Dear all:
What an interesting thread. After all, improper fertilization is
the second cause of bulb loss, after improper drainage. Truly regret not to
have the time to mingle more often. Some comments
Yes, the reason for proper cultivation of Dutch bulbs is the North Sea
climate. It provides perfect conditions for ....those that can be grown in
the North Sea climate. There are not many places where fields of tulips,
hyacinths, Fritillaria imperialis, etc., could be seen like there. No amount
of fertilizer would produce such crops if the range of temperatures were not
adequate for growth.
Yes, the Dutch bulb farm fields are former sand dunes added with peat in
enormous amounts to provide some nutrient retention. They are leached very
rapidly hence the apparently enormous quantities of fertilizer..Actually,
this case is studied in plant nutrition as one in which quantities (kindly
quoted by Jim) can be very misleading. If applied to normal soils they would
burn roots and grow soft, juicy plants that would attract pests like
beacons. In the Dutch bulb fields they are just enough.
Yes, an "organic"" soil would contain very few pests that would devour each
other to reach a peaceful balance. Unfortunately, this can be achieved in a
small garden or plot by adding really substantial quantities of organic
matter which in the Dutch bulb fields is unthinkable. The problem they have
and that force them to sterilize the soil is nematodes that spread viruses
while feeding and living on the bulbous plants roots. In the past strong
chemicals were used to control the nematode population but now these are
forbidden (the chemicals, not the nematodes!). Among them methyl bromide was
easygoing but later found to have terrible effects on the ozone layer and
banned. Dutch bulb producers are desperate with these problems and have come
to find more environmentally friendly procedures (like flooding the bulb
fields in summer when the bulbs have been lifted to interrupt the nematode
life cycle). They know well how dangerous viruses are to their crops and in
fact lots of Narcissus, Scilla, Brodiaea 'Konigin Fabiola', reticulata and
Dutch irises, alliums, muscaris and a number of others can not be cleaned of
their virus infection in any affordable way. A lot of research is being
carried on along this but results are less than mild. The general consensus
among them is not to worry so long as viruses do not affect the sales.
Yes, the information provided first and that kicked the ball rolling
concerning bulbs (winter growing ones, of course) being able to use
nutrients in the Fall period between root emision and leaf emergence and
that raised so many eyebrows originally came from the Dutch Bub Growers
Association research laboratories, not a cookbook recipe as someone
mentioned. Admittedly it sounded odd the first time I learn about it since
it seems so obvious that "no leaf, no feed" but a number of experiments
proved it right. Rodger's experience along with Mr. Zonneveld mention of a
Fall fertilizer application point to it. Actually, it makes a lot of sense
because many of these cold climate bulbs use the Fall rains to produce roots
that remain alive and waiting for the snow melting (in the wild) to produce
foliage and flowers all within a rather short time. It is logic that these
roots would take any advantage to capture whatever nutrient is available
even if "no leaf".
As for info on potassium affecting the availability of magnesium,
comparatively few bulbs will suffer from magnesium shortage, mainly those
growing on dolomite: some bearded irises, Junos, Reticulatas, some tulips,
Ungernias, etc. All the others are positively affected by potassium supply,
including those from the four corners of the world and those that are
poisoned by phosphorous like South Africans and Australians.
As for the fact mentioned that bulb plants would not be able to absorb
nutrients between the flower production and the beginning of dormancy, only
few of them had their leaves gone by flowering time: Leucocorynes,
Conantheras, Zephyra, Calochortus, Brodiaea, Pabellonia, etc. The rest have
leaves then and are very active manufacturing food to fatten the bulb.
On our behalf concerning our frequent errors in fertilizing our bulbs it
must be pointed out that bulbs are pretty indifferent and do not apparently
react properly to nutrients provided! I suggest you the use of indicator
plants. These must no be monocots but rather frugal, not fussy and quite
easy to grow dicots. My favorite for this climate is Lamium maculatum, you
see, no exotic gem. Apply a weak solution (as weak as you want, even VERY
weak) of a foliar formula fertilizer to your bulb plants and then to the
indicator plant. You will not believe your eyes as the dicot will respond
immediately to the extra nutrition by making new growth, even changing the
appearance of the adult leaves. This change will last for a long period even
one or two months. This will give you a proper idea of how much is too much.
By diminishing the amount of fertilizer in the solution you will notice that
effects are obtained even with doses that are very minute. Of course you can
do it with any type of fertilizer but a foliar formula will give cleaner
resutls as there will be no danger of the soil meddling and blocking some
elements.
Bob's naive question is not naive, he knows what he means. He is an
experienced grower and a friend of the late Stan Farwig who had a fabulous
collection in the Bay Area. Stan had made a number of experiments concerning
complete formula fertilizers and found that they adversely affected his
plants and stopped using them altogether. Yes, yes, improper fertilizing
shortens a bulb life. Strangely (or not) there are very few bulbs native the
very nutrient rich pampas of Argentina and Uruguay. And countless ones in
the miserably poor soils of South Africa.
African Violet fertilizers have high potassium formulae. Are they available
in your area?
All the best
Alberto
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