Acorns are highly perishable seeds that quickly lose their capacity to sprout due to drying, insect damage, or fungal infection. Determining viability is the first step before planting or long-term storage. Assessing viability allows collectors to discard non-viable seeds, preventing wasted effort and storage space. Visual, density, and internal checks provide a reliable assessment of an acorn’s potential for successful germination.
External Inspection: Visual Cues of Health
The initial assessment begins with a simple visual and tactile inspection, focusing on non-destructive signs of damage or decay. Healthy acorns typically exhibit a uniform, rich brown color, often with a glossy sheen, and feel heavy and solid for their size. Conversely, non-viable acorns may appear shriveled, possess a dull or grayish coloration, or show signs of exterior mold growth.
Careful examination of the shell is necessary to identify tiny pinholes, which indicate internal insect infestation, most commonly by acorn weevils. Weevils lay eggs inside the nut; the emerging larvae consume the interior, leaving a hollow shell and a small exit hole. The cap connection point should also be inspected; a clean scar where the cap detached suggests a healthier seed than one with a dark or discolored connection point. Any acorn that rattles when gently shaken should be discarded, as this noise indicates the internal kernel has dried and shriveled away from the shell.
The Water Test: Quick Density Check
The most common non-destructive method for rapidly sorting a large batch of acorns is the float test, which relies on differences in seed density. When submerged in water, a healthy, viable acorn is dense and heavy due to its solid, moisture-rich kernel, causing it to sink immediately. Sinking confirms the seed is full and likely undamaged by pests or desiccation.
Non-viable acorns will float at the surface because they have reduced density. This lack of density is caused by the internal kernel being hollowed out by weevil larvae or by significant drying, which creates air pockets inside the shell. The float test is not infallible, as some viable acorns may float if they are slightly dry. To increase accuracy, acorns can be soaked for up to 24 hours before making a final determination, allowing sound seeds to fully hydrate and sink.
The Definitive Test: Examining the Interior
To confirm the health of a batch, particularly those that passed the float test, a definitive cut test should be performed on a small, representative sample. This destructive method involves carefully slicing an acorn in half lengthwise to expose the inner cotyledons and embryonic axis. The appearance of the internal tissue directly reveals the seed’s viability.
A healthy, viable kernel should be firm, moist, and display a light, creamy white or yellowish color throughout. This uniform appearance indicates a well-developed embryo with sufficient stored energy for germination. Conversely, a non-viable acorn will show clear signs of damage or decay, often appearing brown, black, or gray, or exhibiting a soft, mushy, or moldy texture. If the internal tissue is brittle and dry, it indicates fatal desiccation. Performing this test on a small percentage provides an accurate measure of the overall batch quality before planting or storage.