Good morning,

The hard, round, squash-colored knobs you're seeing inside your acorn squash are likely "woody growths" or lignified tissue, a condition that can occur due to environmental stress, genetic factors, or certain nutrient imbalances. This can happen when squash plants experience inconsistent watering, such as during dry spells followed by heavy watering or rainfall, which can stress the plant and lead to irregular cell growth inside the squash. Additionally, this tissue can develop as a result of genetic variation among different types of squash.

Research by university extension services like the University of California Division of Agriculture and Natural Resources explains that this type of "woody" or hardened tissue in squash and melons can be related to growing conditions that disrupt normal fruit development, especially when plants experience temperature fluctuations, drought, or inconsistent moisture. Improving water consistency and monitoring soil nutrient levels might help reduce this effect in future harvests.

For more information, you can refer to the following resources:

• University of California Agriculture and Natural Resources - Vegetable Pest Management Guidelines
• University of Illinois Extension - Cucurbit Crop Issues