Mad About Berries

How to Sow Plants in Plastic Pots

From time to time, one has to plant lots of different seeds. One of the options is to use styrofoam or similar containers with premade holes for plants – this is a very useful and quick method when you have to sow one sort of plant per container (like strawberries).

However, if you want to sow only a few plants of one sort but many sorts, varieties, etc., small plastic cups are perhaps a better option.

Updated: January 19, 2024.

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Preparing Plastic Cups for Sowing Seeds

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Small plastic cups come in different sizes and colors. Usually, I take ordinary white cups with 3-7 ounces (0.1 - 0.2 liters) of volume.

First, you have to make one or more drainage holes in the bottom. If you use brute force, fragile cups will probably end up crushed.

So, take one lighter and, in my example, tweezers with two sharp ends – any sharp metallic object will do. Heat the tweezers on the flame.

Note: be very careful not to burn yourself or cause some damage ...

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Gently push the tweezers through the bottom of the cup. Hot, sharp points will melt the plastic, not damaging the rest of the cup.

If you are quick, you can make holes in five–six cups per heating.

And if you are using tweezers, you'll get two small holes instead of one.

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Fill the cup with the soil. Use good potting soil that can be bought at most garden centers and even supermarkets.

Good potting soil should stimulate the growth of the root system and young seedlings and has good drainage, good water retention and must be well aerated.

However, when sowing some specific plants requiring special conditions (low pH, high Ph, etc.), more optimized soil is recommended.

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Put filled cups in larger containers (plastic, metal, or made from styrofoam).

Sometimes, you will have to press loose soil in the cup and add it once more – practice to make it perfect.

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Since I never know exactly what and how much I will sow, I write the name of the plant just before putting in the seeds.

Usually, I just make three small holes with my finger on top of the soil, add some seeds and new soil, gently press the soil, and put the cups back into the container.

This is not the best method regarding spending the number of seeds per cup, but it is quick and, for small seeds, not so expensive.

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I put larger seeds one by one, for example, 3 seeds of red hot chili peppers per cup to get one plant per cup.

Add some soil over them and press it gently.

Note: larger seeds, for example, beans, peas, and similar, I plant one per cup. With an 80-90% germination rate, it is not an issue if some cups end up empty. If the cups are larger, feel free to plant two seeds of beans or peas (or some similar plants) and leave both plants to grow next to each other - the plants will be very close together, increasing competition for nutrients, water, and sun, but it may even increase the crops.

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Soon, all cups will be used for different plants. Don't forget to use a permanent and waterproof marker, or you will soon end up with a bunch of plants and guessing which one is which – been there, done that :o)

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Water the cups. Use a hand sprinkler that allows you to change the size of droplets. Since there are no plants, you can use larger drops. When plants start to grow, use smaller droplets, and if you have sensitive plants, water cup by cup with water can (with a small spout) – this can be time-consuming, but it is a much better option for plants.

Put the container with cups in a suitable place with adequate warmth, humidity, and light.

Transplanting the Seedlings

When the seedlings are almost large enough for transplanting into the permanent positions, expose them to colder air and direct sunlight, but expose them gradually.

This will harden the plants and increase their chance for successful transplantation.

So, when young plants are large enough, transplant them into permanent positions.

Note: 1-2 days before transplantation, don't water the seedlings - this will help in removing the root ball from their current pots.

Dig a hole in prepared soil slightly larger than the cup itself, take the root ball out of the cup, and place it into the hole.

Gently press the soil to avoid air pockets and water with stale water.

If the plants need support (tomatoes, for example), add support right away while the roots have not spread out - adding support later may damage the roots.

And that is it...

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Plastic Cups vs. Cardboard Cups

Plastic cups are reusable cups that can be used over and over again; just be sure to clean and disinfect them properly to prevent transmission of certain diseases.

Cups made out of cardboard, pressed paper, and similar materials don't last long. In fact, many of them are designed to decompose rather quickly, allowing the gardener to plant the seedlings with paper/cardboard cups, decreasing the stress of young plants.

Which one you choose depends on their availability and your personal needs and preferences.

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