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Why Texas Produces the Best Tasting Grapefruit in the World

Texas Rio Red Grapefruit


Mani Skaria, Ph.D.

Founder & CEO of US Citrus, LLC

Professor Emeritus, Texas A&M University-Kingsville

Sorry other citrus-producing states and countries for the above question.

Obviously, we pay the price – our high heat, many 3-digit temperature days.


Texas Grapefruit

A fine and a balanced blend of tartness, sweetness, acidity, juiciness, color, and flavor are very appealing to consumers of grapefruit. The Rio Grande Valley of Texas is known for providing the best tasting grapefruits in the world, including red-flesh grapefruits. Recent examples of Star Ruby and Rio Red grapefruits were developed by Dr. Richard A. Henz of Texas A&M University-Kingsville Citrus Center in Weslaco, Texas, which has become the backbone of the grapefruit industries in many places like south Texas, South Africa, and Israel. Prior to the Rio Red and Star Ruby grapefruits, Texas produced another red flesh grapefruit called the Ruby Red.

Weslaco, Texas is located at latitude 26 degrees north of the equator and 97 degrees west, so it is only 1,800 miles north of the equator. Citrus is a subtropical climate group, with grapefruit as a heat-loving member of the family. In general, citrus trees show little growth below 13oC (=55oF).


Annual Heat Unit

Annual heat unit is a measure of heat plants need and for proper growth and fruit development. This measure is used well in vegetables, and fruit trees. Crops have upper and lower temperature thresholds, outside of which the physiological functions are not normal.


Grapefruit Temperatures

The ideal temperature for grapefruit is above 60 degrees Fahrenheit. South Texas temperature can reach three-digit numbers some days. Grapefruit trees along the coastal areas maintain a warm and stable temperature. In cooler areas, full sunlight and a south-facing planting help grapefruit tree stay warm.


Best Grapefruit in Texas

Grapefruit produces lots of fruit inside. The large size of a grapefruit tree brings a shading effect to the inside fruit. Together, with internal fruit and warm conditions, a grapefruit tree can produce higher quality fruit in places such as south Texas.


Heat Units and Citrus

Heat units are calculated as a function of:

1)    the number of days in a 30-day month

2)    taking 13oC (=55oF) as the temperature minimum for citrus physiology

3)    average monthly temperature of the region 

4)    and the deviation from the minimum times 30 (days) give the heat units.


Following are some of the calculated heat units in various places in tropical and subtropical conditions.


Location                         Region                   Heat Units (Calculated)


South Texas                    Subtropical                     3,900

Orlando, Florida             Subtropical                     3,465

Riverside, CA                 Mediterranean                 1,700

Valencia, Spain               Mediterranean                 1,626

Wakayama, Japan            Maritime, cool                1,951

Palmira, Columbia           Tropical                          3,918


In extreme temperature conditions, shading from other trees or bark whitewash would reduce sunburn impact. In such conditions, the root system is expected to be kept moist always.


Heat Index Chart

Another heat measure is called the heat index (HI) which is an indicator combining the temperature and relative humidity as a measure of perceived temperature on the human body. It is well-explained with the chart taken from the National Weather Service of the United States of America.

 Grapefruit Heat Units - US National Weather Service Chart

Among all the citrus varieties, grapefruit is the only one with an origin in a tropical island – the Caribbean island, Barbados.


Grapefruit from Texas

Want to grow your own Texas grapefruits?

Here at US Citrus, we offer micro-budded Texas Rio Red grapefruit trees.

Perfect for growing your own grapefruit!

How to Protect my Lemon, Lime, Orange, Kumquat, Calamondin Trees from Ants

How to Protect Your Citrus from Ants

One of the common questions I get from customers is about what to do to control ants in their favourite citrus plant.

Sometimes, while tending to the citrus plants, people find ants moving up and down and would want to know what exactly could they do to keep the ants away. While the question is simple and would warrant a simple recommendation of a chemical, organic or otherwise, my answer usually takes a windy route.

