Tools for Choosing Plants

Pig Plows and Wildflowers

I don’t own a tractor.

There may come a time when I change my mind, but I actually hope to never own one if I can help it.

But I still could use some earth turned from time to time.

Fortunately I have pigs.

And they can beautifully plow up a field. I have struggled to bury a shovel blade in the same soil that my pigs move through with seemingly no effort.

And they only use their nose!

Pig plow in action.

Pigs who root are happy pigs!

Pigs are amazing animals.

This same plowing efficiency is why some people do not want pigs in their pastures. That’s understandable. Especially if it is a good pasture. The pigs will tear it up.

The key to grazing pigs on pasture… and yes, I do mean grazing… my pigs love fresh grass! …but the key to grazing pigs on pasture is to make sure the soil and pasture are not destroyed by the pigs in their process of tearing it up.

And that’s not a contradiction.

A pasture that is torn up and left with patches of bare soil has the real possibility of being destroyed. A pasture that is torn up and then quickly covered again with grasses and other pasture plants is not destroyed, but is stable or even improved.

And this is the process we are implementing on our farm.

The rolling hills and valleys of our pastures.

Our farm has some areas of pretty good pasture and really bad pasture. Not surprisingly, the worst areas are on the ridges of our many hills. The topsoil is very shallow or even non-existent and has almost no organic matter.

These infertile, poor-soil ridges are the perfect place for our pigs.

This is our “soil” on the ridges… not very good

Between the Broomsedge and erosion already present on the ridges, it was pretty easy to see where we should start working to repair the soil.

Here’s our plan:
We set up a paddock on the ridges. We use poly braid electric fencing with a portable electric solar charger. The paddock will not extend too far on either side of the ridge where the pigs can cause significant erosion. We just want the soil turned over. We add hay to the paddock. The pigs eat some of this, but mainly they nest in it at night. After a few days, and this all depends on the size of the paddock and how much rain we get, the paddock will be sufficiently pig-plowed, and the pigs will be ready to be moved to the next paddock. The day before we move the pigs, we will broadcast seed in the pigs’ paddock. The pigs will trample the seeds into the soft earth. The manure and hay will add a good amount of organic matter to start the soil rebuilding process. The seeds will bring even more biomass and biodiversity to rebuild the soil and pastures.


Our pigs have plowed up this paddock and are ready for the next one.

This brings us to the seed.

I have many requirements and desires on pasture species. Therefore my seed list is very diverse.

Here’s the basis of our seed selection:
We desire pasture plants that can feed our animals. We desire plants that produce a lot of biomass (leaves, blades, stems, roots, etc.) to build the soil. We desire plants that can pull nitrogen from the atmosphere and put it into the soil. We desire plants that can break up our clay soil and subsoil compaction. We desire plants that have deep roots that can withstand drought and pull nutrients from deep in the subsoil. We desire plants that increase soil microorganisms and life in general. We desire plants that yield a steady progression of flowers through the season to provide pollen and nectar for pollinators. We desire plants that provide habitat and food sources for beneficial insects.

That is a lot of desires for a seed. No one plant can do all that. There are some species that fulfill many of these requirements, but we also desire to increase the biodiversity of our pastures.

We are going to do this with seeds from two sources, Walnut Creek Seeds and Prairie Moon Nursery.

The bulk of our seeding will be using the Walnut Creek Seed Super Soil Builder Mix. This is a mix of species that will meet the majority of our desires in pasture plants. The seed mix includes:

  1. Field Pea
  2. Cow Pea
  3. Sunn Hemp
  4. Oats
  5. Pearl Millet
  6. Radish
  7. Ethiopian Cabbage
  8. Sunflower

We will also be sprinkling in a small amount of seed from Prairie Moon Nursery every time we seed with the Super Soil Builder. These are seeds from prairie plants native to North America. The majority of these species had original distribution over much of the east, including my home in Tennessee. These plants will fulfill our desire for pollen, nectar, and habitat for pollinators and beneficial insects. They will also greatly increase the biodiversity in our pastures as there are over 100 species in our mix!

