Antelope Horns Seeds - Native Milkweed (Asclepias asperula)

Planting Instructions for Asclepias asperula (Antelope Horns Milkweed) Seeds

1. Direct Sowing Outdoors (Fall & Spring)
Site Selection: Choose a well-drained site with full sun (6–8 hours of direct sunlight daily). Avoid heavy clay soils that retain water.
Soil Preparation: Loosen the soil to a depth of 6–12 inches. If soil is compacted or heavy, amend with sand or compost to improve drainage.
Stratification (Cold Treatment):
Fall Sowing: No stratification needed, as natural winter conditions will break dormancy.
Spring Sowing: Requires cold stratification for 30 days in the refrigerator before planting.
Scarification: Not required.
Planting Depth: Sow seeds ¼ inch (6 mm) deep or lightly press them into the soil without covering them too much.
Watering: Water gently after sowing. Keep the soil moist but not soggy until germination occurs (which may take 2–8 weeks).
Maintenance: Thin seedlings to 12–18 inches apart once they establish. Minimal watering is required once the plants mature.

2. Starting Indoors for Transplanting Outdoors in Spring
Timing: Start seeds indoors 8–10 weeks before the last frost date in your area.
Stratification: Place seeds in a damp paper towel inside a plastic bag and refrigerate for 30 days before sowing.
Scarification: Not needed.
Soil & Container Selection: Use well-draining seed-starting mix in small pots or deep containers (milkweed has a long taproot).
Planting Depth: Sow seeds ¼ inch deep and lightly cover them.
Light Requirements: Place under grow lights or near a sunny window (12–16 hours of light per day).
Watering: Keep the soil moist but not soggy. Avoid overwatering.
Germination Time: 2–8 weeks.
Transplanting Outdoors:
Harden off seedlings by gradually exposing them to outdoor conditions for 7–10 days before transplanting.
Space plants 12–18 inches apart in well-drained soil.
Water after transplanting, but once established, minimal watering is needed.

Maintenance Tips
Mulching: Use a thin layer of mulch to retain moisture but avoid thick layers to prevent root rot.
Watering: Once established, Asclepias asperula is drought-tolerant and only needs occasional watering.
Pruning: Cut back dead stems in late winter or early spring before new growth emerges.
Pests/Diseases: Aphids may appear but can be controlled by spraying with water or introducing beneficial insects (e.g., ladybugs).
Wildlife: Essential for Monarch butterfly caterpillars; avoid pesticides that harm pollinators.
Is Asclepias asperula Invasive?
No, Asclepias asperula is not invasive. It is a native species in the southwestern and central USA, and it does not aggressively spread like some other milkweeds.

Native Plant Map

Dark Green indicates the plant is native within the state, yellow rare, the lime green indicates where the plant is native and seen more within a state.

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