Can You Sew Greenhouse Plastic?

Ideally, you would build your greenhouse from glass panels, glass bricks, or transparent polycarbonate sheeting. Unfortunately, these materials are expensive, and so often, gardeners are left using plastic to create their greenhouse. Sometimes the plastic is too short or narrow for the structure, and you are compelled to join it. You might also have a rip in your greenhouse plastic that needs repairing. An easy way to join greenhouse plastic or repair it is by sewing.

It is possible to sew greenhouse plastic either by hand or using a sewing machine. Do not make unnecessary holes in the plastic and use the correct needle, thread, and stitch length to create a strong seam. The thickness of your greenhouse plastic will influence your choice of needle and thread.

Often gardeners face financial limitations and must find out how to complete projects themselves. It is too expensive to have professionals do the job, which may be the case with constructing a greenhouse. Greenhouse plastic can be sewn to fit over the frame you have made. Sometimes it is also necessary to repair tears in the greenhouse plastic. There are two ways to sew greenhouse plastic. You can either sew it by hand or with a sewing machine.

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Some General Principles For Sewing Greenhouse Plastic.

Cutting greenhouse plastic to the correct size can be tricky as the plastic slips and moves. Use a non-tacky tape (such as builder’s tape or masking tape) to stick the plastic onto a cutting board or surface to keep it still.
A rotating cutter or cutting wheel should be used rather than scissors. These tools give a more accurate cut because they press down on the plastic to cut. Greenhouse plastic slips out of the two cutting edges of the scissors, resulting in an inaccurate, uneven cut.
Use chalk to mark the greenhouse plastic if you need to draw cutting or sewing lines.
If the greenhouse plastic has become wrinkled and creased, it is best to remove the wrinkles to make sewing easier. This can be done by heating the plastic slightly. There are several different ways to warm the plastic:
Use the iron to heat the ironing board by passing the iron over the board several times. Once the ironing board is heated, place the greenhouse plastic on the ironing board and smooth out the wrinkles with your hands.
Place the plastic between two pieces of linen and iron over the top piece, being careful not to touch the plastic with the iron.
Use a hairdryer on medium heat to warm the plastic, which can either be hanging or laid flat.
In all of the above methods, allow the greenhouse plastic to cool before moving it, or it will stretch out of shape.
Avoid making unnecessary holes in the greenhouse plastic. Do not use pins to attach pieces before sewing. It is best to use plastic clips or even paper clips.
Use a sharp needle to sew the greenhouse plastic, whether you are sewing by hand or with a sewing machine. Keep spare needles on hand to change to a new sharp needle if needed.

Here’s a great video about sewing vinyl. This process is used for other types of plastic too, with more info below:

Sewing Greenhouse Plastic With A Sewing Machine.

A sewing machine is the quickest way to sew greenhouse plastic if you have a large section to sew. It is also the best method for producing evenly spaced stitches unless you are a talented seamstress.

There are some essential details to pay attention to when sewing greenhouse plastic with a sewing machine:

Adjust the stitch length to 3 mm or longer. The preferred stitch length is 4mm. The reason for this is that a short stitch length creates extra holes in the plastic. The stitches will be more likely to pull through the fabric creating a nasty tear.
Greenhouse plastic is a relatively thick material, and so a thicker needle is needed. You can start with a universal 90/14 needle. If your plastic is very thick, the needle may keep breaking. If this occurs, change to a thicker needle such as a 100/16 needle. If you are unsure of the needle sizes, you can ask your local haberdashery for a needle used to sew denim.
Use a roller foot, walking foot, or a Teflon foot on your sewing machine when sewing greenhouse plastic. This is necessary to prevent the plastic from sticking to the foot of the sewing machine. If you do not own one of the specialized feet, you can use a regular sewing foot covered in Scotch tape. It will not be as effective as the other feet but will help to reduce the friction between the plastic and the foot.
When sewing greenhouse plastic, use two pieces of tissue paper or newspaper on either side of the plastic so that there is a paper on the bottom and paper on the top. This assists in moving the plastic smoothly through the machine. When you have completed the seam, you can tear off the tissue paper or newspaper without disrupting the stitches.
The greenhouse plastic often sticks to the table or the footplate of the machine. You can reduce the friction and prevent sticking by placing a sheet of tissue paper under the plastic so that it glides more easily. Some people use baby powder sprinkled on the plastic to prevent sticking.
Do not backstitch the seam ends as this creates too many big holes in the plastic, which will be prone to tearing. Instead, leave long threads at the beginning and end of the row of sewing. Tie these ends off, and hand stitch them into the back of the sewing – loop the ends through the back of the stitches.
Sew slowly and do not pull on the greenhouse plastic as it is fed through the sewing machine foot. Pulling will result in tearing the plastic and could pull it out of shape.
It is essential to use heavy-duty or industrial thread when sewing your greenhouse plastic. Some people use ordinary polyester or cotton thread, but this causes a problem as it will decay quickly in the weather. In strong winds, polyester or cotton threads may not be strong enough to hold the plastic together.

Sewing Greenhouse Plastic By Hand.

Greenhouse plastic can be sewn by hand. It is important to use a sharp needle of the right thickness. A denim needle is ideal, but you may need to use a thicker needle such as one for leather or canvas if your plastic is very thick.

Make your stitches 4 -5 mm in length and try to have them as even as possible.
Use a heavy thread to ensure your stitching survives the exposure to the weather.
Sewing a long seam by hand can be done, but it will be time-consuming.
Hand stitching is useful for repairs to small areas of the greenhouse plastic.

How Do You Seam Greenhouse Plastic?

There are a few aspects to remember when joining two pieces of greenhouse plastic to make a seam.

Use tissue paper on the bottom and top sides of the seam.

This facilitates ease of sewing and can be torn off afterward.
Some people like to use tissue paper between the two pieces of plastic as well.
Some gardeners recommend using a strip of thick cotton or canvas on the seam edges to strengthen the join.

Once you have completed the first line of stitches

Turn the seam allowance over to one side over the stitches and double stitch that seam edge down to the main part of the plastic.
This is known as a lapped seam and is a sturdy seam.

It is not necessary to edge the plastic as it does not fray.

Some gardeners like to use pinking shears or decorative scissors to cut the seam edge to make it more attractive.
This step is optional and is not necessary for the strength of the seam.

Conclusion

It is possible to sew greenhouse plastic (source) either to repair it or construct a new greenhouse. If attention is paid to some simple principles, then it is not a difficult job.

Needle and thread choice is crucial. You need to ensure the plastic does not stick and that you do not pull on the plastic if you are using a sewing machine. Avoid making holes in the greenhouse plastic where possible.