Category:

Measuring Microclimates

12/16/2012

Cheap Thermometer

After recording the podcast on climate with Dr. Randall, I decided it was time I tried to measure the temperature in the different microclimates around my yard. I was particularly interested to see how much of a temperature buffer I would get from my 1,000 gallon rain tank. 1,000 gallons is a lot of water, and it would have to get pretty darn cold to freeze the whole tank solid. The tank is a dark green color, and is exposed to almost full sun, so the water inside can get pretty warm by the end of the day. As the liquid water freezes, the latent heat of the water will keep the tank at a constant 32° F. This might not seem like much, but when facing down a dip to 20° F or less, 32° F can mean the difference between life and death for a citrus tree. That's why I have tried to plant more frost-sensitive citrus like pummelos right next to the rain tanks.

I went to the store and looked for the cheapest thermometers I could find, which turned out to be the ACURITE brand thermometer and hydrometer for around $1 each. I bought all they had, and a pack of 12 landscape stakes. While the kids were napping I attached all the thermometers to the stakes using wood screws and rubber bands so that they would be approximately six inches above the ground. I then tried to strategically place the thermometers throughout the yard:

#1 - Open area of the yard (control)
#2 - By 1,000 gallon rain tank
#3 - In side-yard by blueberries
#4 - By covered back porch
#5 - Southeast corner of yard by fence
#6 - Back fence by Cara Cara
#7 - Right outside kitchen window

#8 - By 300 gallon rain tank
#9 - Against north side of greenhouse
#10 - Under pine tree by Wilma avocado
#11 - Under pine tree in front
#12 - Out front by pomegranates
#13 - On play south side of play fort
#14 - On back fence by Republic of Texas

So when the alarm went off at 5 am on Tuesday morning, I put on my coat, turned on my head lamp, grabbed the clipboard, and headed out to take measurements. I'm sure if any of my neighbors saw me they thought I was even crazier than they had previously thought. The Weather Channel app on my phone said that the outdoor temperature was 28° F, so I didn't expect to see anything too drastic. Most of the measurements were consistently within one degree of 32°F, and I didn't notice any significant effects from thermometers being adjacent to the rain tank, the house, or the greenhouse. Dr. Wife wisely pointed out that I didn't place two thermometers side by side to test their precision, and therefore I don't know the potential margin of error. However, I had compared a few of them when I first brought them home, so I'm confident that they are precise enough for this exercise.

I noticed that measurements from thermometers #13 and #14 seemed significantly higher than all the others, but I'm pretty sure it was because I had attached them directly to 4x4 posts of the play fort and fence respectively after I had run out of stakes. By attaching them this way, the entire back of the thermometer was insulated, and therefore these measurements aren't really useful. The coldest measurement of 28° F was recorded at thermometer #5, located in the southeast corner of the yard. This was also the only location where there was no underlying grass cover, and I believe it was the release of the latent heat of the water on and in the grass as it froze that kept the temperature at most of the locations at or near 32°F for the few hours that were below freezing.

I'm going to leave the thermometers out just in case we get a hard freeze, and I really wouldn't expect to see an appreciable difference unless temperatures dropped significantly below freezing. I think I also need to set out a tall stake with thermometers positioned at different heights so that I can measure the vertical temperature gradient. By understanding how individual areas of my yard respond to extreme cold events, I can better plan, plant, and protect my trees, and avoid the damage caused by the heartbreaking freezes of 2010 and 2011. Since then I've learned a great deal about protecting citrus from freezing temperatures, and with the unstable Polar Vortex constantly threatening to collapse, I've got the C7 lights, sheets, mulch, and gallon jugs ready to go at a moment's notice!

14 ACURITE Thermometers

Thermometer secured to yard stake.

Ready to deploy instruments!

Thermometer in open lawn.

Thermometer by 1,000 gallon rain tank.

Thermometer in side yard by blueberries.

Approximate Thermometer Location Map.

Temperature recorded at 5:00 am, December 11, 2012

Temperature Measurement Map

3 Comments

Freeze Aftermath - Preliminary Damage Report

2/9/2011

12 Comments

Temperature Data for Zip Code 77379

I hate freezing weather. When I started planting fruit trees a few years ago, all the weather data for the past 10 years suggested that I wouldn't see temperatures below 27 degrees. Last year I got hit hard with 17 degrees. I thought it was a freak occurrence, and hoped for a mild winter the following year.

BAM! Hit again, this time with a low of 19 degrees, and almost 3.5 days with temperatures near or below freezing. I did my best to protect everything, but there was only so much I could do against rolling blackouts and strong winds. Unfortunately, it's not over yet. Another hard freeze is predicted for tonight and tomorrow. Hopefully this will be the last one of the year. I've tried to summarize the levels of cold protection and their relative effectiveness below. I'll have to wait until early spring to see the full extent of the damage.

