Soil
& Nutrition
lagunahillsnursery.com
(949) 830-5653
Our goal is to create the healthiest root system
possible. Without adequate roots plants
will appear stressed even when irrigation and fertilization are adequate. The major portion of a root system of a
typical plant exists from the soil surface to about 8-10” deep. Rooting depth is heavily dependent upon air
penetration (the soil’s permeability).
Roots consume oxygen and release carbon dioxide just as animals do. Roots can live deeper (10’+) in sandy or
gravely soils where permeability is high.
A woody plant’s root system extends far wider than the plant is
tall. A 20 year-old tree often has roots
that reach 100’ away, but rarely more than 2’ deep. Plants require from the soil the following:
If
any of the above is lacking symptoms of stress occur. These include:
Soil in a complex mixture combining material derived
from rock (mineral) along with air, water and organic material.
Soil is typically a 3-layered cake in
profile. The top layer is called the topsoil. The middle layer is the subsoil and
the bottom layer is the parent material.
These layers rest on the bedrock.
Any of these layers can be a fraction of an inch to several feet
thick. Generally the cake is
3’-6’ deep. We are mostly concerned with
the topsoil.
Unfortunately
local homebuilders are not required to save and put back the topsoil after a
home is completed. Owners of new homes often have to work with
parent material or even bedrock.
Loam is the term given to topsoil containing all 3 of
the major particle sizes: SAND, SILT,
and CLAY.
The
percent volume of these 3 components can range from nearly 100% to nearly
0%. The presence of all three is
required to create good growing conditions.
Without sand there is very little airflow. Without clay there is very little moisture or
nutrient retention. A good loam has a
sand:silt:clay ratio of about 40:40:20.
Soils that are mostly sand, by virtue of the empty spaces between
particles, are lighter than clay soils.
Actually clay soils contain more space (higher
porosity) but this space is normally always filled with water molecules. A sack of kiln-dried clay weighs less than a
sack of kiln-dried sand, but natural clay soil is heavier.
Soils
containing high volumes of sand are called “light” soils. Soils with significant percentages of clay
are called “heavy” soils.
Clay absorbs more water adding to its weight. Clay can hold 2” of water per foot while sand
only holds about ½”. Water molecules are
strongly attracted to soil particles in a layer one molecule thick. The collective surface area of the particles
doubles when the particle size decreases by half. The water holding potential of the soil is
called its field capacity. Mineral
nutrients dissolved in water also accumulate to a higher extent in soils with a
higher field capacity.
Sandy Loam is a technical term for the soil type that farmers
prefer. It is a mixture of
sand:silt:clay in a ratio that is roughly 6:3:1. Compared to loam, a sandy loam has
higher permeability (airflow) for more vigorous roots but looses some nutrient
and water retention.
It doesn’t require a high percentage of clay for a
loam soil to be considered a clay loam.
When the clay content reaches just over 30% it completely fills all the
gaps between the larger particles and permeability declines dramatically.
The gaps that exist
between soil particles are where air and water can move and be stored. If the soil particles were uniform in size
and perfect spheres the unfilled space would be 36%.
Permeability (often incorrectly called the porosity) represents the ease of gas
(air) exchange. Each type of plant has a
minimum value that they can remain vigorous in.
Most easy-to-grow plants get by with low permeability. Conversely just about any plant that has a
reputation for being difficult requires high permeability. The table below represents the lowest volume
of the soil occupied by air that that list of plants can tolerate.
2-5% Conifer, Palm, Rose, Turf
5-10% Hydrangea, Lily, Mum
10-20% Begonia, Gardenia
20%+ Azalea, Fern, Orchid
Nature
can improve permeability of heavy soils.
Lignin (the glue that holds a plant together) is released into
the soil when dead leaves or any other plant tissue decomposes on the
surface. Lignin along with the activity
of soil bacteria glues the smaller clay particles into large clumps
(granulation, agglutination) that act like building blocks.
Humus is the organic
matter found in Nature’s soils.
Humus is essentially inert. It is
either charcoal or plant fibers that won’t decompose further. In Nature’s soils the humus content ranges
from less than 1% to just less than 3%.
Humus, especially charcoal, holds on to nutrients better than any other
material found in Nature. The rich
black soils found in many areas around the World are due to charcoal
deposited after wildfires. Just a small
amount (2-3%) of charcoal makes the soils appear black and become mineral
rich.