The species from Prairie Moon Nursery include:

  1. Wingstem (Actinomeris alternifolia)
  2. Anise Hyssop (Agastache foeniculum)
  3. Yellow Giant Hyssop (Agastache neptoides)
  4. Nodding Onion (Allium cernuum)
  5. Prairie Onion (Allium stellatum)
  6. Canada Anemone (Anemone canadensis)
  7. Pasque Flower (Anemone patens var. wolfgangiana)
  8. Tall Thimbleweed (Anemone virginiana)
  9. Rose Milkweed (Asclepias incarnate)
  10. Common Milkweed (Asclepias syriaca)
  11. Butterfly Weed (Asclepias tuberosa)
  12. Whorled Milkweed (Asclepias verticallata)
  13. Heath Aster (Aster or Symphyotrichum ericoides)
  14. Smooth Blue Aster (Aster or Symphyotrichum laeve)
  15. Calico Aster (Aster or Symphyotrichum lateriflorus)
  16. New England Aster (Aster or Symphyotrichum novae-angliae)
  17. Sky Blue Aster (Aster or Symphyotrichum oolentangiensis)
  18. Canada Milk Vetch (Astragalus canadensis)
  19. White Wild Indigo (Baptisia alba)
  20. Blue Wild Indigo (Baptisia australis)
  21. Decurrent False Aster (Boltonia decurrens)
  22. Pale Indian Plantain (Cacalia or Arnoglossum atriplicifolium)
  23. Great Indian Plantain (Arnoglossum reniforme)
  24. Wild Hyacinth (Camassia scilloides)
  25. Partridge Pea (Chamaecrista fasciculata)
  26. Pasture Thistle (Cirsium discolor)
  27. Lance-Leaf Coreopsis (Coreopsis lanceolata)
  28. White Prairie Clover (Dalea candida)
  29. Leafy Prairie Clover (Dalea foliosa)
  30. Purple Prairie Clover (Dalea purpurea)
  31. Illinois Bundle Flower (Desmanthus illinoensis)
  32. Showy Tick Trefoil (Desmodium canadense)
  33. Illinois Tick Trefoil (Desmodium illinoensis)
  34. Midland Shooting Star (Dodecatheon meadia)
  35. Purple Coneflower (Echinacea purpurea)
  36. Pale Purple Coneflower (Echinacea pallida)
  37. Bush’s Coneflower (Echinacea paradoxa)
  38. Rattlesnake Master (Eryngium yuccifolium)
  39. Flowering Spurge (Euphorbia corollata)
  40. Biennial Gaura (Gaura biennis)
  41. Cream Gentian (Gentiana flavida)
  42. Wild Licorice (Glycyrrhiza lepidota)
  43. Showy Sunflower (Helianthus pauciflorus)
  44. Early/False Sunflower (Heliopsis helianthoides)
  45. Rose Mallow (Hibiscus laevis)
  46. Great St. John’s Wort (Hypericum perforatum)
  47. Kankakee Mallow (Iliamna remota)
  48. False Boneset (Brickellia eupatorioides)
  49. Round-headed Bush Clover (Lespedeza capitata)
  50. Meadow Blazing Star (Liatris ligulistylis)
  51. Prairie Blazing Star (Liatris pycnostachya)
  52. Marsh Blazing Star (Liatris spicata)
  53. Indian Tobacco (Lobelia inflata)
  54. Great Blue Lobelia (Lobelia siphilitica)
