W.S.Department 01 Agriculture

Forest Service General Technical Report SE-18

RECOGNIZING

DEVELOPMENTAL STAGES

1.N SOUTHERN

PINE FLOWERS:

The Key to Controlled Pollination

bY

David L. Bramlettl

and

Claude H. O’Gwynn” ’

. *

: ,~ _.. %

‘Project Leader, Southeastern Forest Experiment Station,

Macon, Georgia.

“Southern Tree Improvement Manager, Weyerhaeuser

Company, Hot Springs, Arkansas.

January 1980

Southeastern Forest Experiment Station

Asheville, North Carolina
Controlled pollinations are vital in southern

pine tree improvement programs. Effective

pollinations depend upon three operations. First,

female flowers must be enclosed in isolation bags

when they are in the proper stage of development.

Then, viable pollen must be supplied to the ovules

when the female flowers are most receptive.

Finally, the developing cones must be protected

until maturity.

The first two operations are highly dependent on recognition of the developmental

stages of southern pine flowers. Timing of flower

development varies among species and is highly

dependent upon spring temperature. This booklet

illustrates the developmental stages described by

Cumming and Righter. z3 It *also gives the pollination procedures to follow during each stage.

Turnming, W.C., and F.I. Righter. 1948. Methods used to

control pollination’of pines in the Sierra Nevada of California. I

U.S. Dep. Agric., Circ. 792, 18 p. Washington, D.C.

2
STAGE1

The female flower bud ( 9 ) is small and tightly

enclosed within the bud scales. One to several

flower buds may occur in a lateral position on a

vegetative shoot bud (v). This is a good time to

identify potential branches for pollination, but it is

still too early to bag the flowers. Bagging at this

stage causes female flowers to be receptive before

fresh pollen is available.

3
STAGE2

Flower buds have enlarged, but the flower

primordia are still enclosed within the bud scales.

Light-colored scales are noticeable at the tip of

the bud. Isolation bags should be installed now.
STAGE 3

The flower has begun to emerge through the

top of the scales. Flowers are normally red, pink,

or light green. Since flowers may have received

pollen of unknown origin, it is too late to bag.
STAGE4

The flower has elongated and extends beyond the bud scales, but the lower one-third to

one-half of the flower is still enclosed by the bud

scales. Delay pollination.
STAGE 4 (late)

The flower has extended almost entirely from

the bud scales, but the maximum space between

the scales has not yet occurred. Some seed can be

produced by pollinating flowers now, but yields

are increased by delaying until stage 5.

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STAGE 5

The flower has completely emerged from the

bud scales. Typically, the bud scales are roll.ed

back, and the flower scales approach a right angle

with the axis of the conelet. The flower is at its

maximum receptivity because the opening between the scales and the bracts offers the greatest

access to pollen. Stage 5 normally lasts from one

to several days. Pollinate at this stage.

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STAGE 5 (cuta)vay)

Pollen is wind-borne to the flower and enters

the space between the scales (S) and bracts (B).

Paired ovules (0) are embedded on the upper

surface of each scale. The bracts are attached to

the cone axis and the lower surface of the scales.

The polien accumulates around the sticky micropyle (M) of the ovule and is transported into the

pollen chamber by a pollination droplet.
STAGE 5 (fate)

The female flower remains receptive as long

as the space between the scales is large enough for

the passage of pollen. The scales gradually increase in size and after one to several days of

‘receptivity (depending on the species and ambient

temperature) the opening between the scales

decreases until completely closed. Flowers may

be pollinated in late stage 5, but seed yields may

be low.

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STAGE6

The flower is no longer receptive because the

growth of the scales completely closes the openings. Pollinations in stage 6 produce no seeds.

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RECOMMENDED PROCEDURES

FOR

CONTROLLED POLLINATION

Bag flowers in stage 2 on strong vigorous

branches. Earlier bagging may hasten female

flower, development resulting in receptivity before fresh pollen is available.

Do not bag flowers that have begun to emerge

from the bud scales (stage 3).

Periodically check flowers for flower receptivity.

When flowers are in stage 4, delay pollination but

observe frequently to determine onset of stage 5.

Inject pollen into bag when most flowers in the

isolation bag are in stage 5.

Use pollen of highest viability available.

If stored pollen is used, test its viability before

pollination.

LJse an adequate quantity of pollen per bag (approximately 0.50 crniS per bag).

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Try to achieve a good distribution of pollen within

the bag. Shake bag after pollinating.

Do not try to pollinate all bags on the same tree on

the same day if flowers are not receptive on some

branches.

If flowers in different stages of development are in

a single bag, pollinate a second time when latedeveloping flowers are receptive.

Delay bag removal until 2 weeks after final

pollination.

Protect conelets with insecticides until cone

maturity.

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ACKNOWLEDGMENTS

Drawings prepared by Mary Wain Ellison,

commercial artist, Macon, Georgia. The drawings

were made from photographs taken by J.G.

Hutchinson when he was with the S.outheastem

Forest Experiment Station, Charlottesville,

Virginia. Hutchinson is now with the North

Central Forest Experiment Station in St. Paul,

Minnesota.

The material in this booklet is adapted from

Chapter 10, “Controlled Pollination,” in pol/e~~

Matiagement Handbook. E. Carlyle Franklin,

Editor. USDA Forest Service.

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