After losing my entire herb garden to frost in 2023, I met Willem at a community garden in Hackney. His method saved my rosemary, thyme, and even my potted lemon tree this winter – with zero electricity.
Last Thursday, London hit -5°C. My neighbour texted: Say goodbye to your plants, Nora.
But my balcony? Still green.
Not because I bought a heater. Not because I brought everything inside.
But because of three simple steps Willem, a retired Dutch gardener, taught me over a cup of peppermint tea last autumn.
He’s 78. Grew up in Utrecht. Says his grandfather used these tricks during the “Hunger Winter” of 1944.
And they work – even on a 4th-floor balcony with no shelter.
Step 1. Bubble Wrap Blanket (but not how you think)
Don’t wrap the pots – wrap the plants.
Gently drape 2-3 layers of bubble wrap over the foliage like a tent, securing it with clothes pegs to the railing.
Leave a small gap at the bottom for air circulation.
❗ Never cover the soil – roots need to breathe, even in frost.
Step 2. Water Bottle Heat Trap
Fill clean 1.5L plastic bottles with warm (not hot!) water at sunset.
Place them around the base of your planters — not inside.
As the water cools overnight, it releases gentle warmth.
It’s not enough to stop frost entirely, but it buys 2–3 critical degrees, often the difference between life and death.
Step 3: Towel Lid
Wrap the outside of the pot in an old wool or cotton towel (thick, dryY).
Then cover the top of the soil with a second towel square, tucked under the pot rim.
This prevents “cold wicking”, where freezing air pulls heat from the roots through the soil surface.
I tried this on:
- Rosemary (survived)
- Potted lemon tree (lost 2 leaves, but green)
- Thyme and sage (thriving)
- Even my cyclamen still flowering!
Willem says: Plants don’t fear cold. They fear sudden change. Slow down the drop, and they adapt.
This winter, I’m not fighting the cold.
I’m negotiating with it.
