C.C. Mitchell, J.R. Kessler, A.S. Harris, and C.B. Pinkston

1. Epsom Salt on Ferns
Practical Research by Alabama Master Gardeners
C.C. Mitchell, J.R. Kessler, A.S. Harris, and C.B. Pinkston
Extension Agronomist, Auburn Univ., AL, Extension Horticulturist, Auburn Univ., AL, East Indian Holly Fern
True Boston Fern Arachnoides simplicior ‘Variegata’
Nephrolepis exaltata ‘Bostoniensis’ (‘Massii’) Regional Extension Agent, Dadeville, AL, and Regional Extension Agent, Cullman, AL
Abstract Results
Epsom salt (magnesium sulfate) is often used by 1 2 3 4 5 6 1 2 3 4 5 6
gardeners as a fertilizer. Because ferns often are grown Table 2. Final ratings for Boston and Holly ferns at all sites
in an acidic potting mix with no other source of Mg, (rating scale 0 to 5).*
Epsom salt could be an important source of Mg in potted Boston fern Holly fern
fern fertilization. Master Gardeners in Alabama tested Color Size Height Color Size Height Sharon’s Boston Ferns
Treatment** rating rating (in.) rating Rating (in.)
this theory by growing Boston ferns and East Indian holly
Peggy’s Boston Ferns 1. Lime + ES 3.4 4.3 13.6c 3.5b 2.8 5.8ab
ferns from May through October, 2008. They used 3 2. No lime+ ES 4.0 4.1 15.5ab 3.2b 2.5 5.4b
different potting mixes with and without Epsom salt. Each 3. Gypsum+ ES 3.5 3.4 13.7c 3.3b 2.8 5.9ab
gardener had 6 hanging baskets (3 potting mixes x 2 4. Lime 3.8 4.1 16.1ab 4.4a 3.0 6.1a
Epsom salt rates) containing 3 fern liners in each basket. 5. No Lime 3.6 4.1 16.5a 3.4b 1.8 5.8ab
Records were kept monthly as to the color and size rating 6. Gypsum 3.4 4.0 14.7bc 3.8b 2.8 5.4b
of ferns. A final rating was made in October when soil P>F ns 0.08 <0.0001 0.0018 ns 0.0479
Dale’s Holly Ferns
samples and tissue samples were also taken from 1-3 *Values followed by the same letter in a column are not significantly different at
4-6 P<0.05.
selected growers at the end of the season. Results ** ES=Epsom salt
indicated no significant effect of the Epsom salt on fern Roberta’s Boston Ferns 1-3 4-6
size or color. There were differences in Mg Although there were significant treatment differences in
concentrations in the fern fronds at the end of the season frond height of the Boston fern and color and height
but all concentrations were in the sufficient range. Soil Methods differences in the Holly fern, Epsom salt apparently had
and tissue analyses suggest that excessive phosphorus Profile of a no consistent effect on the ferns.
Houston clay
• Thirty Master Gardeners (MGs) in Cullman, Blount, and
(P), iron (Fe) deficiency and excessive manganese (Mn) Kaye’s Boston Ferns
may have been factors in the lack of response to Epsom Tallapoosa Counties in Alabama accepted a challenge to
salts. This project also provided an opportunity for conduct practical, applied research with Epsom salt on
Master Gardener volunteers to conduct applied research ferns.
that answered a practical question related to their Table 3. Mean analysis of the saturated extract from 4 growers at the
• Container garden workshops were held in Cullman and end of the growing season. Values followed by the same letter are
gardening experience. Tallapoosa Counties in May, 2008, where MGs mixed not significantly different at P<0.05 level.
potting soils, added lime and Osmocote® 19-6-12 Treatment pH Soluble NO3-N P K Mg
Salts
fertilizer (no Mg) and potted liners of young ferns. mmhos/cm Marian’s Boston Ferns
----------------------mg/L-------------------------
• Each MG received six hanging baskets in which he/she 1. Lime + ES 4.8 b 1.22 94 38bc 90 45a
potted 3 ferns per basket in each of six potting soil 2. No lime+ ES 4.0 d 1.41 89 55ab 99 37abc
treatments (Table 1). 3. Gypsum+ ES 4.3 c 1.19 82 42 bc 92 42ab
4. Lime 5.2a 1.19 78 36c 103 34bc Conclusions
• Each MG selected either (1) Boston fern or (2) East 5. No Lime 3.9 d 1.59 102 60a 117 22d
Indian holly fern (photos above) to grow for six months at 6. Gypsum 4.4 c 1.45 96 46abc 108 31c •Epsom salt (magnesium sulfate) had no effect on the
their home. P>F <0.0001 ns ns 0.036 ns 0.0005
color or size of either Boston fern or East Indian holly
Desirable range* na 0.75-3.5 40-199 3-9 60-249 30+
• All baskets were fertilized with a 20-20-20 grade ferns when grown for 6 months in a potting mix .