Drainage is the ability of the soil
to relieve itself of a saturated condition.
Saturated soils have all spaces filled with water, making gas exchange
very poor. Roots don’t require as much
oxygen as animals but certain species will suffocate if the water stagnates for
more than 35 hours. (By this time the roots and other soil dwelling organisms
have consumed all the oxygen available in the water.) Chronically saturated
soil results in a very shallow root system.
Root rot diseases are promoted when oxygen levels drop. Plants would much rather grow in soils that
are moist but not saturated.
Note that just about any
small plant will survive indefinitely with their roots sitting in a bucket of
clean water. The oxygen circulates
freely when the water movement is not impeded by soil particles.
Poor drainage can be due to:
Farmers
like soils that have good drainage at least 6’ deep.
Drainage can be improved for
extended periods either by:
Be aware that many of the symptoms of poor drainage
and/or overwatering can be attributed to the fairly recent tradition of
amending the native soil with significant amounts of compost or organic
mulches. This standard practice can only
benefit annual row crops involving plants that are harvested in less than 6
months, or incredibly permeable soil where oxygen availability is excellent,
but water and nutrient retention are lacking.
Compost lowers the oxygen level of the soil with which it is mixed with
usually resulting in a shallow, sparse or unhealthy root system. If compost has any nutritional value it is
still capable of decomposing and consuming oxygen. When it is finished decomposing there is
virtually no volume remaining.
A heavy soil often turns black
after it is amended with a lot of compost.
This black color is due to the presence of sewer gasses (like
hydrogen sulfide) that form when decomposition occurs under low oxygen
levels. This is poisonous to the
roots. A black soil created by adding
compost instead of charcoal is dead, not rich!
There are soils in nature that
are 100% organic. These are called peat
bogs and they contain muck.
Nothing will grow due to the lack of oxygen penetration. This lifeless condition can exist for
thousands of years.
Containers
present certain problems not encountered when growing in the ground.
Bonsai, the art of growing miniature
but mature looking trees in small pots has been a part of
During
the 19th century Citrus were grown in huge pots in
In the early 20th
century the Royal Horticultural Society determined that sandy loam was
the most ideal soil for containers.
In the late 1950’s I played in
my father’s pile of container soil. The
soil was a sandy loam with almost no clay.
Local building supply yards carry a similar product called fill sand. This soil gives decent results for 5-gallon
and larger containers. My father told me
that growing plants was simple. He
watered his plants every day and fertilized them every month with excellent
results. The number of plant species
grown 50 years ago does not come close to what is offered today, however my
father seemed to grow Gardenias, Camellias, Avocados, and Citrus with little
difficulty.
In the 1950’s the
In the 1960’s my father added redwood sawdust
to his sandy loam to lighten it. This
worked well as redwood decays very slowly.
A number of growers still use a redwood/sand mix.
In the 1970’s redwood became quite expensive and fir
shavings, fir bark and other materials became quite prevalent. By the 1980’s we were having many problems
with rotting rots in potted plants. The
agricultural agents told my father that he shouldn’t be watering his plants
every day, even though he had done that for nearly 30 years.
In that same decade, the Ball Seed Company’s book, The
Ball Red Book, (still a Bible for greenhouse flower growers) warns that
while peat, sawdust, and bark are fine for growing annuals, permanent plants
require permanent materials for best long term results. “A balance between water-holding capacity and
air-supplying power should be sought. Of
the two aeration is more important.”
Apparently few growers listened.
In the 1980’s the prominent horticulturalists were
pushing the theory that the more compost you incorporate into the soil, the
better the results. In those days I
followed their lead, but was starting to notice puzzling results. In the late 1980’s and early 1990’s I did not
trust that what we were telling customers worked at all. Plants were rotting and everyone was blaming
too much irrigation. I could not predict
what our customer’s results would be.
Growing plants was getting strangely mysterious.
In 1995 I talked to a soil researcher who explained that soil was not
organic. The scientist had me slowly
strip off the soil from a plant that was growing in a bark and peat-based
potting soil. He told me to observe
careful. During the purging
process the plant quite noticeably “pulled” its leaves up and looked much
“happier” as the organic matter was removed.