  55. Wild Bergamot (Monarda fistulosa)
  56. Glade Mallow (Napaea dioica)
  57. Wild Quinine (Parthenium integrifolium)
  58. Wood Betony (Pedicularis canadensis)
  59. Foxglove Beardtongue (Penstemon digitalis)
  60. Tube Beardtongue (Penstemon tubaeflorus)
  61. Narrow-Leaved Obedient Plant (Physostegia angustifolia)
  62. Obedient Plant (Physostegia virginiana)
  63. Prairie Cinquefoil (Potentilla arguta)
  64. Slender Mountain Mint (Pycnanthemum tenuifolium)
  65. Hairy Mountain Mint (Pycnanthemum verticillatum var.pilosum)
  66. Mountain Mint (Pycnanthemum virginianum)
  67. Yellow Coneflower (Ratibida pinnata)
  68. Black-Eyed Susan (Rudbeckia hirta)
  69. Sweet Black-Eyed Susan (Rudbeckia subtomentosa)
  70. Brown-Eyed Susan (Rudbeckia triloba)
  71. Wild Petunia (Ruellia humilis)
  72. Late Figwort (Scrophularia marilandica)
  73. Wild Senna (Senna hebecarpa)
  74. Maryland Senna (Senna marilandica)
  75. Royal Catchfly (Silene regia)
  76. Rosin Weed (Silphium integrifolium)
  77. Compass Plant (Silphium laciniatum)
  78. Prairie Dock (Silphium terebinthinaceum)
  79. Cup Plant (Silphium perfoliatum)
  80. Stout Blue-Eyed Grass (Sisyrinchium angustifolium)
  81. Grass-Leaved Goldenrod (Solidago graminifolia)
  82. Early Goldenrod (Solidago speciosa)
  83. Stiff Goldenrod (Solidago rigida)
  84. Showy Goldenrod (Solidago speciosa)
  85. Purple Meadow Rue (Thalictrum dasycarpum)
  86. Ohio Spiderwort (Tradescantia ohiensis)
  87. Blue Vervain (Verbena hastata)
  88. Hoary Vervain (Verbena stricta)
  89. Yellow Crownbeard (Verbesina helianthoides)
  90. Common Ironweed (Veronia fasciculate)
  91. Missouri Ironweed (Veronia missurica)
  92. Culver’s Root (Veronicastrum virginicum)
  93. Heart-Leaf Golden Alexanders (Zizia aptera)
  94. Golden Alexanders (Zizia aurea)
  95. Lead Plant (Amorpha canescens)
  96. New Jersey Tea (Ceanothus americanus)
  97. Shrubby St. John’s Wort (Hypericum prolificum)
  98. Early Wild Rose (Rosa blanda)
  99. Big Bluestem PLS (Andropogon gerardii)
  100. Side-Oats Grama PLS (Bouteloua curtipendula)
  101. Bebb’s Oval Sedge (Carex bebbii)
  102. Plains Oval Sedge (Carex brevior)
  103. Brown Fox Sedge (Carex vulpinoidea)
  104. Canada Wild Rye PLS (Elymus canadensis)
  105. Virginia Wild Rye PLS (Elymus virginicus)
  106. Dudley’s Rush (Juncus dudleyi)
  107. June Grass PLS (Koeleria macrantha)
  108. Switch Grass PLS (Panicum virgatum)
  109. Little Bluestem PLS (Schyzachyrium scoparium)
  110. Indian Grass PLS (Sorghastrum nutans)
  111. Rough Dropseed (Sporobolus asper)
  112. Prairie Dropseed PLS (Sporobolus heterolepis)

