How To Make Seed Starting Flats or Trays Without Plastic

This is a busy time of year for many home growers. Polytunnel gardeners and those who grow without one of these useful structures will be hard at work sowing seeds. But sowing seeds can often leave us feeling adrift in a sea of disposable plastic. So what do you do if you want to sow seeds without using plastic seed starting flats or trays? How to you manage when seed trays you already own run out?

The good news is that you don’t have to rely on plastic trays to start your own seeds. There are a number of ways to sow and grow without relying on plastic trays. There are a number of ways to make seed starting flats or seed starting trays. We’ll take a look at one interesting option in this article.

The first thing to remember is that gardeners and growers sowed seeds for hundreds of years before plastic seed trays came along. They are by no means a necessity and there are a number of perfectly suitable and sensible alternatives. What is more, you definitely don’t need to spend a fortune to get sowing. Often, you can make use of things that are already available where you live.

You can use natural materials, or items that might otherwise have simply been thrown away. In other articles on this site, we’ve already looked at some of the ways you can repurpose old food packaging, and other reclaimed items from around your home to make seed starting flats, seed trays, pots and containers. These are all great options.

But in this article, we’ll look at how you can make your own seed starting flats using wood, so you have functional items that you can continue to reuse year after year.

Why Make Seed Starting Flats From Wood?

Wooden seed starting flats are what gardeners and growers used before the proliferation of single use plastic. And though they are heavier than the plastic trays you can buy, they are actually superior than the plastic trays for a number of reasons.

First of all, of course, there are the environmental issues that are at play. Plastic trays may last for a few years, especially the sturdier ones. But there will come a point when the plastic cracks or degrades. Usually, the plastic they contain is not then commercially recyclable. So they become a waste problem at the end of their useful life.

While you should use plastic items you already have for as long as possible. But buying new ones is not the greenest choice. Plastic is derived from finite and polluting fossil fuels, and takes a lot of energy – often non-renewable – to make. Plastic can be a very useful material (not least for your polytunnel). But where there is a good and viable alternative to plastic – we should try to take it.

Above and beyond the environmental reasons, there are more reasons why wooden seed flats are a good idea. As a breathable material, for example, wood is better for seedlings, since the wood will allow roots to ‘breathe’. And a wooden seed tray will regulate moisture levels better than a plastic container.

One final benefit is that making your own wooden seed flats can save you money. Since these can often be made using reclaimed wood, rather than new materials. Often, the only cost will be the screws or other fixings used in the simple DIY project.

Sourcing Materials for Your Wooden Seed Trays

Pallet wood, old floorboards, scrap pine and any other untreated scrap wood can be used to make wooden seed trays. It is important to make sure that the wood is untreated and has not been exposed to any dangerous substances when you are going to be using it to grow your food.

You will need to find boards that are 3-6 inches wide and 3/4-1 inch thick for the sides. And some more slats that are that thickness or less for the base. Softwoods are generally good for this purpose, cedar, pine etc… oak is rather heavy.

You’ll need to decide how large you would like your wooden seed trays to be. The standard flat size is 3 inches deep, 24 inches long and 14 inches wide. This will be large enough to sow a range of seeds, yet small enough to be light enough to carry reasonably easily.

However, while 3 inches is deep enough for many seeds like lettuce, etc… and for seedlings that will be pricked out relatively quickly, 4 inches in depth will be required for larger seedlings. And if you plan to continue to grow on your seedlings in the seed trays for longer than 4-6 weeks, then you should use containers that are at least 6 inches deep. Deeper trays are usually made half as long so that the weight does not become unmanageable.

Making the Wooden Seed Trays

You can join the simple wooden trays together using either screws or nails. So in addition to requiring the wood, measured to the right lengths, you will also need these fixings, and the screwdriver or hammer required to join together your construction.

• First, begin by assembling the sides of your wooden seed flats. Screw or nail the pieces together at right angles. (The shorter sides will be inside the longer ones.)

• Once you have made these wooden frames, it is time to nail or screw boards to this frame to make the base. Leave 1/16 inch between each bottom slat for drainage.

• Nail or screw twice through each bottom board at each side, to affix it to the sides.

• Then turn your trays over and fill them with your growing medium, and you can begin growing your seeds.

There is quite a bit of flexibility in how you construct your trays exactly, but the key things to remember are the required depth (at least 3 inches) and the weight. Don’t be tempted to make these trays too big or they may be challenging to move once they are filled and planted up.

Where to Use Wooden Seed Trays

Wooden seed trays are ideal for use in a polytunnel (or greenhouse) where you do not mind the water draining through. If you plan on sowing seeds indoors, it is important to remember that these are not watertight on the base. Wooden seed trays are ideal for use on polytunnel staging, and clever placement could allow you to conserve water by planting below them so other plants can catch the drips.

You can line the trays with newspaper or other untreated scrap paper to stop your potting mix from falling through.

If you wish to grow on a windowsill, the wooden seed tray can also be lined with a waterproof membrane to stop them from leaking. (Though of course some of the benefits will be negated when you use them in this way.) Plastic liners can turn deeper seed trays into useful window boxes. But if you are trying to avoid plastic then a rubber or silicone liner may be an alternative to consider.

Caring for Wooden Seed Flats

The key thing to remember when it comes to caring for your wooden seed flats is that they can last a long time if cared for properly.

Every year, after you have pricked out your seedlings, the trays should be cleaned out throughly. They should be left to dry out completely, and then stored carefully. If you do this religiously every year then the wood should last and you should have seed trays that you can continue to use for years to come.

Do you use wooden seed flats? Did you make your own? How to do you find using them and do you have any tips or recommendations to share? Let us know in the comments below.