Soaking microgreen seeds: which crops need it, and for how long

Soak peas for 6 hours and sunflower for 12, the figures Utah State University Extension’s protocol gives. Most other microgreen crops are sown dry, and basil is kept out of water entirely, because the seed turns to gel.

Two extension sources cover soaking, at two different levels of detail, and they agree. Utah State publishes a per-crop protocol: pea 6 hours, sunflower 12, every other variety in its table sown dry. The UC Master Gardener Program of Sonoma County gives the broader rule that large seeds benefit from a 6 to 12 hour presoak — the same logic extends to a seed that is not large but is wrapped in a hard fruit casing, which is where beet and cilantro sit. Both crop figures sit inside that range, so the general rule tells you why a seed gets soaked and the protocol tells you how long for the two crops it covers.

If you have not sown a tray yet, start with the beginner microgreens method, which covers sowing depth, watering, and where soaking fits into the wider sequence. The decision here is just that one: soak, skip, or actively avoid.

What soaking is actually solving

A seed germinates once it has taken up enough water to activate. For most microgreen seeds, that water comes easily from a moist medium: the seed sits on damp soil or a damp pad, the coat is thin enough to let water in within a day, and germination starts on schedule without any extra step.

Soaking exists for seeds where that path is slower than the grower wants, because something about the seed’s outer layer resists water. That “something” is one of a few physical traits: a genuinely hard, thick seed coat; a hull encasing the seed; a fibrous or woody fruit wall that has to break down before water reaches the seed inside. Presoaking gets that water in ahead of time, in a shallow dish, so the seed hits the tray already partway toward germination instead of starting from dry.

That is the whole decision rule. It is not about seed size on its own, and it is not about which crops “everyone” soaks. It is about whether the seed has a barrier worth pre-wetting through.

How long to soak

Utah State University Extension’s microgreens protocol is the more specific of the two sources, and it is short: pea 6 hours, sunflower 12 hours, every other variety in its table no presoak at all. That table covers arugula, basil, broccoli, cilantro, kale, a mesclun mix, radish and rutabaga alongside pea and sunflower, and all of them are sown dry.

The UC Master Gardener Program of Sonoma County gives the general version: presoak large seeds for 6 to 12 hours before sowing, to speed germination. That is a rule about a property of the seed rather than a list of crops, which is what makes it useful for a crop neither source names.

The two fit together without argument. Six hours for pea and twelve for sunflower both land inside the 6-to-12-hour window, so a grower following either source ends up in the same place. Where they are genuinely useful is at the edges: UC Sonoma’s rule is what you reach for with a crop Utah State does not list, and Utah State’s protocol is what settles a crop where the general rule leaves you guessing between six hours and twelve.

Hour counts outside that 6-to-12-hour window come from supplier practice rather than from either extension source. The one extension figure outside it is for a different crop and a different protocol — Oregon State Extension soaks wheat berries overnight, at least 12 hours, for wheatgrass, which is covered in wheatgrass vs microgreens.

Which crops fit which bucket

Crop	Soak?	Why	Documented duration
Sunflower	Soak	Thick hull around the kernel slows water uptake	12 h (Utah State); inside UC Sonoma’s general 6-12 h
Peas	Soak	Large seed, dense coat	6 h (Utah State); inside UC Sonoma’s general 6-12 h
Beet	Soak	The “seed” is actually a hard, multi-seeded dried fruit that resists water until it softens	Beet is not in Utah State’s table; UC Sonoma’s 6-12 h rule is written for large seeds, and the same barrier logic extends it to beet’s fruit casing
Cilantro	Sources disagree	Dry, two-seeded fruit (a schizocarp) with a tough outer wall	Utah State sows cilantro dry; UC Sonoma’s large-seed rule extends by the same logic to cilantro’s fruit wall. See below
Radish	No soak	Small brassica seed, thin coat, imbibes water fine from a moist covered tray	Utah State sows it dry
Broccoli	No soak	Small brassica seed, same reasoning as radish	Utah State sows it dry
Kale	No soak	Small brassica seed, same reasoning as radish	Utah State sows it dry
Mustard	No soak	Small brassica seed, same reasoning as radish	Not in Utah State’s table; the brassica reasoning applies
Basil	Do not soak	Mucilaginous coat gels in water, making the seed impossible to spread evenly	Not applicable — sow dry

Beet and cilantro are not soaked for the reason peas and sunflower are. Neither one has a genuinely hard seed coat in the way a legume does. What they have is an outer fruit wall — beet’s cluster of dried flower parts, cilantro’s paired dry mericarps — that has to break down or soften before the seed inside can take up water at a useful rate. Soaking works on the same principle either way: get water past the barrier before the tray clock starts.