Note: There are a few of the species listed here that may be toxic to livestock. Then why would I add them to our fields where our sheep and pigs and other animals may eat them? First, none of the species are extremely toxic. Second, toxicity is almost always dose dependent… meaning, a little bit will not cause trouble. If a whole paddock was filled with a mildly toxic plant, then yes, an animal could be harmed. But we are adding so few of each plant, that I am not concerned about this. Third, these are native prairie plants that have been grazed by herbivores on this continent for thousands and thousands of years before modern humans altered the ecosystem… meaning, grazing animals have and can live in harmony with these plants. Fourth, when animals have a choice, and that is key, they will choose the plants their bodies need. Many of these “toxic” plants are likely medicinal to the animals in small quantities. If herbivores have plenty of options for grazing, they will eat what is needed and desired, and not more. Of course, there are exceptions to this, but in light of the other reasons listed above, I believe the benefit from this huge increase in biodiversity is worth the very small risk.

As this system matures, I will add photos!


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Designing A Custom Native Plant List

The first Permaculture Ethic is Earth Care. This can be realized in many different ways depending on appropriate context. Personally, as my family is preparing for our move to the farm, I have been in massive planning mode. For us, one aspect of planning for Earth Care will be the planting of native plants. There are a number of reasons for planting native plants including:

  • Restoring a native ecosystem
  • Increasing wildlife habitat
  • Increasing wildlife food sources
  • Pollen and nectar source for native pollinators
  • Pollen and nectar source for beneficial insects
  • Pollen and nectar source for honeybees
  • Ancillary forage source for domestic animals on the farm
  • Sources of herbal/plant-derived medicinals

Again, there are a number of things to consider when compiling a list like this, and I thought I would share how I built my list. I wanted plants that are:

  • Native. These are plants that should, typically, be designed/well-suited for my climate and grow the best. Of course, this is not always true with how the land has been used/abused/cleared.
  • Commercially Available. Yes, it is possible for me to find wild specimens and collect seed, divide, etc. But this is significantly less practical right now. I may do this in the future, but for now I will need to purchase these plants. Ideally, I will be able to get seed for these plants.
  • Attract Beneficial Insects, Pollinators, and Honeybees. This was described above, but it is important enough to reiterate. These plants provide food sources for birds, bats, native bees, bumble bees, parasitic wasps, predatory wasps, predatory insects, etc. All these animals greatly reduce pest damage (and many diseases by reducing the pests that introduce the diseases) and increase pollination rates. This equates to higher yields with less damage. It also increases general biodiversity with its many known and unknown benefits.
  • Non-Toxic… mostly. When I started looking through all the plants that met the above criteria, I decided to eliminate certain plants that were known to be highly toxic to people or livestock. Plants like White Snakeroot (Ageratina altissima var. altissima), Butterflyweed (Asclepias tuberose), and Green-Headed Coneflower (Rudbeckia laciniata), to name but three, attract beneficial insects, but can also kill a cow or a child. That is not compatible for us. There are a number of plants I did chose to keep that are potentially toxic to horses, but since we don’t plan on keeping horses, these plants fit within our context. In addition, there are other plants, Black Cherry (Prunus serotina) is one example, that is known to have toxins in pretty much all parts but the fruit; however, the birds and I enjoy the fruits so much that I thought I would keep this one on my list. Finally, I kept a number of plants that have “some reports of toxicity”. This may mean that if a plant or person eats too much of it, they can get sick, so keeping a wide variety of plants mitigates this risk. I believe that many plants are harmful if eaten in excess, but a cow taking a nibble once in a while may have a health benefit – the plant may be slightly anti-parasitic, or it may contain certain trace nutrients an animal needs in very small quantity. I do know that these plants existed with grazing and browsing animals for a long time before we got rid of them, so it stands to reason that if a plant is not deadly toxic in small amounts, it likely deserves a place on a regenerative farm.
  • Non-Invasive. This can be a little controversial. I will likely be adding some plants to my landscape that some people would not because of a “risk of invasiveness”. I believe many “invasive plants” are only invasive because we have degraded the land so much that these plants are the only ones able to grow on it anymore. If we are dealing with healthy soils and pastures and forests, then many (NOT ALL) of these invasive plants are not a problem. With that said, I will not actively be planting Ironweed (Vernonia spp.) or Trumpet creeper (Campsis radicans).
  • Finally, and this is more of an organizational method, I wanted a variety of plants that would flower throughout as much of the year as possible. You will see below how this works.

