Upcycling A Plastic Bottle To Grow Spring Onions

Do you want to make a decorative and edible planter for recycled materials? We are going to learn how to grow spring onions in a plastic bottle.

To grow spring onions in a plastic bottle: first, choose a bottle that is the right size to accommodate the onions you are growing. Then remove the top of the bottle and cut grow holes in the sides. Fill the bottle with soil, positioning an onion (either a bulb onion or a green onion) at each hole as you go. Keep it watered and the onion tops will soon “spring” out of each hole. Harvest these green tops as you need and they will continue to regrow.

Spring onions are a fresh and delicious addition to any culinary endeavor. Growing them in a plastic bottle creates a recycled, regenerating planter that is ornamental as well as tasty.

Growing Spring Onions In A Plastic Bottle

What is a spring onion? This term means different things in different countries. Where I come from, a spring onion, green onion, scallion, and bunching onion all mean the same thing: the green top of an onion that is usually eaten fresh. In other countries, spring onions are the green top of a bulb onion. We are not going to split hairs over technicalities, but we are going to use the term “spring onion” to mean the green onion top. Here is a step-by-step guide to growing spring onions in a plastic bottle by using both onion bulbs, and green onion scraps.

  1. Choose a bottle
  2. Cut grow holes
  3. Fill and plant
  4. Harvest

This video is a great visual representation of the following instructions.

Spring onion by Colin
Image by Colin

1. Choose A Bottle

You can use any size bottle to grow your spring onions. Choose a bottle that conveniently holds the type of onion that you want to grow. You want to have enough space inside the bottle to have several onions on each side of the bottle and so their roots won’t crowd each other. A 5L plastic bottle is an ideal size for most onions, but you can also use a 2L pop bottle, an ice cream bucket, or even a yogurt container if you want to start small. If you are really ambitious, an 18L water jug would have plenty of space to hold enough onions to feed a small army.

Choose a bottle or plastic container that is food grade, otherwise, it might leached toxins into your soil and your onions. In general, a food-grade container will have the number 2, 4, or 5 in the recycle symbol on the bottom. It also might show a knife and fork symbol, or something similar.

2. Cut Grow Holes

Using scissors or a craft knife, cut off the top of the bottle where it begins to taper towards the spout. Next cut holes in the side of the container. Make the holes big enough that the top of the onions you are using can poke out. Use an electric drill if you have one to make the holes nice and round, or, if you are using a knife, it might be easier to cut little triangles instead of circles.

You can make the holes in any pattern you like. Space the holes about 5cm (2inches) apart from each other, but you need to adjust this distance depending on the size of the onion you are growing.

3. Fill And Plant

Put a layer of soil in the bottom of the jug so it is level with the bottom of the first layer of holes. Place an onion at each hole with the onion top pointing out of the hole. Cover these onions with soil, and fill the bottle until the bottom of the next set of holes. Continue this process until the bottle is almost full.

To finish off, plant some onions on top of the soil with their tops facing upwards. Cover these with soil, and you are ready to go. Alternatively, you can use the top layer of soil to plant the onion buds that you grew from an onion bottom.

Sprouting onion by Theen Moy
Image by Theen Moy

You can use any soil you want. Soil from your own garden is excellent, or bagged potting soil also works well. Onions are heavy feeders, so it is worthwhile to mix in a couple of handfuls of compost if you have any. If no compost is on hand, your onions might thrive with the addition of some organic fertilizer.

If you are using green onions…

If you are using green onions, you can also fill the whole bottle first, and then stick the green onion cuttings in through the holes afterwards.

4. Harvest

Now it is time to sit back and watch your “garden” grow. Of course, keep your onions well-watered without making the soil wet or saturated. The onions should send up greens quite quickly. When the spring onions are your desired size, cut them off with scissors or a knife, and leave the bulb to regrow.

One jug full of onions should give you a continuous harvest for most of the year. Over time, you might see the onions’ production start to diminish. If this is the case, simply dump out the jug, mix in a bit more compost to replenish the soil, and refill the jug with new onions.

Upcycling Your Plastic Bottle

Using a plastic bottle or container gives a second purpose to plastic before it is recycled or thrown away. I’m not sure if the bottle depot will accept a bottle after you have riddled it with holes, but you be able to use your new vertical garden onion planter for years to come.