Cilantro is the one crop where the two sources point different ways, and it is worth naming rather than smoothing over. Utah State lists cilantro among the varieties it sows dry. UC Sonoma’s rule, applied to the mechanism, says a hard-cased fruit is exactly the case a presoak is for. Utah State is running one protocol on one set of conditions, not testing whether soaking cilantro helps, so its “no presoak” is an absence rather than a finding against it. If you are following Utah State’s protocol end to end, sow cilantro dry; if you are working from the general rule, a 6-to-12-hour soak is a defensible choice on a crop this slow. Beet is simply not in Utah State’s table at all, so the general range is what you are left working from.

The case where soaking is actively the wrong move

Basil is the clearest exception among these crops, and it is not a borderline case. Basil seed is mucilaginous: on contact with water, the coat swells into a thick, slippery gel around the seed. That gel is not a minor inconvenience — it makes the wet seed nearly impossible to spread evenly across a tray, and it is the same property that makes chia and cress awkward on a soil-free pad, where they hold surface moisture and are prone to mould, as covered in growing microgreens without soil. The correct handling for basil is to sow it dry, directly onto a moist medium, and let it take up water at its own pace on the surface. There is no soaking step to add here, and no duration to look up, because soaking basil solves nothing and creates a seed you cannot sow cleanly.

If you keep any gel-forming seed on hand — basil, chia, cress — treat “do not presoak” as the rule for the whole group, not just for basil specifically.

Soaking is not sprouting

Soaking ends where sprouting begins, and sprouting is a different process with a different risk profile. University of Tennessee Extension describes sprout seed as fully submerged for the first 12-16 hours, grown without light, with the semi-germinated seed and root eaten along with the shoot, and treats sprouts as carrying higher food-safety risk than microgreens. That extended submersion in a warm, wet environment is part of why.

A microgreen presoak is meant to be a short, bounded step: seed goes into water for roughly the 6-12 hours UC Sonoma and Utah State’s figures fall within, then comes out and goes onto its growing medium in open air, where it germinates like any other seedling. If a soak runs long in a warm room — overnight and then forgotten about into the next day — it starts drifting toward the submerged, dark, warm conditions that define sprout production rather than a microgreen presoak. Rinse and drain the seed properly once the soak window is up, and do not treat “a little longer won’t hurt” as a safe assumption. The fuller food-safety picture, including why sprouts and microgreens are handled differently, is covered in microgreens food safety and sanitation.

How to soak correctly, for the crops that need it

For sunflower, peas and beet — and for cilantro if you are working from the general rule rather than Utah State’s protocol — the practical version of the 6-12 hour presoak looks like this: cover the seed with room-temperature water in a shallow dish or jar, enough that the seed can move freely as it swells, and leave it for somewhere in that 6-12 hour window — overnight is the easiest way to land inside it without watching a clock. Drain the seed through a fine strainer, rinse briefly, and sow it onto the medium the same way you would dry seed, pressing gently for good contact. Do not let soaked seed sit around wet after draining; sow it promptly so it is germinating in open air rather than sitting damp and unaerated.

If a seed still has not germinated on schedule after a proper soak and sow, the presoak itself is rarely the culprit — check viability, sowing depth, and moisture consistency using why microgreens aren’t germinating before assuming the soak duration was wrong.

Common mistakes

• Soaking small brassica seeds like radish or broccoli out of habit, when the sources give no benefit for that group and wet seed is genuinely harder to sow evenly.
• Applying Utah State’s pea and sunflower figures to a crop it does not list, instead of falling back to UC Sonoma’s general 6-12 hour rule for large seeds, and the same barrier logic where the seed is small but hard-cased.
• Soaking basil, chia, or cress, which turns the seed into an unsowable gel instead of speeding germination.
• Letting a soak run well past 12 hours in a warm room, which drifts toward sprout-like conditions rather than a bounded microgreen presoak.
• Assuming that extending the soak further speeds germination; past the point where the seed has taken up enough water, extra time in the water does nothing documented and adds handling risk.

Sources

• Utah State University Extension — Grow Your Own Microgreens is the source for the per-crop protocol: pea 6 hours, sunflower 12 hours, every other listed variety sown dry.
• UC Master Gardener Program of Sonoma County — Growing Microgreens is the source for presoaking large seeds 6-12 hours to speed germination.
• University of Tennessee Extension W1261 — Regulatory Considerations for Marketing Sprouts, Microgreens and Baby Greens is the source for sprout seed being fully submerged for the first 12-16 hours and for sprouts carrying higher food-safety risk than microgreens.
• Penn State Extension — The ABCs of Microgreens describes crop grouping by growth speed and is the basis for treating brassicas as a distinct, fast-germinating group that does not need the same handling as large or hard-coated seeds.