Indoors or outdoors: the simplest way to decide where to start seeds
In cool, short-season climates, the main question is not “can this crop grow here?” but “will it have enough time?”
- Starting seeds indoors gives you warm soil, steady moisture, and a head start while it is still cold outside.
- Starting outdoors is easier and often produces stronger root systems for crops that dislike being moved.
A practical rule:
- Start indoors when the crop is slow, needs warmth, or benefits from a long season (tomatoes, peppers, celery, many brassicas).
- Start outdoors when the crop grows fast, tolerates cool soil, or hates transplanting (carrots, parsnips, peas, radishes, dill).
| Crop | Start (Indoors/Outdoors) | When to start | Brief sowing notes |
|---|---|---|---|
| asparagus | Indoors | 10–12 weeks before last frost | Slow from seed; many gardeners plant crowns outdoors for faster results. |
| basil | Indoors | 4–6 weeks before last frost | Needs warmth and light; plant out only when nights are warm. |
| beans | Outdoors | 1–2 weeks after last frost | Warm soil matters; direct sow. Soaking is optional, but not required. |
| beetroot | Outdoors | 0–2 weeks after last frost | Direct sow; thin seedlings for proper roots. |
| broccoli | Indoors | 6–8 weeks before last frost | Transplant out when sturdy; protect from pests early. |
| brussels sprouts | Indoors | 8–10 weeks before last frost | Long season crop; transplant out early for best size. |
| cabbage | Indoors | 6–8 weeks before last frost | Transplants handle cool weather; keep growth steady. |
| carrots | Outdoors | 0–4 weeks after last frost | Do not transplant; keep seedbed evenly moist for germination. |
| cauliflower | Indoors | 6–8 weeks before last frost | Sensitive to stress; transplant gently and avoid setbacks. |
| celery | Indoors | 10–12 weeks before last frost | Tiny seed; sow on surface, keep moist, needs long indoor time. |
| chives | Indoors | 6–8 weeks before last frost | Easy; clumps up over time. Can also be divided later. |
| coriander (cilantro) | Outdoors | 0–4 weeks after last frost | Best direct sown; bolts in heat, so sow in waves. |
| cucumbers | Indoors | 2–4 weeks before last frost | Fast; don’t start too early. Plant out only when warm. |
| dill | Outdoors | 0–4 weeks after last frost | Dislikes transplanting; direct sow and repeat sowings. |
| fennel | Outdoors | 2–6 weeks after last frost | Many types dislike transplanting; direct sow for best roots. |
| garlic | Outdoors | Best in autumn; or early spring | Plant cloves, not seed. Autumn planting gives bigger bulbs. |
| kale | Indoors | 4–6 weeks before last frost | Very hardy; transplant out early or direct sow later. |
| lavender | Indoors | 10–12 weeks before last frost | Slow; keep warm and bright. Some seeds benefit from cold time. |
| leeks | Indoors | 10–12 weeks before last frost | Long season; transplant out while still pencil-thin. |
| lettuce | Outdoors | 0–6 weeks after last frost | Cool-loving; sow small batches often for steady harvest. |
| marjoram | Indoors | 6–8 weeks before last frost | Small seed; warmth and light help. |
| melons | Indoors | 3–5 weeks before last frost | Needs heat; plant out late and use shelter if possible. |
| mint | Outdoors | Plant as a plant (spring/summer) | Usually propagated from plants; spreads aggressively—contain it. |
| onions | Indoors | 10–12 weeks before last frost | From seed: start early indoors; from sets: plant outdoors in spring. |
| oregano | Indoors | 8–10 weeks before last frost | Small seed; slow start, then becomes hardy once established. |
| pak choi | Outdoors | 0–6 weeks after last frost | Fast; sow in cool periods to reduce bolting. |
| parsnips | Outdoors | 0–2 weeks after last frost | Slow to germinate; do not transplant; use fresh seed. |
| parsley | Indoors | 8–10 weeks before last frost | Slow germination; keep evenly moist and be patient. |
| peas | Outdoors | 2–6 weeks before last frost | Likes cool soil; direct sow early. Support for climbing types. |
| peppers | Indoors | 10–12 weeks before last frost | Needs warmth and strong light; transplant out late. |
| potatoes | Outdoors | 2–4 weeks after last frost | Plant tubers; “chit” (pre-sprout) indoors for earlier growth. |
| pumpkins | Indoors | 3–4 weeks before last frost | Fast; transplant after warm nights; protect from cold wind. |
| radishes | Outdoors | 0–6 weeks after last frost | Very fast; sow often. Best in cool weather. |
| rhubarb | Outdoors | Plant crowns in spring or autumn | Usually planted as crowns/plants; seed is uncommon for home gardens. |
| rosemary | Indoors | 10–12 weeks before last frost | Slow and heat-loving; many people prefer cuttings over seed. |
| sage | Indoors | 8–10 weeks before last frost | Start indoors; transplant once strong; drought-tolerant later. |
| shallots | Outdoors | 2–6 weeks after last frost (or autumn) | Usually planted as sets/bulbs; needs a long season to size up. |
| spinach | Outdoors | 2–6 weeks before last frost | Cold-tolerant; sow early and repeat sowings for steady leaves. |
| spring onions | Outdoors | 0–4 weeks after last frost | Direct sow; thin for size; can also start indoors for extra-early. |
| squash | Indoors | 3–4 weeks before last frost | Same approach as pumpkins; do not let seedlings get root-bound. |
| stevia | Indoors | 8–10 weeks before last frost | Small seed; warmth + light; plant out only in warm weather. |
| sweetcorn | Indoors | 2–4 weeks before last frost | Indoor start helps in cool climates; transplant carefully when warm. |
| swedes (rutabaga) | Outdoors | 0–4 weeks after last frost | Direct sow; thin well; steady growth gives best roots. |
| tarragon | Outdoors | Plant as a plant (spring/summer) | French tarragon is usually a plant, not seed; grow in a warm spot. |
| thyme | Indoors | 8–10 weeks before last frost | Tiny seed; slow start; needs light and patience. |
| tomatoes | Indoors | 6–8 weeks before last frost | Warm germination and strong light; plant out after frost and cold nights. |
| turnips | Outdoors | 0–6 weeks after last frost | Fast; direct sow; best in cool weather. |
How to use this in real life
If you only remember one thing: Start indoors for long-season warmth lovers and slow growers; sow outdoors for quick cool-season crops and anything that dislikes transplanting. Add simple protection (fleece, cloches, low tunnel) and you can often shift outdoor sowing earlier without risking everything.