That same year I started growing vegetables (broccoli, strawberry,
artichoke) in pure sand and pure pumice and saw incredible results. Growing plants in pumice is a form of
Hydroponics.
The European Hothouse industry spent a lot of
research money to determine the best materials (substrates) to use in their
hothouses for their crops. Greenhouse
operations are so costly that it is imperative that the plants grow and produce
at the highest levels possible. They
recommended sand, perlite, pumice, rock wool, pelletized clay, peat moss,
coconut coir and rice hulls as dependable materials.
Perlite and pumice are both silicon dioxide (same material as glass)
that have a lot of air pockets. Perlite
is a mined ore that is popped in an oven like popcorn. Pumice is made by Nature in volcanoes by
gasses blowing through moulten rock. Rice
hulls are actually quite similar being about 90% silicon and are used as a
perlite substitute. Rockwool is a
thick sheet of mineral fibers commonly spun from basalt. Pelletized clay are fired (stable)
clay pellets somewhat larger than sand. Peat
Moss, which is composed of hair-like plant fibers, will retain its form and
character for at least several months. Coconut
coir, the fiber from Coconut shells, is similar but not quite as water
retentive as peat moss.
All of these materials are available at a reasonable cost, have
well-documented characteristics, and are extremely permeable. The high permeability promotes explosive root
and plant growth, but the grower has to irrigate and fertilize carefully and
constantly. All of these materials are
discarded and replaced periodically.
The hothouse researchers determined that the
characteristics of wood, bark, green waste and other types of organic products
(ground up pallets, etc.) to be unpredictable.
This means that they could not get consistent results when using wood,
bark or other “bio” materials as a growing medium. The characteristics of wood and bark vary
greatly from tree to tree, even from one end of the plank to the other
end.
Currently most of the large growers of container plants in the
1.
Sold
2.
Moved into a larger container surrounded with fresh
bark, or
3.
Discarded.
It
appears to me that this researcher considers landscape plants to be the same as
florists’ plants. Sell and/or discard.
I believe that growers honestly
think that organic materials become good soil somehow and/or become replaced by
the surrounding soil once installed.
When these plants are planted into extremely free breathing soils like
the coarse soils found in the inland valleys, the results are decent. However, if these same plants are planted
into heavy soils typical of
In the retail market there are a
wide range of nationwide brand name and locally bagged potting soils. A few years ago a UC researcher studied a
number of these potting soils. There
results showed that most brands killed most of the species of trial
plants. Only one plant (Impatiens)
survived in all the soils. Among the
brands tested the Scott’s (aka Miracle Gro) had the best
results. The researcher pointed out that
these soils are meant to perform for 6 months. The main ingredients in Scott’s is
peat moss and composted forest products (wood and/or bark pieces)..
Our custom potting soils also
contain peat moss. However our 2 soils
are 50%:50% peat:pumice and 60%:30%:10% pumice:peat:sand. Our soils perform much better after 1 year
than the others primarily because they contain much more material that is
permanent.
Pure sand is still the best long
term potting soil (for pots taller than 12”) but the weight can be a
problem. At my home we like a mixture of
roughly 50% sand, 25% peat, and 25% pumice.
This is essentially mixing plaster sand with our Laguna Hills
Nursery Acid Mix Potting Soil in equal parts. The plants that we grow here at our store are
grown in a very similar soil.
You may note that our soils do
not have much nutritional value. This
leads us to my next rule.
Fertilize Organically
All plants contain the
following minerals:
Their
relative abundance is roughly the same order, although a few will change places
depending upon the type of plant or the age of it. Young plants are higher in nitrogen. Older plants collect calcium as part of their
wood. Animal bodies contain 16 of the 17
minerals found in plants. Some plants
contain more than 17 minerals, though in many they may not be essential.
The main structure of a mature
plant is the cell wall (cellulose a.k.a. wood), a converted sugar molecule
containing H, C, and O. The cell
membranes are mostly protein which is made of C,H,O, and N. The sap contains water and a significant
amount of K. Most of the other minerals
are involved in energy capture and transfer, or with enzymes.
Four of these are found in air
or water and need not be added. We need
to be aware of the presence of 13. Most
homeowners cannot juggle these with any sense of accuracy.
