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Sowing Seeds

Sowing seeds — how deep, and how long to wait.

Seed sowing has a narrow margin for error and very clear rules. Almost every failure traces back to one of three things: sown too deep, allowed to dry out, or sown into soil that is too cold. None of them are visible until nothing comes up.

The three things that matter

Depth first. A seed carries only enough stored energy to reach the surface once. Sown too deep it exhausts itself underground, and you never find out why. The general rule is to cover a seed to roughly two or three times its own thickness, which for many small seeds means barely covering them at all.

Moisture second, and it must be constant. A seed that begins germinating and then dries out is dead, not dormant. This is the reason seed trays fail more often than direct sowings — a small volume of mix dries in hours on a warm day.

Soil temperature third. Germination times assume a suitable temperature; below it, seeds sit and wait, and may rot before they sprout. The same seed can take twice as long in cold soil as the figures below suggest.

Sowing depth and germination time

Sorted shallowest first. The shallow end of this list is where most mistakes happen, because those seeds need barely any covering at all.

CropSowing depthGerminationCategory
Apple cm30-90 daysFruits
Apricot cm30-90 daysFruits
Avocado cm14-60 daysFruits
Blackberry cm14-30 daysFruits
Blackcurrant cm14-30 daysFruits
Blood Orange cm14-30 daysFruits
Cherry cm30-90 daysFruits
Cherry Guava cm14-56 daysFruits
Feijoa cm14-42 daysFruits
Finger Lime cm14-30 daysFruits
Gooseberry cm14-30 daysFruits
Grape cm14-30 daysFruits
Grapefruit cm14-30 daysFruits
Guava cm14-56 daysFruits
Kiwifruit cm30-90 daysFruits
Kumquat cm14-30 daysFruits
Lemon cm14-30 daysFruits
Lime cm14-30 daysFruits
Loquat cm14-30 daysFruits
Makrut Lime cm14-30 daysHerbs
Mandarin cm14-30 daysFruits
Meyer Lemon cm14-30 daysFruits
Nectarine cm30-90 daysFruits
Olive cm30-90 daysFruits
Orange cm14-30 daysFruits
Persimmon cm30-90 daysFruits

Germination times assume reasonable soil temperature and consistent moisture. Cold soil can double them, and a dry spell mid-germination will end them.

Direct sowing or trays?

Direct sow root crops

Carrots, radishes, parsnips and most root crops resent transplanting, because disturbing the taproot causes forking and stunting. Sow them where they will grow.

Trays suit slow starters

Crops with a long lead time benefit from a head start in trays, where you can control warmth and moisture precisely. They also protect expensive seed from pests at the most vulnerable stage.

Trays dry out faster

The trade-off is vigilance. A tray holds very little mix and can dry in a single warm afternoon, which is fatal mid-germination. A ground bed is far more forgiving of a missed check.

A reliable sowing routine

Check the depthLook it up rather than guessing. Too shallow is recoverable; too deep is not.
Water before sowingMoisten the bed or mix first, so you are not washing seed around afterwards.
Sow and cover lightlyFirm gently so the seed contacts damp soil, without compacting it.
Keep it damp, not wetConsistent moisture until emergence. This is the step that fails most.
Note the dateWithout it you cannot tell a slow germinator from a failed sowing.

Know when it should appear

Recording the sowing date is what lets you tell slow from failed. If the germination window has passed with nothing showing, re-sow rather than keep waiting.

FAQ

Common questions from home gardeners.

How deep should I sow vegetable seeds?

A common rule is to cover a seed to two or three times its own thickness. For fine seeds such as lettuce and many herbs that means barely covering them; for large seeds such as beans and peas it means a few centimetres. Individual figures are on each plant guide.

Why did my seeds not come up?

The usual causes are sowing too deep, letting the seed dry out part-way through germination, or sowing into soil that is too cold. Old seed and sowing outside the crop's window are also common. Recording the sowing date makes it possible to tell a failure from a slow germinator.

Should I soak seeds before sowing?

Some large or hard-coated seeds benefit, but most vegetable seed does not need it and soaked seed is more awkward to handle. Consistent moisture in the soil after sowing matters far more.

How long do seeds take to germinate?

Anywhere from a few days to several weeks depending on the crop and the temperature. Each plant guide records a germination range; treat the upper figure as the point at which to consider re-sowing.

Can I sow seeds too shallow?

Yes, though it is less often fatal than sowing too deep. Very shallow seed can wash away, dry out faster, or fail to anchor properly. Firming the soil so the seed makes contact with damp soil helps.

How does Plotera help?

Sowing dates are recorded per zone alongside the expected germination window, so you can see at a glance whether something is late or simply has not had time yet.

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