048-The Simple Science Behind Great Gardening, with Lee Reich

| Podcast, Prepare

In today’s podcast, I’m joined by Lee Reich, and we explore some of the subjects in his new book, The Ever Curious Gardener – Using a Little Natural Science for a Much Better Garden. As curious gardeners, Lee and I are always pursuing the “why” behind the workings of the garden. I believe this drives us to be better gardeners.

Lee’s new book explores the fascinating world of activity below the bed surface and how it impacts the health of our plants. I often say “Feed the soil, and the soil will feed the plants.” – it’s all about partnering with the natural systems at work.

Warning: Science ahead – but it is fascinating and elegant in its simplicity. This is a very close-up look at life in constant motion. Life that is very small – but it wields a mighty impact.


Dr. Lee Reich

Dr. Lee Reich has just released his new book, The Ever Curious Gardener – Using a Little Natural Science for a Much Better Garden


The Silent Life of Soil

Success in your garden begins with the soil, but where does the soil begin? Good soil is made up of approximately 5% organic matter. Although it may not sound like much, that 5% is fundamental to the ability of the remaining 95% – comprised of water, air and various forms of minerals (sand, silt and clay) – to sustain healthy plant growth.

What is organic matter? Soil organic matter is anything in the soil that was or is living. Examples of organic matter include worms, fungi, bacteria, and plant roots; and each of those examples exist in living and decomposing form. This is the Circle of Life at the most basic level – the living matter eventually die and decompose to feed the remaining living matter.

This means that, unlike the remaining 95% of soil, the organic matter is in a constant state of flux – always new birth, always decomposition. Simple right? Yet, there is an entire spectrum of reactions and benefits – physically, biologically and chemically – that come as a result of this cycle and which work in unison for a bountiful result.

Where the Nutrients Are

When you add synthetic fertilizer to your garden soil, that synthetic blend of nutrients penetrates the soil and is immediately available for your plants to take up through their roots.

While this may sound like the best situation, it’s not necessarily a good thing. Plant roots can take up too much of the available nutrients, which results in the plant foliage being burned. Whatever of the synthetic fertilizer solution isn’t taken up right away – is washed away. It leaches out of the soil when you water or during rain.

In contrast, Lee has said that organic matter bleeds a slew of nutrients as it decomposes. The living organisms and materials that comprise soil organic matter are made up of nitrogen and other elements. As the living die off and decompose, their nutrients are released – some to feed the living organisms in the soil and some to be taken up by plant roots.


Young plant

Feed the soil, and the soil will feed your plants.


Did you know that most key nutrients carry a positive ion charge? Potassium, calcium and magnesium are just a few examples.

Organic materials carry a negative charge. So when the positively-charged nutrients make contact with the negatively-charged organic materials, the organic matter binds the nutrients. It holds the nutrients and releases them into the soil gradually as the organic material degrades.

In other words, the fluctuation of the organic matter – that Circle of Life – is perpetually binding and releasing nutrients. This continual release provides a steady supply for plant roots.

When you stop to consider how much more quickly all things decompose under warm and moist conditions, it makes sense that the same would be true of the organic materials in your soil. As it warms and is increasingly moist (to a point – think proper irrigation and warm summer days here) organic matter decomposes and breeds life at a faster pace. Consequently, that decomposition bleeds nutrients at a higher rate.

Do you know what else responds to proper warmth and moisture? Your plants do – they grow and fruit at a faster pace. Translation: The organic matter in your soil is releasing nutrients at a rate that is proportional to your plants needs.

Once more for the sake of emphasis: Synthetic nutrients in fertilizer are designed to be immediately taken up by plant roots – what’s left can be washed away. Organic nutrients are constantly being regenerated and released within the soil at a rate that is proportionate to the maturity and needs of plants. This is why I rely on organic materials to provide nutrients in my garden beds.


Lee Reich compost bins

Compost is an ideal soil amendment, as it is pure organic matter. (photo: Dr. Lee Reich)


Soil’s organic matter also contains acids which eat away at the minerals (like the ground rocks in sand) which form a large percentage of overall soil volume. Minerals hold key nutrients that plants – like humans – need to thrive. As the organic matter acids degrade the minerals, they release those nutrients and make them available to be taken up by plant roots as well.

