This searchable text version was produced from the document found at the following link:
You can also view, print, and download a Word version of this article here:
PACHYPODIUM
The Complete Guide
To Cultivation
Learn all the basics for success in
growing these valuable plants
CONTENTS
l. Form and
Function
A little theory but not too much
We construct a cultural profile based on form and behavior
II. Methodology
Now down to culture basics
No laundry list of Do’s and Don’ts but a highly integrated
approach
Key issues specific to Pachypodiums are examined in detail.
We examine all factors under our control and how to put them together
in a way that’s right for your growing conditions
Learn How To
Grow Quality Plants Like These Large Perfect Specimens
Pachypodium rosulatum - interesting
twin stem plant. 5 years old grown from seed
.
Pachypodium saundersii compactum - the beautiful
Zimbabwe form. 6 years from seed.
Pachypodiums are some of the most
popular in-demand plants in horticulture today but unfortunately very little
cultural information exists to help the large number of attempting to grow
them. The special appeal of these plants lies in their exotic form and very
beautiful flowers both of which cannot be realized without a sound
understanding of their culture.
You're On
Your Own
Most of the
truly interesting plants usually present us with a challenge on how to care for
them This is part of what makes them rare and interesting. Pachypodiums
certainly fall in this category and require a certain degree of personal
involvement a little beyond the “it’s putting out leaves so I guess I should
water it" level.
This guide
is presented in the spirit of developing a consciousness or greater awareness of
what you can learn from your plants just by trying out sound cultural practices
along with your own ideas and observing the results. All of us possess, to some
degree, the ability to "pick up" on these cultural ideas or we
wouldn't be attracted to these strange plants in the first place. The solutions
to our problems are usually there right in front of us. All that's left is to
train ourselves to see them.
Your efforts
will be rewarded. With a little experience, the end result will be a degree of
independence in solving your own problems. If you want to grow very good plants,
you actually have no choice. Your plants are totally dependent on you for their
care and only you can make the most of them. You are in every sense on your
own.
l. Form and Function
The Two
Schools
Culture
studies can usually be divided into two groups. One school of thought which you
still see quite often is that plants should be grown in a manner that mimics
their habitat conditions. This is a holdover from the early days of the 50s and
60s. The other more contemporary school favors maximizing their potential in
the man-made artificial environments we have set up for them. This will be our method.
What exactly
do we mean by maximizing their potential? Above all else, it means growing
plants that look natural. No plant grown under artificial conditions will ever
look exactly like those found in the wild but in most cases we can come very
close. By the time you finish this guide, you will be to recognize a natural looking
plant.
All plants possess
a genetic make-up which makes them favor conditions similar to those of their
native habitat but when we are growing them under artificial conditions, all
the rules change. It is totally impossible to duplicate habitat conditions but
we do incorporate these habitat preferences into our cultural methods, but only
as one element and not the big picture.
Life Cycle
Good culture
depends on your understanding of the different phases your plants undergo
during the course of a year. When to water, feed, repot. prune, and rest all
relate to an understanding of the basic life cycle of Pachypodiums. It is actually
quite simple follows: Reproduction - Growth - Rest.
Figure 1. Healthy Pachypodium roots
Here in the
northern hemisphere, flowering and hence reproduction for most species begins
in late February and merges with the growth cycle in May. It can take from 4 to
10 weeks for flowers to fully develop on their long peduncles and a slow
process, Most are in full flower in April and May with a few taking until June.
The rest period is from November - January when they will shed most or all of
their leaves as they sleep for three months or longer.
Between
reproduction and rest we of course have growth. Even though all species are
indigenous to the African mainland and Madagascar, which is in the southern
hemisphere where spring normally begins in September, they readily adapt to our
northern biological clock and shift 180 degrees. The only exception is the rare
P. namaquanum which does not have one set growing period in cultivation.
Instead it will bust into growth usually three times per year roughly occurring
in June. October, and January depending on your conditions. Many succulents exhibit
this "confused" state and you simply must play along.
Most
cultivation naturally must take place during the growth period but what is most
critical is not stopping altogether during the rest period.
This is
the number one reason for failure.
Certainly at
this point you have a good idea that there is considerably more to cultivation
than just watering. Pachypodiums must absolutely receive some moisture when
dormant but by not stopping cultivating we mean you can't just forget about
them until spring. All of your observations and attention to keeping conditions
just right must also continue through the winter months. For example: moisture,
temperature, and light levels must be monitored and you need to be constantly
on the lookout for root loss, insects and a fungus that causes tip dieback. These
are just a few.
