Planting flower seed at the right depth can be the difference between a full, uniform tray and an expensive do-over. Tiny seeds such as petunia, begonia and lisianthus often need light and should stay on the surface, while larger seeds such as zinnia, marigold and sunflower need enough cover to hold steady moisture. This practical flower seed sowing depth chart gives gardeners, flower farmers, greenhouse growers and landscape professionals a fast answer for more than 50 popular flowers.
Ready to plant? Shop commercial quantities at Trailing Petunia Bulk Seeds, or visit our regular seed collections for smaller packs. Use the chart, then choose the featured varieties below and order directly from this guide.
Quick Rule: How Deep Should Flower Seeds Be Planted?
Cover most seed by approximately two to three times its thickness. That rule does not apply to dust-like seed that needs light. Surface-sown seed should be pressed onto moist seed-starting mix without being buried. Pelleted seed is easier to place, but the coating does not mean it should be planted deeper.
- Surface sow: press onto moist mix; do not cover.
- Light cover: use about 1/16 inch of fine vermiculite.
- Shallow sow: cover approximately 1/8 inch.
- Medium sow: cover approximately 1/4 inch.
- Deep sow: cover 1/2 to 1 inch, depending on seed size.
Pair this chart with our published seed germination temperature chart and flower seed germination times chart.
Flower Seed Sowing Depth Chart for 50+ Flowers
Always follow variety-specific instructions when available. “Surface” means pressing seed into pre-moistened media and leaving it uncovered.
| Flower | Depth | Light | Method | Grower note |
|---|---|---|---|---|
| Achillea (Yarrow) | Surface | Light | Tray | Press firmly into moist media. |
| Ageratum | Surface–1/16 in. | Light helpful | Tray | Use only a dusting of vermiculite. |
| Alyssum | 1/8 in. | Light cover | Tray/direct | Keep evenly moist. |
| Amaranthus | 1/8 in. | Light cover | Tray/direct | Do not bury deeply. |
| Angelonia | Surface | Light | Tray | Pelleted seed stays visible. |
| Snapdragon | Surface | Light | Tray | Press in; do not cover. |
| Aster | 1/8 in. | Cover lightly | Tray/direct | Use fine vermiculite. |
| Bacopa | Surface | Light | Tray | Place pellets on moist media. |
| Begonia | Surface | Light | Tray | Never bury dust-like seed. |
| Calendula | 1/4–1/2 in. | Cover | Tray/direct | Firm soil gently. |
| Calibrachoa | Surface | Light | Tray | Keep humid, not saturated. |
| Campanula | Surface | Light | Tray | Do not cover. |
| Canna | 1/2–1 in. | Cover | Pot/tray | Scarify hard seed if needed. |
| Celosia | 1/8 in. | Light cover | Tray/direct | Avoid cold, wet media. |
| Cineraria | Surface | Light | Tray | Press onto media. |
| Coleus | Surface | Light | Tray | Do not bury. |
| Columbine | Surface–1/8 in. | Light helpful | Tray | May benefit from cold treatment. |
| Coreopsis | 1/8 in. | Light cover | Tray/direct | Cover finely and evenly. |
| Cosmos | 1/4 in. | Cover | Tray/direct | Direct sow after frost. |
| Dahlia | 1/4 in. | Cover | Tray | Warm media speeds emergence. |
| Delphinium | 1/8 in. | Cover | Tray | Cool conditions often help. |
| Dianthus | 1/8 in. | Light cover | Tray | Cover with fine vermiculite. |
| Foxglove | Surface | Light | Tray | Press in without covering. |
| Dusty Miller | Surface–1/16 in. | Light helpful | Tray | A dusting is enough. |
| Echinacea | 1/8–1/4 in. | Cover | Tray/direct | Cold treatment may help. |
| Eucalyptus | 1/8 in. | Light cover | Tray | Never waterlog media. |
| Lisianthus | Surface | Light | Tray | Do not bury pellets. |
| Gaillardia | 1/8 in. | Light cover | Tray/direct | Firm seed before covering. |
| Gazania | 1/8 in. | Cover | Tray | Provide warmth. |
| Geranium | 1/4 in. | Cover | Tray | Cover fully and keep warm. |
| Gomphrena | 1/4 in. | Cover | Tray/direct | Pre-soaking may help. |
| Heliotrope | 1/8 in. | Light cover | Tray | Use thin vermiculite. |
| Hollyhock | 1/4 in. | Cover | Tray/direct | Firm soil for good contact. |
| Impatiens | Surface–1/16 in. | Light helpful | Tray | Use little or no cover. |
| Larkspur | 1/4 in. | Darkness helpful | Direct | Cool soil is preferred. |
| Lavender | Surface–1/8 in. | Light helpful | Tray | Cold treatment may help. |
| Lobelia | Surface | Light | Tray | Do not cover. |
| Lupine | 1/2 in. | Cover | Pot/direct | Scarify or soak. |
| Marigold | 1/4 in. | Cover | Tray/direct | Lay long seed horizontally. |
| Nasturtium | 1/2–1 in. | Cover | Pot/direct | Minimize root disturbance. |
| Nemesia | 1/8 in. | Light cover | Tray | Keep cool and moist. |
| Nicotiana | Surface | Light | Tray | Press fine seed in. |
| Osteospermum | 1/4 in. | Cover | Tray | Avoid excessive heat. |
