good gardening practices
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Good Growing Practices - an Overview for Beginners
My hope is that this thread becomes a gathering place for beginners and the experienced
alike, a place where reliable information that is rooted in sound science and horticulture
can be found. Well see how that gathering part goes, but I have enjoyed enthusiasticparticipation on many of my other threads, so I am optimistic.
As I consider what I am going to share with you and how to go about sharing it, I amcompelled to offer some background that will hopefully allow you some degree of
comfort in placing some measure of value on my commentary. I enjoy the growing
experience tremendously. I have worked hard toward increasing my skill level for more
than 20 years, and I look at sharing what I have learned about the growing sciences as anatural extension of the enjoyment I get from nurturing plants - sort of nurturing people
who nurture plants. I am invited to lecture frequently in the mid-MI area, and
occasionally beyond. I lecture, conduct workshops, and do demonstrations on a variety of
subjects related to growing, but most frequently I talk about things related to containerculture, with maintaining houseplants being one of the most requested topics. I also enjoy
participating here on Daves and at another popular garden forum. Hopefully we will beusing some links to some of my other offerings here that will help you share some of the
confidence others have in the reliability of my offerings. Those that know me know I am
not after recognition or glory, I simply feel I can help any beginner with a willingness to
learn and apply the newfound information, as have so many others, and I get a largemeasure of personal satisfaction from the feeling I may have helped someone along the
path to becoming a better grower.
The first challenge is to offer information that a beginner can digest, and in such a way
that he or she feels it is important enough to act on. I am first going to flesh out the mainissues that, if understood, will make anyone a better grower and hope Ive created enoughinterest that there will be plenty of questions so I can go into greater detail in the answers.
For what it is worth, I tend to look at growing anything in containers from the perspective
of what is best for the plant, not what is best for the grower. Far more often than not, thetwo ideas are mutually exclusive, so if grower convenience is a large priority of anyone
reading this, there is not much sense in reading on. Growing well does take a little
thought and a little effort.
The houseplants we grow are perennials nearly all, capable of growing for many, many
years and of being passed from generation to generation. With attention to the areas Ill
cover in this post, you will discover you can maintain your plants in good health for aslong as you continue to commit to providing favorable cultural conditions. Your plants
are all genetically programmed to grow well and look beautiful. It is only our lack of
knowledge and skill in the area of providing the cultural conditions they prefer thatprevents them from growing to their potential. That sounds harsh, but its the truth.
I have never seen anyone other than me discuss growing plants in containers from this
perspective, that is (and it bears repeating) your plants are already genetically
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programmed to grow well and look beautiful, but its up to you as a grower to
eliminate the limitations so often associated with growing in containers. This post is
about isolating some of the factors that are commonly the most limiting and helping youto reduce the limiting effects. For more information on the concept of limiting effects, do
a search using the words Liebigs Law of the Minimum
Soil choice - Growers should realize that the most important choice they will make
when establishing a new planting or when repotting is their choice of soil . A poor soil
is probably behind more than 90% of the issues that growers come to the forums seekingremedial help for. Collapsed or dead plants, spoiled foliage, insect infestations, disease
issues are all symptoms usually traceable directly or indirectly to a poor soil. This is so
important to understand, that I will devote the bulk of my effort toward making it clear
why I offer this contention.
Light is extremely important to plants. Plants make their own food, using water, CO2,
and energy from the sun. Inadequate light means the plant cannot make enough food to
grow to the potential it was genetically programmed for. I will not go into great detailabout light because when it comes to houseplants, you either have good light or are
forced to deal with the limiting effects of inadequate light. If the thread takes off, we candiscuss supplementing light and how to prune to help compensate for the leggy
appearance caused by insufficient light, or other topics of interest relating to light.