The majority of farmers use
chemical fertilizers. Farmers get their
soil and/or their plants analyzed periodically by laboratories. Soil lab technicians have stated that it is nearly
impossible to guess what mineral is missing by the appearance of the
foliage. If you apply the wrong mineral
the problem is often compounded. An
overabundance of one will often block the uptake of another. The soil lab’s technicians tell the farmers
what minerals are needed and how much to apply typically one mineral at a
time.
Many homeowners apply a
“complete” chemical fertilizer that has N, P and K. Of course, these are not truly complete. If you only apply 3, or any number less
than13 the plants will eventually become chlorotic (anemic), pale in color due
to a lack of one of the essential 13 minerals.
Typically it is a mineral involved with the chlorophyll molecule and
contributes to the normal green color of the leaves. I have yet to find any single chemical
fertilizer that has 13 minerals. On the
other hand, most organic fertilizers have all 17 minerals. This is because organic fertilizers contain
dead plants and/or animals.
The reason why chemical
fertilizers remain in heavier use is that:
The
use of organic fertilizers is catching up quickly. This is because:
How Plants in Nature Acquire Minerals
The majority of plants in Nature are recyclers. 95% of known plant species utilize a
symbiotic fungus known as Mycorrhizae.
This soil dwelling organism breaks down the duff (layer of fallen
leaves, stems, etc.) and returns the minerals to the plants. Mycorrhizae were discovered to exist only a
few decades ago. Mycorrhizal fungal
hyphae, the bulk of the fungus organism, are very difficutl to distinguish from
plant roots and are intimately connected to the roots of plants. Mycorrhizae essentially increase the surface
area of a plant’s roots capable of collecting water and nutrients five fold. A well-known variety is the Truffle,
which is attached to certain Oak trees in
There are a number of plant
species that are called pioneer plants. These are specialized plants, like Wild
Mustard, that evolved to live on the availability of soil nutrients in certain
areas. They have no need for Mychorrizal
fungus. They usually appear following a
fire (that releases nutrients from the plants into mineral form) or new soil
deposits (from landslides or fresh river sediment). Pioneer plants gather the available nutrients
with a highly evolved fine textured root system. The minerals are concentrated into the
foliage of these plants. As soon as
these plants have produced ample dead foliage the recyclers can take
over and the pioneer plants die out only too reappear following the next
fire.
In most climax ecosystems the
soil no longer contains significant amounts of available nutrients. Everything the plants could extract is now
either in the living plants or in the duff layer on the ground. In forests and especially in rainforests,
where wildfires are rare, the soil is essentially devoid of minerals useful to
the plants. The only way to recover the
minerals is to burn the trees down.
A few decades ago the U of
California Davis did a survey of the
Compost Versus Duff
Mycorrhizal fungi recycle the nutrients found in duff, a layer
of plant debris. It is essentially a
closed system. The nutrients freed by
the fungus are primarily available to the plants the fungus is associated with. Most perennial woody plants depend on this
fungus recycling system.
When plant debris is recycled by
the compost method it involves bacteria.
The bacteria consume the debris and nutrients are released freely into
the soil when the bacteria later die.
Most annuals and many grasses depend upon this compost recycling
system.
The two systems can exist
together but aren’t good neighbors.
Bacteria can kill fungi. When I
use my chipper to chip and shred plant debris I no longer allow it to compost. I’m hoping that the garden will get fewer
weeds (most weeeds are non-Mycorrhizal plants) if the Mycorrhizae
dominate.
Mulch Deeply
Plants are much healthier when the ground around them is covered with
an organic mulch. We recommend 2” to 3”
deep. Deeper is fine if the mulch is coarse. (Do not mix the mulch with the soil
below.) Compared with bare soil, a deep
covering of mulch accomplishes the following:
1.
Releases nutrients constantly.
2.
Provides a home for beneficial soil organisms.
3.
The products of decomposition along with the action
of soil organisms improves soil permeability.
4.
Improves absorption of rainfall and irrigation.
5.
Slows evaporation.
6.
Insulates the soil from excessive heat or cold.
7.
Prevents germination of (weed) seeds.
As
organic mulches decompose they provide both minerals and energy to the soil
organisms. Previously it was thought
that minerals from a dead leaf were recycled within 2 years through bacterial
compost recycling. Research has shown
this time to be as little as 3 months using the fungus recycling system.
Certain types of mulches resist
breakdown and serve longer as a cover.
