Seed Collection, Processing and Handling Objectives: • Know the properties of ‘high quality’ seed. • Understand basic seed biology and the reproductive cycles for different BC conifers. • Be familiar with biotic factors which affect the size and periodicity of seed crops. • Know the different methods of cone collection. • Be able to describe the steps in conifer seed processing and storage. High quality seeds are: sound, store well, and have a high capability to produce healthy seedlings that are well adapted to the reforestation site and meet product objectives.
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Seed Collection, Processing and Handling
Objectives:
• Know the properties of ‘high quality’ seed.
• Understand basic seed biology and the reproductive
cycles for different BC conifers.
• Be familiar with biotic factors which affect the size and
periodicity of seed crops.
• Know the different methods of cone collection.
• Be able to describe the steps in conifer seed processing
and storage.
High quality seeds are: sound, store well, and have a
high capability to produce healthy seedlings that are
well adapted to the reforestation site and meet product
objectives.
Use of seed orchard seed is increasing yearly, but wild seed
collections still account for the majority of seed used in BC.
60%
90%
80%
80%
10%
Natural seed production varies from year to year - why?
11 crops
5 crops
35 years
Conifers are monoecious, having male and female flowers on same tree.
There are 4 key phases in the reproductive cycle:
Initiation
Differentiation
PollinationMaturation
There is an extended period between flower initiation and seed maturity.
The length of the reproductive cycle varies between species, from 16
months (‘2 year cycle’) to 30 months (‘3 year cycle’).
Year 1 Year 3Year 2
Large seed crops require different conditions during each developmental
phase. Heavy crops result from a series of optimal weather conditions at
each stage.
Initiation Differentiation Pollination Maturation
Date: spring, year 1 summer, year 1 spring, year 2
Factors: lots of
photosynthate
reserves and
shoot apices
warmth, high light,
good nutrition,
moisture stress
abundant,
well
distributed
pollen
good nutrition,
adequate
moisture,
warmth
Weather: cool, cloudy,
moist
warm, dry, sunny dry warm and
windy, no late
frosts
warm sunny,
periodic
rainfall
Cone crops vary from tree to tree within stands.
What factors does this depend on?
Quantities of cone and seed vary by species
and with position in crown:
Species Period-
icity
(years)
Location
of cones
in crown
Cones
/hl
Viable
seeds
/hl
Seeds
/
Cone
Clean
Seeds/
gram
Container
seedlings
/hl
Seed/
Seedling
Ratio
amabilis fir 2-3 Top 1/4 700 30000 43 33 18000 1.67
subalpine
fir
2-4 Top 1/4 850 40000 47 106 32000 1.25
interior
spruce
6 Top 1/3 10000 350000 35 512 73000 4.79
lodgepole
pine
2-4 All 8300 70000
interior
8 372 21000
interior
3.33
Douglas-fir
coast
interior
2-10
2-10
Top ½
Top ½
2800
2800
40000
70000
14
25
110
108
9000
14000
4.44
5.00
redcedar 2-4 All 110000 900000 8 882 260000 3.46
western
hemlock
3-4 All 83000 367000 4 528 98000 3.75
For wild seed collections, the objective is to collect during
medium or heavy seed years – why?
Sx Sx
Knowing the biology of seed production and the factors which
contribute to heavy, high quality seed crops informs seed
orchard management.
With these factors in mind, where should seed orchards be
located in terms of climate and proximity to natural stands?
• Sites should promote the growth of trees, but allow for drought stress
when desirable.
• Trees should be well spaced.
• Flowering can be induced through girdling, application of hormones
(gibberelic acids) and nitrogen fertilization; or delayed using sprinklers to
lower temperatures.
• All genotypes should produce pollen and seed cones at the same time –
so pick good producers as parents.
• Pollen contamination from surrounding stands introduces maladaptation
to source climate and reduces genetic gain.
• Insect and diseases can be reduced by maintaining tree vigour,
removing old cones (sanitation) and by orchard siting.
Conduct a ‘seed need analysis’ for all species and
populations (provenances) within your operating area.
Maintain a 5-10 year seed supply in a secure location.
Seed production from orchards is more consistent year to
year than from wild stands, so less storage is needed.
Consider all propagule sources including: improved (‘Class
A’) seed, vegetative cuttings, emblings, wild (‘Class B’ and
‘B+ seed’).
Use the best source first during inventory withdrawals.
Principles of seed inventory
Example seed need
calculation:
(a hectolitre is 100 litres)
Evaluate wild stands of the appropriate provenances for a
potential seed collection when seed inventories drop below
a 5-10 year supply.
This evaluation begins with ‘cone crop forecasting’ and is
followed by ‘crop monitoring’.
For 2 year cycle species, forecast next fall’s crop during the
previous winter by bud sampling:
• Collect a branch from the cone producing region of the crown for
several mature dominants/codominants in the stand.
• Count the female and vegetative buds for 3 internodes in from the
branch tip.
• A higher ratio of female:vegetative buds means a greater potential
crop (e.g. for Fd >0.2 indicates medium+ crop).
What is an easier way to forecast next fall’s crop for Yc and
pines (3 year cycle)?
Fd
Crop monitoring occurs in three phases: cone crop rating,