Temperature requirements of softwood cuttings-Part 1 of 4

December 9th, 2009 by Dane

Cuttings require many specific variables to root. One is temperature.

The rule of thumb when rooting cuttings under mist is to keep the tops cool, the stems moist, and the bottoms warm. So essentially what we are shooting for is a range of temperatures when rooting our cuttings.

Cool tops

What is meant by cool tops? Basically we need to keep the top of the cutting cooler than the stem and bottom. The reason for this is to reduce the amount of water that is lost through the cuttings leaves. As moisture evaporates from the cuttings leaves it draws moisture up through the stems to replace what has evaporated and cools off the leaves. Because the cutting has not formed roots, this transfer of water to the leaves is essential for the cuttings survival. The higher the temperature, the more evaporation, however, too high a temperature is detrimental to the cuttings because the leaves will not be able to draw enough water through the un-rooted stems to replace what is lost and the leaves will get hot and begin to wilt.

Moist stems

Moist stems means keeping the stems moist enough to allow them to supply the leaves with the amount of moisture they require. However, stems that are too moist will begin to rot or diseases or fungus will begin to appear. This is why the rooting medium needs to be well drained. Well drained rooting medium retains enough moisture for the cuttings to root but is dry enough to not allow the stems to rot. Again, the stems need to transfer only the amount of water the leaves require because of the evaporation.

Warm bottom

The bottom of the stems should be kept warm because roots tend to develop quicker. 68 to 70 F is a safe range to shoot for. Higher rooting medium temperature can be beneficial, but because the sun will raise the medium’s temperature anyway, shoot for the 68 to 70 F range and you will be less likely to cook the cuttings. If you try for a higher medium temperature and the sun warms the soil even higher, the cuttings will surely suffer.

So how do we actually go about keeping the tops cool, the stems moist, and the bottoms warm?

Read parts 2 through 4 for the answers!

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