Do I have to pre soak my microgreens and sprouting seeds? 

So you’ve heard all about the health benefits related to growing and consuming microgreens or maybe you even want to start an urban farm selling to chefs, restaurants and local outlets and you’ve run into the issue of pre soaking your microgreen seeds (or not) and want to know more. This article is for you.

At Grow Sow Greener we advocate a regenerative approach to gardening and look to the natural world for the correct way rather than a chemical fix which costs the hip pocket as well as the environment for most of the actions we take- both indoor and outdoor.

Most of us grow microgreens indoors, under artificial LED lights on sometimes soilless grow mats or pads. This admittedly is a process far removed from nature, however our natural philosophy can still be extended to the pre soaking of microgreen seeds and we’ll throw in a little science as well 😊

The natural world is a beautiful complex balance. Plants, pollinated in the spring and summer, drop seed in the autumn and winter where they lie dormant until the warm spring rains (and higher ambient temps) trigger an awakening from dormancy. This spring rain soaks and softens the hulls, it hydrates and triggers the seeds to grow. This is why seeds are stored dry cold conditions. 

THEN WHY DON’T WE PRE SOAK ALL OUR MICROGREEN SEEDS? 

The short answer is it isn’t necessary, small seeds up to the size of radish seeds can absorb enough moisture through the medium and they’ll germinate happily with out any interference from us. Go right on ahead and sow your trays dry from the packet.

WHICH VARIETIES SHOULD WE PRE SOAK?

Some seeds such as peas, sunflowers, beets, grains and grasses have an inbuilt defence mechanism preventing them from germinating at the wrong time. Their hulls contain a chemical called Abscisic acid (ABA) which is a compound that regulates the dormancy of the seed. That is it prevents germination until the environment has sufficient moisture to ensure the plants survival after germination.  When we pre soak, we dilute this chemical and hydrate the seeds and soften the hull. This ensures all the seeds germinate at the same time for a uniform consistent crop.

Pre soaking these varieties is extremely important. It relates directly to the seeds germination and ensures all seeds germinate at the same time and the whole batch germinate fully. Should you not pre soak some seeds will grow and others wont, some will partially germinate and these stragglers will cause problems for your whole crop when they rot and go bad. When growing microgreens for health or profit we aim for complete germination at the same time achieving a good uniform consistent crop.

So with microgreens, even grown in controlled somewhat artificial environments, we’re really just mimicking a very natural seasonal occurrence to trigger a very natural biological effect. Were intentionally getting the seeds and hulls very wet (and warm) so that they can absorb enough water as well as to shed or dilute inhibiting compounds kick starting the process of germination and growth.

ARE THERE ANY MICROGREEN SEEDS I SHOULDN’T PRE SOAK?

Don’t pre soak mucilaginous seeds. Mucilaginous seeds form a gooey gel like coating once wet and will be impossible to spread evenly over your microgreen growing tray or container if you do. Some examples of these gell forming seeds are basil, flax, chia and rocket.

Smaller microgreen seeds such as the brassicas- broccoli calabrese, cabbages, red Russian and Tuscan black kales, daikon, china rose and Rambo radishes, mustards chives and cress can all be soaked. We find however that its an unnecessary and time consuming hassle, especially as these small seeds stick together making tray preparation a nightmare with uneven clumps of growth 

Another reason why we soak the larger seeds, aside from the fact they are easier to spread when wet than their smaller cousins, is related to how we grow microgreens. When we look at nature the seeds are encapsulated in damp soil, the whole surface area of these seeds are in contact with it and are able to absorb the moisture necessary.

When we grow microgreens we surface sow, this makes for a cleaner harvest however more of the seed is exposed to air rather than the damp growing medium, be that compost, coco coir or a hemp or coco coir grow mat. Smaller seeds have a larger proportion of their surface area in contact and able to absorb moisture. Being smaller they also have less volume needed to absorb to trigger germination.

On the other hand larger seeds require a larger volume of water to germinate. They also have a smaller area (in proportion to their total surface area) in contact with the damp media. A good soaking helps remedy this unnatural position on the soil.

OTHER BENEFITS OF PRE SOAKING MICROGREEN SEEDS

Pre soaking also helps seedlings shed their husks, some seeds such as beets and chard have multiple seeds inside the hull, and  a good pre soak softens and splits the hulls allowing the seeds inside to germinate and grow undisturbed. It softens the husks of the sunflower seed making their removal from the crop a much easier affair.

SO WHICH MICROGREEN SEEDS DO YOU PRE SOAK?

Peas, sunflowers, beets, chard and any no gel forming seed larger than that of a radish seed benefit from a pre soak.

HOW DO I PRE SOAK MY MICROGREEN SEEDS?

Pre soaking is an extremely easy activity, Simply work out how much dry seed you need per tray and immerse them in room temperature tap water for six to 12 hours. Any longer we recommend a rinse and drain to prevent anything unwanted growing in the soak water. Much like we do when growing sprouting seeds.

There are many methods for pre soaking, you can simply put your organic microgreen seeds in a jar and cover with water for smaller batches or fill a natural hemp sprouting bag and immerse in a bucket of water overnight for larger grows. The hemp has the added bonus for having anti mould properties. Whatever method you use its important when filling to ensure enough agitation so pockets of bubbles cannot become trapped resulting in uneven germination. Some urban farms automate this and other process saving time and labour. Click here to learn more about automising your urban microgreen farm.