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RE:Cult Over Wintering

Sandra Barss <barsssa@mb.sympatico.ca> wrote:
>Chuck Chapman wrote:
>Good point Sandra. Not sure I can answer this other then established plants have more root mass and perhaps more heat sink. ie: the more mass in the ground the cooler the rhizome is and less temperature differential between top amd; bottom. This is just a wild guess. Current soil is well drained (usually) sandy loam, but last garden was hard clay and I don't notice any difference re overwintering except that plants seem to tolerate being planted deeper.

>Are you sure about the physics involved here, i.e. heat expands, cold contracts ? nbsp;I keep on thinking of water in a pump, bottle, or any other closed container. nbsp;What happens when the water freezes is the container bursts. nbsp; I nbsp;am wondering if the same sort of thing isn't happening with irises and that by letting  them dry out for a period before planting wouldn't help with this problem.

Water is an exception to this in that it expands when frozen. It has to do with its crystalline structure in solid (frozen) state. With all other elements the opposite is true.  I believe that until it freezes, and forms crystals,  water volume does get less as it gets colder.
If the water is telling factor then it would be the opposite, (tops contract while bottoms stay the same) but the temperature differential would still be there resulting in micro cracks. If the water was bursting the plant cells, the ones on the surface would be more damaged. Again, why with newly planted vs established plants? Drying out can remove some water but not all of it. Plants left in water over winter in garage and barn (left over after shipping) freeze solid in winter yet are alive and viable in spring. This includes bearded iris by the way which seems to defy convention and expectation. Being immersed in water means that they are well pumped up before freezing.

Established plants will also be able to put early growth energy into green growth while newly planted plants have to put energy into root growth. My theory re spring soft rot is that it grows well when it is still cold and plants are not growing. As the plant starts growing it out grows the soft rot. The quicker the transition between cold and warm weather the less the problem with soft rot as the better the plant can deal with it. This season here is a good example. We had a very cold long winter and quickly went to warm weather. Almost no problem with soft rot this year. We usually have an early thaw followed by several weeks of very cool overcast weather. When that happens there is lots of soft rot.  Also the more freezes and thaws the more plants get heaved. This damages new hair roots and depletes plant energy (even if not completely heaved), making them more susceptible to diseases. Established plants have long roots for anchors so donbt get heaved.

This leads to a number of possible experiments. Moving earlier, different periods of drying, and planting at various depths.

I have often joked that the best was to transplant is to prepare the soil and then drop the plants on the top of the soil, and plant them in the spring when the ground thaws.

Keith notes that planting deeper doesnbt affect blooming the following year. Plants send up daughter rhizomes to surface where they are exposed to sun and perhaps set bloom stalk before being dug and replanted. Established clumps find their own level for new plants, so planting deeper shouldnbt really effect blooming and if it helps plants overwinter, a bonus. 

I have discussed this often with others and the water content is one theory often put forward, but I don't buy it as it  doesn't seem consistent with all the facts. It happens (planted rhizomes dying while ones on ground survive) with plants grown in my own garden, which are smaller then fat Oregon rhizomes, and happens regardless of size of rhizomes and how long they have been out of ground before being planted. Leaving plants out to dry before planting (mail order) is always helpful, but may just provide a time for surface to dry and kill surface pathogens and healing of small liaisons (small cuts) rather then just drying out "fat" rhizomes. New rhizomes treated in a chemical soak seem to survive well regardless of size. When plants arrive in the mail they are usually damp (sweating in box) and have some mould on rhizomes  or rot on leaves, often both. I usually clean them up as best as possible and then let them dry off. Leaving them in the sun would work even better as the ultraviolet light from the sun and the heat (the hotter the better) are very good anti bacteria and anti virus treatments.  I suspect that a couple of days would work effectively on killing the bbadb guys. A test of this would be a shipment of plants (best if same cultivars). Both cleaned up, one in sun for three days then planted, one for several weeks (use time as suggested by Walter) and then planted. Compare survival rates. If the antibacterial factor then there will be no difference or the short period of time will survive better. If drying out is telling factor, the ones left out the longest will survive best. 

Chuck Chapman, Guelph, Ontario, Canada. Zone 4/5

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