Do Microgreen Trays Need Holes?

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Microgreens are a great way to grow nutritious salad greens and sprouts in an indoor or hydroponic setting, but since they’re typically grown indoors you might wonder whether they need holes for drainage. 

So do microgreen trays need holes? Microgreen trays with a soil-based medium don’t need holes for drainage because the root systems of microgreens are so shallow. Microgreens also typically grow too fast to become waterlogged. However, holes in microgreen trays can be useful for watering the tray from underneath. 

Because microgreen trays don’t require drainage holes, microgreens are versatile when it comes to what they can be successfully planted in. Keep reading to find out more about holes in microgreen trays. 

Most Planters Require Holes

The reason that many people assume that microgreen trays require drainage holes is that gardeners have been trained from a young age that plants in a sealed container like a pot need to have some way for the water to drain away from their roots to prevent root rot and plant death. This means that most planters come with holes for drainage and a water tray that is placed underneath to catch excess water.

People are used to this rule as applied to indoor gardening, so it comes as a surprise to many gardeners that if they are planting trays of microgreens, their microgreens shouldn’t require any drainage. There are a few different reasons for this, but microgreen trays don’t require the holes that most planters do. 

Why Don’t Microgreen Trays Need Holes? 

There are a couple different reasons why microgreen trays don’t need holes for drainage while larger plants do. Here are a few of them: 

  • Microgreens are grown and harvested quickly. Most microgreens are grown and harvested within a two-week period, which means that most microgreens aren’t placed in standing water long enough to cause any root damage. 
  • Microgreens have shallow root systems. Unlike other kinds of seedlings, microgreens have shallow root systems that don’t go to the bottom of the planting tray, which means they are somewhat protected from any water that may gather at the bottom of the tray. 
  • Microgreens are often grown on hydroponic grow mats. These grow mats provide the necessary moisture retention and drainage necessary to prevent seeds from becoming waterlogged, but hydroponic grow mat trays do not need further drainage in the form of holes. 

Even though microgreen trays don’t necessarily require holes, they are still a good idea in many cases. Holes in the bottom of a tray with microgreens being grown in a soil-based medium can allow water to be wicked from a tray underneath, eliminating the need for overhead watering of the microgreens.

What Other Design Elements Do Microgreen Trays Need? 

Microgreens are a very simple crop to grow, and as long as a microgreen tray is flat and shallow, they can be grown in just about anything. Plain black nursery style growing trays are the kind that many growers use due to their durability and relatively low cost. 

Because they are so simple to grow, those growers who would prefer to recycle can use any number of found household objects as a functioning microgreen tray, from plastic takeout trays to disposable pie plates. Since the tray doesn’t require drainage, this greatly extends the versatility of microgreens as an indoor crop. 

A microgreen tray needs access to light, whether from an artificial light setup or a strong light from a sunny window. How much sunlight is required for strong growth is dependent on the species of microgreens being cultivated. 

How to Sanitize a Microgreen Tray

While microgreen trays don’t need drainage holes, they do need to be sanitized before use. This is because they will be used to sprout seeds, and seedlings are quite fragile when they first sprout. 

Any kind of pathogens in the soil can cause seedlings to be damaged, so it’s important that anything used as a microgreen tray is sterilized between growing periods. This helps prevent soilborne disease from spreading. While older plants may be able to fend off a soilborne pathogen, young seedlings are quickly overwhelmed by any kind of contact with disease.  

To sanitize a microgreen tray for reuse, wipe clean and spray down with hydrogen peroxide or another greenhouse cleaner, allowing the tray to air dry in a sunny area. As long as they are properly sanitized, seed trays can be recycled and used over and over from year to year, reducing the need to generate new plastics for annual replacements. 

Hydroponic Microgreen Trays vs. Soil-Based Microgreen Trays

The two major methods of growing microgreens in indoor trays are through hydroponic systems and soil-based systems. In hydroponic systems, the microgreen seeds are grown on a hydroponic mat that holds water and nutrients that the seeds can germinate on. Because microgreen seeds are shallow and germinate from the soil’s surface, they don’t actually require a soil-based medium to grow.

Soil-based microgreen trays can also be used, and these trays are set up similarly to the hydroponic systems except that a high-nutrient seed starting soil is used in the tray instead of the hydroponic grow mats. Seed starting soil typically has mycorrhizae added to stimulate root growth and encourage the health of new seedlings.  

While neither hydroponic microgreen trays nor soil-based microgreen trays require holes for drainage, hydroponic microgreen trays have the additional benefit of being soil-free, which can reduce the amount of mess generated by gardening projects indoors. It also helps prevent soilborne pathogens and allows the grower to have very precise control over nutrient input.

RELATED: The 12 Best Microgreen Trays on the Market

How to Figure Out How Many Seeds You Need for Your Microgreen Tray

Since you need approximately an ounce of microgreen seeds per standard 10-inch by 20-inch tray, that gives a good guideline to estimate how many ounces of microgreen seed you’re going to need over the course of the growing season. Microgreen seeds have a limited shelf life, so it’s important to have an idea how many you’ll need before you invest in them. 

The number of seeds you need for your microgreen trays will depend on how many trays you plan to grow. For household use, a grower might only need a few trays and a few ounces of microgreens, but others who are growing for commercial or culinary uses may end up planting several dozen ounces of microgreen seeds at a time. 

Types of Microgreens to Grow in Microgreen Trays

There are many different kinds of microgreens that can be grown in trays with or without drainage holes. Here are some of the types of microgreens you can grow indoors in a microgreen tray: 

Different types of microgreens have different textures, colors, and flavors that they can add to sandwiches and salads. Microgreens are also great as a garnish for roasted meats and soups. Since many types of herbs such as mint and basil can also be grown as microgreens, these seedlings can then be used in place of more mature herbs for a more delicate herb flavor. 

The fact that many different varieties of plants can be grown as microgreens gives growers versatility when it comes to cornering markets, as they may be able to provide a specific subtype of microgreens that other local growers aren’t producing. 

Microgreen Trays Are a Versatile Choice for Indoor Gardening

Whether you’re looking into growing microgreens to supplement your family’s kitchen or you’re considering growing them for niche commercial use in high-end culinary markets, microgreens are a great choice for anyone who is interested in getting into indoor gardening. 

Microgreens Corner
Microgreens Corner
We are Janette & Jesper, and we love microgreens.

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