Research

1981

Potting Media Affect Growth and Disease Development

of Container-Grown Southern Pines’

William H. Pawuk

SUMMARY

Longleaf pine (Pinus palustris Mill.) and shortleaf

pine (F! echinata Mill.) seedlings grew best in equal

parts of peat and vermiculite with a low pH. Seedlings grew better in shredded pine cone media than

pine bark media. Growth increased when soil or vermiculite was added to cone or bark chips. Commercial bark-vermiculite media with high pHs produced

the smallest seedlings: Disease loss was related to

drainage and pH. Seedling mortality was greatest in

commercial media with pHs above 6.0. Losses, lowest in bark media, increased as the proportion of

vermiculite increased.

Addltional keywords: Pinus, Pythium, Fusarium, damping-off, seedlings, tubelings.

Media, whether blended by growers or commercially produced, can affect containerized forest tree

seedling growth. Typically a mixture of peat and

vermiculite is used. In the South, pine bark mixes

have gained prominence in recent years and are

widely used for growing woody ornamentals but

are not generally used for containerized tree seedling production.

‘Use of trade names is for information purposes only and is not an

endorsement by the USDA Forest Service.

Like peat, pine bark can be used alone or mixed

with additives. Hammermilled cone chips, abundant

at pine seed extractories, are another possibility.

Though cone chips are usually burned or piled as a

waste product, they are potential potting media. This

study compared growth and development of containerized pine seedlings grown in peat, pine bark,

and pine cone formulated media.

, MATERIALS AND METHODS

Twelve potting media were evaluated for growing

containerized longleaf and shortleaf pine seedlings

(table 1). Three were commercial media, containing

lime and fertilizer: Jiffy Mix@ (equal parts peat and

vermiculite), Jiffy 70-30@ and Jiffy 50&O@ (Pine barkvermiculite mixes). Nine media were formulated by

mixing peat (P), pine bark (B), or pine cone chips (C)

with vermiculite (V) or soil (S). Materials included

horticultural grade peat, well rotted cone chips and

uncomposted bark chips. Seventy-five percent of

both cone and bark chip particles were less than

2.36 mm. Top soil was from the A horizon of a Ruston

sandy loam (relatively infertile) and #2 vermiculite

was obtained from South Carolina.

Recently germinated seeds with l- to 2-inch radicles were transplanted from trays to 7-inch media

filled bulb pots. Aqua-Gro’@, a wetting agent, was

applied in the initial watering to promote infiltration.

Fertilizer was injected into the watering system 2

weeks after transplanting and applied thereafter

Southern Forest Experiment Station/T-l0210 U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, Eastern Oklahoma, Tennessee, Eastern Texas.

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with each irrigation at 150 parts per million nitrogen.

A Q-45-15 (N-P-K) fertilizer was used for the first 2

weeks, followed by>6 weeks of 20-20-20, and then 2

weeks of Q-45-1 5.

Five seedlings per pot were evaluated for growth.

Each species was tested separately using a 12 X 12

Latin square design. To evaluate disease development, 10 recently germinated longleaf seeds per pot

were established in media previously infested with

Pythium or fusarium, by mixing 5 ml of infested

wheat grain with each liter of medium. This test was

designed as a randomized complete block with five

blocks.

Measurements included seedling dry weight, shortleaf height, and number of fascicle bundles on each

longleaf seedling. The final pH of each medium was

determined from averaging readings from five pots.

Disease loss was determined by counting the surviving seedlings.

RESULTS

Long/e&Growth. - Seedlings grown in PV-50 and

Jiffy Mix were significantly heavier than those in all

other media (table 1). Except in C-100, cone media

Table 1 .-Seedling growth and fascicfe bundle development of long/eat pine grown in peat, cone, and bark media