The reason is that ants could occur due to different reasons. Unless we know the exact reason why ants are occurring, it would be difficult to recommend the specific control measure. The alternative would be to recommend any of the Broad spectrum pesticides (chemicals that kill a wide range of insects). However, they tend to have unintended consequences by allowing other secondary insects that weren't a concern before.  Hence it is important to know what is causing ants to be present on your citrus in the first place. In most situations, ants do not feed on citrus directly.

First of all, there are fire ants and other ants species that form colonies in the ground and feed on the roots ending up killing your citrus trees. This rarely becomes an issue in container grown citrus. However, if they do, you could use any of the fire ant chemicals that are available in garden centres.

Secondly, there are leaf-cutter ants that take pieces of leaves to their colonies where they grow fungus which is used to feed the colony. Again chances are that you might not encounter these in container grown situations. If this does happen, you would need chemicals specific to leaf-cutter ants. If you ask for a leaf-cutter ant chemical, most garden centres would have them. On most packages, they would also have pictures of ants holding leaves, like in their names- leaf-cutter ants.

The third and most common situation where you would find ants is when you have other insect infestations that provide conditions beneficial for ants to thrive. Some insects like mealy bugs or scales that feed on the plant material end up pooping a sugary substance called honeydew. Ants feed on the honeydew and in return protect the insect from natural enemies like wasps. This sort of symbiotic relationship is not uncommon in insects where in exchange for the free food they provide protection from other species of insects or predators. The honeydew, in this case, would also cause fungus to grow, resulting in black leaves which are also aesthetically not pleasing. To control these ants, we need to control the insect that is hosting the ants on the plants. Once we eliminate the primary insect, the secondary insect, and the fungal growth can be controlled. We will look into mealybug control in another blog

                                                   Cheri Abraham, PhD

Eight Steps to Growing Kaffir Lime Trees in Containers

8 Steps to Growing Kaffir Lime Trees in Containers

Kaffir Lime is also known as Makrut lime, Mauritius papeda or Combavas with the Latin name Citrus hystrix

This exotic citrus fruit produces an incredible amount of oily juice that is wonderfully fragrant, and the leaves are highly prized in Thai and Indonesian cuisine as a spice and garnish.

Kaffir Lime Fruit

Features of the Kaffir lime:

  • The peel or rind is used to make Thai curry paste and in aromatherapy.
  • This small and bumpy citrus fruit has both culinary (garnish) uses and medicinal properties in many cultures. 
  • Also, oils from the rind have uses ranging from sour dish flavoring to an insect repellant.
  • The pulp of Kaffir limes is yellowish green, very sour, slightly bitter, and very fragrant.
  • The fruit is not edible, is incredibly oily and has a fragrant aroma.
  • The lime tree reaches full maturity in late winter to early spring, with the rind turning yellow.

Kaffir Lime Tree

Features of the Kaffir lime tree:

  • The lime is more commonly known and used for its leaves consisting of a large petiole and a equally sized leaf blade.
  • The Kaffir lime tree is grown and harvested primarily for its dark green leaves to create spices or oils.
  • Dried Kaffir Lime leaves are sold online for nearly $30 an ounce!
  • Other uses include blending into massage oils, natural shampoos, and various herbal products.
  • The tree is less cold hardy than Persian Lime.
  • The tree exhibits good growth with full sun. 
  • The Kaffir Lime tree produces some of the most exotic limes in the world with all of its unique uses!

Where Will Kaffir Lime Grow?

Generally in the US, planting citrus in the ground is limited to certain regions such as California, Arizona, South Texas, Louisiana and Florida.

If you do not live in those regions, we recommend planting kaffir limes as container plants. We consider this a good thing, because it's going to make your kaffir lime growing a lot easier.

Growing Kaffir limes Outside of Growing Zones

There are several options for growing kaffir limes as container plants.  You can use a plastic barrel, a wooden planter, a nice decorative pot, or really any sort of container that has adequate holes on the bottom for drainage.

Fabric pots are another option. Even though they do not have holes, the entire container is made of a fabric mesh which allows proper drainage and aeration of the soil.

The Planting Process for Growing Kaffir lime Trees in Pots

Below is the simple step by step process for planting our citrus trees. 

