Winter Chill for Fruit Trees in Southeast Texas 1992-2012

The attached pdf table below summarizes the accumulated chill units at every National Weather Service Weather Station in Southeast Texas between fall 1992 and fall 2012 that reported 10 or more years’ data. What the table makes clear is that all areas experience a very wide range of chilling unit accumulations from one year to the next with the last five years being a textbook case of this. The winter of 2012 was in most places the lowest chill in the last 20 years, while 2009 was one of the coldest.

In the low chill areas, fruit growers should  plant trees requiring very low chill because late frosts are very rare and the plants will fail to thrive if they get too little chill. In areas of medium high and higher chill, the dangers of late freezes are strong, so in some areas it may be best to pick trees with chill toward the center of what is possible.

The attached table lists chill unit accumulation (what once was called chill hours) by percentages of time the winter in the last 20 years had the chill listed in column headers.

Southeast Texas Chill Unit Ranges 1992-2012

Annual Winter Low Temperatures in Southeast Texas 1992-2012

The attached table in PDF  represents a concise summary of annual low winter temperatures (October to April) for all official national weather stations in Southeast Texas for which there is 10 or more years of data since 1992. Most of them are for the full 20 years of data. The table lists weather stations first by Houston area locations (Harris County), followed by other sites in coastal and near-coastal counties bordering these (that is 0 and 1 county from the Gulf).

After this are other “interior” counties in Southeast Texas.  For these, there are 2 or 3 counties that must be passed through to get to the coast. “County numbers to the coast” is a rough proxy for distance from the Gulf, and in rural areas is a very rough approximation of winter temperatures. The warmest areas generally are within a few miles of the Coast, and with some significant warmer exceptions for dense urban areas and Galveston Bay, temps get colder as you go inland. Lastly there is a a table of selected sites north or west of Southeast Texas.  These are included to help interpret information about fruit tree performance in those areas, in order to use such information in Southeast Texas. For example, avocados that do well in Devine, Texas will likely do well in College Station south, because temperatures south of College Station are warmer than Devine, while north of College Station are typically colder, so would need increased protections.

The numbers in the cells represent temperatures F. If for example a cell has a temperature of say 28 in a column labeled 30% (as it does for Intercontinental Bush Airport), this means that 30% of the annual winter lowest temperatures during the last 20 years were at or above 28˚F.  If you are considering planting a fruit tree that needs temperatures above 25˚(like a mango) , you can use this information, plus a comparison between your site and the nearest National Weather Station’s temperatures, to determine how much freeze protection a mango (or any other tropical or semi-tropical) would require.

Southeast Texas Winter Low Temps 1992-2012

When is the New Edition? A few months at most! (Last revised June 2019)

In brief, the book is in its final stages. Editing the last chapter and working on the cover. Expecting copies July 2019.

Book History

Thank you all for supporting my effort to rewrite my book. The latest edition of Year Round Vegetables, Fruits and Flowers for Metro-Houston is the 12th edition. It has a yellow cover. It was last revised in 2004 and is clearly in need of a major overhaul.

The next edition will be about 500 pages and only cover food crops, so it is a major overhaul. The draft title is Year-Round Organic Food Gardening for Houston and Southeast Texas. This effort has taken a lot of time and effort, not just because I continue to teach permaculture, fruits, and vegetables through Urban Harvest, but also because I am a Board Officer of OHBA http// and the Permaculture Institute of North America http//

Why Did it Take So Long?
1. Since the last time the book was updated, the internet has mushroomed enormously as has people’s access to it. Gardening books these days need to not only provide a reliable guide to plants and techniques for our area, but also good and bad internet sources of information.

2. The ongoing climate chaos in our area means that increasingly we need to tell people not just what to plant and what week, but under what conditions of temperature, precipitation and wind plants will thrive or even survive. Part of the area south of both I-10 and TX 59 is now in USDA zone 10 some years and above 30 F all winter. Galveston stayed above 40F one winter and all airports are reporting record or near record annual temperatures. What was a fairly easy to predict set of temperatures is now much harder. Should you plant Russian kale or Papayas or even Pineapples?