There are some minerals, such as iron, which are needed but difficult for plant roots to absorb. The iron content in your spinach is in relation to the amount of iron the plant was able to take up through the soil. Interestingly, organic material in your soil assists in this process too. If you’ve ever heard of the product Iron EDTA or Chelated Iron, you know that this product binds itself to the iron mineral to make it absorbable by plant roots. The organic matter in soil acts in the same way – as a natural chelator – binding to iron, so your plant roots are able to take it up.

The organic matter in your soil is also what helps to hold healthy quantities of oxygen and water. It creates more pore space for oxygen and hydrogen molecules, so your plant roots can breathe and receive moisture at optimal levels.

Clay soil, for example, is made up of very fine particles which suck up water but leave no room for oxygen. Organic matter aggregates the clay soil – it clumps the fine particles into larger groupings which allow room for both water and oxygen.


Clay soil demonstrates gardening science principles

When soil is deficient in organic matter, water retention is severely affected. This heavy clay soil is so dense that the lack of proper air and water movement is visibly apparent. (photo: Dr. Lee Reich)

Too Much of a Great Thing

You might be wondering: if this 5% is doing such amazing things, why not use 20% organic matter or, even, pure organic matter in garden beds. But the “more is better” philosophy loses sight of the complexity of the system at work in healthy soil. This system relies on the minerals and water, which make up the majority of soil volume. Take those elements away, and the system suffers.

Yes, you could increase the amount of organic matter in your soil above 5%, but frankly, it can be cost-prohibitive to go much higher. I make a lot of compost – pure organic matter – but I still can’t make enough to provide levels above 5% in my garden or landscape. I often need to purchase compost to meet my garden and landscape needs.

Think of 5% as a good goal – it doesn’t need to be exact. If you begin with less, you can continue to add organic matter over time and watch the benefits increase year after year.

Some organic materials can be applied too generously. Unlike synthetic nutrients, an overload of organic nutrients won’t burn plant foliage, but it can set off a temporary imbalance in soil nutrients and availability. Nitrogen and carbon are two of the primary elements used by soil microorganisms, and their use of these elements is interdependent.

As example – if you add lots of sawdust to your soil, it will provide a flush of carbon – but no nitrogen. The microbes in the soil will feed on available nitrogen to help them break down the carbon. This results in a temporary shortage (and starvation) of nitrogen available to be taken up by plant roots. Those same microbes will eventually die and release their nitrogen back to the soil, but it will take time for the system to rebalance.

The opposite is true also. If you provide an abundance of nitrogen, the microbes will offset that by feeding on the carbon in your soil, reducing the amount of organic matter overall. So when you add nitrogen fertilizers – which are devoid of any organic matter – you may be losing organic matter in the bargain.

The moral of this story: Try to amend in moderation and with some understanding of the primary nutrients in the amendment itself. Balance is key.


Lee Reich amending garden beds

Like me, Lee amends his garden beds with compost. This source of pure organic matter rewards us with healthier soil year after year. (photo: Dr. Lee Reich)

Let the Water Flow

Organic matter provides benefits in container gardening as well. Good drainage is a primary requirement for plants grown in containers. Plants need moisture available but not so much that they can’t breathe. Organic materials aggregate your container soil to provide optimal moisture and oxygen – unlike the common practice of adding a layer of filler.

If you’ve spent any time on my website or checked out my joegardenerTV channel on YouTube, you may have read about or watched my demonstration on how what we had been taught about container drainage is wrong. Although you may think it’s a good idea to add gravel to the bottom of a container in order to improve drainage, this filler actually produces the opposite effect.

It’s been discovered that any significant change in surface porosity creates a barrier to water flow. At the interface of two different surfaces, a water table will build – inhibiting water from moving from the higher surface to the lower surface.

Did you catch that? Let’s try again:

If you place sandy soil over clay soil, water will build up where the two soils meet. Is this because the clay soil is more dense? No. The buildup is caused by the juxtaposition of the different surface structures of the clay and sand. If you placed clay soil over sandy soil, water would still build up where the clay meets the sand.

Lee uses the example of a sponge set in a pan, and you could try this experiment for yourself. Saturate the sponge with water and lift it carefully from the pan. The water doesn’t run out into the pan. The sponge will hold the water. This is not because of the sponge material – this is due to the lack of hydraulic pressure needed to push the water from one surface (the sponge) to the next surface (the pan).

