Material to cover plants

[Trópico]

During this near freeze event, I noticed something really interesting. I think that my covering plants in temperatures near freezing (as opposed to below freezing) actually did more damage than if left uncovered. Here's why: The thermal emissivity of the cloth I was using was higher than the bare leaf of, for example, a banana plant. I noticed that the leaves got burned right where the cloth made contact with the leaf. So the best solution is to use a material with the lowest thermal emissivity possible (cotton cloth being  0.77 and polyester being 0.75 - 0.85), and minimizing contact with plant leaves.

Thermal emissivity is a measure of a material's ability to absorb and radiate energy, measured from 0 to 1 and the best material would be as close to 0 as possible for protecting plants.

Plastic goes as high as 0.95 - 1.00 (do not use!) and human skin is 0.99 (brrr!!!). Also the shape counts. A palm sock has less surfaces parallel to the sky therefore less thermal emissivity.

Have you paid attention to this? What type of cloth are you using?

[SubTropicRay]

Comforters, sheets and blankets from the local Salvation Army and Goodwill work very well.  There are some homeless people walking the streets cursing my name.

Ray

[Howeadypsis]

what are the TE figures for horticultural fleece? this is very thin yet insulating material often used in allotments over here. the only thing is it tears quite easily.

[STEVE IN SO CAL]

Great topic, Frank. Most frost blankets are made from a 1.5 to 4 ounce non-woven geotextile, typically polypropolene. I will be using an 8 ounce in the future. Because of its weight, I will need some sort of frame work. Probably pvc...BTW, the oz weight refers to weight of fabric per sq yd.

[Neofolis]

Surely leaf contact will be an issue with most materials at a low enough temperature.  The air space below the material provides further insulation, so a framework of some kind will always be a better option, but obviously more work and inconvenience.

One way to help overcome the leaf contact problem would be to use many layers of very lightweight thin material, which will usually allow some air between layers to help insulate, assuming the material is not stretched tightly over the surface.

[freekypalmguy]

Also, what is the best way to cover. Do you just lay the material over the plant or is it better to build a structure to support the fabric.

Does anyone have pics of how they successfully protected their babies from the cold?

What about larger palms. Is it possible to protect them? or do you just have to let the cards fall where they may?

[BobbyinNY]

Also, what is the best way to cover. Do you just lay the material over the plant or is it better to build a structure to support the fabric

I would think that would depend on the wind. I put a tarp over one of my palms when it got down into the high 30's and the next morning I found it on the lawn - blown off by the wind.

[STEVE IN SO CAL]

In our area, wind usually means no freeze.

[Neofolis]

(m_crowther @ Jan. 31 2007,16:12)

QUOTE

Also, what is the best way to cover. Do you just lay the material over the plant or is it better to build a structure to support the fabric.

Does anyone have pics of how they successfully protected their babies from the cold?

What about larger palms. Is it possible to protect them? or do you just have to let the cards fall where they may?

I would say for smaller plants, it is definitely worth the extra effort of creating a structure around the plant.  It doesn't have to be elaborate or time consuming, just a few thin metal poles stuck deep enough into the ground so that they are secure and then the material can be secured to the poles.  This has the advantage of better insulation and also allows for more weight of material, which may otherwise damage a smaller plant.  For very large palms the weight of the material is less of an issue and they are also likely to need less protection, but, if it is possible to cover the plant, the material can be secured to the ground or even the base of the trunk.  Most tarpaulins have the advantage of built in eyelets, providing a location to use tent pegs or similar to hold the tarp in place.

[Alicehunter2000]

Good topic, I have noticed the same thing. Near or right at freezing, plants that have sheets (usually cotton or cotton/polyester blend) seem to have more damage than do uncovered plants on areas of the plant that have direct contact with the leaf. Plastic much more so (don't use it anymore). Plastic pots also a no-no (if touching the leaves)

Three things that should be considered is ease of use, whether or not frost is expected, and wind. In my experience if there is wind and no frost leave uncovered. If no wind and frost then framework with blankets or sheets would be best but is not practical  for me. So I just throw a sheet directly on the plant and pray for the best.

To be honest I don't think there is a good answer to this problem other than

A. Plant cold hardy stuff and/or have a good vegetative cold hardy canopy.

B. Move to Hawaii or other tropical climate  

I try to do the former while praying to do the latter

[Trópico]

I forgot to mention that last year (during our St. Valentyne's freeze) the sheets themselves had FROST in them, so the plant parts touching the sheets collapsed immediately.

Proper protection is where palm growing becomes an art: "How do you grow that in this climate!"

We only have to worry about two nights or so of freezing temps so I think it's worth the effort.

I read somewhere about frost cloth. What is that?