These sets of questions are much harder to answer than you would expect. We need to know what the weather has been like lately all over Southeast TX and what temperatures each plant and seed needs to thrive/survive/avoid dying. For the most part, this information is surprisingly difficult to find for many food plants. How hot is “too hot” for oats, for example? As well, it results in a dizzying number of tables that many readers might find daunting to understand and use, so there are writing challenges too.

I have nevertheless made a lot of progress on a new edition and 12 chapters have been completely rewritten

* Two new fruit chapters are finished and much better than anything previous;

* The chapter on ecological pest management has been completely changed; and

Dynamic Plant Lists and Dynamic Planting Schedules Adjustable by the Grower
I am finished with the most difficult effort: two vegetable chapters. I have had to break with the traditional way of presenting vegetable planting schedules. Rather I am going back to relying on the temperatures different plants need to do well, giving people that information, and then a suggestive planting schedule that needs to be reconciled with temperature needs of proposed plantings, and the likely temperatures in the months ahead in different parts of Southeast TX.

This has required an enormous amount of data collecting that is both tedious and difficult to do since it doesn’t seem to be centralized anywhere. Broadly, it seems like the world’s agricultural establishment is very slow to understand the implications of climate chaos on traditionalist planting schemes. So people are wasting a lot of effort and seed.

Thanks to cooperation from Texas A&M Climatology, I have been able to create RECENT  tables of temperatures month by month for the last ten years at 28 locations spreading from Galveston Island to Crockett, and Liberty to Columbus. This has allowed the creation of vegetable planting zones based on low temperatures month by month year-round and in summer high temperatures. Roughly, monthly mean average low temperatures get lower from coast to interior by about 10 degrees and urban areas are higher than surrounding rural areas. Summer high temperatures go from 89 in Matagorda to 99 far inland. By contrast, at night in summer, coastal places are near 80˚F low temperature and the northern part of Southeast Texas is near 70˚ especially in rural areas.

The upshot of this is that my new planting schedule will specify planting dates by 7 planting zones. This will make it much easier for people in different places to plant at the correct time for their location and to adjust to the weather.  I have completed the chapter that does this and a companion chapter detailing most possible annual food plants we can grow. I have also updated almost all of the early book chapters and as of mid-December am closing in on the draft of the last substantive chapter: soils.
Once this is done, there will be editing, final work on the cover, and a preface, but publication should be sometime in the first third of 2019. 15 years is long enough! 

 CHECK THESE PAGES AGAIN in late July 2019 for updates.

Bob Randall
June 2019



Weird Weather

201004 Weird Weather

Permaculture Guilds in Houston

One important aspect of permaculture design is the effort to place things so they benefit each other.

Permaculture Guilds

Use Nature and Permaculture Stacking to Increase Yields

In the classes I teach, home owners who have become aware of the thousands of possible vegetables, fruits and herbs they could grow, often lament “I just don’t have any more space for that.” 

As a possible solution, they usually ask me what will grow in shade, and I usually tell them that many herbs, vegetables where you eat the leaves, and blackberries are the best possibilities. But that brief answer is simplistic.

What I would say if I had time to explain is that, “Permaculturists have a technique called stacking that may help you.” Stacking is useful in situations where you think there isn’t enough land for your goals, and you want to get more out of less.

Permaculture is a design philosophy and methodology. It integrates ancient and modern technologies with an understanding of nature and detailed observation, to guide effective plans for sustainable living. It is taught in 72-hour classes in periods from ten days to a year.

In aged natural forests, there is a tall tree canopy layer fifty feet or more above the earth, with shorter, more shade tolerant trees below them, and even more shade tolerant low-growing bushes, shrubs, herbaceous plants, ferns, and fungus living close to a heavy mulch layer and the earth itself. On the trees, there are often vines such as wild grapes, Virginia creeper, or cross vine.

These forests contain many times the biomass of a similar acre of less layered vegetation such as prairie, most gardens, lawn, or edged walkways.  So per square foot they produce much more soil-building plant liter.  That in turn, prevents runoff and holds much more moisture for much longer.

The shade canopy acts like a 50 ft. insulation, keeping temperatures cooler, so there is much less evaporation from the surface. The mulch layer also keeps the surface damp even in summer, so the roots, mainly near the surface have a continual supply of moisture to support growth.

The tree layer provides millions of square feet of leaves whose water content keeps them from cooling or heating as fast as the surrounding air. So dew condenses on them, producing more precipitation. The plants then use a high portion of the water collected, and eventually transpire it back into the air.