Let me know walk you through how I created a list of Native Plants for a Tennessee Permaculture Family Farm. How do you start?

You may happen to live in an area where someone has already created a seed mix. Peaceful Valley has a seed blend for California called the Good Bug Blend. For the rest of us, we need to make our own list and obtain our own seeds.

One great resource for lists of North American native plants that attract pollinators is the Xerces Society. Their site has a List of Regional Bee-Friendly Plants. Find your area and start a spreadsheet or list of plants for your area.

Another amazing resource (if you live in the USA or Canada) is the Lady Bird Johnson Wildflower Center of The University of Texas at Austin. They have an extensive listing of native plants that are commercially available. There is a listing for each plant that also provides its blooming time. I recommend you find your state or province on their Collections Page. Add this list to your master list.

Next, I evaluated each species for invasiveness and for toxicity to humans and livestock. I utilized a number of sites for this including the NRCS Plant Factsheets, the Center for Invasive Species and Ecosystem Health, and Cornell University’s Plants Poisonous to Livestock.

Using the above resources, I created a list of plants that met my criteria (yours will probably be different). I then made a table where I highlighted the months when the plant blooms. Next, I rearranged the table so that the plants were listed in order of bloom time. In addition, I left a blank for additional notes, and I color-coded the plant name based on its growth habit (Vine, Herbaceous, Shrub, or Tree).

This is the result:

Microsoft Word - Design Your Own Good Bug Blend - 4.docx

Microsoft Word - Design Your Own Good Bug Blend - 4.docx

Microsoft Word - Design Your Own Good Bug Blend - 4.docx


Click to download a PDF of this document: Native Plants for a Tennessee Permaculture Family Farm

I hope this article provides you with some tools and motivation to produce a custom native plant list. While it takes a bit of research and time, this list will be a reference for your land forever. To me, that is time well spent!


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Photo References:



Infographic – Pioneer Species for a Temperate Climate

I compiled information on Pioneer Species and Succession a few years ago, and I posted it in a series of articles:

A friend (Jake) suggested I make an infographic. That thought was in my mind for the last few years, and I finally took the time to do it.

Click here to download the high-resolution PDF.

For a quick review:
Pioneer species are plants, often considered weeds, which nature uses to transition from bare soil to a climax forest. They cover the soil quickly and reduce erosion. They often have deep taproots that pull nutrients from the depths. They can thrive in drought, full-sun, and bare soil conditions, and they pave the way for slower growing plants that need more moisture. The first pioneer plants are annuals and herbaceous perennials. Eventually shrubs and then trees appear. Pioneer species can be all of these types of plants, but the larger shrubs and trees often take many years to appear.

By using pioneer species with modern forest garden, agroforestry, and permaculture techniques, we can speed up the natural succession process to develop (or redevelop) sustainable and regenerative ecosystems for wildlife, agricultural, or personal use.

This infographic provides key information on growing conditions, attributes, and edible parts of many important pioneer species.



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    Permaculture Tips: Tree Identification Apps for Mobile Devices

Permaculture Tips: Tree Identification Apps for Mobile Devices

While watching a video lecture from Geoff Lawton, he referenced LeafSnap (see below). This got me thinking about appropriate technologies we can use in our Permaculture designs. I wanted to share a few tree identification guides. Unfortunately for my international readers, these are just for North America. There are a few available for England (TreeID and ForestXplorer are two I know of).


LeafSnap is a tree identification app for Iphones and Ipads. This is the product of a collaboration between Columbia University, the University of Maryland, and the Smithsonian. They use the technology in facial recognition software to identify tree leaves. After doing a bit of research, I think this program has the most potential, but it is not quite there yet. You need connectivity to a network, and not all places in the wilderness have it all the time. Because, this is a new program, the data recognition database is still being built. So the more people use the app, the better it gets… it learns as it grows. You take a photo and submit it, then the app gives you a listing of the possible tree choices. You look through the choices (and description and photos) and you can identify the tree. It is a bit more work, but it should get better and easier with time. But it is free, and has pretty good photos of all aspects of the tree (leaves, fruit, trunk, etc.).