You can keep any citrus tree pruned back, but the Kaffir lime is naturally a smaller dwarf type variety which gets to be about 4 to 6 feet, while still producing an abundant harvest.

Step 1: Container for Kaffir lime trees

Proper container drainage is crucial for successfully growing kaffir lime plants. Ensuring that your choice of container has adequate number and size of holes at the bottom of your planter is important for proper plant growth. We typically recommend SmartPots which are composed of a mesh cloth in order to allow good soil drainage.

In addition to container drainage, container size also plays an important role in successfully growing container plants. For citrus trees, the size of the pot should be at least 5 gallons, with our favorite size recommendation being 15 gallons. We find that anything above 25 gallons is quite difficult to physically move by only one person.

Step 2: Soil for Kaffir lime trees

Choosing soil for your Kaffir lime trees is simple. All you need is potting soil that can be purchased at your local hardware store or gardening center. We would advise against the use of gardening soil or topsoil to use for container gardening, because of the varying composition of soils throughout the US. 

For example, US Citrus is based in the Rio Grande Valley, and we have a wonderful sandy loam type soil which drains very well. Other types of soils may contain different levels of clay or limestone leading to inefficient draining. This can lead to poor root growth and general plant health overall. 

With a standard potting soil for your container gardening, you do not need to worry about any of these factors. You also don't have to worry about the pH balance of the soil. We have just removed a large part of the headache of growing citrus by having all customers grow their kaffir limes in containers and using any standard potting soil which is available at your local nursery garden center supply store.

Step 3: Watering for Kaffir lime trees

 Typically, when kaffir limes are planted into the ground there is a worry of proper drainage and/or overwatering your trees. Kaffir lime trees planted in the ground prefer to have their roots a bit on the dry side. We have found that overwatering of container citrus is mostly not an issue if the container has proper drainage.

See the watering schedule for our citrus trees based on their size and the outside conditions.

An alternative way to determine if your tree needs watering is to take a look at the leaves. If the leaves are wilted and dry, your tree needs more water. After watering, the tree’s leaves should perk up. However, keeping to a regular watering schedule is the ideal option.  

Overwatering Your Potted Kaffir Lime Tree

Overwatering is a possibility and we find that this especially happens when the trees are indoor and there's a garden saucer used underneath the pot. A garden saucer under the pot impedes drainage. That is helpful while you're on vacation and cannot water your tree for a week, or when you have trees indoors to prevent water seeping onto the floors and causing damage.

However, if trees are over-watered, the plant leaves will wilt and may turn a bit yellow and look sad. Watering more will not improve the condition of the tree obviously, and you will likely notice that the soil is waterlogged at this point.

Giving your tree a break by taking it outside if possible or letting the soil drain without a garden saucer in the bathtub for a day is a good solution. Afterward, you can adjust your watering schedule appropriately. Our watering schedule also has a section for indoor planting.

Step 4: Fertilizer for Kaffir lime trees

Your Kaffir lime tree will need both macro and micronutrients, just like a human. The macronutrients that all plants need are Nitrogen, Phosphorus, and Potassium. You have likely seen fertilizers and soil which state three numbers together, this is the N – P – K system which shows the concentration and relative amounts of nitrogen, phosphorus and potassium respectively.

These macronutrients are very important for the color of the leaves, development of the root system, proper flowering, fruiting, and taste of the fruit respectively and appropriate photosynthesis, the growth of the trunk of the tree in general. See our blog article on nutrition for more information.

Micronutrients are also very important - think of these as vitamins for humans. They are needed in much smaller quantities and plants can have characteristic symptoms if they have a micronutrient deficiency. We will detail out micronutrients and symptoms of deficiencies in later articles.

However, our promise to you is that we make this simple. Between regular potting soil and the fertilizer we recommend, you will have all the macronutrients and micronutrients that your tree needs and a simple fertilizing schedule for easy and effective fertilizing when you get your tree and for every February, May, and August. See our fertilizer schedule below for amounts that we recommend.

