The amount of water held by punnets in which seedlings are grown is fairly small, and there is nothing quite so demoralising as coming home after a weekend away or a particularly hot day to find all of your seedlings have dried out and are now fried.
Fortunately there is a piece of kit which you can throw together quickly, most likely from stuff you already have hanging around, which can prevent fried seedlings from ever happening again. Enter the capillary bed!
Another advantage of using a capillary bed is that it allows you to keep your punnets moist without having to water them from above and possibly washing some of the seeds out. This can be a real problem, particularly with the smaller seeds.
In basic terms a capillary bed is a container of coarse sand which acts as a store of water. Seedling punnets or other plant pots are sat on the sand and water passes up into them and keeps them moist by, you guessed it, capillary action. The better ones have a method of keeping the water topped up too.
To start making your capillary bed get hold of a cat litter tray, they are available from the el cheapo shops for a few dollars and are mind bogglingly handy for plant propagation and other grow-it-yourself tasks. They are great for mixing seed raising/potting mix, carrying stuff like punnets or pots around and they can be used when sorting seeds from trash. Let’s face it, if all else fails you could use it for your cat!
To fill the cat litter tray, you need coarse river sand. Course sand is best because it doesn’t crust over and river sand has no salt issues attached as beach sand may. Fill your cat litter tray almost to the top with the coarse sand and then water with a watering can until the sand is saturated. It is then just a case of resting your seedling punnets, newspaper pots etc on the moist sand.
I have operated these for years and they work very well, and no fried seedlings!
With a little bit of effort you can extend the period between waterings even more. Get hold of a small pot, the one I use is 70mm long by 50mm in diameter at the top, and sink it into the sand as far as it will go. Then get hold of a small empty bottle where if you insert the neck into the small pot it comes about half way down.
Fill the bottle of water (I use a 600mm soft drink bottle) and insert it neck down into the pot. As the water level drops below the level of the bottle neck due to evaporation and usage by the seedlings, more water till flow out of the bottle to maintain the level. This will happen until the bottle is empty and requires refilling.
It is a simple thing to make, but it makes growing your own from seed much easier and more secure.