When you squeeze the sponge, you generate that hydraulic pressure, and the water is released from the sponge. You can also tip the saturated sponge so that the end of the sponge is facing downward. Once there is less horizontal sponge surface to suspend the water, the weight of the water generates hydraulic pressure, and water is released.

So what does all that mean for your container gardening? Simply this: The most effective way to improve container drainage is by adding organic matter or perlite or some form of aggregate to the entire mixture in your container. This will increase the porosity and the capillary action throughout the entire structure, and your plants will breathe and grow more vigorously.


Potting bench

Traditional container fillers will hinder, rather than help, drainage. Instead, amend container soil with organic matter to improve drainage throughout.

To Till or Not to Till

You may already know that I am a proponent of not tilling in the garden. Tilling is a common gardening practice, but I’ve learned that tilling can do harm to that microbial, organic matter party going on in my garden beds.

Tillage can be beneficial under certain circumstances, such as breaking ground for the first time to create a new bed. However, there is often a better way.

Lee also recommends against tilling – and he even goes so far as to avoid it when creating new beds, except in very poor soil. When building new beds on most surfaces, he relies on a layering method. For example – soil under a lush, vigorously-growing field or even under lawn is typically filled with good organic matter. If he tills that ground, he will be adding a lot of oxygen to the soil, which burns off much of the nutrients held in the organic matter. Tilling also breaks down important structure, and it brings new weed seeds to the surface (to germinate in the sunlight).

Lee prefers to mow the surface as low as possible, cover it with wet paper and, then, a layer of compost. He plants directly into the compost and finds that the seeds germinate and grow through the wet paper into the turf surface. The original turf breaks down under the layers of paper and compost; so that, in time, he is left with a garden bed teaming with nutrients and the organic matter necessary to optimally deliver those nutrients to his plants.

I don’t even need to mention how much easier this method is versus tilling, right?


Lee Reich garden beds

Lee doesn’t till his garden beds. He knows that tilling would break up the healthy soil structure, burn off organic matter, and bring weed seeds to the surface. (photo: Dr. Lee Reich)

The Science of Seeds

Seeds, like all living things, come with some built-in mechanisms to start them off right in this big beautiful world of ours. So, outside of their natural germination cycle, some seeds won’t grow just by being plunged into a container of soil. They require stratification.

Stratification is simply mimicking the natural conditions in which a seed would germinate on its own. One example is purple coneflower seeds which require cold weather in order to germinate.

In nature, those seeds drop in fall, but they require protection through the cold winter before they germinate in the warmth of spring. These seeds contain abscisic acid – a germination inhibitor. As the seed remains chilled, the abscisic acid begins to break down, until it degrades to the point at which the seed is no longer inhibited from germinating. For any seed which requires this type of chilling period, Lee recommends using your refrigerator. The 30-45 degrees inside a refrigerator is an ideal “chilling bank.”

Lee places a small amount of potting mix in a bag, places the seeds in the mix, and puts the bag in his fridge. He checks the bag regularly and, once the seeds have reached their internal requirement for chilling hours, he will begin to see sprouts. (Every type of seed will require a different length of chilling time.) Once the seeds germinate and sprout, they are ready to plant.


Lee Reich seedlings

Lee’s seedlings enjoying some spring sunshine during the “hardening off” period. (photo: Dr. Lee Reich)


Some seeds have a tough coat to prevent moisture from reaching the seed embryo. Without moisture, germination can’t take place. In their natural element, microbes and consistent moisture soften these seed coats, eventually allowing moisture to penetrate to the embryo. But these seed coatings can be breached manually through scarification.

Scarification is simply scratching the seed coating, creating an entry point to allow moisture into the seed. There are many ways to do this, but take caution. If you damage the seed embryo, the seed won’t germinate. Lee prefers to use a file to nick the seed, or he files it just to the point that he can see a bit of white. That small amount of white is his signal that moisture will be able to penetrate the seed, and it can be placed in potting soil to germinate.

I demonstrated scarification on an episode of Growing a Greener World®, so you can watch for yourself. It’s easy – it just requires a light touch.

There are other many other types of seed dormancy which can be stratified, but these are the most common.

