Eucalyptus Seed: Harvest it Right

Harvesting and Extracting Eucalyptus Seed from Specimen Trees: The Basics

Gustavo Iglesias Trabado
GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS

We had discussed elsewhere that it is possible to find an Eucalyptus tree having at once flower buds in formation, blooming flowers, pollinated but yet immature capsules, fruits reaching maturity within the same year of collection, and older capsules of at least the previous two seasons. Today EUCALYPTOLOGICS brings you a pictorial example of this in which several of these stages are easily visible at once.

Fig. 1: Different simultaneous stages of the reproductive cycle and seed maturation process in a standing Snow Gum Eucalyptus tree.(Click to enlarge)

This matters for Eucalyptus seed collection methodologies, both at capsule harvest and seed extraction stages.

As a totally selective harvest focusing on mature capsules only would require good access to sometimes large Eucalyptus trees via climbing or lifting the collector to upper branches, in most cases whole branch removal is the standard procedure for capsule harvest from specimen eucalypt trees. It can be carried on from the ground using relatively simple equipment.

Capsule Harvest in Eucalyptus: Specimen Trees

• If performed via whole branch removal, it should focus on targeting those branches bearing noticeable amounts of mature capsules (normally brownish and woody, but not yet open). Thus, branch selective Eucalyptus seed harvest.
• If performed via whole branch removal, it should aim to reatain some of those branches bearing noticeable amounts of flower buds in development or immature capsules (normally greenish and not yet fully woody). This way further Eucalyptus seed crops are possible in the next year and new pollinated flowers can develop into capsules for subsequent years. Thus, sustainable Eucalyptus seed harvest.

Seed Extraction in Eucalyptus: Aim to the Best Seed

If performed via whole branch removal, harvest of some amounts of senescent and immature Eucalyptus capsules ("seed pods") and some flower buds might be inevitable. In such cases, some implications for seed quality can have importance because germination rates are not the same for seed contained in each type of capsule.

• Grouping senescent (already open valves, some seed yet in) and mature (brownish, woody, not yet open capsules) capsules for Eucalyptus seed extraction yields germplasm with the highest potential for good germination rates. Even if both seed and chaff are present, the number of mature seeds per weight of seed and chaff mix is higher in these. Thus, higher purity seed mix.
• Separating non mature capsules (greenish, non totally woody, valves closed) for seed extraction can give you an indication of the purity of the Eucalyptus seed mix in these cases, which would be variable depending on harvest date. In some cases, after extraction and seed depuration (removal of non fertilised ovules or chaff, plus removal of fertilised but not yet mature hence non germinant seeds) can still yield a little extra % of high purity seed.
  
• Eucalyptus flower buds, blooming flowers and recently pollinated flowers have no interest from the point of view of seed harvest, but if in the right phase (anthesis), some of these could be worthwile for pollen collection.
  

Interesting links

Eucalyptus Seed Collection: The Importance of Good Timing

Fig. 2: Maturation stages for fruits collected on Corymbia calophylla trees in a single visit, showing some of the internal organs within Eucalyptus infrutescences in each phase. (Click to enlarge)


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© 2008 Gustavo Iglesias Trabado. Please contact us if you want to use all or part of this text and photography elsewhere. We like to share, but we do not like rudeness.