Rooting stages of cuttings and the proper use of heat mat

OttawanZ5
1235115030

This question is to those who have used heat mat to expedite start of callusing and rooting but others may have knowledge from other perspective to answer this question.

How long do you keep (or should be kept) the cuttings on the heat mat after observing the start of root formation or small roots?

I just learned what others might have known all along that keeping the rooted cuttings on the heat mat gradually starts deterioration of the roots because of the continuous high temperature (around 80F) of the rooting mix in the pot bottom, and this deterioration could sometimes be irreversible.

My experience now (after losing some plants this way) tells me that after callusing and rooting has started, the cuttings should be placed in cooler environment (or room ambient) with decent humidity or some kind of dome if there are already some shoots, but no bottom heat any more.

Is this a valid observation/deduction?

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SteveNJ
1235133607

I use a temp controller to keep the temp about 70-75F. It is on a rack above standing water in the nursery. The temp sensor is inserted into a rooting container so I can control the root zone temp.

http://www.amazon.com/Hydrofarm-MTPRTC-Heat-Mat-Thermostat/dp/B000053F9I/ref=pd_bbs_8?ie=UTF8&s=home-garden&qid=1235132623&sr=8-8

I keep the nursery ambient humidity above 75%. After rooting and putting into clear bottles, I watch for good root development. Nice white roots. The clear containers let you see the roots clearly. If you start to see browning it is a sign of rot starting and you must move them to pots immediately (they will go south on you really quick). Without any temp control you will over heat and accelerate rot.

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OttawanZ5
1235147980

Thanks Steve
We have to hurry up. That Hydrofarm HeatMat is on sale from $34.99 to $34.95!

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SteveNJ
1235149744

I know Dan recommends not to use a heating mat but I've always been a rebel :) It seems to work for me, so I'll stick with it.

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OttawanZ5
1235159323

Steve

While searching on the topic of bottom heat I came across the following site: http://cru.cahe.wsu.edu/CEPublications/pnw0152/pnw0152.html

Under the sub-topic "Factors that Affect Rooting" it states "After rooting has started, however, the cuttings must be subjected to cold temperatures according to individual plant requirements". It is not specific o fig hardwood cuttings but a general statement for hardwood cuttings of deciduous plants.

I am not 100% sure if it applies directly to what I said in the starting post that continuous bottom heat can harm the roots but it does indicate that bottom heat is not required for further rooting progress.

Dan may not be opposed to bottom heat theoretically but probably just indicating that he has more patience and can wait longer.

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SteveNJ
1235160449

I have noticed that you can not leave the bottom heat on too long. Once I see nice roots, I move them off the heat and into pots at room temperature. For some, I have put the potted cuttings back into the nursery on the heat but more for the humidity and only as a short 1 week or so transition. They are then removed to ambient room conditions.

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OttawanZ5
1235165047

Yes Steve, I agree with your statement as I learned it by losing some good rooted plants by leaving them on heat mat longer.

However, this does not solve all issues related to bottom heat like what happens if you do not see a sign of root formation through the clear glass sides after reasonable time. There may be callus but no roots and there is risk of the bark rotting if left over the heat mate longer. My gut feeling is that a cutting not showing sign of root formation also be taken off the heat mat after reasonable heat treatment for callusing purpose before the bark starts rotting.

I have checked some cuttings left on on heat mat with no visible progress and found the basal end with tiny dead roots and bark slipping due to rot. Probably I could have saved them if removed from heat mat after some time (but how much time is good time to leave?).

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