A Starting
Point
After you
have grown many different types of plants, you easily see cultural patterns or
traits begin to emerge. Often you can just look at a new plant and have some
idea of how it should be treated. This is exactly what we mean by developing a
greater sense of awareness about your plants. It's amazing what you can learn
just from observation and it pays off with superb, not average plants.
In the
natural world form usually follows function, so as a cultural starting point, let's
make a few simple observations of the inner structure and outer form of a typical
Pachypodium. We begin with the way water and nutrients move through the plant.
Pachypodiums
have huge fibrous feeder roots (see Fig. 1) that mop up moisture very rapidly.
In habitat. rains are far and few between so they must act quickly. By their
very size you can see they mean business. Must succulents have much smaller,
hair-like roots.
Most species
have large leaves relative to body size and therefore transpiration is fast and
plants rapidly make food. This is an obvious sign that they require generous
amounts of moisture and nutrients compared to must succulents.
The caudex
or stem is composed of a soft pith structure for water storage with the
vascular tissue lying close to the epidermis as two narrow concentric rings
This enables plants to withstand periods of less than ideal moisture. Next time
a plant is lost, make a cross section and you can see these features.
The
epidermis or outer skin bright and shiny. This highly reflective covering
directs the harsh sun away from the body thereby conserving moisture.
So what does
all this tell us? If we sum it up, we must conclude that Pachypodiums are
relatively fast growers and in general are very opportunistic plants In
habitat. The growing season is short so they must make the most of it. In cultivation
where conditions are so much more generous they really move and this means that
they will make too much of a good thing if given the chance. By comparison,
plants in the wild are held in check by the ever present force of the elements
and have that "natural" compact look so desired.
So our
cultural profile can now be fairly well defined. Pachypodiums can be a little
too robust in cultivation. We can't just let them go their own way so they must
be held in check somewhat. We know that they must have a definite winter rest
and be carefully monitored during this period. By holding them back a little we
certainly don't mean starving them or making them weak. On the contrary, this
will produce the exact opposite result which is a more compact natural looking
plant. Many growing techniques are available to us which will work with this
approach.
II.
Methodology
The big
three: Light. Temperature, and Water form the basis for most discussions on
cultivation. All aspects of growing usually relate in some fashion to one of
these key elements.
What is normally
presented however is a big list of do's and don'ts which reduces cultivation to
a mechanical process with little regard for the relationship between these
primary elements. If you want to be a first rate grower, you must know why you
are doing something. Merely following a prescribed list will take you nowhere.
For example, no one can possibly tell you how often to water. You must
determine this yourself.
Our approach
will therefore be that the three elements Light. Temperature, and Water define
your growing. They cannot be considered separate entitles but are
interdependent parts of your cultural formula. Change any one and the others
must also change.
Light
Requirements
All species
of Pachypodium require strong, hard light. This means at least 3-4 hours of
direct light each day. Direct light is defined as an unobstructed southern exposure.
It does not mean so many hours of sunshine, but only that the exposure not be
blocked by trees. house eaves, or anything that will create shade. Nothing
should come the sun and your plants except the window or greenhouse glazing if
that.
Pachypodiums
grown in low light hardly resemble their true form and are indeed a sad sight
with their etiolated (stretched out) stems and huge floppy leaves. Plants grown
under such conditions become very weak over time and generally fail. The
classic symptom that plants are not receiving sufficient light that the new
leaves will turn black.
Properly grown
specimens will always have what is termed a small internode distance. This is
the distance between the stipular spines. Figure 2 illustrates this point with
two plants of the same species. Notice the distance between the spines is much
greater for the poorly grown specimen on the left while the other is nice and
compact.
Temperature
Maximum
temperatures are usually not a concern as all species will tolerate the very
hot and dry conditions of habitat. Plants grown in greenhouses without proper
ventilation (total inside air replaced once per minute) can easily be damaged. The
first sign of this is the clear sap weeping from the growing apex. This is
permanent damage and branching occurs around such an injury. Quite often,
plants grown in excessively hot conditions will just go dormant.
