Sunday, August 9, 2009

More on Frost

It looked like it was going to be another frosty night but the clouds came over and a frost didn't eventuate. The first two photos are from yesterday morning and illustrate the difference between a mulched bed and bare earth when it comes to frost. The play area is covered with a thick layer of tanbark and so is always covered with a heavy layer of frost (first photo). The log in the second photo defines the limit of the tanbark and shows bare earth to its right before giving way to lawn. Note the bare earth has no frost on it at all. The theory is (I think) that bare soil is a darker colour and absorbs more heat during the day thereby making it less susceptible to frost. This is good for plants helping them to maintain some growth with slightly warmer soil. I know of some gardeners who remove the mulch layer from their garden beds every autumn and replace it in late spring for this very reason. I think this amount of effort may only be worth it for marginally frost hardy plants. I think there is also a difference between bare soil being compacted and fluffed up - I think the fluffed up one gets more frost on it - probably because of all the little air pockets in the soil.
I checked my Prostanthera magnifica again today. Its tips are still nodding but not as badly as yesterday (third photo) and the leaves look ok. I hope it will be allright because it will be coming into flower soon and as its name suggests, it has magnificent flowers!

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