Nutrition supplementation is a requirementfor normal growth and good health whengrowing plants in containers. In the earth, many of the nutrients are supplied by minerals
in the soil. Container soils usually have no mineral component (and it is best that they
dont in most cases - more later), and the sol components break down so slowly and arewashed from the soil so quickly that deficiencies are virtually assured if you do not
fertilize.
Repotting vs. potting up - that there is a difference is a concept foreign to most hobby
growers. One practice ensures your plants will at least have the opportunity to grow to
their genetic potential within the limits of other cultural conditions; that would berepotting, with its accompanying root maintenance, complete or partial bare-rooting, and
a change of soil. Potting up, on the other hand, only temporarily allows the plant to grow
a little closer to its genetic potential before root congestion and a lack of fine roots
quickly returns the plant to the state of limited growth and vitality it was experiencingbefore potting up.
Watering habits - extremely important and inextricably linked to soil choice, which iswhy I saved it until the end - so it would lead me back to the most important
consideration - the one most apt to determine the difference between frustration and a
rewarding growing experience.
Air is as important as water in soils. Plants absolutely love plenty of air, and rebel very
quickly at too much water in the soil. Im going to describe what happens when you
water plants growing in a soil that retains too much water. There are actually two
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possibilities. The first is, you water, and a part of the soil near the bottom of the container
does not drain. This water has a name, it is called perched water, so named because it
perches (like a bird) in the soil above the pot bottom. This excess water is criticallyimportant because it very quickly begins to kill roots growing near the bottom of the pot,
within hours. The first roots to die are the roots that do the lions share of the work - the
very fine roots often referred to as hair roots. The longer the soil remains saturated, thelarger the diameter of the roots killed. When air finally returns to this once saturated soil,
roots then begin to regenerate. This takes energy and is extremely expensive to the plant
in terms of that energy outlay. The plant is actually forced by chemical messengers thattell it to grow roots, to direct energy that would have gone into growing more leaves,
branches, blooms, fruit, or just increasing the overall mass of the plant, to replacing the
lost roots.
The second thing that might happen when you water if you are using a water retentive
soil is, you water in small sips to prevent root rot. It makes sense to only give the plant a
little water at a time - right? That might be a workable option if you have the luxury of
using water that has been processed through a reverse osmosis water filter, or if you arewatering with distilled water, but regular tap water has things dissolved in it, like
magnesium, calcium, iron, sulfur, and others. If you water in sips, these dissolved solidsremain in the soil and build up over time. This has an impact on the plants ability to
absorb water and the nutrients dissolved in water. To illustrate the potential impact these
dissolved solids have on a plant, picture in your mind what curing salt does to ham or
bacon. It literallypulls water from the cells & dries out the meat. Any solute in thesolution surrounding plant roots can have the same potential effect on plant cells. It can
make it difficult for plants to absorb water and nutrients, it can make it impossible, and in
some cases can actually reverse the flow of water so it moves OUT of cells, effectivelycollapsing and killing them. We commonly call this fertilizer burn, but it doesnt
necessarily have to result from an over-application of fertilizer. When people come here
wanting a remedy for foliage that is dying, with dried edges & tips, its almost alwaysfrom over-watering and the accompanying limitation that has on root function and
metabolism, or a high level of dissolved solids from fertilizers and tap water having
accumulated in the soil making it difficult for the plant to take up water. Misting cannotcorrect a problem related to over-watering or a high level of solutes in your plants soil.
Low humidity can be a contributingfactor to the common symptoms of necrotic (dead)
leaf tips and margins (edges), but for the actualcause, look to impaired root function
from over-watering or a high level of dissolved solids in the soil. BOTH of theseconditions are nearly always linked to a poor soil.
When using water-retentive soils, it seems almost as though we are on the horns of adilemma. If we water generously, we risk the soil remaining saturated so long it causes
root rot, or at a minimum - impaired root function. If we water sparingly, in small sips,
we risk an accumulation of dissolved solids from tap water and fertilizer solutions in thesoil so what to do? Well - I think we should look at an option that solves both issues
and makes things much easier for the grower, while also providing the grower with
considerably more latitude when it comes to watering and fertilizing.
