Problems Associated with Immature Seed

Immature seed produces deformed or slow-growing seedlings that have low vigor and low viability. Laboratory tests indicate that seed collected 20 days before it is fully mature has a germination rate that is 20 to 40 percent lower than mature seed. Although seed generally matures before the cones flare (when the cone scales open to release seed), fleshy fruits drop, and dry fruits dehisce. Cones of high-elevation species may flare and lose seed or birds may prey on cones before they reach full maturity. Insects also can cause cones to flare and release seeds early. Once cones begin to open, seeds may disperse rapidly. The collection period may be no longer than 10 to 14 days, depending on the weather. Seed maturity needs to be checked almost daily as cones approach maturity.

If cones are collected too early, the nursery may have problems extracting the seed. Cones may not open, resulting in little or no seed recovery. Cones that are collected when they are immature may develop mold or overheat, significantly reducing seed viability. The endosperm of immature seeds has not completely solidified. Early collection can allow the endosperm to shrink, reducing germination.

Some conifer cones afterripen (ripen after being picked from tree), but cones of each species vary greatly in their ability to afterripen. It is best not to depend on this trait. Reliance on afterripening should be reserved only for situations where seed needs are critical, cone crops are rare, and fully mature cones cannot be collected. The seeds of many angiosperms (flowering plants rather than conifers) will afterripen.

The approximate cone collection date will vary by species with the seed maturity varying substantially depending on the weather, elevation, and species. The seed of most conifers matures sometime after early August, but maturity may vary. Squirrels may be cutting cones, but their activity does not indicate that seeds are mature. Most collection indicators are subjective and require experience to judge.