Fertilizer Schedule

Ounces to use every Feb, May, and Aug

Year 1

Year 2

Year 3+




Miracle-Gro for Citrus, Avocado and Mango (13-7-13)




 Espoma Citrus (5-2-6)




Step 5: Sunlight for Kaffir lime trees 

Sunlight is crucial to kaffir lime trees, especially because it is A tropical plant. In most areas of the United States, you want to maximize sunlight with full sun exposure. If you are planting indoors, make sure that it has full sun next to the window, but we would also recommend having a grow light.

Citrus does best when it has at least six hours of sunlight a day. If the temperature is consistently above 90° especially for younger trees, there may be some wilting of the leaves. This wilting will reverse however and at this point, it would be advantageous to keep your tree by elementary and partial shade. 

Step 6: Winter Protection for Kaffir lime trees

We recommend that under freezing temperatures, you move your citrus tree into a warmer area such as a garage or indoors for the entire winter. Utilizing a grow light would be a great supplement for continued growth.

There is nothing more frustrating than losing years of work and future decades of fruit than losing your citrus tree to a freak cold-snap which occurred while you were vacationing out of town! Citrus can die with exposure to temperatures in the teens for even up to 12 hours. 

Step 7: Where do I buy my Kaffir lime tree?

First of all, if you live in the states of California, Arizona, Louisiana, or Florida, you will need to purchase your citrus tree locally as citrus cannot be imported into your state because of USDA regulations.

Otherwise go to and buy your tree today!

Step 8: Harvesting your Kaffir limes

The crop is distributed around May to October, with the fruit taking about 4 months to ripen.

Check out our Kaffir lime tree blogs for more insightful information about this wonderful citrus tree, including valuable tips on how to care for a Kaffir lime tree.

Mistakes I Have Made Growing Lemons, Limes, Kumquats , Mandarins, Australian Finger Limes and Kaffir Lime Trees: Part 1

Growing Citrus Tree Mistakes

One of the most important factors with regards to citrus tree planting is ensuring good root health.  There are multiple factors which affect this including proper soil, container size, avoiding any over or under watering, and proper nutrition.  Of course secondary problems like root rot because of fungal infections and other pathogens can affect your root system.

However, I believe that for the average gardener will face a much more significant issue when they transplant their tree.  Without proper planting into the initial pot, the roots will never go out into the soil and will not develop, this will lead to a stunted tree.

A stunted tree has characteristic signs and symptoms, it will not die, however it will sustain a prolonged state of smaller growth with occasional shoots of new leaves but without any vigorous growth.  Also if you pull on the base of the trunk of the tree anytime after a few weeks, it will easily pull up.  This is a clear sign that the tree never took proper root into the soil.  Unfortunately at this point, there is NO hope for the tree, it is best to discard of the tree and start over and not waste more time, that is why proper initial planting is so important!

I have planted many trees in my backyard in West Texas.  Unfortunately for myself, but fortunately for you I have made this mistake enough times that I thought it would be very important to share in this blog post!

Of course, when planting your new citrus tree you always want to have a proper size container, at least 5 gallons in size and have proper potting soil.  One tip is to always use new potting soil.  If you use old potting soil from a tree that was previously planted in the area, the dirt has become impacted around where the root was. Unless you fully take out the soil and break it all apart and then put it back in it will be very difficult for the roots to go into the new soil because it is not light and aerated.  So, I always recommend just using new potting soil. This is especially important to remember if you are replacing a tree.

Secondly, it is important to open up the root system of the new tree.  Use your fingers to pinch open the roots, this will help the roots have a proper orientation and surface area contact to grow into the pot.  However, do not strip the roots of all the soil, just pinch enough to loosen it.  Also if you keep the roots submerged in water, even overnight, this will kill your tree! Run some water into the tube if you are not ready to transplant, about 4 ounces a day and transplant as soon as possible!

Third, it is impossible to have good growth of a citrus tree if there is not proper depth to the container.  I have been tempted and have attempted to plant citrus trees into very nice decorative pots that were too shallow and short.  The way you can tell if it is too short is if you stand the cone onto the bottom of the pot, the height of the pot should be at least a bit taller than the plastic cone portion of the tree.  This is because the cone contains the roots of the tree and this soil must completely cover all of the roots and you should still be able to push in the roots slightly.  I have NEVER had a citrus tree do well in a container that was too shallow.  100% of these became stunted and a few months later I would pull on the base and there would easily pull up without any good root catching into the soil.

