Tasting Better after Frost - And the Plantpot Heaters are Back. Do they work?

 Plant pot heaters, do they work..?

We didn’t really get a frost last year. I agree we had a few mornings that were white over on the ground but that’s about all. I say that, not because I was looking at my pinecones or analysing weather data, it’s because of my own observations in the garden. My frost tender plants survived outside with no protection, I’ve mentioned before about my cacti and geraniums surviving without any sign of frost damage. The frostless weather also meant that a lot of slugs were free to multiply; it’s been one of the worst years for slug damage for that very reason, chickens are happy though.

The frost also plays a big part in improving the taste of certain vegetables and although we only got the touch of frost last year, I am sure it was enough to make the broccoli taste a bit sweeter

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Plants taste better after a frost

Brussels sprouts, kale, mustard greens, cabbage, parsnips, carrots, celery root, beets, turnips, rutabagas(swede and turnips) ,Kohlrabi (German for cabbage turnip) and oca (New Zealand yam) all taste a bit sweeter after frost. Leeks and celeriac also benefit.

Why is that?

When really cold weather happens, carrots parsnips and other root vegetables convert some of their starch stores into sugar. They do this to keep the water in their cells from freezing, and it works in the same way that putting salt on a road keeps it from freezing over. When another substance mixes with cold water, it makes it harder for enough water molecules to reach the surface and freeze there. This lowers the freezing point. The cells inside a carrot might have icy-cold water, but that water won't turn into ice, which is a good thing as the formation of ice crystals within and around a cell can destroy it. 

There’s a more technical explanation if you want to impress your friends. “Sugar accumulation in living and non-living tissues during winter in cold-hardy plants has long been observed and is thought to be important in cold acclimation because it increases viscosity, which reduces ice crystal formation, helps stabilize membranes by binding to the free phosphate groups of membrane lipids, maintains respiration in living cells, and allows cell metabolism to recover after freezing." Just incase anyone asks!

The resulting increase in sugars makes them more palatable for a lot of people. This post-freeze deliciousness will be true of any of the vegetables that can survive a hard frost, including the ones I have mentioned earlier such as broccoli, kale and celery. There are a few exceptions. Leeks for example produce their sugars after dormancy and frosted potatoes can cause carmelisation when they are being cooked which turns your spuds brown. I can cope with that and I for one am hoping for a few harsh frosts this winter. Lag your pipes!

Heat your home with a tea light and plant pot -NOT

There are a lot of youtube posts and facebook entries popping up promising to “Easily Heat Your Home or Greenhouse Using Flower Pots and Tea Lights”. The idea is that you upturn 2 terracotta pots, of different sizes, one inside the other and space them out with washers and bolts. These are put on stands to allow air flow and then tea lights are put underneath to create a “thermal heater” More and more elaborate designs are coming out but they all have the same level of efficiency.

This concept has been around a while and seems to come back every autumn as the weather gets cooler. Here’s an explanation of the science behind the phenomena, and you can decide if it works for you.

A naked candle puts out a very small amount of heat into a room (approximately 263 BTU/h or 77w), so you would need 19 candles burning to equal the typical 1500w room heater.

But a flower pot makes it put out more heat, right?

No, a flower pot converts the candles convective (air) heat, to radiant (body) heat. It also shifts the time period, as the clay takes a while to heat up, and also to cool down. If you are sitting directly next to the pot, you would feel warmer, but the room would take longer to heat up. Both methods would bring the room up to the same temperature.

19 candles would incur sooting and corresponding lung issues, so there will be a cleaner heating source. For comparison purposes, a 77 watt light bulb running 24 hours per day costs €0.18 (at €0.10 / kWh). That’s cheaper than buying candles, a whole lot safer to use, and better for your health. You could put it in a flower pot to give the impression of candles burning if you like; I’ll put on a jumper and wrap my plants up with horticultural fleece.