*Desirable range for greenhouse crops adapted from Warncke and Krauskopf.
fertilizer (no Mg) dissolved in water (1 teaspoon per 1983. Michigan St. Univ. Ext. Bull. E-1736.
gallon) every two weeks. •Boston ferns and East Indian Holly ferns have very
Saturated extract of the potting mix from 4 MGs at the different growth patterns and may respond differently to
• Appropriate baskets (#1, 2, & 3) also received Epsom end of the season indicate that Mg was within the lime and fertilizer.
salt dissolved in water every two weeks (1 teaspoon per desirable range in all except the “No Lime” treatment (#5).
gallon). Phosphorus concentration was extremely high in all •Saturated extract of soils and tissue analysis from one
samples. Treatment differences were found in site indicate possible problems from (1) excessive P, (2)
• Monthly, each MGs rated their own ferns on a scale of
extractable Mn and Zn but not with the other iron deficiency and (3) manganese toxicity, but certainly
0 (worst) to 5 (best) based on color of fronds and overall
micronutrients (data not shown). not magnesium deficiency.
growth (size) of plants.
Situation • In October, a team of MGs visited each gardener for a •MGs gained experience conducting practical, applied
•Epsom salt (magnesium sulfate) is sold and used by final, impartial rating of the ferns (only the final ratings are research and had a good time doing it and sharing it with
gardeners for many plants, especially potted ferns. shown). gardening friends.
Table 4. Tissue analysis of Boston fern fronds from one of the tests.
•Epsom salt is a good source of both Mg and S for plants. • Soil samples and tissue samples were collected from Treatment N P K Ca Mg B Cu Fe Mn Zn
selected growers. -------------------------%------------------------- -------------------ppm------------------
•Most gardeners have no idea why they use it or even if 1. Lime + ES* 2.86 0.70 1.98 0.89 0.89 53 22 4 213 55
they need it. • Each grower was treated as a replicate. 2. No lime+ ES 3.16 0.83 2.15 0.81 0.91 43 28 11 219 78
1 2 3 4 5 6
3. Gypsum+ ES 3.20 0.81 2.08 1.09 0.98 55 30 40 334 74
4. Lime 2.97 0.73 2.16 1.16 0.69 58 19 15 287 59
Table 1. Potting soil treatments used in the study. 5. No Lime 3.19 0.78 2.19 1.07 0.66 47 19 23 321 77
Initial soil Treatments added by 6. Gypsum 3.33 0.75 2.16 1.05 0.63 44 30 45 271 80
treatments MGs every 2 wks Optimum 2.5- 0.25- 1.6- 0.8- 0.25- 20- 50- 40- 20- Cindy’s Boston
Objectives Treat.
no. Description
Ag.
Lime
Ag.
Gypsum
Epsom
Salt
NPK
fertilizer
range** 3.0 0.7 3.8 2.5 1.0 70 6 - 50 300 200 200
Ferns
* ES=Epsom salt
1) Determine if growth and color of ferns in containers 1 Lime + Epsom Salt + 0 + + **Optimum range from J.R. Kessler, Jr. 2004. Greenhouse production of Boston ferns.
Alabama Coop. Ext. Syst. Cir. ANR-1095.
are influenced by the addition of Epsom salts. 2 No lime + Epsom Salt 0 0 + +
3 Gypsum + Epsom Salt 0 + + + Tissue analyses were run on only one set of treatments but
2) Determine the effect of added dolomitic limestone and 4 Lime; No Mg + 0 0 + results indicate some problems. Phosphorus concentrations
gypsum (calcium sulfate) on the growth and color of ferns 5 No lime; No Mg 0 0 0 + were above the optimum range, and excessive P could induce
in containers. 6 Gypsum; No Mg 0 + 0 +
iron deficiencies. Iron (Fe) concentrations were very low
indicating a possible Fe deficiency, and Mn concentrations Darrell’s Boston
Ag. lime was a finely ground, dolomitic limestone with 10% Mg applied at a rate of Ferns
3) Involve Master Gardener volunteers in replicated, 5 lb/yd3. Gypsum was a powdered, agricultural gypsum applied at 5 lb/yd3. NPK were extremely high. Potentially toxic Mn concentrations are
fertilizer was a slow-release Osmocote® 19-6-12 applied at 14 lb./yd3 to potting mix
applied research in a subject that is relevant to their (4 parts pine bark: 1 part peat). Every two weeks during growing season, an all
difficult to explain in this organic potting mix. Magnesium
gardening experience. purpose 20-20-20 (without Mg) was applied every two weeks dissolved in water (1 deficiency was not an issue in these potting mixes.
teaspoon per gallon).