Introduction

You’ve likely heard microgreen farmers talk about soaking their seeds before planting. Why soak your seeds? Why only soak certain varieties? This blog will cover why it can be beneficial to soak certain varieties. We’ll also cover our preferred method for soaking seeds.

The Science of Soaking

A vast majority of food crop seeds have their germination process triggered by water.

• Water is considered the primary germination regulator for seeds. Germination begins with seed imbibition, which is the absorption of water by the seed.
• Sufficient moisture must be present for germination to take place in most crops. A lack of water availability is often the primary limitation affecting seed germination.
• Water is necessary for several critical processes during germination.
  1. It softens the seed coat and improves seed permeability.
  2. It activates enzymes that break down stored food reserves in the seed - the endosperm.
  3. It enables the mobilization of nutrients like lipids, carbohydrates, and proteins.
  4. It initiates cellular activity and growth processes in the seed embryo.
• Seeds need water for germination, even if they need other triggers, like specific temperatures or light. With some exceptions, it's safe to say that water triggers germination in over 90% of food crop species. The ability to detect and respond to water availability is a fundamental trait for seeds, as it indicates suitable conditions for the growth and survival of the emerging seedling.
• Soaking benefits certain varieties by helping overcome seed dormancy.
  1. Softens hard seed coats.
  2. Leaches out germination-inhibiting compounds.
  3. Triggers biochemical processes that lead to germination.
• Not all seeds benefit from soaking. It's most helpful for larger seeds with thick coats like peas, beans, and sunflower.
  1. Avoid soaking smaller seed varieties.
  2. Soaking for too long can lead to rotting or reduced germination.
  3. The optimal duration to soak is 6-18 hours.
• The drawback to soaking seed is that it makes it harder to spread the seed around your 1020 tray when it’s time to plant. Thankfully, larger seeds are easier to spread around evenly with your hands when they’re wet. Trying to spread around, say, soaked celery seed, which is much smaller than pea seed, would be a nightmare.
• My farm, Piedmont Microgreens, soaks fava, tendril pea, field pea, and sunflower. We plant the other 30+ smaller varieties dry. The only other large-seeded variety we grow is nasturtium. It could benefit from soaking, but we don't soak nasturtium. I know most people also soak wheatgrass, although we don't grow wheatgrass at my farm.
• Soaking seeds is not required. Plenty of large-scale producers do not soak their seeds because it’s too cumbersome. Imagine you’re planting 300 trays of peas at a time. You’d need a literal kiddy pool, or two, to soak that kind of volume of peas. You’d need to drain all the excess water afterward, and then physically manage all that hydrated seed. A farm of that scale likely uses an automated planting machine, and not all automated planters are capable of handling wet seeds. Although soaking seeds can be beneficial, it also adds an extra step to the production system, which is an inherent drawback. So, don’t let anyone tell you soaking is a required step.

The Best Method for Soaking

Now that we understand why soaking can be beneficial, I want to share a few methods for efficiently soaking your seeds. The two primary methods I’ve seen are the bag method and the bucket method. The bag method uses any sort of flexible mesh strainer bag, such as a paint strainer - Home Depot. You can buy multiple small bags if you want to isolate one tray of seeds at a time. You can use a larger bag if you’re comfortable putting multiple trays of seeds together. The former is advantageous because you can guarantee every tray gets the correct amount of seed. The latter is advantageous because you need fewer bags, but you have to eyeball the distribution of seed across multiple trays. Some trays could get slightly more seed, while others receive slightly less. I think a slight variation in the seed amount is okay. So, I prefer the efficiency of soaking multiple trays of seed together.

The second method uses rigid buckets, like the classic five-gallon Home Depot buckets seen in the photos below. There’s a bit more upfront preparation because you’ll need to drill drainage holes in a few buckets. I call this method the Double Bucket System. You weigh out the volume of seed needed for one or more trays and place it in a bucket with pre-drilled holes. Make sure the hole size is smaller than the smallest seed variety you intend to soak. This is your drainage bucket. Put the drainage bucket with the seeds inside another identical bucket with no holes. When it’s time to soak your seeds, usually starting the night before planting, fill the top bucket with water. After the seeds soak overnight, simply lift the top bucket up and out of the bottom bucket. The excess water will drain out the bottom. You can then use the rigid bucket to distribute the seeds evenly across multiple trays. We have three bucket sizes to use depending on the number of trays we need to soak. We’ll also mark each bin with a piece of tape to indicate how many trays of seed are soaking together.

If you use the Double Bucket System, you only need one bucket of each size to have holes. For example, if we plant ten trays of sunflower and ten trays of peas every Monday, both varieties will soak overnight. We’ll put one variety in the drainage bucket and place that bucket inside a no-hole bucket, as described above. The other variety will soak in another no-hole bucket. When it comes time to plant, we’ll drain the first variety and plant it. With the drainage bucket now free, we'll dump the other variety into it, then plant that as well. To skip this step, just match the quantity of drainage and no-hole buckets for each size. Keep in mind that soaking seeds in a mesh bag still requires you to put the mesh bag inside a bucket or plugged sink to soak.

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