Final DW Seedlings with Fasclcle bundles

Medium1 PH Weight fascicle bundles per seedling

mg percent number

Peat

PV-50 5.1 e* 798 a 89a 4.45 a

Jiffy Mix 8.2 b 755 a 82 ab 3.83 ab

Pine Cone

cv-50 6.1 bc 638 b 79 ab 2.73 cdef

cv-70 6.1 bc 819 bc 89a 3.18 bc

c-100 5.9 c 562 cd 69 ab 2.75 cdef

cs-70 5.9 c 628 b 73 ab 2.92 bcde

Pine Bark

BV-50 5.2 d 510 de 59b 2.07 def

BV-70 4.9 f 452 ef 61 b 1.94 ef

B-1 00 4.6 g 460 ef 61 b 1.85f

BS-70 5.1 e 530 d 84 ab 3.03 bed

Jiffy 50-50 6.4 a 420 f 64b 2.83 bcdef

Jiffy 70-30 6.4 a 410f 81 ab 2.79 bcdef

‘The number following the medium designation indicates the percentage of peat, bark, or cone chips present.

*Means followed by the same letter are not significantly different, Duncan’s Multiple Range Test at the 0.05 level.

produced larger seedlings than bark media. Certain

mixtures of vermiculite or soil with cone and bark

chips also increased growth. Poorest growth and

chlorotic seedlings occurred in commercial bark

mixes, which also had the highest pH (table 1).

The percentage of seedlings that produced fascicle

bundles ranged from 59 to 89 percent and was significantly greater in PV-50 and CV-70 media than

in W-50, BV-70, B-100, and Jiffy 50-50. No other

differences were significant.

The number of fascicle bundles per seedling was

significantly greater in PV-50 than in all other media

except Jiffy Mix. In general, media that promoted

fascicle bundle development on individual seedlings

were the ones with a high percentage of seedlings

with fascicle bundles.

Shortleaf Growth. -Seedling weights of shortleaf

pine were almost identical to longleaf pine patterns

(table 2). The heaviest Seedling8 developed in peat

media and the smallest in bark media. Growth was

intermediate in cone media except that seedlings

in C-100 were comparable to seedlings in the commercial bark,media. As with longleaf, shortleaf seedlings grown in PV-50 were significantly heavier than

in all other media.

William H. Pawuk was Research Plant Pathologist (now with Tongass NF, Petersburg, Alaska), Southern Forest Experiment Station,

Forest Service- USDA, Pineville, Louisiana 71360.

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PV-50 produced significantly taller seedlings than exchange capacity, long moisture retention, and low

all other media. Feat media produced significantly pH of this medium. In the test, best growth of longbetter seedlings than all others and cone media were leaf and shortleaf pine seedlings also occurred in

generally better than bark media. equal parts of peat and vermiculite with a low pH.

Disease Development. -Seedlings survived well

in the Fusarium-infested media and no mortality

occurred in six treatments. Those treatments were

PV-50, CV-50, C-l 00, BV-50, BV-70, and BS-70. Jiffy

Mix and the Jiffy bark media produced a slight, but

significantly higher mortality than other media (table

3). While survival was high, seedlings grown in Jiffy

Mix were chlorotic.

Mortality from Pythium was much greater than

from Fusarium. It ranged from 9.4 seedlings per pot

in Jiffy Mix to 0.6 seedling in B-100. Addition of

vermiculite to bark and cone chips appeared to increase seedling susceptibility but the differences

were not significant. Mortality in the three commercial media was significantly higher than in all others.

Although longleaf seedlings grew well in Jiffy

Mix, peat-vermiculite mixes with high pH should be

avoided when growing pine seedlings. Despite satisfactory growth, susceptibility to disease organisms

is increased. The high water-holding capacity of

peat-vermiculite media creates conditions favorable

for Pythium, especially when the pH is high. Loss to

Pythium was 54 percentage points higher in Jiffy

Mix(pH 6.2-6.4) than in PV-50(pH 5.1-5.4)although

both had the same 50-50 peat:vermiculite formulation. The high pH of the Jiffy bark media, opposed

to lower pH formulations, probably contributed to

the increased mortality.

The well-drained character of pine bark media is

desirable for ornamental production grown outside

in large containers. This media drains well during

frequent rainfalls and disease losses are reduced.

However, soil moisture in small containers must be

monitored closely and frequent irrigation is often

required.