MyNature Tree Guide is an app you need to buy (it costs $6.99 USD). Instead of visual recognition software to identify the tree, the user needs to work through an algorithm… simple yes or no questions that guide you to the right tree. I have used these in booklet form as well, and I really like this system. It is easy. It requires no connectivity. I haven’t spent a lot of time with the app yet, but I like it quite a bit. This will likely be my go to app until LeafSnap improves.

There are a number of other online tree identification guides, but these two are the only apps worth looking into right now. I do think the best online identification guide is What Tree is That by the Arbor Day Foundation. This uses a similar algorithm of simple yes or no questions as well… in fact, I think they are the first ones to take it mainstream for trees. I have used their booklets many times and really like them. And, for that matter, you can buy the booklets themselves on the Arbor Day Foundation website.

Take a look at these. Load them on your mobile device. I think it is wise to use technology in appropriate ways to further our knowledge and aid in building sustainability.



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Photo References:

  • All other photos are from the referenced sites.


Hardiness Zones, Heat Zones, and Sunset Climate Zones

The USDA (United States Department of Agriculture) has been producing a Hardiness Zone Map for many years. This map divides the U.S. into Zones 1 through 10 based on minimum temperatures (1 being the coldest and 10 being the warmest). A plant is placed into one of these Hardiness Zones based upon the lowest temperature it can withstand. Over the years, the concept of Hardiness Zones have been applied to all areas in the world. The most recent USDA Hardiness Zone Map is from 2012 (see photo above) and can be searched on their site here.


2006 National Arbor Day Foundation Hardiness Zone Map

Also, through work from the American Horticulture Society, the Arbor Day Foundation has created the 2006 Hardiness Zone Map. This takes into account the warmer temperatures the U.S. has been experiencing over the last decade. If you are interested in seeing the changes, the Arbor Day Foundation has a great animation on this page. Just click the Play button.

Probably the most useful site for locating your Hardiness Zone is located here. Just enter your zip code and your Hardiness Zone will be shown.

The benefit of Hardiness Zones is that it provides a starting point for planning which plants can winter-over where you live. However, there are a few drawbacks to the Hardiness Zone Map. It does not consider day length (changes considerably the further from the equator you go), snow cover (moderates soil freezing and insulates roots), humidity, frost, or soil moisture. Probably the biggest drawback is that it does not consider how warm your summer will be. The classic example is comparing the Shetland Islands north of Scotland and southern Alabama. Both are listed as bewteen Hardiness Zone 8-9. However, the Shetland Islands are sub-artic and southern Alabama is sub-tropical. There are almost no plants that can grow in both places.


American Horticultural Society Plant Heat Zone Map
…no longer available to the general public!

The variations in summer heat around the globe is what prompted the American Horticultural Society to create their Plant Heat Zone Map. The AHS Plant Heat Zones are listed from 1 through 12. The zones are based on the average number of days per year that the temperature will rise above 86 degrees F (30 C) as this is the temperature above which plants start to show heat stress. This is a great tool to augment the Hardiness Zones in your planning. You used to be able to download the map and search your zip code to find your Heat Zone. The AHS has recently removed those options. Not sure why, but I am not happy about it.


Sunset Climate Zone Map

The last map that I want to share was produced by Sunset Magazine. This company, which has a large gardening focus and has been around since 1898, divided the U.S. into 45 Climate Zones. These zones are based on Latitude, Elevation, Ocean Influence, Continental Air Influence, Mountains, Hills, Valleys, and Microclimates. It is a much more ambitious undertaking.

Here is a searchable map to find your Sunset Climate Zone, but I prefer going to the Sunset website and selecting the U.S. region here, as it provides a map as well as information on that growing region. Sunset also provides a pretty substantial searchable plant database for their Climate Zones on this page.

