Subtropical Experrmen cr
1e Route 2,o -
F I INFORMATION ON M InNiftA rN
Horticulture Department Mimeo Report 54-2
R.H. Sharpe and Austin Griffiths, Jr.
Florida Agricultural Experiment Station
Mist propagation refers to the use of a fine water spray over
cuttings to keep them healthy and turgid. It contrasts strongly with
the methods generally in use where shading, covering with glass, frequent
watering, and constant attention are needed to keep cuttings from drying.
The need for trained labor in watering and ventilating beds is
eliminated with the mist method. Only an occasional check is required to
see that the mist nozzles are running properly. Also unnecessary with
the mist method are the glass-cover and shading facilities needed with
the older methods.
Other advantages for mist that we have found during our four
years of experience with it are virtual elimination of loss from damping-
off disease, easier handling of large or very soft cuttings and, in many
cases, higher percentages of rooting Some plants root well only from
very soft growing tips; for these mist is especially valuable, being the
only method we know to handle them successfully.
In mist propagation, a simple arrangement of suitable nozzles
is used to provide constant protection for cuttings at least during day-
light hours. Three satisfactory nozzles we have used are: -
l1 Monarch H-261, size 3.00 standard 900 angle. Monarch Mfg. Co.,
2501 East Ontario Street, Philadelphia 34, Penna.
2. Thompson baffle-spray nozzle 215-A (1/2") or 216-A (3/""),
Thompson Mfg. Co., 2251 East 7th Street, Los Angeles 23, California.
3. Fog-mist nozzle 550-A, Sprayers and Nozzles Co., 2575 28th
Avenue, N., St. Petersburg, Floridao
Their listing is not intended as an endorsement of these types only.
The principal need is for a simple nozzle that cannot readily clog or
get out of adjustment. Our experience indicates that about 4 to 6
gallons of water per hour per nozzle may be needed at high pressures.
More exact specifications for varying water pressures are available
from the manufacturers. These nozzles have given trouble-free service
with a hard water supply when cleaned annually. They require 30 or
more pounds pressure for good operation.
The nozzles should be spaced about 5 feet apart in the lines.
For single-line installations, the line is set over the center of the
bench with nozzles directed upwards and discharging about one foot
above the surface of the media. A better distribution of mist can be
obtained in larger installations where several parallel lines are
placed 8 to 10 feet apart. In such cases, it is suggested that the
lines run between benches of 5- to 6-foot width with nozzles set
perhaps 3 feet above the bench except for the outside lines. The out-
side lines should be set just above the cuttings to prevent strong
steady winds from blowing beneath the mist and drying cuttings along
the outer edges. Valves should be installed to cut off the water as
Benches of standard types, flats and raised ground beds on
open sandy soil have all been satisfactory. Excellent drainage of
beds and media is the essential requirement. Several media were used
which gave about the same degree of rooting. Good rooting has been
obtained in old pine sawdust alone or combined with peat, perlite,
or vermiculite. Peat in combination with sand, perlite or vermiculite
has also been satisfactory. The usual type of propagation sand has
been fairly satisfactory; but rooting has been slightly better in
mixtures using peat or sawdust. When 1/8-inch mesh hardware cloth is
used for bench bottoms, mixtures including peat or sawdust do not go
through the bottom as does sand.
Rooting under mist in mid-winter has been unsatisfactory in
initial tests at Gainesville, when temperatures of 600F. or lower were
generally recorded for both water and media. An attempt was made to
maintain 700 or higher temperatures with electric cables in the beds
in a warm greenhouse but it was not very successful, as the cold water
kept the media at about 600 except in a small area near the cable.
The possibility of using gas or oil heaters under the beds or the use
of warm water has not been studied.
Beds can be placed wither in full sun or partial shade. There
is some evidence that loss of color from leaves is greater in full sun
than in partial shade and further studies are in progress on this point.
Windbreaks may be desirable in small installations, though we have not
found them essential in most of our tests. It is recommended not to
use more water than necessary to keep cuttings in good condition as
we have noted poorer rooting of some species in areas immediately under
the nozzles, apparently due to excessive water. Intermittent-mist
controls have not been available for study. Manual or automatic cutoff
of mist at night is suggested in order to reduce water consumption,
although rooting has been good when mist was allowed to run constantly.
We have had little wilting trouble from 5330 PM to 7:30 AM with mist
Examples of plants considered difficult or impossible to root,
which we have been able to root successfully under mist are dogwood,
muscadine grape, blueberry, peach, oriental magnolias, several hollies
and others. We still have not been too successful with feijoa, Cattley
guava, a few of the hollies, and some native plant materials like tar-
flower and rosemary. Many soft herbaceous annuals and perennials have
rooted well but leaves of some were in poor condition at the end of the
rooting period and low survival was obtained. Dormant hardwood cuttings
generally have not rooted satisfactorily under mist. Plum, blueberry
and several others have typically developed weak, chlorotic leaves and
none or weak roots from dormant cuttings. Softwood cuttings of azalea,
camellia, pyracantha, ligustrum, ixora, gardenia and many others which
root fairly readily have given good to excellent results under mist.
We have not generally observed much faster rooting compared to standard
methods except when more succulent leafy cuttings were used to advant-
age. It is possible under mist to maintain a large leaf surface and
consequently to obtain better root development in some cases.
Good aftercare of rooted cuttings is extremely important.
Compared to standard methods, the cuttings may lose color and become
hardd0" Chemical analysis shows a severe reduction of NPK content
of leaves by the time cuttings have rooted. To insure survival, the
rooted cuttings should be removed from full mist promptly and planted
in fertile soil. Although only a few species have responded to hormone
treatment with faster rooting, it has been of distinct benefit with
those that respond since the cuttings can be removed more quickly from
the mist. We have found it desirable to give the transplanted cuttings
careful protection from wind and sun and in most cases to apply soluble-
type fertilizers to hasten thrifty growth.
As with any new technique, much testing and improvement of
practice under varied conditions must be done before we know the full
usefulness of mist in propagation. We have had very promising results
with some hard-to-root plants and like the ease of handling those which
root readily The full potentialities, we feel, are just now being
A few readily available published articles suggested for
further reading aret -
1. Gardner, E. J. Propagation under mist.
Amer. Nurseryman, May 1, 1941. p. 5-7.
2. Griffiths, Austin, Jro, H.N, Miller, and R.H. Sharpe
Constant-mist propagation of camellia cuttings.
Amer. Camellia Yearbook, 1953; 206-212.
3. Wells, J. S. Outdoor propagation under constant-
mist. Amer. Nurseryman, June 1, 1953t p. 14,