| Pansy | 1/8 in. | Darkness helpful | Tray | Cover lightly; keep cool. |
| Pentas | Surface | Light | Tray | Pellets need moisture, not burial. |
| Petchoa | Surface | Light | Tray | Keep pellets visible. |
| Petunia | Surface | Light | Tray | Do not cover. |
| Phlox | 1/8–1/4 in. | Cover | Tray/direct | Check species instructions. |
| Portulaca | Surface | Light | Tray/direct | Avoid overwatering. |
| Primula | Surface | Light | Tray | Cool conditions are best. |
| Rudbeckia | Surface–1/8 in. | Light helpful | Tray/direct | Cover very lightly. |
| Salvia | 1/8 in. | Light cover | Tray | Avoid deep sowing. |
| Scabiosa | 1/4 in. | Cover | Tray/direct | Use free-draining media. |
| Stock | 1/8 in. | Cover lightly | Tray | Keep plugs cool. |
| Strawflower | Surface–1/8 in. | Light helpful | Tray | Cover very lightly. |
| Sunflower | 1/2–1 in. | Cover | Pot/direct | Use deep cells if transplanting. |
| Sweet Pea | 1 in. | Cover | Pot/direct | Provide cool conditions. |
| Verbena | 1/8 in. | Darkness helpful | Tray | Cover and keep moist. |
| Vinca | 1/4 in. | Darkness | Tray | Warmth plus darkness helps. |
| Viola | 1/8 in. | Darkness helpful | Tray | Cover lightly; avoid heat. |
| Zinnia | 1/4 in. | Cover | Tray/direct | Warm soil speeds emergence. |
Shop Seeds Featured in the Chart
These live varieties represent surface-sown pelleted crops, shallow-sown seed and larger direct-sown seed.
How to Surface Sow Tiny and Pelleted Seeds
- Fill a clean tray with fine seed-starting mix and water before sowing.
- Let excess water drain so the surface is moist, not muddy.
- Place raw or pelleted seed on top without pushing it under.
- Press gently for good seed-to-media contact.
- Use controlled mist, bottom watering or a humidity dome so seed never dries.
- Provide light immediately for light-requiring crops.
- Vent the dome after emergence to improve airflow.
For a full tray workflow, read How to Start Flower Seeds Indoors and What Flower Seeds Need Light to Germinate?
Pelleted Seed Versus Raw Seed
A pellet makes tiny seed easier to handle, but it does not convert a light-requiring seed into one that should be buried. Petunia, begonia, lisianthus and many other pelleted crops remain on the surface. Give the pellet enough moisture to dissolve and enough oxygen for germination. Saturated media can be as damaging as dry media.
Direct Sowing Versus Tray Sowing
Larger, fast-growing flowers such as zinnia, sunflower, nasturtium, cosmos and marigold can often be direct sown after frost. Slow, tiny or high-value seeds usually perform better in controlled trays. Commercial growers should calculate the desired transplant or market date backward and combine depth with crop-specific plug and finish times. Use our flower-seed planting calendar by USDA zone.
Five Mistakes That Reduce Germination
- Burying tiny seeds: petunia, begonia, lisianthus, lobelia and snapdragon may fail beneath too much mix.
- Letting surface seed dry: one dry period can stop germination.
- Using coarse media: large particles create uneven depth.
- Overwatering: saturated media limits oxygen and encourages disease.
- Ignoring crop differences: darkness helps pansy, vinca and verbena, while light supports many tiny-seeded crops.
Frequently Asked Questions
How deep should flower seeds be planted?
Most are planted two to three times as deep as the seed is thick. Dust-like, light-requiring seeds should be surface sown.
Which flower seeds should not be covered?
Petunia, begonia, lisianthus, lobelia, coleus, nicotiana, portulaca and snapdragon are commonly surface sown.
Can pelleted flower seeds be buried?
Only when the crop calls for covering. Pelleted petunia, begonia and lisianthus normally remain on the surface.
What happens when seeds are planted too deep?
Small seedlings may use their stored energy before reaching the surface, causing slow, uneven or failed emergence.
Should I use vermiculite over flower seeds?
Fine vermiculite works for seeds needing a light cover. Leave light-requiring seed visible unless variety instructions say otherwise.
Is direct sowing or tray sowing better for bulk flower seeds?
Tray sowing offers control for tiny, slow or expensive seed. Direct sowing is efficient for larger, fast-growing flowers in suitable field conditions.
Where can commercial growers buy flower seeds in bulk?
Shop Trailing Petunia Bulk Seeds for commercial quantities. For smaller quantities, browse Trailing Petunia’s regular collections.
Related Flower Seed Growing Guides
- Seed Germination Temperature Chart Guide
- Flower Seed Germination Times: Complete Chart by Variety
- What Flower Seeds Need Light to Germinate?
- How to Start Flower Seeds Indoors
- When to Plant Flower Seeds by USDA Zone
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