The Hard Freeze of 2008

The National Weather Service predicted a hard freeze for my area on January 3, 2008 with temperatures expected to get as low as 22 - 24 degrees. In response I spent four hours the day before securing the plants around my house. Here are the steps I took:

The freeze warning came out four days in advance, giving me time to buy three rolls of Weed Block fabric to wrap the plants along with fabric staples and clothes pins to secure them. I also brought my Brugmansia, three Hibiscus seedlings, and six Pentas seedlings inside the garage for protection.

As I laid out the fabric the day before the frost and time and materials began to run out, I realized I needed to bring more plants inside. So I took two Plumeria and three Epidendrum, put them in pots and moved them inside.

Before
After

I put the Weed Block fabric around the Stromanthe, Flax Lily and Bromeliads beside the pool. But here's the problem - there are two types of freezes: radiant and advective. Radiant cooling occurs in calm air when the air from the warm earth rises and is replaced by cool air from above. Wrapping plants during radiant cooling is an effective means of preventing damage from the frost that develops as the cool air chills the moist warm air. Advective cooling occurs when the wind is above 5 mph and there is no inversion of warm and cold air (with the wind, everything is cold). The National Weather Service is predicting winds of 5 to 10 mph tonight, so we will have advective cooling and the covers will have minimal effect. The other point is that if there was no wind, the pool would provide enough localized heat that I probably would not even need to cover the plants.

The Pygmy Date Palm in the center turned out to be too large to cover effectively, so I left it exposed to the elements. I'll be running the pool tonight to keep the pipes from freezing and hopefully the circulating water may provide some extra heat.



Before
After
I also covered the White Bird of Paradise, Anthurium, Pygmy Date Palm, Pansies and other plants at the front of the house. By 8:00 PM I noticed that the wind was not too strong and it might be worthwhile trying outdoor lighting as a source of heat. I put a couple of strands of Christmas lights under the large bag on the right to see if it helped.
One of my Plumeria's was too large to repot, so I covered it with fabric (on the left). By that point I had run out of fabric and could not cover one of my other Plumeria that had already lost its leaves. I had read on a Plumeria forum that you can cover the buds with socks to protect them. Yes, it looks silly and silly usually means it won't work. But hopefully in a few months this Plumeria will be sending out new leaves.
Having run out of fabric, I became desperate and had to resort to begging my wife for old sheets. Here is a Tibouchina under a bed sheet. I had no choice but to leave the young Tabebuia tree in front of it uncovered. I had just planted a few Impatiens by the Magnolia. They would have turned to mush in the freeze, so I took the last scrap of fabric and covered them.


The Weather Underground predicted a low of 22 degrees for Thursday morning in Lithia. As the temperature began to plummet on Wednesday night, I sincerely hoped that they were being far too conservative, since 22 degrees will do significant damage regardless of my efforts.

