With their colorful daisy-like blooms, asters are a quintessential flower of late summer and fall. Growing these beauties from seed is a thrifty way to add jewel-toned color to beds, borders and containers. Follow this complete guide to sowing, transplanting, and caring for asters grown from seed.
Getting to Know Asters
Astsers belong to the extensive Asteraceae family which includes other familiar flowers like sunflowers, zinnias, dahlias and chrysanthemums. There are over 180 wild and cultivated aster species suited to various climates and growing conditions.
Popular garden types include
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New England Aster – Vibrant pink, purple or white flowers on bushy 1-4 ft. plants.
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Michaelmas Daisy – Classic fall-blooming aster with blue, lavender or white flowers Grows 1-3 ft tall.
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Alpine Aster – Low-growing 4-12 inch plants with flowers in blue, pink or white.
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Stokes’ Aster – Heat-tolerant asters with blue or white 2-3 inch wide blooms.
When to Start Aster Seeds
Asters grow best started from seeds sown early indoors:
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Start seeds indoors 6-8 weeks before your last expected spring frost date.
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Use a seed starting mix and provide 65°F – 70°F soil temperatures for germination.
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After sprouting, grow seedlings on at 60°F – 65°F with plenty of light.
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Harden off and transplant outdoors after all danger of frost has passed.
You can also direct sow seeds outdoors about 2 weeks before the last frost date.
How to Plant Aster Seeds
Follow these simple steps for starting aster seeds indoors or out:
Indoors:
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Fill starter trays or pots with moist seed starting mix. Press seeds into the surface.
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Cover seeds lightly with 1/8″ of mix. Keep evenly moist but not saturated.
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Expect sprouting in 7-21 days. Provide ample light once seedlings emerge.
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Transplant outdoors at 6-8 weeks when hardened off, spacing 12″ apart.
Outdoors:
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Prepare a planting bed in full sun with compost or organic matter worked in.
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Press seeds onto the surface of warm, moist soil. Cover with 1/8″ of fine soil or compost.
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Water gently to avoid washing away seeds. Keep soil moist but not soggy.
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Thin or transplant seedlings 12″ apart when they reach 2-4 true leaves.
Caring for Asters Grown from Seed
Keep your asters thriving with proper care:
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Water asters 1-2″ per week. Add mulch to conserve moisture.
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Pinch back tips of young plants to encourage bushy, compact growth.
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Stake taller asters to prevent toppling, especially after rain or wind.
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Deadhead spent blooms to extend flowering into fall. Stop deadheading by early fall.
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Monitor for common pests like leafhoppers, Japanese beetles, slugs and snails.
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Divide congested clumps every 2-3 years in early spring as needed.
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Cut back dead growth in late fall and apply compost around the base of plants.
Tips for Growing Asters from Seeds
Follow these tips for success with starting asters from seed:
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Purchase fresh seeds each year for best viability. Store unused seeds properly.
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Give seedlings 14-16 hours under grow lights or bright sunny windows.
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Avoid letting started seeds get leggy and weak. Provide air circulation.
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Harden off transplants gradually over 7-10 days before planting out.
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Water new transplants consistently until they establish deep roots.
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Mulch to keep soil moist and reduce competition from weeds.
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Deadhead to prolong blooms. Leave last flowers to go to seed.
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Grow different aster species each year to prevent disease buildup in soil.
Recommended Aster Varieties for Seeds
Some top-rated asters for success from seed include:
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King Asters – Extra large, long-blooming daisy flowers on 2-3’ plants.
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Matsumoto Asters – Compact mounded plants with profuse blooms in mixes or solids.
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Monte Cassino Asters – Floriferous, mildew-resistant plants with 5” blooms.
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New England Asters – Classic, cold-hardy asters reaching 3-4’ tall.
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Wood’s Pink Asters – Vibrant hot pink flowers on compact, early plants.
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Alpine Asters – Dwarf plants under 1’ tall perfect for rock gardens and edging.
No matter which aster variety you select, growing these cheerful flowers from seed is easy and rewarding. With a little care and patience, you’ll have vibrant asters gracing your garden beds and borders from late summer through fall.
Where to Plant Aster Seeds
If you plant directly outside, make sure the soil is moist, nutrient-rich, and well-drained, and make sure the plants get at least four to eight hours of full sun every day. Do not plant asters in areas where the soil retains water, or alternately, where it readily dries out. Prepare the planting site by mixing in a source of organic matter like compost, or composted manure.
If starting indoors, use a seed starting soil mixture and cover the seeds lightly with ⅛ of soil. When you plant the seeds, water them and keep them evenly moist until the seedlings appear, which could take one to three weeks depending on the type. Harden off the seedlings and transplant out into the garden once danger of frost has passed. Read more about how to harden off seedlings here.
When to Plant Aster Seeds
After the last frost of the season, plant outside, or start indoors six to eight weeks before the last frost date.
How to Grow Asters from Seed
FAQ
Is aster easy to grow from seed?
What month do you plant aster seeds?
How do you germinate aster seeds?
Do aster seeds need cold stratification?
How do you plant an Aster seed?
Whether planting indoors or outdoors, cover the seeds with 1/8 inch (3 mm.) of fine soil. Aster seed sowing by scattering the seeds in a wildflower planting is also perfectly fine. Water the seeds after planting, then keep them evenly moist until seedlings emerge. This can happen between 7 and 21 days after sowing, depending on the aster variety.
Can you grow aster flowers from seeds?
While you can grow aster flowers from seeds planted in the springtime, it may take several years for them to mature into full-sized plants. More often, asters are planted from potted nursery specimens. They do best in loamy, well-draining soil, and desire a good amount of space around the plants to allow room for their roots to expand.
How do you grow an aster plant in a container?
Asters aren’t too picky about their first home, but make sure the container you choose has good drainage to prevent waterlogging, which can cause the seeds to rot. Fill each cell of a clean, sanitized seed tray with pre-moistened seed starting mix. Press down on the soil surface to eliminate any air pockets.
Can you plant aster seeds indoors?
While you can sow aster seeds directly outdoors when the soil temperature is optimal (between 65 and 70 degrees), starting them indoors gives you a bit of a head start and more control over their growing conditions. Plan to plant your aster seeds indoors 6-8 weeks before your last frost date. What do aster seeds look like?