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The factor that determines how water retentive and difficult to grow in a soil is, is the size
of the particles it is made from. The smaller the particles - the greater the water retention
and the greater the degree of difficulty for growers. Soils made of any combination ofpeat, coir, compost, sand, topsoil, and other fine particulates are going to be very water
retentive, which we know is undesirable from the perspective of the plant, and they
cannot be suitably amended to correct drainage or the height of the perched water byadding perlite or other drainage material. If anyone disagrees with that statement, please
ask for an explanation before mounting an argument or offering individual observations.
Adding perlite to soils reduces the overall water retention of the soil, but it does nothingmeasurable for drainage (flow-through rates) or the height of the perched water table, the
later being the critical consideration when it comes to a healthy root zone.
Soils made of a high % of pine bark or other inorganic particles will have lots of large airspaces called macropores. These are pores that will not hold water, only air, even when
the soil is as saturated is it can be. They are critical to a healthy root zone. If you build a
soil with plenty of air space, it hardly matters what the soil is made from. What is
important is how the soil is structured. I will grow a perfectly healthy plant in a bucket ofbroken glass on a dare and a wager if anyone is interested in taking me up on it. If you
have a soil with a healthy structure, a good nutritional supplementation program, andhave good available light, the rest is so easy anyone can do it - honest. Ive seen it happen
over & over and over again. You will not go wrong if your primary focus is providing a
healthy - a truly healthy environment for roots. Roots are the heart of the plant. Roots
come first. If you cannot keep the roots happy, there is no chance you can keep the rest ofthe plant happy. That was a paraphrased quote from Dr. Carl Whitcomb, PhD, who wrote
the bible on Plant Production in Containers.
This ends the beginning discussion about soils. Until you are able to grow plants, thegrowth rate and appearance of which you are happy with, focusing on removing the
limitations placed on your plants by soil choice will almost always constitute the best
use of your energies. After reading this far, if nothing else, I hope you take that from
this offering. It is the most important point and the best piece of advice I can give
you. If you are interested in knowing HOW to make soils that will help you remove
the limitations, now is the time to ask.
Nutrition is an area that is very misunderstood when it comes to container culture, but it
is actually very easy. Its also very easy to become confused because there are so manynumbers that represent different fertilizer NPK percentages and so many different kinds
of fertilizers. I will need to use some numbers, but I think an understanding of NPK
percentages as opposed to fertilizer RATIOS is important. NPK %s tell us how much(N)itrogen, (P)hosphorous pentoxide, and (K) potassium oxide (the symbol for potassium
is K) are in a fertilizer by weight. So a fertilizer that is labeled All Purpose 24-8-16 is
24% nitrogen, 8% phosphorous, and 16% potassium. 12-4-8 is also a common all-purpose fertilizer. It has exactly half the nutrients of 24-8-16, but both are 3:1:2 RATIO
fertilizers. Ratios are a way of describing the amount of nutrients in a fertilizer as they
relate to each other. Why is this important? It is important because we know that on
average, plants use about 6 times as much N as P, and they use about 3/5 as much K as N,
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and now I will tell you how we can use this information to our plants advantage.
The ideal way to fertilize is to supply fertilizer at the same ratio in which plants use thenutrients. The reason is because optimal growth and vitality can be had only when
nutrients are in the soil at overall levels low enough that it doesnt become difficult for
plants to take up water and nutrients dissolved in that water. Remember what we saidabove about a high level of soluble in the soil making it difficult for roots to absorb water
and nutrients? Nutrients also need to be present at levels high enough to prevent
deficiencies. If we think about it for a second, we can see that the best way to achieve thisend is to supply nutrients at the same ratio in which they are used.
