, minutely hairy to glabrous. The seeds are broadly oval with a length up to 0.8 centimeters (.3 in). They are tufted with white to tan hairs at their tips.
Most Asclepias are toxic if consumed in large quantities due to cardiac glycoside and resinoid content.
A. quadrifolia is native to the United States from Kansas and Oklahoma in the west, to Mississippi and Alabama in the south, and New Hampshire in the north and east. It is an endangered species in Ontario. Unlike more commonly known species such as common milkweed or butterflyweed, fourleaf milkweed is a woodland denizen. It usually occurs in dry, rocky open forest. It is frequently found on upland slopes.
II. How to Grow and Care
Sunlight
Four-leaf milkweed thrives in full sun, where it receives unfiltered sunlight for at least 6-8 hours a day, which is crucial for its robust growth and floral development. Although it prefers full sun, four-leaf milkweed shows a notable tolerance for partial sun, adapting to receive some intermittent shade. In suboptimal light, such as dense shade, its growth may be stunted, and it is less likely to bloom profusely. Outdoors, four-leaf milkweed is best planted in open areas that allow for maximum sunlight exposure without obstruction. Not typically an indoor plant, four-leaf milkweed does not require recommendations for indoor placement.
Temperature
It can be planted in most areas if you would remove it after planting for just a year. The suitable temperature range for its growth is 18 to 30 ℃. It can tolerate up to 35 ℃ and withstand a minimum temperature of 8 ℃ in winter. It will stop growing below 5 ℃ and gradually die below 0 ℃.
Four-leaf milkweed likes a humid environment, so provide it with sufficient water in all seasons except winter. If the air humidity is too low, the leaves will gradually lose their luster.
Watering
Thriving in its native woodland settings, four-leaf milkweed has adapted to moderate moisture levels, indicative of the understory’s dappled light and well-draining soil. It maintains a balance between drought resistance and a preference for consistent humidity. Care should include watering every week to mimic these natural conditions. As an herbaceous perennial, four-leaf milkweed is more commonly grown outdoors where it can benefit from natural rainfall patterns, aligning with its growth cycles and water needs.
Soil
Four-leaf milkweed adapts to various soil environments. The most suitable soil is slightly acidic and well-drained. If the planting soil is sticky, add some leaf mold, organic fertilizer, river sand, or a similar compound and stir evenly to improve soil texture. You can also add a little soil at the base of the plant to encourage growth. This will prevent plant lodging and provide more nutrients to the roots.
Fertilizing
For four-leaf milkweed, use balanced nutrition fertilizers to promote robust growth and vibrant blooms. Apply a quarter-strength, water-soluble blend monthly during active growth in spring and summer. Decrease to bi-monthly in fall and withhold in winter to align with four-leaf milkweed’s growth cycle. Light application is key to avoid overwhelming four-leaf milkweed, which thrives in lean soil conditions. Observe four-leaf milkweed’s response, adjusting frequency to support plant health without inducing excessive foliage at the expense of flowers. Always water four-leaf milkweed thoroughly post-application to distribute nutrients and prevent root burn.
Planting Instructions
Four-leaf milkweed can be sown in spring, planted in flower pots or placed directly in the garden. You can keep seeded pots indoors. Sow at warmer temperatures for best results. The seeding depth is about 2.5 cm. Press the soil slightly, so that the soil and the seed make firm contact. After sowing, water seeds thoroughly. Generally, they will germinate after two weeks with a germination rate of about 80-90%.
When the seeds in the pot germinate with 2-3 pairs of leaves, they can be transplanted into the ground. When transplanting, keep the soil on the roots to avoid damaging the root system. Remember to water thoroughly after planting. Four-leaf milkweed grows best in a ventilated environment, such as by a road, wall, or window. Without good ventilation, pests will appear, which can threaten the plant’s growth.
Pruning
Regularly remove infected plants and wilting leaves to keep four-leaf milkweed healthy. If you are located in a tropical or subtropical climate, you can cut off branches in early spring to promote germination. Given the high toxicity of four-leaf milkweed, wear gloves when handling plants to prevent poisoning. Keep four-leaf milkweed away from children, avoid direct contact, and do not eat the plant.
Propagation
Four-leaf milkweed is a perennial herb that consists of multiple, slender stems and characteristic whorls of leaves. To effectively propagate this species, use fresh seeds that have been cold-stratified to encourage germination. Sow the seeds in well-draining soil with full to partial sunlight exposure, placing them just below the surface. Ensure ample moisture and patience, as four-leaf milkweed may take several weeks to germinate. Transplant the seedlings once they’ve established a robust root system and are large enough to handle.
Transplanting
The optimal time to transplant four-leaf milkweed is from the awakening of early spring until the vibrancy of late spring, which accommodates root establishment before the heat of summer. Choose a well-drained spot with dappled sunlight. Gentle handling is key to avoid disturbing the sensitive root system.
III. Uses and Benefits
Four-leaf milkweed is a vital ingredient of butterfly gardens, meadows or prairies, cottage gardens, rock gardens, or mixed borders.