Adding soil or vermiculite to cone or bark media

improves growth, increases water-holding capacity

and makes nutrients more available. Adding soil,

however, increases media weight more than vermiPhipps (1974a) compared nine media and found

that containerized red pine (Pinus resinosa Ait.)

seedlings grew best in equal parts peat and vermiculite. He attributed this response to high cation

Table P.-Seedling growth of shortleaf pine grown in peat, cone,

and bark media

Medium’

Final

PH Weight Height

Peat

PV-50

Jiffy Mix

Pine Cone

cv-50

cv-70

C-100

cs-70

w cm

5.4 c* 523 a 10.87 a

8.4 a 383b 9.72 b

5.9 b 301 c 7.85 c

8.0 b 259 de 7.48 cd

5.8 b 125 ij 8.08 fg

5.9 b 270 cd 7.79 c

Pine Bark

BV-50

SV-70

B-l 00

BS-70

5.4 c

5.0 d

4.9 d

5.3 c

218 f 8.18 fg

201 fg 8.15 fg

175 gh 5.83 g

224 ef 8.98 de

Jiffy 50-50 8.4 a 9Oj 5.54 g

Jiffy 70-30 8.5 a 154 hi 8.82 ef

‘The number following the medium designation indicates the percentage of peat, bark, or cone chips present.

*Means followed by the same letter are not significantly different,

Duncan’s Multiple Range Test at the 0.05 level.

Table 3.-Mortality of 70 longleaf seedlings in peat, cone, and

bark media infested with Fusarium or Pythium

Medium’ Fusarium Pythium

Peat

PV-50

Jiffy Mix

0.0 a*

0.8 bc

4.0 cd

9.4 f

Pine Cone

cv-50

cv-70

c-100

cs-70

0.0 a 4.8 d

0.8 abc 4.0 cd

0.0 a 3.8 bed

0.2 ab 2.8 abed

Pine Bark

BV-50

BV-70

B-100

BS-70

0.0 a

0.0 a

0.2 ab

0.0 a

2.4 abc

1.8ab

0.8 a

1.8 ab

Jiffy 50-50 1.8d 8.8 e

Jiffy 70-30 1.2cd 8.8 f

‘The number following the medium designation indicates the percentage of peat, bark, or cone chips present.

2Means followed by the same letter are not significantly different,

Duncan’s Multiple Range Test at the 0.05 level.

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culite and therefore increases shipping costs. While

vermiculite is sterile, unfumigated soil contains a

wide variety of soil fungi. Beneficial fungi, such as

mycorrhizal symbionts and some saprophytes, coexist with undersirable pathogens. Fumigation or

heat sterilization removes soil-borne pathogens but

also destroys beneficial fungi.

Cone media held water better and generally produced larger seedlings than bark media. Cone chips,

unlike bark chips, were well rotted. Had well-rotted

bark chips been used, improved water retention

and cation exchange properties may have increased

growth. Rotted pine bark chips are generally not

available from commercial sources, however. Results of this study suggest that rotted cone media

could be substituted where bark media are now used.

The pH of cone media, while not ideal for pine seedlings, is compatible with many ornamental crops.

Equal parts of peat and vermiculite with a low pH

provided the best medium tested for growing containerized southern pine seedlings. Other peatvermiculite mixes may be as good. Mixes of 1 to 3

parts peat moss and 1 part vermiculite are commonly

used to grow containerized seedlings in the Pacific

Northwest (Cleary et al. 1978). Phipps (197413) also

has reported some improvement in seedling development of red pine when the ratio of peat to vermiculite was increased from 1 :l to 3:l.

Cleary, D. B., R. D. Greaves, and K. H. Hermann.

1978. Seedlings. In Regeneration of Oregon’s

Forest, Oregon State Univ. School of Forestry.

p. 85-95.

Phipps, H. M.

1974a. Growing media affect size of containergrown red pine. U.S. Dep. Agric. For. Serv. Res.

Note NC-165 4 p.. North Central For. Exp. Stn.

St. Paul, Minn.

Phipps, H. M.

1974b. Influence of growing media on growth and

survival of container-grown seedlings. In Proc.

North Am. Containerized Forest Tree Seedling

Symp., Great Plains Agric. Count. Publ. 68:

398-400.

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