A Brush Up On Hardening Off

Starting plants from seeds has been a big deal in my world this year, and many gardeners – like me – are eager to master the art of bringing those tender seedlings through the hardening off process without injury.

Although it seems bright under the artificial grow lights we provide indoors, that intensity is a pale substitute for the sun.

Leaf structure undergoes a physical change as it is exposed to sunlight. Leaf chloroplasts actually align differently as they transition from indoors to outdoors. These changes happen gradually, which requires foliage exposure to sunlight to be gradual as well. Too much sun before those structural changes have fully taken place results in sunscald.

In addition to light adjustment, seedlings are also acclimating to wind (which increases evaporation rates in foliage) and temperature variations. So, move through the hardening off process slowly.

Lee has found that a daily brushing helps his seeds to toughen up for outdoor conditions. Using the phenomenon of thigmotropism (plant response to touch), Lee brushes the tops of the plants once each day. He does this with a brush normally used for wiping snow off of a car windshield. I’ve followed the same principle just using my hand. I’ll brush along my seedlings once each day to strengthen the foliage cuticles.

Although this trick does help foster plant resilience, the safest and best way to avoid damaging your seedlings during hardening off is to patiently increase their outdoor exposure about an hour per day.


Brushing seedlings

Lee brushes his seedlings daily to foster hardiness. (photo: Dr. Lee Reich)


You can check out Lee’s book for much more on the natural science at work in the garden. It’s a great read with a wealth of information to improve the bounty of your garden.

If you haven’t already done so, I encourage you to listen to this podcast recording – linked at the top of this page. You’ll hear some additional examples of all this science at work in simple ways, why Lee no longer uses the term “humus” and you’ll also hear Lee’s suggestions on testing your own garden theories.

Links & Resources

joegardener Blog: The Numbers on Fertilizer Labels, What They Mean

joegardener Blog: Backyard Composting: A Simple Recipe for Making Great Compost

joegardener Blog: No-Till Gardening: If You Love Your Soil, Ditch the Tiller

joegardener Video Blog: How to Get the Best Drainage for Your Container – Why What You’ve Been Taught is all Wrong

joegardenerTV on YouTube

Growing a Greener World®

GGW Episode 605: Starting Seeds; A to Z

Dr. Lee Reich’s Book: The Ever Curious Gardener – Using a Little Natural Science for a Much Better Garden

Milorganite® – Our podcast episode sponsor and Brand Partner of

0 Responses to “048-The Simple Science Behind Great Gardening, with Lee Reich”

  • Forrest Jones says:

    Joe, I especially enjoy your conversations that include soil science. Since discovering GGW and JG I have an entirely different view of my landscape. This includes my lawn, garden, flower beds, shrubbery, and woodland. Let me tell you some of the ways.When I see a dandelion in bloom in my lawn I am reminded that my lawn is no longer being treated with synthetic chemicals. Instead I use milorganite and corn meal gluten. It doesn’t bother me if there are not enough dry days for the corn meal gluten to work. In my mind it is organic and not harmful and maybe it is good feed for the worms. And when I see the Robins in my lawn all summer I know that there are worms at work helping to build healthy soil.In stead of planning what garden bed I am going to spade first, I know that I can just pull back the mulch and compost covering any bed and scratch the surface and plant at the proper depth anytime. That sure saves a lot of time.
    I don’t waste time cleaning leaf debris and twigs from around shrubs and perennial flower beds before putting down fresh mulch. I know that material is organic too and I simply cover it with the fresh mulch.
    Leaf burning is one of my pet peeves , I have never done that. But I did gather and burn those twigs and branches that come down with snow storms and wind every winter and spring. Now I have some out of view areas in the woods where I pile the ones that I gather to slowly decay in place. The rabbits and ground squirrels make those piles home and I guess I should note there is no concern for forest fires here. And the ones that fall in the woods I just try to get them down to ground level to speed up the decomposition. They are hidden by the native ferns that are up by the end of May. If I wasn’t so cheap I suppose I could buy a wood chipper and turn that wood into mulch.
    All of my pruning material goes to a compost pile. I even look at seed free weeds and any other unwanted vegetation as compost material.
    So Thank You Joe, You and your generous guests are having an impact and making gardeners young and old look at the way we view soil health and the environment around us.

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