October 23, 2026

How to water seeds after sowing until they sprout

Sown seeds need the top skin of soil kept damp every day until they sprout. In warm, dry weather that takes a gentle watering once a day, and on hot, windy days twice. A soil probe in the bed reads moisture deeper down, below the seed, so for the first week or two you water by the surface and by the rain.

Why the seed layer dries first

A seed takes up water through its coat before it has a root. The water wakes enzymes that break down stored food, and the embryo starts to grow. Once that starts, a seed that dries out can die, because it has no root to pull water from deeper soil.

The surface is the driest place in the bed. Sun and wind strip moisture from the top layer faster than capillary action can lift water up from below. A probe buried in the bed sits in that wetter zone. It can show a comfortable number while the soil around your seeds has gone pale and crusted.

In our own garden we sowed lettuce and spinach in the ground bed on July 29. Between July 24 and August 6, that bed's probe dropped from 62% to 32%. The 32% low came one day after the year's hottest afternoon in our garden, 97°F. That reading stayed above the 25% level where a per-bed dry alert fires. The probe had no view of the seed layer during that stretch.

Step 1. Soak the bed the day before you sow

Water deeply enough that the soil is moist well below sowing depth. A wet subsoil feeds the surface from below by capillary rise, which slows how fast the seed layer dries. Dry soil underneath does the opposite. It wicks water down and away from the seeds.

Step 2. Firm the soil over the seeds

Press the soil down with your palm or the back of a rake once the seeds are covered. Firm contact lets water move from soil particles into the seed coat. Loose, fluffy soil leaves air gaps around the seed, and air carries no water to it. Our guide to seed-starting soil mix and when to sow covers the bed you sow into.

Step 3. Water gently right after sowing

Use a watering can with a fine rose or a hose on a mist setting. A hard stream washes small seeds out of place. It also packs the surface into a crust that seedlings struggle to push through. Keep going until the surface turns dark and stays dark for a minute.

Step 4. Check the surface each morning

Touch the top of the soil before the sun reaches the bed. Damp soil looks darker and sticks to your fingertip. Pale soil that crumbles off your finger needs water that day. In hot spells, check again in mid-afternoon, because the surface can dry out before evening. Our guide to the best time to water your garden covers timing once plants are established.

Step 5. Let the rain guidance decide the skip days

Log the sowing in Siltwell so the bed has an active planting. The Today screen shows garden-level watering guidance only when a garden has active plantings. It shows one of three states.

• Hold. The forecast for today and tomorrow totals 5 mm of rain or more.
• Covered. The past three days brought 5 mm of rain or more.
• Water. Neither of those applies, so the garden has had little or no rain.

For seeds, treat hold as a reason to leave the can in the shed. Treat covered with more care. Rain three days ago soaked the root zone, but the surface may have dried since, so check it with your finger before you skip. Without a connected station, the recent-rain figure comes from a weather model's estimate for your area.

Step 6. Cover slow-sprouting seeds

Lay burlap, a board, or shade cloth over rows of slow seeds such as carrots and parsnips. The cover blocks sun and wind, so the surface loses water more slowly. Lift it each morning to check underneath. Take it off the day the first seedlings show, or they grow pale and weak in the dark.

Step 7. Hand off to the bed probe once roots reach it

Once the seedlings carry a few true leaves, their roots are growing down toward the zone the probe reads. How soon that happens varies with the crop and with the depth of your probe, and we have no fixed day count for it. From that point the probe reading starts to track the water your plants can draw on.

If your bed has a probe connected to Siltwell, the per-bed dry alert takes over here. On a capacitive probe, the alert needs its latest two readings under 25%. A Watermark sensor triggers it when its latest two readings both pass 60 cb. The alert names the dry bed, and watering it stays your job. Our guide to reading a per-bed soil moisture probe explains what the number tracks.

What can go wrong

• Crusting. Heavy water on fine soil seals the surface as it dries, and small seedlings can't break through. A thin layer of fine compost or vermiculite over the row keeps the surface open.
• Washout. A strong stream drives seeds into clumps and leaves bare patches. Two light passes with a fine rose move less soil than one heavy soak.
• Damping off. Constantly soggy, cool soil favors the water molds that rot seedlings at the soil line. Keep the surface damp and let it lose its shine between waterings.
• Trusting the probe too early. A buried probe can show a healthy number while the seeds above it dry out. Go by the surface until the seedlings root.

Nothing in the app sees the seed layer. The rain guidance works at garden level and the probe reads below the seeds, so your finger is the only gauge of the top skin of soil until the seedlings root.

Suppose your bed reads 40% the morning after you sow, and the surface is pale and dry. Water the seeds that morning. The 40% describes the soil below them, and the seeds sit in the layer that dried overnight. If rows keep failing in a bed you water daily, sow a short test row under a board next to an open one and compare when each sprouts.