How to make a homemade rhubarb forcer

The science behind forcing rhubarb is that in the absence of light, the rhubarb stems grow taller, quicker. This is in the hunt for sunlight, growing tall in the hopes of finding it. This is also why it grows sweeter; the absence of sunlight means the plant produces less chlorophyll. Without chlorophyll, the stems are pinker because of less green pigment and are sweeter; chlorophyll is thought to be bitter.

What is a rhubarb forcer?

These are typically terracotta containers, which you position on top of your rhubarb. These sit over your rhubarb as it grows, cancelling out the light. They often have a removable lid, allowing you to check on your rhubarb’s progress without letting too much light in.

Remember – Don’t force newly planted rhubarb or force the same rhubarb two years in a row. Newly planted rhubarb needs time to establish a strong root system before forcing. If you’ve already forced your rhubarb, give it at least a year to recover, as forcing uses a lot of energy.

What ican you make a rhubarb forcer out of?

There are a few options. I’ve recycled some plastic plant pots, which I’ll explain in more detail below, but there are other options:

• Plastic dustbin
• Recycled plant pots
• Old plastic or metal bucket
• Cardboard box

The cardboard box option is meant to be temporary, as it won’t withstand wet weather. However, if it’s getting late to start forcing, and you don’t have a forcer yet, it’s a great temporary option. Once you’ve made your more permanent rhubarb forcer, you won’t need the cardboard box anymore.

You could go to your local garden centre or landscapers and see if they have any large pots they plan on recycling. I’ve been landscaping in my garden, and the trees I’ve planted came in quite large containers, so I’ve used those.

Materials

You will need:

• A plastic plant pot or dustbin
  • I would recommend black, as it will let warmth in from the sunshine, but other dark colours are suitable.
  • Also, make sure it is opaque and not see-through
  • It needs to be deep enough to allow room for rhubarb growth.
• Electric drill
• Jigsaw cutter, utility knife, or heavy-duty scissors
• Screws

Instructions

Step One – Cut the hole

Using an electric jigsaw cutter (if you have one), cut a hole in the bottom of your container. If you don’t have a jigsaw cutting, drill a hole into the base as a starting point and use some heavy-duty scissors. Alternatively, use a utility knife.

Whilst you’re doing this, if your container has handles overlapping the rim, remove these too. Otherwise, they may lift your rhubarb forcer above ground level, letting in more sunlight.

Safety note – When cutting plastic with scissors or a blade, wear gloves to prevent slips and hand injuries. Cut slowly and securely on a stable surface. If using a heated knife, work in a well-ventilated area to avoid inhaling fumes.

Step Two – Create your lid

Use another piece of dark plastic that is slightly larger than the hole you’ve cut. Drill a hole into the edge and through the base of your container next to the hole.

Using a screw, fasten this piece of plastic to the base of your pot. The plastic should completely cover the hole when closed. You should be able to pivot the plastic around so you can look inside the container to check on your rhubarb.

Step Three – Extend your rhubarb forcer

Once you’ve done this, you’ve got a completed rhubarb forcer. However, if you don’t think it’s quite tall enough, you can extend it.

Take another slightly wider container and cut the base off completely. Slide the larger container over the top of your forcer until the top is flush with the bottom of your forcer. Nail it into position, and now your rhubarb forcer is likely twice the original height.

If too much light is coming through where the containers have been secured together, cover the gaps with some black tape.

Step Four – Place your rhubarb forcer

Position your rhubarb forcer over the top of your rhubarb plant. If your garden is quite exposed, it may be worth drilling holes into the bottom rim to stake it into place. This should stop it from blowing over in strong winds.

If the weather turns cold, you can protect your rhubarb forcer by wrapping it in horticultural fleece or bubble wrap. This will insulate the forcer from the cooler temperatures.

And there you have it. A homemade rhubarb forcer. Position this over your established rhubarb plants between December and February to produce a much earlier crop. Keep an eye on your rhubarb as it grows so you can crop it at the perfect time. Your stems should be ready to harvest up to eight weeks after being covered. The stems should be thick and between 25 and 35 cm long.