Combining Hardiness Zones, AHS Plant Heat Zones, and Sunset Zones, you will be able to more confidently chose plants that are well suited to your local conditions. These are great tools for planning your Permaculture System.

Here is a link to my article on Hardiness Zones for the World.

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Chilling Requirements for Plants


An apple tree in the snow.

As we are entering the hottest part of the year (in the northern hemisphere), I thought I would discuss a much cooler topic… Chilling Requirements for Plants.


There are certain plants that require cold temperatures to produce fruit. This is why, for example, apples are not grown much in Florida. Apple trees require a minimum number of hours below a certain temperature, and Florida just doesn’t get cold enough for long enough. Now there are always exceptions to the rule, and certain apple varieties have been developed to grow in warmer temperatures, so if you live in southern California, you are not without hope for growing apples. However, we need to be aware of what our chilling hours are and what our plants need to fruit reliably.


Chilling Requirement is a term used to describe the idea that a plant needs a period of cold to blossom. The requirement is usually expressed with the interchangeable terms Chilling Units orChilling Hours. One unit or hour is equal to one hour at or below the chilling temperature. Some plants have a Chilling Temperature that is below freezing, some others may need to be under 45 F (7 C), and others only need to be under 60 F (16 C) for example. Every plant has a certain chilling temperature. If a plant does not obtain its required chilling hours it either may not flower at all or will flower much less and therefore produce a lot less fruit.


Now, there are two stages of chilling. I always consider the first stage of chilling to be like a baseball pitcher’s windup. The first stage is reversible. As the season starts to cool down, the plant is getting ready for its period of dormancy. If the temperature warms up for a few days or a week or so, then the plant gears down from its dormancy preparation. It’s like the pitcher stepping back off the mound. It’s a do-over. No damage is done.


The second stage of chilling is like the pitch. It is the point of no return. It is irreversible. At some point (a certain temperature or a certain temperature for a specific amount of time), and this is very difficult to tell, a plant has committed itself to dormancy. Even if things warm up, the plant will remain dormant until other triggers cause it to break dormancy. If the temperatures are low enough for long enough throughout the winter, then the plant will be able to blossom well in the spring. If it is not a very cold winter, or if we have a plant that should be growing in a colder climate, then we may get little or even no flowering… and then our fruiting is poor.


It is important to know that the Chilling Hours do not need to be consecutive. Typically, the plant just needs cumulative Chilling Hours. We may have nightly temperatures that drop below the required threshold for our plant, but our days warm up above that temperature. If we have enough nights doing that, then that may be enough for most plants.


On the flip side, some plants have hair triggers to break out of dormancy. It the temperatures rise too high for too long, let’s say in an uncommon warm spell in the late winter, then a plant will wake from dormancy and may start production of blossoms. When temperatures drop again, the new growth may be damaged or killed. This is what causes concerns about late frosts or early blooming plants in a garden.


So how does this affect us and our plants on a day to day basis? All it means is that we need to select plants that are suited to our climate. That’s it.


We need to find out what our Chilling Hours/Units are for our area and then select plants that fall within or under our cut-off. I could only find one map that provided general chilling hours for the U.S. I did find a number of local state maps, but you will have to do a little looking on your own to find your specific local information. Most plant sellers will have this information for you if it is important for the species you are looking to purchase.


Plants that have a Chilling Requirement to produce blossom well

  • Pretty much all fruit that grows in a Temperate Climate (Apples, Blueberries, Cherries, Grapes, Peach, Pears, Plums, Strawberries, and many, many more)
  • Oranges and other citrus (although they don’t really go completely dormant, the chill produces more flowers and better tasting fruit)
  • Many vegetables need some chill to produce seeds (Cabbage, Carrots, Celery, Sugar Beet, and many more)
  • Almost all Bulb Plants
  • Many seeds need a period of cold to sprout.


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