In cultivation our biggest concern is
the minimum temperature which coincides for duration with the rest period. Due to
the general robust nature of Pachypodiums with some moisture required during dormancy,
a minimum of13°C (55°F) should be maintained while 16°C (60°F) is preferable.
Some will tolerate lower levels but most will not. The Highland reference
collection of seed stock Pachypodiums, consisting of hundreds of plants
including all known species is kept at 18C (65°F).
Figure 2. Internode distance for two plants the same
age of horombense.
Watering
Pachypodiums
are heavy feeders requiring generous amounts of water. This is the main obstacle
for growers new to the genus to overcome. It's a natural tendency to be overly
conservative with watering especially with the rarer more costly species but
the idea should be not how much but when to water. As a good starting point use
this simple rule: do not let containers become dust dry at any time. It works.
Water, wait until it uses what you gave it, then water again.
How can you
tell if a plant has used what you have given it? Pick it up. If the pot feels
light, water it. If you want to call yourself a real plant person learn to do
this. Experienced growers can tell if a plant needs water just by looking. You
won't catch them lugging pots around! Again it's that special sense of awareness
that makes the difference.
Don't think
of watering as an exact science where every drop must be measured. It’s just not
that critical. Make sure your plants are well watered and forget it. More Pachypodiums
are killed by underwatering than everything else combined.
Finally, do
not push anything into the container to test the moisture level. This means
your finger or those dreaded moisture meter probes. Succulents have delicate,
fragile roots and you will only damage them. Pachypodiums are especially
sensitive to this treatment and broken roots can rapidly lead to rotted plants
from this bad habit.
The Dormancy
Dilemma
The most
critical and least understood time in caring for Pachypodiums is the dormancy
or rest period. Most losses occur during this time because plants are kept too dry
and not monitored. It's not that they are difficult and in fact are no more demanding
than most caudiciforms. Due to their very robust nature and general character
of quickly responding to culture, these plants will simply not survive long
periods, i.e. months. with no moisture. Yes some will make it but many will
not.
Dormancy is
a fact of life. Plants gradually move into a rest period in response to dropping
light and temperature levels. You can 't force them to do anything by applying
or withholding water. You simply must give them what they require.
Pachypodiums
just don't sit there like rocks while dormant. You can’t see much happening on
the outside but on the inside transpiration is still going on at reduced levels,
and this moisture must be replaced. They need feeder roots to take up this
moisture so naturally plants cannot be kept so dry that these roots are lost.
This can easily happen and the consequences will not become apparent until
spring when growth commences and plants begin to fail. Plants are failing not
because of what you are doing in April but because of what you did over the
winter months.
So how often
should you water during dormancy? It largely depends on humidity levels, i.e.
how fast plants dry out If you live where it's cool during the winter. Your
house or greenhouse will be dry so one or two waterings per week may be required.
If you live in a mild climate with little heating equipment operating, possibly
once every other week will work. Just water, give them a good dry spell to the
point where the pots feel light. then water again, but do not keep dust dry!
The
relationship between light, temperature, and water should now be coming into
focus. Each certainly is a topic by itself but often it is extremely helpful to
think of them collectively. Solutions to problems can usually be found in the cause-effect
type relations that exist.
As an
example consider the winter situation for growers with no greenhouse. When you
move your plants inside in autumn. you are significantly altering your
environment. If you think of this in terms of the three key elements the most
obvious change is a big decrease in available light It thus becomes crucial to adjust
temperature and water accordingly keeping growth to a minimum and thereby avoiding
ruinous etiolation. Conversely plants must be watered enough to maintain roots
so you can see it becomes a delicate balancing act of providing the three
essential elements in the correct amount.
Root loss
With any sizable
collection you will have a few Pachypodiums each year that lose their roots and
in this condition their survival depends on careful and quick treatment. Signs
to look for are a shriveled caudex. small irregular leaves. Pots that stay wet,
and algae on soil.
Figure 3. The proper removal of roots should be back
to healthy white tissue.
First,
ascertain that the roots are in fact dead. Do not unpot to check this. Disturbing
live roots one of the worst things you can do. Water well and wait 7-10 days.
If the caudex fills back out even a small degree, leave the plant alone and monitor
it carefully until it recovers. It is very easy to make the wrong diagnosis
that a Pachypodium is rotted because the caudex has become soft, only to find
after removing all the soil that the roots are in perfect shape and all it
needed was a good watering. This is especially true in very hot weather when
plants can desiccate in a hours. Usually it takes much longer for a plant to
fill back out than to shrink.
