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how to use seed starting plugs

Pros and Cons of Polymer-Bound Seedling Plugs

Wanted: the perfect media

People have been trying to start seeds in weird stuff for a long time. From gravel to packing peanuts, just about everything has been tried.

The great thing about seeds is that they come pre-packaged in a neat shell with all the nutrients they need to germinate and thrive for the first few weeks of their lives.

This means that the requirements of a seeding material are few. Most seeds require only three things from their media:

  • consistent moisture (but not wetness)
  • aeration (oxygen throughout the media)
  • lack of disease (not recycled from diseased crops)

(Of course, seedlings also require light and warmth, but these aren’t connected to the type of media.)

With these three things, almost anything will do for seedlings—but this doesn’t mean that anything will do for you. Different types of systems and the personal preference of farm managers will determine other characteristics of the seedling media you choose.

For example, you’ll need a media heavy enough to provide stability, but light enough to handle and move. You may care deeply about using sustainable materials, so you want something you can either recycle or reuse. These farmer-specific goals will whittle down your media options.

Recently, flexible or polymer-bound plugs have risen in popularity, especially for systems with recirculating irrigation (like hydroponic systems) and limited space. There are several nice qualities that bring them to the top of the list.

Pro: clean and neat

Polymer-bound plugs incorporate an organic material like peat or coco coir and bind it together with a polymer—picture a rubbery glue. This makes the plug very contained.

Unlike a soil, plain peat, or plugs made of loose media, little bits of material will not break off and clog up irrigation.

Pro: Easy to handle

Polymer-bound plugs are separate from each other, and one piece. This means you won’t have to cut or tear plugs apart, avoiding root damage and saving time.

Handling polymer bound plugs won’t create dense portions in the root zone either, which happens with some media types and causes damage and anaerobic zones.

*This does not mean that you should be handling seedlings a lot! The less they are handled, the fewer disease opportunities there are!

Pro: convenience

Another trait desired by many growers in tightly spaced systems with a need for labor efficiency is that polymer bound plugs can be extremely convenient. Many are shipped already in the seedling tray, and already damp; growers simply pull the tray from the package, adds seeds, and place it into their seedling system.

This saves time sorting plugs (or loose media), filling trays and wetting the material.

Pro: faster germination

Compared to some other types of media, polymer-bound plugs have shown faster germination.

Even a few days can speed up your growing cycle. If you save 2–3 days every turn, you can fit in one extra harvest a year; that translates into more revenue! This could very well make polymer plugs worth the investment, depending on what your current seedling operation is.

Con: hard to reuse

Polymer-bound plugs can’t be reused in the typical sense. Once seeds grow in a plug and are transplanted into the maturing system, roots tend to take over. By the time you harvest the crop and take the root ball out of the system, the plug is too overgrown or torn apart by roots to be reusable.

Growers can reuse plugs in which the seed did not germinate, but this can open doors for disease and is more labor intensive. The final option is composting. Polymer-bound plugs will decompose and compost over time, but it takes 3–4 years for them to break down.

Balancing benefits with cost

Of course, an important factor in choosing the substrate is weighing the benefits gained against the cost. In a comparison between polymer plugs and soil plugs for a small grower, for example, polymer plugs will come in second for initial and recurring costs.

Something that growers must calculate into that is how long it takes them to plant each tray of plugs. If it takes growers 2 minutes longer to plant a tray with soil, that might make up the price distance between the two types.

So which is better?

We’ve used polymer-bound plugs, soil, rockwool, peat, oasis, and more. None is universally best, and growers have many options. But polymer bound plugs are the best for growers who want to run a clean hydroponic system and reduce labor time.

Want more info on hydroponic substrates?

There’s a whole course on substrates (media) and how to choose the best one for your system. Check it out here:

The benefits of polymer-bound seedling plugs have caused a rise in popularity, especially in systems with recirculating irrigation & limited space.

How do you use seed starter plugs?

Herein, how do you use a seed starter?

Use a pencil or chopstick to break open the surface of the soil plugs and form a small indention for the seeds. About ¼ inches is deep enough. Drop two seeds into each indention. Place the included cover over the seed starter kit to keep the seeds warm and retain moisture while they germinate.

Likewise, how do you start seeds with peat pellets? How to Start Seedlings Indoors with Peat Pellets

  1. Decide how many peat pellets you need and place them in the tray.
  2. Add enough water to the tray to cover half the height of the peat pellets.
  3. Wait 5 to 10 minutes for the pellets to fully expand.
  4. Slightly tear the top of the netting on each pellet.
  5. Now the fun part – plant your seeds!

Consequently, what is a starter plug?

A starter plug, or starter plant plug, can be defined as a small, compact mass or sample of a solid growing medium that is used mainly for seed germination and rooting cuttings. Gardeners can add their seeds or cuttings to empty plant plugs, or they can purchase plugs that already contain seeds.

How long can seedlings stay in peat pellets?

Fill the tray with 1 inch of water and allow the pellets to fully absorb the moisture and expand to their full height of about 3 inches. It can take the pellets 30 to 60 minutes to fully absorb the water, and in dry conditions, they may require more water to completely hydrate.

To use jiffy plugs for seed sowing purposes, you need to soak them in water or a mild nutrient solution . Place the jiffy plugs in a tray and gently pour water or nutrient solution of low EC. Give it 5 minutes and all the jiffy plugs will expand to 3-4 times its height. Now they are ready for planting.