Heating Mats for bonsai plants?

Winter is fast approaching and I'm worried how my plants will hurdle the coming cold weather. I normally leave the evergreens outside while I'm still debating whether to leave the deciduous out or inside the greenhouse with the tropicals. My small lean-to 8 X 6 greenhouse is on the upper deck (2nd floor) facing south. Last year I laid a rubber (garage use) flooring over the wood slats. A portable heater with thermostat kept the temperature range approx 55 to 85 degrees. Yet by the end of the winter, some plants did not make it through. It's quite a challenge to create a microclimate in a small greenhouse when the ambient temperature here can drop below zero. I'm thinking of using a heated mat this year if this will help at all. Does anyone use these mats and successfully raised the bonsai's through the winter? Thanks. Philip

Deciduous trees, by definition, need a dormant period. How long that period is and how much cold the tree can withstand depends on the species. I doubt it would ever get cold enough in Maryland for any cool temperate zone deciduous plant to not survive it.

Deciduous trees that are native to Mediterranean climates or warm temperate climates may need to be stored outside with their pots buried in mulch.

So it will depend on what trees you have.

For most deciduous species, however, I think a heating mat might keep them too warm and they might not get the dormancy they need.

You didn't make it clear which plants you had in the greenhouse last year. Which ones did not make it through the winter? If they were tropicals, the temperature was probably not the issue. Do you have a humidity gauge? As Jim said, keep the temperate deciduous trees out of there!
Iris

Hi Jim and Iris, Right now, the plants in my collection are chinese elm, japanese zelkova, common fig, trident maple, bald cypress, japanese larch, satzuki azalea, fukien tea and japanese maple. A common azalea did not make it inside the greenhouse and a jaqueline hillier elm and a dwarf chinese elm also did not make it while left outside on the deck. The rest of my trees- junipers, cypresses and pines are left outside and they all survived except for four less than a year old dwarf spruces I got from Canada. Thanks. Philip

Ebbtide wrote:chinese elm, japanese zelkova, common fig, trident maple, bald cypress, japanese larch,

These are all hardy trees. They should survive outside in a sheltered area covered with mulch or rose cones, or in a garage or cold-frame. Also the Japanese maple.
The greenhouse is too warm for azaleas. They need a cool dormant period.
The Fukien tea is the only tree on your list that belongs in a warm greenhouse for the winter.

Ebbtide wrote:a jaqueline hillier elm and a dwarf chinese elm also did not make it while left outside on the deck.

Winter them with your azaleas, a little warmer than outdoors, close to freezing.

Hi, Yes, I used a seedling heating mats from 2009-2010 winter in my garage. The coldest it got in Colo. was -15 (f) and it was 15 (f) in the garage. I used the mats on 2 Japanese Black Pines, 1 Trident Maple and 1 Cork Bark Elm. I checked the soil on the -15 day and the soil was not frozen on any of them. All of them survived the winter just fine the following spring. The garden center says the mats should keep the soil 15 degrees warmer then the air temperature. I have 2 remote thermometers that I use to track daily temps. They keep track of the high/low for 24 hours. 1 is outside and the other in the garage. Sure beats watching a thermometer. The soil does dry out quicker so be sure to check that from time to time. I am using the mats again this year.

Mike

Lost2301 wrote:Hi, Yes, I used a seedling heating mats from 2009-2010 winter in my garage. The coldest it got in Colo. was -15 (f) and it was 15 (f) in the garage. I used the mats on 2 Japanese Black Pines, 1 Trident Maple and 1 Cork Bark Elm. I checked the soil on the -15 day and the soil was not frozen on any of them. All of them survived the winter just fine the following spring. The garden center says the mats should keep the soil 15 degrees warmer then the air temperature. I have 2 remote thermometers that I use to track daily temps. They keep track of the high/low for 24 hours. 1 is outside and the other in the garage. Sure beats watching a thermometer. The soil does dry out quicker so be sure to check that from time to time. I am using the mats again this year.

Mike

Mike,
Have you considered getting one of those thermostat controlled plug to power your heating mat? Might save you on utility bill as well.

Mike,
Have you considered getting one of those thermostat controlled plug to power your heating mat? Might save you on utility bill as well.[/quote]

Dario,

Yes I have considered that. Storm fronts come through here pretty fast and there might not be enough time to keep them from freezing. We can go from 60 (f) to -5 (f) pretty fast. I don't really know, I suppose I could try it on a pot with out a tree and see how it goes.

Mike

Ebbtide wrote: a dwarf Chinese elm also did not make it while left outside on the deck. The rest of my trees- junipers, cypresses and pines are left outside and they all survived except for four less than a year old dwarf spruces I got from Canada. Thanks. Philip

I have been practicing bonsai for around 40 years now mostly living in southern Florida and California. Since I moved to the Reno / Lake Tahoe area my collection keeps getting smaller and smaller... Most of the tropicals are long gone. I live in a second floor apartment with a balcony facing east with some southern exposure.

Three 20 year old Pyracantha 2 the first year one last year succumbed to the cold. I lost a Yapon holly the first year in my mini green house. Several Chinese elms did not make it after last year. I think most of them are dying because the roots are freezing. Anytime the temps dropped below 30 I covered them through the nights.

I have a 45 year old Escollnia fradesii it is 24 inches tall with a 6 inch trunk it has made it through so far although it does get some frost bitten foliage each year and I keep wondering if it will make it one more year.

My 44 year old Juniper Procumbens has hung in there so far but, the soil comes close to freezing each year and these Junipers do not like temps below 40.

Last year I wintered most of them in my mini green house it is only 4 feet wide, 2 feet deep and 6 foot tall with a heater that came on at 45 degrees. It worked well at night but inside temps would hit 90 to 100 during the day. My juniper and the fradesii had some leaf damage where they are in contact with the plastic sides of the green house. I may install a second controller to ventilate it during the day to keep the day temps more ambient.

I have been thinking also of using a temperature controlled heating mat and leaving some them outside to allow the plants to get the cold but hoping to keep the roots from freezing at night.