The Plumeria Society of America, Inc. Come to the January meeting! d Introduction of 2014 PSA Board of Directors d d Winter Plumeria Care Q&A Session d Date and Time: January 14, 2014, 7:30 p.m. Location: Metropolitan Multi-Service Center, 1475 West Gray, Houston, Texas Anyone with an interest in plumeria is invited to attend! Faces of Corona Surprise (photos courtesy of Mike Atkinson) President’s Corner Mark Wright page 2 In Preventing Sunburn—Part 1 George Hadjigeorge page 3 this Lemon Drop for the Mayor Emerson Willis page 7 issue ... In Memory of Viola Guillot page 9 Photos page 12 January 2014 President’s Corner by Mark Wright, Texas Trying to write this right now is hard. Nostalgia problems and frustrations we have dealt with in the has nothing to do with it. This may be my last past. “President’s Corner,” but staying warm is more My years as president have been challenging important to me at this moment than thinking of my and rewarding. I have met many great people and tropical plants. By the time you read this, there will have participated in functions I would not have be a new PSA President and Board of Directors. otherwise. In all honesty, I have enjoyed the last four Looking back over my four years as president, I years. Having help with fulfilling your obligations is a feel as if we’ve moved forward in some areas. Using reward not to be overlooked. I have had lots of help our new digital method, eleven new plumeria with all aspects of this job: articles for the newsletter, cultivars have been registered with more to follow the newsletter itself, plant sales, yard tours, the soon. general meetings, etc. Our board members and A new website is coming around the first of the volunteers cannot be thanked enough for the hours year. Many parts of the current website have not they put in and the job they do. been operating, including the option to pay through I will continue to work behind the scenes for the PayPal ™. The new site will address many of the PSA and care for my plumeria trees at home. The current address for PSA meetings is Metropolitan Multi-Service Center, 1475 West Gray, Houston, TX 77019 The location will change again when the new garden center at Hermann Park is completed. 2 | Plumeria Potpourri | January 2014 Preventing Sunburn—Part 1 by George Hadjigeorge, Texas Plumerias, especially cuttings, get sunburned Houston area), sometimes. Typically, only a few out of many plumerias even though sitting next to each other get sunburned. In part 1 they are of this article, I will explain how radiation of heat exposed to the works and what kinds of conditions are necessary sun all day. for a plumeria to get sunburned. In part 2 of this Clearly, article, I am going to explain how and why sunburning of plumerias get sunburned at the base of the trunk, the trunk of which is the most common place where plumerias cuttings and plumeria plants is not due to direct get sunburned. I will show many examples from exposure to the sun alone; otherwise, both the top of various geographical locations and explain why the cuttings and plumeria plants would get sunburned plumerias got sunburned. In part 3 of this article, I all the time too (they receive the same amount of am going to show examples of plumerias that were radiation from the sun as the trunk bottom). For a sunburned from reflection radiation from nearby plumeria trunk to get sunburned, it means that heat objects, and I am going to explain why the plants coming from somewhere else, in combination with got sunburned. I will also talk about sunburning of direct heat by radiation from the sun, is overheating plumerias in greenhouses. Then I will give the bottom of the trunk. As I will show in this article, guidelines on what to do to avoid sunburning of this something else is reflection radiation from plumeria plants and cuttings. nearby objects and from the soil surface. Usually, only the first few inches of the trunk In order to understand why plumerias get next to the soil line and facing the sun get sunburned and what to do to avoid it, we need to sunburned (picture below, provided by Mike understand the basics of what radiation is and how radiation of heat works. This is an extremely complex subject, and it is very difficult for non- technical people to understand. I am going to try to keep this subject as simple as possible so that the average person can understand it. The sun via sunlight warms up the earth. Sunshine is a combination of bright light and radiant heat, which are part of the electromagnetic spectrum. Even though the core of the sun is extremely hot, the radiative surface of the sun (photosphere) has an average temperature of 5800 degrees K. The Inverse Square Law governs the Atkinson of California). The back of the trunk (next amount of radiation intercepted by the various picture) and the top of the cuttings rarely gets planets and stars. This law says that the intensity of sunburned. radiation striking a planet decreases by the square Plumeria tops might get sunburned in hotter of the distance between the sun and the particular desert areas and in greenhouses. Plumeria branches planet. The total energy emitted by the sun at its do not generally get sunburned (at least in the surface is enormous, about 63 million watts per January 2014 | Plumeria Potpourri | 3 square meter. Because of the Inverse Square Law, other words, the earth and all objects on it, emit the amount of sun radiation that strikes the upper thermal radiation into space all the time. However, atmosphere of earth is only about 1,400 watts per the intensity of this thermal radiation is very low square meter. Why am I explaining this? Because because of the low average earth temperature the Inverse Square Law also applies to radiation of (about 300 degrees K). The radiation intensity heat involved in sunburning of plumerias, and it depends on the absolute temperature of the plays a major role on how plumerias get emitting object to the fourth power. On the other sunburned. It is the reason why plumerias get hand, the sun’s radiation intensity is orders of sunburned just very close to the soil line and not magnitude higher than that of the earth because higher up. The whole plumeria plant would be the sun radiation-emitting surface is at 5800 scorched in direct sunlight all the time if this law of degrees K, versus 300 degrees K for the earth. nature were different. Whenever an object absorbs electromagnetic Another important factor to understand, which radiation such as sunlight, heat is transferred. The is a major factor of how plumerias get sunburned, thermal energy that object emits has a much lower is the difference between sunlight and thermal intensity than sunlight. This is how the sunlight that radiation. Both sunlight and thermal radiation reaches the surface of the earth changes character. consist of electromagnetic waves. However, Sunlight comes in with high intensity and part of it sunlight consists of both light and heat, whereas is re-transmitted back as low intensity thermal thermal radiation consists only of heat. Thermal radiation, mainly in the infrared region. So, with radiation is all in the invisible region (mainly respect to plumerias, reflection radiation off various infrared) and it is invisible to the human eye. For nearby objects has relatively low intensity and example, if you are standing next to a fire, you can cannot by itself sunburn plumerias. feel the heat, and it makes you warm even though Thermal radiation exchange between two the air around you is cold. However, you cannot see objects depends on the temperature difference it. Sunlight can go through a glass or clear plastic between them. If both are at the same temperature window and strike objects in a greenhouse. there is no thermal radiation exchange between However, when sunlight reaches objects in a them. greenhouse, it changes character; it changes to The intensity of radiation is a big factor in how thermal radiation. The reflected infrared radiation much damage to plant tissue it can do and on how cannot go back out through the glass or clear long it will take to achieve it. As we have seen, plastic window because both glass and clear plastic reflected radiation has low intensity and by itself it are opaque to infrared radiation. As a result, the cannot sunburn plumerias. However objects like heat that comes into the greenhouse via sunlight is mirrors and shinning metals, can deflect sunshine. trapped in the greenhouse and cannot escape— Deflected radiation has high intensity-like sunlight then the contents of the greenhouse heat up. This and could be very damaging. If deflected or is called the greenhouse effect and plays a major reflected radiation falls on the same spot as direct role as to why plumerias in greenhouses can get sunlight, the two become additive, even though sunburned so easily. their intensities could be very different. They will Let us now try to understand how thermal both contribute in raising the temperature of the radiation works. All objects in the universe that area they fall on. As I will explain later, this effect is have a temperature above absolute zero emit the main mechanism on how plumerias get thermal radiation all the time, day and night. In sunburned. 4 | Plumeria Potpourri | January 2014 Radiation can also be concentrated by using a between them.