I noted that the NPK percentages actually tell us how much phosphorous pentoxide and
potassium oxide are in a fertilizer so I can show you how fertilizer manufacturers arrivedat a 3:1:2 ratio as their all-purpose blend. Only 43% of the P reported on a fertilizer
label is actually P, and only 83% of the K reported is actually K. Once you apply these
factors to any of the 3:1:2 ratio fertilizers (24-8-16, 12-4-8, and 9-3-6 are all popular
3:1:2 ratios, youll see they supply nutrients in almost exactly the same ratios as theaverage that plants actually use, and these fertilizers are excellent at keeping overall
levels of soluble as low as they can be without nutritional deficiencies.
There is no need to usespecialty fertilizers; and many specialty fertilizers, like the
advertised bloom boosters with up to 30 times more phosphorous than a plant could
ever use (in relation to the amount of N used) can be moderately to severely limitingbecause the excess nutrients are a limiting factor.
The question often arises, Should I use a synthetic or an organic fertilizer? The answeris: Use whichever you wish; but the qualifiers are: Organic fertilizers are actually more
accurately called soil amendments. They are mixed into the soil in the hope that at some
point soil organisms will digest them and make them available in elemental form soplants can absorb them. The problem with that approach is that the populations and
activity of soil life populations in containers are erratic and unreliable, making the
delivery of nutrients from organic sources just as erratic and unreliable. What you applytoday, may not be available until next month, and there is no way to determine what
residual amounts of which elements remain in the soil. Soluble fertilizers like Miracle-
Gro and others are completely available as soon as applied, and we know exactly what
our plants are getting. They are simply much easier to use and deliver nutrients muchmore reliable than other fertilizer types. You can lump controlled release fertilizers like
Osmocote and others in with the soluble synthetic fertilizers. With them, you get an extra
measure of convenience but sacrifice a measure of control. As with all fertilizers, it isimportant to note the NPK percentages to be sure you are supplying the fertilizer in a
favorable ratio if you want your plants to be all they can be.
It isnt going to kill your plants if you use a fertilizer with a less favorable ratio because
plants tend to take the nutrients they need from the soil (solution) and leave the rest, but it
is important to understand that it is the rest that constitutes a limiting factor, so avoiding
excessively high levels of any one nutrient whenever possible is to your (plants) benefit.
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As noted above, most growers draw no distinction between repotting and potting up. I
have spent literally thousands of hours digging around in the root-balls of containerizedplants. Old plants from nurseries of greenhouses are probably the closest examples to
what most houseplants are like below the soil line, so I'll offer my thoughts for you to
consider or discard as you find fitting.
I have helped salvage many plants that had been containerized for long periods and were
circling the drain. Not long ago, our bonsai club invited a visiting artist to conduct aworkshop on mugo pines. The nursery (a huge operation) where we have our meetings
happened to have purchased several thousand of the mugos somewhere around 10 - 12
years ago and they had been potted up into continually larger containers ever since. Why
relate these uninteresting snippets? In the cases of material that has been progressivelypotted-up only, large perennial roots occupied nearly the entire volume of the container,
plant vitality was in severe decline, and soil in the original root-ball had become so hard
that in some cases a chisel was required to remove it.
In plants that are potted up, rootage becomes entangled. As root diameters increase,
portions of the roots constrict other roots and impair the flow of water and nutrientsthrough them, much the same as in the case of girdling or encircling roots on perennials
grown in-ground. The ratio of fine, feeder roots to more lignified (woody) and perennial
roots becomes skewed to favor the larger, and practically speaking, useless roots.
The initial symptoms of poor root conditions are progressive diminishing of branch
extension on plants that branch, loss/shedding of foliage on the parts of branches nearest
to the trunk, often giving the plant a poodle look, and reduced vitality. As rootagebecomes continually compressed and restricted, branch extension stops and individual
branches might die as water/nutrient movement is further compromised. Foliage quality
may not (important to understand) indicate the tree is struggling until the condition issevere, but if you observe your plants carefully, you will find them increasingly unable to
cope with stressful conditions - too much/little water, heat, sun, etc. Trees that are
operating under conditions of stress that has progressed to strain, will usually bediagnosed in the end as suffering from attack by insects or other bio-agents/disease while
the underlying cause goes unnoticed.
