How to Grow Butterfly Weed Seed
Instructions for preparing and planting Butterfly Weed seed (Asclepias tuberosa)
Let’s Get Started: Understanding Butterfly Weed Seed & Germinating
Step 1: To start Butterfly Weed seed, we recommend starting inside, but before this happens Butterfly Weed seeds need to go through a cold stratification period. Cold stratification is very important for the germination and growth of Butterfly Weed. It helps break the seeds natural dormancy cycle. To do this, we recommend placing Butterfly Weed seed in a damp paper towel or damp sand in a zip lock bag and place in your fridge for 3 – 6 weeks (30 days). Place in an area of the fridge, where it won’t get damaged. We taped ours to the bottom of a refrigerator shelf.
Growing Indoors
Step 2: Planting - Once the 30 days are complete, it’s time to plant the cold stratified Butterfly Weed seeds. We recommend planting in 2-4” peat pots. Fill peat pots ¾ of the way with seed starting potting soil and gently add water. Water should be able to drain through the peat pots. Once the soil is damp, place 1-2 cold stratified seeds into each pot. To finish, place 1/4 inch of soil on top of the seed.
If peat pots are unavailable, it is possible to plant in plastic pots; the ideal pot size is a small 2 1/2" diameter x 3” deep. If Butterfly Weeds plants are properly rooted in plastic pots, there is minimal root disturbance at transplanting time.
Watering - Gently water the planted seed to give additional hydration. The best way to water is from the bottom up. Use a flat pan under the peat pots and add a half inch of water to the bottom of the tray. Don’t over water as it can cause fungus. Water every day or every other day as needed, the best way to test the soil dampness is to touch it. If the soil seems dry then add water; if it’s wet, wait for the soil to dry out to water.
Light Requirements - For the next few weeks, make sure the Butterfly Weed is either in a sunny window, in a green house or under a grow light. Butterfly Weed needs lots of sun and warmth to grow. If you’re using a grow light, make sure to lower the bulb closer to the pots or your seedlings may become leggy, as they stretch to the light. Ideally a sturdier stem is better. Cold stratified seeds should germinate and sprout within 10-15 days once planted. In total Butterfly Weed from the day they are cold stratified to growth can take 40 plus days, so be patient!
Other planting options:
Place dry seed (not stratified) in seed starting soil and plant in peat pots under a grow light or in a greenhouse to germinate seeds. The success rate for this is low and more difficult to accomplish. If you choose to use this option it can take months for the seeds to germinate.
If you are planting seed outside, we suggest seeding in late fall, and let the Butterfly Weed seed lay on the ground through winter. Butterfly Weed seed will have a long winter of dormancy, so once the sun comes out and the ground warms in the spring, the seeds will germinate on their own.
Planting Butterfly Weed Seedling Outdoors
Step 3: Butterfly Weed does well in open areas with full sunlight exposure, areas like fields, parks, cultivated gardens, roadsides, highway medians, and road sides. Soil moisture and temperature are very important when growing Butterfly Weed. Butterfly Weed plants like growing in sandy, well drained soil. We suggest transplanting Butterfly Weed when the plant is no larger than 3 inches tall. In most cases in transplanting, the Butterfly Weed plant will go though some shock and could lose all its leaves. This happens, don’t panic. The plant is trying to establish its roots and will eventually grow leaves again. This is the main reason we suggest planting seeds in peat pots, because Butterfly Weed roots can be finicky. Peat pots breakdown over time in the ground, which allows the Butterfly Weed roots to grow without being disrupted. The best way to grow and transplant Butterfly Weed is minimizing the time growing in a pot and transplanting them as young plants is the best approach.
When to Plant Butterfly Weed
The best time to plant Butterfly weed is in early spring after the danger of frost has passed. If you plant seeds late in the spring, the seeds may not grow due to germination time and temperature.
Caring for Butterfly Weed Plants
Once your seedling is planted, water it for a few days to get it established, but after that, the plant doesn’t need a lot of supplemental water. Only water if you have an unusual dry spell. Peat pots are nice to use, but you need to be sure there is no top edge above the soil line after transplanting. In dry climates, this will wick away valuable soil moisture.