Direct Seeding: How to Sow Seeds Straight Into the Garden
Not every crop needs to start life indoors. Many of Canada's most productive vegetables — carrots, beans, radishes, peas, beets — grow best when sown directly into the garden bed. Direct seeding is faster, simpler, and avoids transplant shock entirely. This guide covers which crops to direct seed, when your soil is ready, and how to thin for proper spacing in 30" biointensive beds.
Which Crops Are Direct-Seeded vs Transplanted?
The decision to direct seed or transplant depends primarily on the crop's root system and cold tolerance. Root crops (carrots, beets, radishes) have taproots that do not recover well from being moved — they must be direct seeded. Large-seeded crops like beans and peas germinate quickly in warm soil and grow so fast that transplanting offers no meaningful time advantage. Meanwhile, slow-developing crops with long seasons (tomatoes, peppers) must be transplanted because they cannot mature from seed in Canada's short frost-free window.
Best Direct-Seeded
Best Transplanted (Not Direct Seeded)
Soil Temperature Requirements
Air temperature gets all the attention, but it is soil temperature that determines whether your seeds will germinate or rot. Seeds planted in soil that is too cold sit dormant and are vulnerable to fungal disease, insect damage, and moisture rot. A simple soil thermometer pushed 5 cm (2 inches) into the bed gives you the information you need.
Minimum Soil Temperatures for Germination
Peas, spinach, radish, lettuce, arugula, cilantro. Can be sown as soon as soil is workable in spring — often 3-4 weeks before last frost.
Carrots, beets, chard, turnips, parsnips. Sow 1-2 weeks before last frost once soil has warmed above 10C.
Beans, corn, squash, cucumber (if direct seeding). Wait until 1-2 weeks after last frost.
Melons, watermelon, okra. Rarely direct seeded in most of Canada — transplant instead.
Canadian tip: Raised 30" beds warm faster than in-ground gardens because more surface area is exposed to sun and air. This can give you a 1-2 week head start on direct seeding compared to flat-ground gardens — a meaningful advantage in short- season areas like the Prairies or Northern Ontario.
Seeding Depth Rules of Thumb
Seeding depth is one of the most common mistakes new gardeners make. Too deep and the seed exhausts its energy reserves before reaching sunlight. Too shallow and the seed dries out before roots can establish. The universal rule is simple: plant seeds at a depth of 2-3 times their diameter. Here is how that translates for common direct-seeded crops.
Barely Cover (1-3 mm)
Tiny seeds — press into soil surface, barely cover with fine soil or vermiculite
- Lettuce
- Carrots
- Celery
- Dill
Shallow (6-12 mm / 1/4-1/2")
Medium seeds — plant at 1/4 to 1/2 inch depth in fine soil
- Spinach
- Beets
- Radish
- Arugula
- Turnip
Deep (2.5-5 cm / 1-2")
Large seeds — push into soil to finger-depth
- Beans (bush and pole)
- Peas
- Corn
- Squash / Cucumber
Thinning After Germination
Direct seeding always results in more plants than you need — and that is intentional. You sow densely to ensure good germination coverage, then thin to the proper spacing once seedlings have established. Many gardeners find thinning emotionally difficult (pulling out perfectly healthy seedlings feels wasteful), but overcrowded plants produce stunted roots, reduced yields, and increased disease pressure. Thinning is essential.
The best time to thin is when seedlings have their first true leaves (the second set of leaves that appear, which look like miniature versions of the adult plant). At this stage, plants are large enough to handle but small enough that removing neighbours will not disturb the roots of the plants you are keeping.
Thinning Guidelines
- Carrots: Thin to 2" apart. Thinning carrot seedlings are edible as microgreens in salads.
- Beets: Thin to 4-6" apart. Each beet "seed" is actually a cluster of 2-4 seeds, so thinning is always necessary.
- Radish: Thin to 2" apart. Radishes grow fast — thin within 7-10 days of emergence.
- Beans: Thin to 4" apart. Snip extra seedlings at soil level rather than pulling — pulling can disturb neighbours' roots.
- Spinach: Thin to 3" apart for full-size leaves, or leave dense for baby leaf harvest.
Direct-Seeded Spacing in 30" Beds
After thinning, your direct-seeded crops should match the spacing patterns shown below. Notice how dense crops like carrots and radishes use 5 rows across the 30" bed width with tight 2" in-row spacing, while beans use only 2 rows with 4" spacing. These patterns are optimized for the biointensive system — maximizing plant density while ensuring each plant has enough space to produce well.
Carrots — 5 rows, 2" spacing (dense)
Maximum density for root crops. Thin to 2" after the first true leaves appear.
Radish — 5 rows, 2" spacing (dense)
Same dense pattern as carrots. Radishes mature in 25-30 days, making beds available for a second planting.
Beans (Bush) — 2 rows, 4" spacing (moderate)
Wider spacing gives bean plants room for their bushy growth habit and allows air circulation to prevent mildew.
Succession seeding tip: Direct-seeded crops like radishes and lettuce mix are perfect for succession planting. Sow a new bed every 2-3 weeks from early spring through midsummer for continuous harvests. Our planner calculates these succession windows automatically based on your zone's frost dates.
Common Direct Seeding Mistakes
Seeding too early in cold soil
Seeds planted in cold, wet soil rot before they germinate. Patience pays off — wait until soil temperatures match the crop's requirements. Two weeks of waiting results in faster germination than four weeks of sitting in cold ground.
Planting too deep
Small seeds like carrots and lettuce need light to germinate. Burying them even 1 cm too deep can prevent sprouting entirely. Follow the 2-3x seed diameter rule.
Letting soil crust over
Heavy rain or overhead watering can form a hard crust that tiny seedlings cannot push through. Keep the surface lightly moist and consider covering small seeds with vermiculite instead of soil.
Skipping thinning
Overcrowded carrots produce thin, twisted roots. Overcrowded beets stay marble-sized. Overcrowded beans get powdery mildew. Thinning feels wasteful but produces dramatically better results.
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