by This is part 3 in a series of 4 fertilizer posts. It has the lesser
elements and the critical element iron and what to look for in
iron-poor plants.
Opinions vary, as will your rose blooms...
(c) 1998 by Scott G.***inson, All rights reserved.
Permission given to the Honolulu Rose Society to reprint by
the author, 3/6/98.
Rose Fertilizers Defined, part III
OK, now that I have discussed the main fertilizers and pH of soils and how it
affects fertilizers, I will delve into the lesser fertilizer elements and what
plants do with them. Secondary elements are calcium, magnesium and sulfer. Trace
elements are iron (very important in alkaline soil though), boron, chlorine,
copper, manganese, molybdenum and zinc. All of these elements are found in
broad-spectrum fertilizers like Miracle-Gro.
Calcium:
This is used in making plant cells and required for root growth. Plants take
up a lot of calcium. It is not easy to spot calcium deficiency, but sometimes
the stems will be deformed. Some fertilizers add calcium, and most liquid forms
include it. An excellent source of calcium is gypsum (lime sulfate). I like
to use gypsum as it is really cheap and helps break up clay soil too. By the
way, gypsum is used in human *fertilizer* too (in your daily vitamins!). Two
bucks for a big bag... I use a shovelfull dug in around each rosebush.
Magnesium:
This is used to promote good growth. At the heart of every chlorophyll molecule
is a magnesium atom, and thus critical in plants. It is hard to tell if roses
are lacking in magnesium. Epsom salts are an excellent and cheap source of
magnesium. I swear by the stuff and add a handfull at the base of each rose
bush after hard pruning in the winter. It is said that this will promote
basil breaks, and I have observed that this is the case. At a buck a box, how
can you lose?
Sulfer:
Sulfer is used in combination with nitrogen to create plant compounds, and it
is as essential as nitrogen in plant process. However, it is not nearly as
lacking in soils as nitrogen, and thus not as critical to apply. A lack of
sulfer will result in a similar yellowing of leaves as in nitrogen-chlorosis.
In places like the Willamette Valley in Oregon it can be a problem though, as
sulfer leaches from the soil there in the semi-continuous rains. It is
available and cheap in many common fertilizers: Sulfate of ammonia, Epsom salts
(magnesium sulfate), and gypsum (lime sulfate).
Iron:
Iron is used by plants to make chloropyll, and is an essential element in that
process. The indicator that plants are lacking iron is that the *new* leaves
turn yellow (called iron-chlorosis). This is because iron is not very mobile
in plants, and plants cannot move any needed iron from the old to the new
leaves (like it can nitrogen). Iron becomes fixed in alkaline soils above about
a Ph of 7.1 (just barely alkaline). At a Ph of 6.8 or lower, iron in the soil
will become available to plant roots. Use chelated iron (a form of iron that
does not latch into the soil) if you have alkaline soil. Typical store brands
are Ironite and Sequestrene, which are chelated. Many soluble fertilizers
like Miracle-Gro have enough chelated iron in them as well. Other good sources
of iron are *** meal and hoof and horn meal (hoof and horn meal is not as
available now as it was 10 years ago).
*Insuider tip* Watch out for plants potted in and around concrete. The
concrete will cause alkaline leakage and can cause the pH to change near it
(usually within the first 20 years of pouring concrete). Concrete containers
are likely to have alkaline soil, regardless of what the pH was when the soil
was addd to the container.
Manganese and Zinc:
Manganeze and zinc are thought to be used as catalysts in plant processes.
They act as an agent in transforming compounds within plants and helps to
increase nitrogen extraction, but may not be used as elements in compounds
themselves. Plants lacking in manganese may have a pale mottling of leaves.
Lack of zinc can cause poor growth and plant form. Manganese and zinc are
usually found as a trace element in rose fertilizers. An old trick to ensure
zinc availability in fruit trees is to pound a few galvanized (zinc coated)
nails into the trunk. There are forms of these two elements that can bind
in soil, so use chelated froms for better delivery.
Chlorine, Copper, and Boron:
These elements are required for goor growth and form. Chlorine is so common
in water and salts that many fertilizers advertize themselves as being
"chlorine-free". Mirical-Gro has about 12% chlorine which is quite high.
Copper should be applied in chelated form. Copper and boron are usually
found as a trace element in many rose and complete fertilizers. Plain old
table salt has clorine in it too (but I have never seen or heard of a
chlorine-deficient plant in my time as a gardener). I do not recommned
salting your Garden with Morton's :).
Molybdenum:
Pronounced like "Molib-knee-um", is essential to good growth. A lack in
this element can lead to poor leaf form. Usually found as a trace element
in rose fertilizers. Usually it is the lowest percentage by weight of any of
the trace elements listed.
In review of secondary and trace elements: iron is required for making
chlorophyll, and is not very mobile in plants or soil. Iron tends to be
lacking in alkaline soils, where you should add chelated iron. Other
secondary and trace elements are critical in plant growth. Several of these
(iron, copper, manganese and zinc) are best if applied in chelated forms.
Sulfer is usually abundant in most soils, but it can be leached in areas
whre there is steady rain. Magnesium, calcium and sulfer can easilly
and cheaply be applied using gypsum and Epsom salts. All of these trace
elements are usually found in water soluble fertilizers.
Quiz: If plants lack nitorgen, which leaves turn yellow? And if they lack
iron? That's right, the *new* leaves will be yellow if they lack iron, and
the *old* ones if they lack nitrogen. Do you remember why?
Now quit reading these posts and go out there and feed those ravenous pigs
in your garden!!!
Scott
Campbell, CA