GROWING MILKWEED
Where to plant:
Most milkweeds require full sun (at least 6 to 8 hours a day). Because they self-seed readily, locate your plants in a part of the garden where you can better control their rampant spread, such as at the back of the border or in a corner. A spot that’s protected from the wind will also help prevent the spread of seeds while providing a more hospitable environment for butterflies. It's important to note that milkweed plants have a taproot and do not transplant well.
When to plant:
If you’re planting milkweed from seed, sow the seeds outdoors in the fall, which will give them the period of stratification (exposure to cold, moist conditions) they need to encourage spring germination and ensure a good display of flowers the following summer. If you purchase starter plants, plant them in the spring after the danger of frost has passed.
Soil: There is a Milkweed variety for every landscape.
- Common Milkweed grows well in average garden soil.
- Swamp Milkweed, as its name implies, will do best in a moist environment, making it great for wet meadows or rain gardens.
- Tropical Milkweed performs beautifully in hot, humid conditions, and can be grown as an annual in the north.
- Butterfly Weed and Whorled Milkweed grows best in dry conditions.
Light: Young Milkweed plants need plenty of diffuse light as they grow. Plant in full sun locations.
Fertilizing: Milkweed does not require fertilization. This native plant performs well in poor soils.
How to plant:
To ensure successful germination of milkweed seeds, plant them in a smooth, clump-free soil bed worked to a fine consistency using a rake or rototiller. After you’ve sown the seeds, compact them into the soil (but don’t cover them) to provide good soil-to-seed contact. Keep the planting bed moist until the seedlings become established. As your plants begin to take off, thin out any plants that are spaced too closely together so they don’t compete for sun and soil nutrients.
Spacing:
To attract multitudes of monarchs to your garden, plant milkweed in groups of six or more, spacing plants or thinning seedlings to about 6 to 24 inches apart, depending on the species. “Monarchs are very good at finding a milkweed plant, but the more you have in your yard, the more likely they will find it and lay their little eggs all over it. Plant as many plants as you have room for,” recommends Kelly Ballard of Joyful Butterfly, a supplier of butterfly plants and seeds.
MILKWEED CARE
Like most wildflowers, milkweed is easy to grow and requires very little pampering. Most species are not seriously bothered by heat, drought, deer or other pests. And because milkweed is a native plant that tolerates poor soils, fertilization isn’t necessary.
Mulching:
You can mulch milkweed if you want to control weeds or retain moisture, but not all varieties will benefit. Swamp milkweed will appreciate your water-retention efforts, but milkweeds that prefer dry soil, such as common milkweed and butterfly weed, are usually better off with no mulch.
Pruning:
As with many flowering perennials, pruning the flowers soon after they have withered will result in new buds and may extend the blooming period for several weeks. Clipping spent flowers to stimulate new growth will also prolong the availability of nectar for monarchs and other pollinators.
Pest control:
Some plant pests such as aphids, whiteflies and milkweed bugs are immune to the toxic effects of milkweed and may feed on the leaves and seed pods, but they rarely cause significant damage. Also remove leaf litter and spent stalks in the fall to eliminate overwintering sites.
How to control spreading:
If you don’t want milkweed to take charge of your garden, remove the seed pods in the fall before they split open and release their contents or tie them closed with string. For plants with rhizomes, thin them out by hand by pulling the entire plant, including the roots, removing as much of the rhizome as possible. This will be easier to do when the plants are young and before the roots are well established.
How to Grow Milkweed Plants
Plant milkweed about 18 inches apart; their rhizomatous roots will quickly fill in the space between plants. There's no need to fertilize milkweed plants, as they tolerate poor soils. Your biggest maintenance challenge with them will probably be in containing them. Asclepias syriaca spreads both via seeds and rhizomes, forming colonies.
At the very least, you may wish to remove the seed pods before they open. Otherwise, they will spread to distant corners of your yard (and beyond), thanks to the silky appendages that allow the seeds to waft on the slightest breeze. They are rather like the seeds of dandelions in this regard.
Propagating Milkweed Plants
Milkweed spreads easily via rhizomatous roots; cutting root sections and planting them so the roots are just buried will easily propagate the plants.
Pests & Disease: Typically there are no serious pests or diseases that affect mature milkweed. In certain situations, aphids or whitefly can overrun your milkweed plants. Use a jet of water to hose them off. When you spray, be sure to avoid any clusters of Monarch eggs that are growing on the affected plants. Move any Monarch larvae that have already hatched to a clean place before spraying.