Tree	Protection	Damage
Okitsu Wase Satsuma	Mulch Bank and Bucket of Water	Minor Leaf Damage
Changshou Kumquat	No Protection	Minor Leaf Damage
Meiwa Kumquat	No Protection	Minor Leaf Damage
Meyer Lemon	Few Xmas Lights & Bucket of Water	50% Leaves Damaged
Rep of Texas Orange	Few Xmas Lights & Bucket of Water	Upper 30% Damaged
Sarawak Pummelo	40W Bulb, Mulch Bank, & Sheet	Minor Leaf Damage
Pong Koa Mandarin	Xmas Lights, Mulch Bank, & Sheet	Minor Leaf/Twig Damage
Cara Cara Navel	Xmas Lights, Mulch Bank, & Sheet	No Damage
Sarawak/Pong Koa (small)	40W Bulb, Mulch Bank, & Trash Can	No Damage
Hirado Butan Pummelo	Xmas Lights, Mulch Bank, & Sheet	Minor Leaf Damage
Orlando Tangelo	Xmas Lights, Mulch Bank, & Sheet	No Damage
Bloomsweet Grapefruit	Xmas Lights, Mulch Bank, & Sheet	No Damage
Wekiwa Tangelo	Xmas Lights, Mulch Bank, & Sheet	Minor Leaf Damage
Owari Satsuma	Mulch Bank, Next to Rain Tank	Minor Leaf Damage
Ujukitsu	Brought Inside Shed	No Damage
Jaboticabas	Brought Inside Shed	No Damage
Ruby Grapefruit	Brought Inside Shed	No Damage
Everhard Navel (Sour Orange)	40W Bulb & Sheet	30% Leaf/Branch Damage
Kishu Mandarin	40W Bulb & Sheet	New Growth Killed
Calamondins	60W Bulb & Sheet, On Covered Deck	Minor Leaf Damage
Moro Blood Orange	60W Bulb & Sheet, On Covered Deck	Severe Damage
Mexican Lime	60W Bulb & Sheet, On Covered Deck	Severe Damage
Buddha's Hand Citron	Xmas Lights & Plastic, On Covered Deck	Severe Damage
Lakeland Limequat	No Protection	90% Defoliated
Mexicola Grande Avocado	Soil Bank & Bucket of Water	100% Leaf Damage
Lila Avocado	Soil Bank & Bucket of Water	No Damage
Miho Satsuma (Sour Orange)	Wrapped in Towel/Bubble Wrap	No Damage
Improved Meyer Lemon	Brought Inside Garage	No Damage
Surinam Cherry	Brought Inside Garage	No Damage

Mexican Lime - Severely Damaged

Moro Blood Orange - Severely Damaged

Buddha's Hand Citron - Severely Damaged

Republic of Texas Orange - Upper 30% Damaged

Mexicola Grande Avocado - All Leaves Damaged

Lila Avocado - No Freeze Damage

Comparison of 2010 and 2011 freezes.

12 Comments

Fighting the Cold

2/2/2011

0 Comments

View of the covered porch.

I never used to mind cold weather until I began growing citrus. Now I hate freezing temperatures. The quickness and the severity with which this latest front came down has really made it difficult to protect all of my trees. Last night the low was 19.7 degrees. I did the best I could with what I had, and I just have to hope that everything survives.

I've taken several different approaches to cold protection throughout the yard. First, I dragged the Jaboticabas, Ujukitsu, Ruby Grapefruit, and fig cuttings into the shed, and the Meyer Lemon and Surinam Cherry into the garage. These are all in 10-gallon pots, so they're relatively easy to move around.

There are several ways to protect your trees. A study conducted by Danny Gabb of Simonton, Texas found that the most effective way to protect a young tree was to surround it with wire fencing, and then fill the fencing to the top with leaves, insulating the tree. The best and most effective cold protection method I have found for use for in-ground trees is to wrap the tree in C7 Christmas lights,bank mulch/leaves around the graft, dump a big bag of leaves over the tree, and cover all the remaining exposed branches with a fitted sheet.

I can get away with this now because my trees aren't that tall, but when they get bigger I'll have to devise another method. For example, my Republic of Texas orange is way too tall to cover, so I banked leaves around the graft, hung lights in the tree, and placed a covered 5-gallon bucket of hot water under the tree.

The Mexicola Grande and Lila avocados are supposed to be cold hardy to low 20's and high teens respectively, although I suspect their rootstocks are Lula, and only hardy to the mid to high 20's. Last year it got down to 17 degrees in my yard, and though it killed several twigs on the Mexicola Grande, the tree survived and recovered very well. To protect these, I banked potting soil around the grafts, dumped a big bag of leaves over the tree, and placed a covered 5-gallon bucket of hot water next to the base of the tree.

All of the potted citrus on the porch were covered with sheets or plastic, and I placed 60W bulbs or Christmas lights at the base of the trees. When I went out this morning at 5:15am, the sheet I had placed over the Moro blood orange and the Calamondins had blown off. I don't know how long they were uncovered, but I won't know how bad the damage is for a week or so.

I have 3 satsumas that I'm hoping make it because I ran out of lights and sheets. The Owari satsuma (on flying dragon) is supposed to be very cold hardy anyway, and it is planted next to my 300-gallon rain tank with leaves banked all around it. It should be Ok. The Okitsu Wase (on trifoliate) is planted right next to the south side of the house, and I covered it with leaves and set a 5-gallon bucket of hot water next to it, so it should also be fine. The Miho satsuma (on sour orange) is in a 30-gallon pot placed in a sheltered location, but with no lights or bucket of water. I wrapped the graft with an old towel and t-shirt, and covered the rest of the tree with bubble wrap. I hope it makes it. Good luck everyone!