Redwood sawdust and bark can last well over 5 years. Cedar lasts nearly as long. Large chunks of Fir Bark last many years but
finely ground bark may disappear within 2 years. Chopped up plant clippings from my garden
disappear within a year. Mulches that
last longer release nutrients slower.
I’ve seen a thick layer of
redwood sawdust totally stop erosion on a steep slope. Water from sprinklers and rain moves tiny
clay particles easily but can’t seem to budge coarse gravel, sand or
mulches.
In
Mulches allow a plant to have a
much larger root system. Without mulch
the soil close to the surface is too hot and dry. With mulch the roots can inhabit the zone up
to the soil surface where there is more oxygen.
Planting
Replanting
&
Irrigation
10-02-09
lagunahillsnursery.com
(949) 830-5653
You may want to check you
soil for drainage before you start.
The goal is to keep all
the roots alive while they are getting established. The problem is that many of the deeper
roots that come with the container plant are too deep to breathe in our local
soil (especially when you install plants that were grown in containers taller
than 8”). This problem is also due to
the fact that the drain holes at the bottom of the containers gave the roots an
unnaturally deep source of air. The
ground has no such air source. We have
to provide sufficient airflow to the bottom of the planting hole to keep the
deep roots alive.
Small container plants (up to 8”
deep) have such shallow root balls that it is not critical to create a
breathable zone. They get enough air
from the surface passing through their own root ball.
For a larger container plant we
recommend:
All
of our soil mixes contain pumice, the most efficient material at aerating the
soil. It is best not to backfill with
pure product although it can work. We
are creating a halfway house and want the roots to enter the native soil
fairly quickly.
If the soil in the planting
bed is essentially rock or pure clay you will get better results if better soil
is brought in. Here are 3 strategies:
The
plants can then be installed using the previous instructions.
Here
are a few precautions:
If your soil is heavy clay
the permeability can be increased if the entire bed is amended. (Amending the soil cannot improve
drainage.) Adding pumice is the
most efficient (adds less volume) and permanent method. To be effective the pumice should be from
10-20% of volume. This is 1”-2” of
pumice mixed in with 9”-8” of soil to create 10” of highly permeable
earth. This can be fairly
expensive.
Sand can be added to increase
permeability, however, depending upon the clay content of the soil, you may
have to increase the sand content of the soil anywhere from 10% to nearly 70%
to change the soil’s character.
According to studies by the
If you soil has been
artificially compacted (construction equipment, vehicle traffic, excessive
play, etc.) it is beneficial to turn over or till the area. Dry soil should be well irrigated several
days before tilling to soften it. After
tilling the soil should be smoothed out and firmed using a landscape rake and
water roller (or by walking on it). The
correct firmness is when, walking over the soil, your heels sink but your toes
don’t. The soil is now ready for sod or
seed.
If you are intent on creating
turf for constant use, such as a sports field, there is a different
approach. To prevent compaction the top
2 feet of soil is replaced with sand. Below
the sand a drainage system is installed.
During the warm months turf growing on sand is irrigated nightly.
Choose a Good Plant
Now that you have good soil in
your garden it is up to you to get the best plant possible. The best plant may not be the most
convenient, or the easiest. Here’s my
list in descending order:
Repair a Plant Growing in Bad Soil
Although it is a better
strategy to find a perfect plant, sometimes what you desire is only grown in
temporary (non-permanent) soil. You can
purge a container-grown plant that is growing in improper soil. This involves removing all, or at least 50%,
of the growers potting medium and replacing it with a more permanent, more
natural soil. Before starting you may
need to have a location that will provide shade while rehabilitating the
plant.
The danger faced with purging a
leafy plant is that the roots are always damaged and water uptake is
compromised for up to 1-2 weeks following the procedure. Leaves use (lose) water; the rest of the
plant (stems and woody structures) loses very little. During the time it takes for the roots to
regenerate, the leafy plant can totally dehydrate to death, especially if
exposed to hot, dry conditions. If the purged plant
is placed in a shady, humid location (under a bush or low tree) its water needs
will be lessened. Removal of a
significant amount of foliage or cutting back foliated stems will also lessen
the water usage.
Deciduous plants are easy to
purge without stressing in the winter during dormancy. They can also be done in summer if at least
90% of the foliage is removed.
Tropical plants are best
purged in summer. Be sure to remove at
least 90% of the leaves before starting if no shade is available. Houseplants are simply left indoors away from
direct sun.