[Howeadypsis]

I know a lot of people who use bubble wrap inside their greenhouses for winter insulation. Wonder if this could be used on outdoor palms too

[MattyB]

(STEVE IN SO CAL @ Jan. 31 2007,09:04)

QUOTE

In our area, wind usually means no freeze.

Exactly, which is why I just throw a sheet over the palm.  Unless the wind picks up, blows the sheet off, and then it drops below freezing.  That happened one night this year.  Doh!

[Steve - Alafia]

What I do is use layering and supplemental heat.  First tie up the fronds using bungee cord just like a when a palm is bound for delivery from the nursery.  Next take a sheet or sheets (king size matress covers work great with the elastic edge) and cover the fronds entirely and closely.

Then, use the thinnest blue hurricane tarp you can find and loosely cover the palm from the top over the sheet.  I think of it as just like a windbreaker jacket with a cloth lining.

To avoid cold creeping under the tarp in the sheet, use a 75 watt trouble light underneath the tarp next to the bud so that heat rises into the tarp - [make sure the bulb is not touching the fronds though - a fire is not helpful].  With this protection, frost might hit the tarp, but the cold does not hit the palm due to the sheet underneath and the mini greenhouse created by the trouble light.  

A triple adonidia I have out front has consistently survived cold including 25 deg for several hours and thick frost [i had to use hot water from inside in the am to get the outside spigot to run due to ice freezing the line solid] with nothing whatsoever to show by way of damage using this method - not even a speck of cosmetic damage on the fronds and no stunted growth in the summer.  By way of comparison almost all unprotected adonidias in my neighborhood were killed on Feb 14, 06 - those few that survived are still only putting out stunted fronds - mine did not miss a beat and threw off two new fronds a few weeks later and look like they are in El Yunque.    

The worst you might see using this is to the tip of the growth spear - sometimes the weight bends the tip - small price to pay in my view.  

Best of luck to you - and stay warm - the end of winter is days away!

[SunnyFl]

Steve, that's very interesting and I think I'll clip your post and keep for future reference.  I've always been a bit leery of having a light bulb or any other electric thing inside the cloth wraps though.... but if it means saving a palm..... hm.

That's a shame about the adonidias - that 2/14/06 freeze sure nailed a major part of this state.  My area was soooo lucky with that - the unprotected adonidias here were fine.

I got panicky listening to the forecasts this past Monday and my husband protected my front garden.  He put up one of those metal-framed gazebo-things with the canvas-tarp on top, then wrapped all the sides of the gazebo in more tarps.  The plants never touched the tarps, and we never got down below 40, but it's better to have the protection and NOT need it.

[Brett in Mission Viejo]

Here in Mission Viejo in So Cal where I live in a poor microclimate near a valley floor, I use a 1.5 oz product called N-sulate by DeWitt.  It worked fine during the recent freeze event protecting my smaller palms just fine. I think they claim 7-8 degrees frost protecton and I believe it. I got down to 26 degrees F.  I can use weights to hold down the cloth on smaller palms.  I have a larger Pritchardia Hildebrantii where the my largest cloth piece did not hang low enough to contain the ground heat and I provided supplemental heat using a parabolic radiant heater.  In my location, calm clear low humidity nights are the worst.  When the wind picks up, I consistently see a 5-6 degree F raise.  I recommend this frost cloth for So Cal inland valley locations.  I have been using it for three years and it has not failed me yet.

[ruskinPalms]

Well, I recently just threw cotton sheets over the landscape beds in back. I didn't notice any increased yellowing or damage with a low of 36F, but some things are starting to look a little tired anyway after the winter cool. There was indeed frost on roof tops and car tops but not on grass or palms. The sheets were absolutley soaked. If I had hit 32F, I think I would have been in trouble as they would have frozen to the damn palms. On the bright side, it probably would have just caused cosmetic damage that the palms would have grown out of. What I am trying to say is that I would still probably throw sheets over the palms in the future because I think if things got real bad, even if the sheets froze, they would still provide protection to the growth point, trunk and roots allowing the palm the chance to recover in the spring. I did thrown a sheet over a little mango tree then put a hefty cinch sack over the top making a makeshift palm sock for it. I think having the plastic over the top of the sheet can keep it from getting too saturated although the plant may put out a little water vapor under the plastic anyway.

[BS Man about Palms]

Where are these Palm socks? Are they made or purchased?   ???

[Neofolis]

If the protection insulates sufficiently an extra heat source may not be necessary, although an alternative to electricity would be to put a bucket of hot water on the ground and extend the protection over the bucket.  This will inevitably increase humidity which may not be suitable for some species and is again relying on sufficient insulation for the heat to be retained after the water has cooled.  It can also result in the inner most layer of the insulation becoming damp, so it would be besat with plastic a inner layer then an insulation layer, then more plastic outside to protect from rain/frost.  A plastic inner layer shouldn't, however, be a problem, if sufficient heat is retained and it is only a short term measure.