Aftermath (January 3) - It turned out the weather predictions were, thankfully, wrong. We only experienced temperatures around our house of 31 degrees. Was it worth the effort? It's hard to say. At 31 degrees most of my plants would probably have survived, but some would likely have suffered some minor damage. The problem is that, if the temperature had dropped only a few more degrees and the plants were unprotected, I would have lost a significant amount of vegetation. So it was clearly good insurance in case the temperatures had dropped only a few degrees further. A good test will be to see how the Chinese Yellow Banana survived. I did not have enough fabric to cover them and they did suffer significant damage last year when I left them uncovered in a frost. If they show damage from last nights freeze, then it will help justify the steps I took to protect the other plants.
Aftermath (January 4) - The full extent of the damage is becoming more apparent. Most of the plants that were under the covers survived with minimal or no damage. However, several uncovered plants that I thought would pull through without any problems were damaged. At this point it does not look like I will have completely lost any plants (except for one Impatiens), but I have some very sad, pathetic plants that will need extra care over the next few months. The extent of the damage also leads me to doubt whether my outdoor thermometer is accurate. My guess is that several areas around the house probably experienced temperatures in the high 20's. In addition, some of the plants may have been effected by direct exposure to the dry winds that accompanied the freeze.
You can see from the picture above that I had covered the Tibouchina and left the Tabebuia tree uncovered. The gamble on the Tabebuia appears to have paid off as there was no damage. Even though the Tibouchina was covered, several of the top leaves that were in contact with the sheet were damaged (see below). If I cover the Tibouchina in another frost, I will likely have to improve the insulation by using some internal supports to keep the fabric away from the leaves.
Frost protection is an imperfect science and Impatiens are especially sensitive to cold. Even though I covered the Impatiens under the Magnolias, one of the plants (on the left hand side of the picture) was turned to mush by the cold. Probably we failed to completely seal up the edges of the cover allowing just enough cold air to seep through and kill the plant.
All three Firebush plants that were left uncovered were severely damaged by the freeze. IFAS says that Firebush, even if the plant is killed to the ground, will still quickly recover. One of my plants is nearly 3' tall and it is difficult picturing such a large plant completely recovering. Time will tell.
The Butterfly Garden was particularly hard hit. Except for the Mandevilla vine, I left the garden uncovered. Most of the plants sustained some damage. The Penta to the right suffered about 50% damage and, hopefully, should recover.
Our problems with the Awabuki Hedge are documented elsewhere on this site. On top of those problems many of the new leaves on the Awabuki were killed by the freeze. Likely they had not had enough growing time and exposure to the elements to harden them enough to withstand the cold.

Several of my Hibiscuses were damaged. Some of the damage may have been caused by the dry winds. I have two Hibiscuses at the South corner of the house. The one Hibiscus that is on the corner and exposed to the winds was damaged, but the one only a few feet around the corner was not.

The house also appears to have created several microclimates where the temperature may have varied as much as five degrees during the freeze. All the plants on the south side of the house survived unscathed, probably because of the residual heat from the sun stored in the walls. We also have several Ixora planted in front of the house. The plants that were within five feet of the entry showed no damage, but the plants that are approximately 20' away from the foundation showed significant tip burn.

Update January 27, 2008 - As I garden I am constantly reminded of how little I know. For example, above I had written off one of my Impatiens as too far gone. The freeze had left it a twisted pile of mushy leaves and stems. Three weeks later it (the Impatiens on the left in the picture) has sprung forth with new leaves and has begun to flower again. Granted, Impatiens aren't the most exciting plants, but to see this level of endurance is astounding.
To my dismay all three of my Firebush plants were decimated. The large plant above on the left is now just a stand of sticks with no sign of life. However, one of the smaller Firebushes on the right is starting to show signs of life.
Right after the freeze I was very pleased with how well the Anthurium had survived. They showed no signs of damage from the cold. That was amazing considering Anthurium are only hardy in Zones 10b and 11. I was feeling pretty good about my gardening skills. Three weeks later - I'm not so sure. Both Anthurium are now showing signs of significant die off and it's not clear at all whether they will make it.
Now comes the hard part. Waiting. There is still the possibility of another frost before the season ends and it's not clear if some of the plants will make it or not. It's just too early to get out the pruning shears and start whacking away at the garden. Patience.
I'll end this update on a high note. Most of the new growth on the Awabuki was killed off in the freeze. You can see the blacked leaves on the left in the middle of the picture. But look what has happened in just three weeks. A whole new set of leaves is emerging. I may not know what I'm doing all the time, but that doesn't seem to stop Nature from keeping things going.
Update - Everyone will tell you not to panic after a frost, just give Nature some time to recover and everything in your garden will be fine. But patience is hard to find in the dark days of February when your garden has turned brown and black from the frost damage and there is little indication of new life. And then March comes and there is a little bit of hope, followed by April when nature kicks in and you wonder why you ever doubted her. The best example is the Silver Leafed Princess Flower or Large Leaf Princess Flower (tibouchina grandifolia or tibouchina heteromalla) and the before and after pictures below. Why did I ever worry?
Tibouchina
Or the before and after pictures of the Butterfly Garden:

January 2008

April 2008
Butterfly Garden
July 2008

See also:
Cold and Frost Protection

Materials to Use in a Frost

Cold Weather Terms