If the plant
fails to respond to your initial watering, unpot and remove all mix. The dead
roots will usually fall away with mix but trim them back to clean white tissue
and apply a rooting hormone. Fig 3 illustrates the procedure where the dead
feeder roots have been removed and the primary roots trimmed back.
Finally, let
things dry for a few days to heal the root tips then pot in straight perlite or
pumice. Place in bright but not direct light and keep evenly moist When new
growth evident. unpot- shake off excess perlite or pumice and pot in your
regular mix It works just about every time. Plants can even stay in rerooting pots
until the next season if it becomes too late in the year to disturb the
delicate new roots. Timing is critical and must always be considered.
Figure 4. Ratio Rule applied to two plants the exact
same age. L-2.5" pot. R-4" pot
Technique: The Ratio Rule
Now that we
have the basics down we return to the idea of restraint developed in our
cultural profile and explore techniques you can use to keep your plants in
check. One of the most effective is the standard horticultural principle called
the Ratio Rule. It states simply that for any plant there exists an ideal ratio
between its roots, stem (caudex}, and leaves. This is right from Hort 101.
This
principle can be applied to Pachypodiums by restricting root space. In habitat
they grow in cracks and chinks between rocks and this is what gives them their
nice globular character. In cultivation most new growers overpot in the mistaken
belief that you must give your plants plenty of root space if you want them to
grow well. In fact it has the opposite effect as plants slow to a crawl. If
roots are grown out of proportion to the rest of the plant, the growth energy
will be channeled to the branches and leaves and not the caudex ie. the ratio of
roots to stem and leaves is not correct. Plants with a large crown of branches
and leaves but without much of a caudex are usually in a container much too
large in relation to plant size.
Figure 4
illustrates this principle applied to a pair of densiflorum. The nice fat one
on the left is in the correct size container while the one on the right is over
potted. When selecting a container choose one in which the plant will just fit
and move up in increments of one half inch. This technique can be used with
many types of plants and it works! Bonsai enthusiasts use it extensively to develop
big fat trunks.
Growing
Medium
The key
factor for any good Pachypodium mix is light weight. The large roots can simply
push themselves through a light and airy mix easier than a heavy one. A degree
of moisture retention is also required as in any quality medium.
The new
soilless mixes that have been developed for commercial growers the past few years
are excellent. These come in a variety of formulations with the composted bark based
being the best. Few growers today use soil based medium as the results realized
with soilless mixes are so outstanding. You can adjust the porosity of any
soilless product with perlite for an excellent Pachypodium growing medium.
Superior results are obtained with perlite over pumice. Avoid using any mix
containing sand, gravel, or any aggregates. Sand based mixes are heavy,
compact, and suffocate roots.
A
constructive way to think about this subject is that any quality mix will provide
a margin of error in watering. Your plants should be able to withstand short periods
of over and under watering such as outside during summer rains. If you
experience frequent plant losses, you may want to consider another mix no
matter how good you think your current one is. Go slowly and experiment.
A constant
low dosage feed strategy is best. Use a commercial brand of fertilizer with
trace elements, such as Peters, at one-quarter strength or 50 ppm nitrogen
every time you water. Avoid hobby or gimmick brand products. Your feeding
program should commence in March and end in October.
Pests
Fortunately
most insect pests are not attracted to Pachypodiums. Most collections will see
the odd breakout of mealybug but difficult pests such as mites and whiteflies
leave them alone. If the need arises for chemical controls. absolutely do not
use petroleum based products. These are labeled "liquid" this or that
such Malathion and are designated emulsifiable concentrate, "EC", or
just “E”. Systemics such as Cygon also fall in this group and are highly toxic
to you and your plants. EC's will severely burn succulents so avoid them at all
costs and use wettable powders and water based (aqua flow} products. It's up to
you to do your homework on the insect you are trying to control and the right
chemical to use for your plants.
The Big Picture
It is hoped
that if you obtain one piece of practical advice from this guide it is that
quality plants are the result of quality cultivation. Just about anyone can get
Pachypodiums to grow even in the worst conditions. Cultivation can indeed be
negative. It's the quality of that growth that is the whole point and true measure
of your efforts.
Consider
this guide no more than a starting point. Use the ideas presented here along
with your own to experiment and observe. You are on your own.