I will mention again that I draw distinct delineation between simply potting up andrepotting. Potting up temporarily offers room for fine rootage to grow and do the
necessary work of water/nutrient uptake, but these new roots soon lignify, while rootage
in the old root mass continues to grow and become increasingly restrictive. The largerand larger containers required for potting up & the difficulty in handling them also makes
us increasingly reluctant to undertake even potting up, let alone undertake the task of
repotting/root-pruning, which grows increasingly difficult with each up-potting.
So we are clear on terminology, potting up simply involves moving the plant with its root
mass and soil intact, or nearly so, to a larger container and filling in around the root/soil
mass with additional soil. Repotting, on the other hand, includes the removal of all or part
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of the soil and the pruning of roots, with an eye to removing the largest roots, as well as
those that would be considered defective. Examples are roots that are dead, those
growing back toward the center of the root mass, encircling, girdling or j-hooked roots,and otherwise damaged roots.
I often explain the effects of repotting vs potting up like this:I will rate growth/vitality potential on a scale of 1-10, with 10 being the best. We're going
to say that plants in containers can only achieve a growth/vitality rating of 9, due to the
somewhat limiting effects of container culture. Lets also imagine that for every year aplant goes w/o repotting or potting up, its measure of growth/vitality slips by 1 number,
That is to say you pot a plant and the first year it grows at a level of 9, the next year, an 8,
the next year a 7. Also imagine please, we're going to go 3 years between repotting or
potting up.
Here's what happens to the plant you repot/root prune:
year 1: 9
year 2: 8year 3: 7
repotyear 1: 9
year 2: 8
year 3: 7
repotyear 1: 9
year 2: 8
year 3: 7You can see that a full repotting and root pruning returns the plant to its full potential
within the limits of other cultural influences for as long as you care to repot/root prune.
Looking now at how woody plants respond to only potting up:
year 1: 9
year 2: 8year 3: 7
pot up
year 1: 8
year 2: 7year 3: 6
pot up
year 1: 7year 2: 6
year 3: 5
pot upyear 1: 6
year 2: 5
year 3: 4
pot up
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year 1: 5
year 2: 4
year 3: 3pot up
year 1: 4
year 2: 3year 3: 2
pot up
year 1: 3year 2: 2
year 3: 1
This is a fairly accurate illustration of the influence tight roots have on a plant's
growth/vitality. You might think of it for a moment in the context of the longevity ofbonsai trees vs the life expectancy of most trees grown as houseplants, or the difference
between less than 4 years versus more than 400 years, lying primarily in how the roots
are treated.
I have not yet mentioned that the dissimilar characteristics of the old soil as compared to
the new soil when potting-up also carries the potential for trouble. With a compacted soilin the old roots and a fresh batch of soil surrounding the roots of a freshly potted up plant,
it is nearly impossible to establish a watering regimen that doesn't keep the differing soils
either too wet or too dry, both conditions occurring concurrently being a limiting factor
and the rule rather than the exception.
Most who read this would have great difficulty showing me a containerized plant that is
more than 10 years old and as vigorous as it could be, unless it has been root-pruned atrepotting time; yet I can show you hundreds of trees 20 years to 200 years old and older
that are in perfect health. All have been root-pruned and given a fresh footing in in new
soil at regular and frequent intervals, the same treatment all my houseplants get.
Thanks to any/all who made it this far. This is only an overview, but with even a
rudimentary understanding of how to go about reducing the effects of the limiting factorsthat restrict growth and vitality, I know you can improve on how well your plants can
grow, as well as on the degree of satisfaction you get from your growing experience - my
only reasons for writing this. Hopefully the offering leaves you with many questions.