Worldwide, 60% of all rainfall is from plant transpiration. Inland the percentages are higher and near the ocean lower.  Thus Galveston rain is mainly from the ocean, but Houston tap water, coming as it does from the Trinity, is mainly of botanical origin. So natural forests and woody landscapes are not just the lungs of the planet, but also its blood supply! Native understory plants like ferns, beautyberry, scarlet buckeye, and parsley hawthorn do a lot of good for us.

Another natural design found in forests is the guild. This is an assemblage of plants, animals and other items that provide benefits for each other, thus making it possible for more to live in a smaller space. For example, a blackberry thicket might protect a young tree from deer, and later, the older tree might provide mulch and bird droppings to help the blackberry grow.

A third natural design we can use in our gardens is ecological succession. If a forest is partially cleared by an avalanche, disease, or fire, new sun-loving plants occupy the cleared ground quickly.  These provide shade and organic matter to nurse small shrubs and trees, and these in turn help even taller trees to emerge.

Thus without any human help, nature has sustained itself here for millions of years because it has a very efficient system for growing plants close together. But we too can use natural and other designs to stack our yards.

Stacking is related to understory, guild and succession, but embellishes these designs for the purposes of gardening. Vertical stacking is an effort to plant several useful plants of different heights in the same space.

In horizontal stacking, by contrast, several useful plants are planted adjacent to each other in order to benefit each other This is done using the guild concept—beneficial assemblages promote higher production.

Temporal stacking places plants near each other that will enjoy most of their growth during different seasons, or years.

In my own garden, I use stacking to squeeze more and more production out of my house-lot. I grow several sweet varieties of hybrid muscadine grapes on a wire between ten-foot U-stakes. Vertically stacked below these are domestic blackberries tied to the stakes. And below them on the ground suppressing weeds is our favorite summer green– sweet potato spinach.  These three plants all do well in sun, but two are still productive in partial shade, so we can make use of this to vertically stack.

Horizontal stacking uses mutually beneficial qualities of plants such as the different micro-climates created by different plant heights. In winter, the warmest part of my yard is on the southwest side of my house in a sunny space between two tall grapefruit trees. That’s where I have my tropical plants—papayas, guavas, pentas, tropical passionfruit and two coffee plants. There is no room for more grapefruit but plenty for these heat loving smaller plants.

The typical temporal stacking is to understory a preferred tree that when it gets big enough, can replace what was above it. I am growing a very hardy experimental avocado under a poor quality citrus. But a less obvious example is the strawberry patch.  Strawberries need winter sun to produce and summer shade to be perennial.  The solution is to leave two-foot wide spaces in the strawberry patch so that summer vegetable plants such as basil, peppers and okra can be planted where they will shade the strawberries all summer.

Stacking is just one of more than two-dozen sustainable land design concepts to be taught in permaculture classes through Urban Harvest at


Shifting to Local Food

Shifting to Local Food

In September 2008, Gary Edmondson and I presented the above to a Houston Tomorrow HGAC Conference on improving the Houston Food Supply.

Climate, Weather, and Landscaping in the Years Ahead

Climate, Weather and Landscaping in the Years Ahead

I gave a short talk on the drought and the increasingly chaotic climate in the Houston and Southeast Texas area.  The talk was in mid-November 2011 at the Organic Horticulture Business Alliance (OHBA) Drought Symposium.

Weblinks for Monitoring Weather and Climate in the Houston Area

As best I can tell, all or most predictions come from the same 10 or so models. Radio/TV/newspapers typically just use government predictions. Commercial media often though exaggerate threats and possibilities possibly for commercial reasons.

General Weather information: Go to ; then click on the map of the Texas Gulf Coast, then click on area map of Houston or wherever. You can enter a zip code there and bookmark it. If it matters a lot whether the prediction is correct, read the detailed discussions at the bottom right of that website. There are hourly forecasts for your zip code for the next 3 days and radar maps that show you how rain is moving through the area.

Longer-term info: A summary of what is expected for the months ahead is updated monthly. Typically, they run 10 computer models and pick the middle one.

What weather happened:

For summary information about historical weather averages and extremes:

For info relevant to landscaping and gardening, go to

For drought:

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