Fourth, push and make a hole into the center of the container with your plastic tube, this will create a perfect size planting hole for your tree.  When you plant your tree into the hole, give it a firm push and then gently push some soil around the top of the root system to really have it nice and covered.

Only plant one plant per container!  No negotiation on this!

Of course, maximize sunlight for your tree, use a grow light if you do not have access to a very warm window, or if your tree is not outdoors, protect it from cold. Water at the base of the trunk every day at least 1 gallon, for 1 month.

Afterwards, in about 2-3 weeks it is very satisfying to see new leaf/coming from your branches and trunk. At this time you can give a firm tug to the base of the trunk and it is also very satisfying to feel a very firm resistance, indicating that your root system is thriving in that you are doing a great job!

When you are at this point, you are well on your way to decades of harvest of delicious Meyer lemons, Eureka lemons, Kaffir limes, Persian limes, Australian finger lines, Calamondins, Kumquats, Rio Red Grapefruits, Pineapple oranges, Navel oranges, Valencia oranges and Blood oranges!


The History of the Meyer Lemon in America

The History of Meyer Lemons

Improved Meyer Lemon

Citrus x meyeri

The Meyer lemon represents a popular lemon variety in the United States and has a rich history. It is sweeter than other lemons even with an orange flavor. It is named after Frank Meyer, a plant explorer of the United States Department of Agriculture, in 1908.

Lemons from Meyer lemon trees are sweeter than other lemons, sometimes even taking on an orange-like aroma and flavor. This lemon is so named because they were identified in 1908 by Frank N. Meyer. It is thought to be a cross between a lemon, either Eureka or Lisbon, and a mandarin, that originated in China. The University of California-Riverside lists a biological and parentage in its citrus variety collection.

Meyer lemons are prized by Chefs and home cooks for certain recipes where a lesser acidic lemon is preferred. However, Martha Stewart, an American-business woman, and a TV personality popularized this variety in the United State through her dozens of recipes that contained Meyer lemon.

Meyer lemon will grow well in USDA Hardiness Zones 8-11.

However, it can be grown in colder places as a container-grown plant. With more attention and proper pruning, it can be grown even in colder regions, especially when the tree is grafted on a cold-hardy rootstock.

Meyer lemons micro-budded on trifoliate rootstock made at US Citrus would make it a more appropriate for Meyer lemon enthusiasts even in colder places as in Canada as a well-protected patio-plant, kept indoor during severe winter.

A grafted Meyer lemon tree would grow with about six hours of sunlight.

Meyer lemon became popular in California by the mid-1940s. Two viruses, Citrus tristeza virus (CTV) and Citrus tatter leaf virus (CTLV) were found to be widespread in California Meyer lemon plantings. The University of California-Riverside scientists initiated a tissue culture program and the efforts of Dr. Chester N. Roistacher made a new selection of Meyer lemon free from virus infections. The new, improved selection is referred to as Improved Meyer lemon.

All the Meyer lemons from US Citrus are also the improved version via the Texas A&M University-Kingsville Citrus Center budwood program, initiated by the author of the article in the early 1990s. My gratitude to Chester Roistacher and Dr. John da Graca – two scientist that were involved in the citrus improvement program in Texas.

There are millions of Meyer lemon enthusiasts in the U.S. and worldwide. But not many Meyer lemon tree owners know that Frank N. Meyer who explored the wilderness of south China regions for the USDA lost his precious life in the waters of the Yangtze River. The Plant Genetics Resources has established a Distinctive Service Medal for Plant Genetic Resources as a tribute to Frank N. Meyer who served for 13 years as Agricultural Explorer of the Office of Foreign Seed and Plant Introduction.

“It appears that Mr. Meyer while traveling down the Yangtze from Hankow to Shanghai on the S.S Feng Yang Maru of the Nisshin Kisen Kaisha was drowned near Wuhu.” - Excerpt from the American Consul in Charge, Shanghai, China, June 14, 1918.

-Mani Skaria, PhD