There are several techniques used to purge the roots of the wrong soil mix:
Once
the roots are clean make certain they remain wet until replanted. You may be surprised at how few roots some
plants are surviving with.
If you wish to retain more foliage the plants should
be repotted into better soil and placed in the shade for a minimum of 2 weeks
until the roots have recovered.
If there are few or no leaves the plant can be
installed in its final location immediately.
Set the plant in a hole at the proper depth, carefully surround the
roots with pulverized native soil (try to keep the roots within 4-6 inches of
the surface) and water repeatedly (minimum of 3 times) until it can be certain
that the roots and surrounding soil are wet.
Make certain the plant doesn’t lean as the soil settles.
You may wish to supply a mild fertilizer at the same
time. During the growing season expect
plants to initiate new growth within 2 weeks of when the soil was purged.
When plants are put into better soil you will notice
that the new leaves are larger and greener and that the plants suffer less
stress. When I have changed the soil on
Bougainvilleas going dormant for the winter they awaken and become evergreen
plants (like they should be) and bloom throughout the year. The Gardenias we have purged also begin to
bloom all year!
Plants already in the ground can also be repaired,
but with larger specimens you may only want to work on a portion of the root
system at a time.
The Replant Syndrome & Crop Rotation
Farmers rotate their crops. For example Tomatoes are usually planted once
every 3 years (a 3-year cycle). Roses
for the bare root trade are grown on a 5-year cycle. Roses take 2 years to harvest and other crops
are grown for the next 3 years. Farmers
rotate to avoid having to deal with the diseases and pests associated with the
remains of the last crop.
The ground surrounding any
living plant will accumulate dead roots of that plant over time. When an annual farm crop is harvested there
is suddenly a lot of dead and dying roots of that crop. If the same or related plant is installed
immediately, it will be stunted, often severely, fighting diseases associated
with the decaying root tissue. Unrelated
plants are generally not affected.
Lets talk about Tomato farming
in more detail. You can grow Tomato
plants for 2 or even 3 consecutive years, but each year the yield is less and
the plant shows less vigor and more yellow foliage. By the 3rd year the yield may not
justify the crop. Without sufficient
time between crops the volume of dead Tomato root is increasing faster than it
is decomposing along with the associated diseases. Tomato plants may not grow well for another
4-5 years. If the crop is only planted
every 3rd year the carry over of dead tomato root and the associated
diseases becomes insignificant. The
farmer makes certain that the in-between crops are not related to
tomatoes.
Crop rotation can also be
called the replant syndrome and I have seen literature discussing this
phenomenon in Rose gardens and Apple orchards.
Farms can get around crop
rotation with soil sterilization using fumigation. Fumigation apparently neutralizes the build
up of dead tissue.
Forestry experts know that a
severe fire will renew the forest.
Cooking the soil, even just the top foot or so, is enough to allow
regrowth of the same trees. Surveys have
shown that in rainforests (where fires are rare) 2 trees of the same species
are separated by an average of 175 yards.
Lack of fires (and lack of Ice Age glaciers) results in much more
diversity in rain forests than in drier areas.
Some plants are much more
tolerant of replanting than others.
Grasses are highly tolerant, however, the first time a lawn species is
planted it shows the most vigor.
If you desire to replant
immediately you can always rotate the soil instead. In Apple orchards replacement of ½ cubic yard
(3 feet by 3 feet by 18 inches deep) of soil (from a location away from the
Apple trees) gives excellent results.
In Rose gardens
replacing about 1 cubic foot of soil gives good results. If the plant being installed has its own soil
ball the replacement volume can be reduced.
You must also do that same soil
replacement when installing a plant within the root zone of an existing related
plant, such as, when squeezing in a new rose plant in-between older,
established rose bushes.
Double-digging a bed is another
method of soil rotation. The top 12”
layer of soil is exchanged with the 12” layer directly below it. Because plants don’t root much deeper than
12”, the underlying layer will contain very few roots of the previous
crop.
The replant syndrome is related
to plant longevity.
Penstemons are known to
perform well in the same soil for about 3 years. After that period they falter and eventually
die. Simply replanting the same plant a
few feet away can rejuvenate them. Our
container growers have told me that during winter they cut them down, pull them
out and put them back into the same container with fresh soil for another year
of good vigor. Also, Penstemons are
usually propagated with stem cuttings.
