Do Microgreen Trays Need Holes?

If you're new to growing microgreens, you might not know whether to buy trays with holes or trays without holes. The holes in these microgreens trays actually have everything to do with watering and water containment. I've been watering the same exact way since I first started my business four years ago. This way is really simple, and it works really well. In this blog, I’m also going to share a more automated way of watering.

Trays with holes and trays without holes serve two different purposes. Trays with holes allow for water drainage, as well as for water to come up into your growing medium when you're bottom-watering your microgreens. Trays without holes don't allow for any water drainage and will actually contain all of the water within the tray. Commonly, these two trays are actually used together in tandem, but I'm going to share some other ways where you can actually get away with using one tray. 

I’ve seen people use only the one tray without holes method, and I actually don't recommend it at all. If your growing medium becomes fully saturated, this water is going to have nowhere to go. In this case, the roots of your plants are going to be sitting in this water-logged environment. They're going to be deprived of oxygen, and you’re going to run into certain problems that often come along with over watering, such as mold, fungus, and damping off. 

There are two correct ways that I recommend using these trays. The first way is the most common and simple—taking a tray with holes and placing it inside of a tray without holes. This allows for some water drainage out of the top tray, but also keeps the water contained in the bottom tray. So this way, when you're watering, water isn’t flowing out and all over the place, or onto whatever's below, whether it's the floor or trays beneath that you really don't want getting wet. Speaking of getting plants wet, not only can you use these trays for top watering, but you can separate these two trays, and add water beneath, which is called bottom watering. This allows the water to seep up into your growing medium from the bottom, preventing your microgreens from getting wet during watering. 

The same method of watering can be done on a larger and more automated scale by using flood and drain tables. So, instead of putting a tray with holes inside of a tray without holes (as in the first method), you're essentially putting between 4 and 16 trays with holes inside 1 huge tray that doesn't have holes.

This way, the water is pumped into the huge tray without holes, rises up, hits the growing medium of the trays, and gets the growing medium wet and saturated. Then, the water flows back out of the large flood and drain tray, hence the name flood and drain, which then allows your smaller trays with holes to drain the water back out. This is a very similar concept to putting a tray with holes inside of a tray without holes, but it's more automated, and it allows you to water on a larger scale.

This is more effective because, let’s say you did bottom watering with your two trays, and you over watered. If that water goes above the bottom tray and just sits in the top tray, there is nowhere for that water to go. It can't drain out of that top tray, even though there are holes, because there's so much water in there. However, with the flood and drain tables, the water simply rises up, hits the trays, and then flows back out. This method essentially keeps your growing medium at the perfect moisture content. Not to mention, you can put on a timer so that it goes off automatically, maybe at a time when you wouldn't be in your farm, like early in the morning. This is an amazing way to water your plants because it's automated, it's borderline perfect, and it reduces human error. 

Microgreens trays definitely need holes, whether you're growing a tray inside of a tray, or whether you're growing with the flood and drain tables, you should really have holes in your microgreens trays, instead of using a tray that doesn't have holes because of the problems I mentioned before. 

Now, you know the whole deal with these holes in the microgreens trays, but what if you have other questions or concerns? I created a Microgreens Support Group on Facebook, where you can ask any questions that you might have. There are growers from all over the world in there who are happy to help, including myself. This specific group that I started is actually known as the most positive, supportive, and helpful microgreens group on the internet.