This is equivalent to putting virgin soil around an old plant (the
cutting).
The replant syndrome in plants
is analogous to human public health practices.
Human babies cannot thrive if in close proximity to dead tissue of other
humans. There is little or no effect if
the dead tissue is fish, mouse, snail or insect. There is also little effect if the dead human
tissue is cooked or cremated.
Plants need average to ample water to perform. Many plants are drought tolerant and/or drought resistant. Even these, however, prefer average to ample water to perform the following:
There
are certain plants that can thrive with less than average water but the majority
of plants will, at minimum, stop growing.
Many drought tolerant plants in Nature will only grow, flower and
reproduce following a significant rain event or an unusually wet season.
In an established garden that is
composed mostly of foliage plants, keeping the soil somewhat dry during the
summer can be beneficial because of less pruning.
Lawns, flowering plants,
vegetables and fruit trees require average to ample moisture.
Be aware that mature bushes and trees can have
extensive roots that can capture water over 100 feet away and therefore give
the appearance of being drought tolerant.
You cannot train roots to grow
deep. Roots will grow as deep as they
can breathe. A UC Davis study of root
depth in an Almond orchard subjected to deep, infrequent irrigation compared to
light, frequent irrigation gave (at least to the researchers) unexpected
results. Daily, light irrigations
resulted in a deeper root system.
In general the soils in
There are areas in
For grass lawns the average
number of minutes of sprinkler irrigation per week is as low as 4 minutes in
winter to as many as 50 minutes in summer.
During the hottest summer weather a lawn may require 3 watering periods
per day. Most shrubs and trees require
about 1/3 less water.
You can utilize an old farmer
method in order to measure moisture in the ground (if the water is being
applied to the surface). A 4’ long piece
of rebar or similar metal rod is pushed by hand into the ground. The depth to which you can push it is
directly related to the depth of moist soil.
It is very difficult to push a stick or rod into dry soil. If you can push the rebar into the ground 12”
the soil contains ample moisture to 12” deep.
Locally most plant roots live in the top 12” of soil.
Grass lawns require 12-18” of
moisture. Most grasses start looking
stressed at less than 8” and show browning at 6”. A Tall Fescue lawn goes totally dormant at
less than 4”. Brown patches on lawns in
summer are commonly due to lack of moisture, resulting from not watering
frequently enough usually accompanied by applying water faster than it could be
absorbed.
Dormant (brown) lawns are not necessarily dead. Research shows that all grasses commonly used
as a lawn can be dry and dormant for at least a 3 month period, and recover
fully when moisture is restored. This
capability can make grass lawns valuable where drought is eminent, since they
can be left all summer without irrigation.
In Agriculture the goal is a
consistently moist soil. With many types
of fruiting plants a wildly fluctuating moisture level results in small fruit
or cracked fruit. There is a vineyard in
A current theory of orchard irrigation is to “top off the tank” rather than allow the soil to run dry.
With all plants the amount of
water they use increases with size. A
full size Citrus in the middle of summer will commonly use 50 gallons of water
per day. Mature shade trees can use 100
gallons of water per day.
Apparently, with actively
growing or producing plants there is little net loss of water when plants are
irrigated mid-day compared to mid-night.
A lawn evaporates water (transpires) faster than a pool of water
covering the same area. Watering a plant
at mid-day will cool it tremendously and significantly lower the transpiration
rate for a short period. Water
evaporating off the ground near plants also lowers their transpiration
rate.
Leaves and flowers that stay wet
for long periods (3 hours or more) can get diseased (leaf spot, foliage blight,
rust). If you have a choice it is best
have the sprinklers go on when the foliage will dry quickly. During hot weather this can by any time day
or night. During mild weather the
watering should be done between mid morning and noon.
Plants react in different ways
to dryness. With most plants the leaves
will loose turgidity and wilt with the foliage color appearing less green
and/or glossy. Some plants will fold or
roll their leaves. If kept dry over an
extended period the leaves tend to develop dead, dry tissue either at the leaf
tip or between the veins. Dryness is
usually expressed over the entire plant evenly, although areas most exposed to
heat usually show the strongest symptoms.
If dry foliage is only seen on a few isolated branches the problem is
usually due to disease.