Why Are My Asparagus Spears Hollow Inside?

Slicing a freshly cut asparagus spear and finding a hollow centre is surprising and slightly worrying. Hollow asparagus is actually fairly common and in most cases is not a sign of disease. It is usually a physiological issue tied to irregular water supply, rapid growth, or the natural characteristics of certain thicker varieties. Understanding the cause tells you whether you need to change anything or simply accept that hollow spears are occasionally part of the crop.

Rapid growth after dry periods

The most common cause of hollow spears is a burst of rapid growth following a dry spell or after irrigation after drought. When the crown is suddenly flushed with water and nutrients after a period of stress, the spear grows so fast that the outer tissue expands before the inner cells can fill in, leaving a hollow core. This is particularly common in late spring when warm weather arrives suddenly after a cool, dry period. The spear is safe to eat — there is nothing wrong with the flavour — but the texture is slightly different.

Boron deficiency is a less common cause

In some soils, particularly sandy or very alkaline ones, low boron levels can cause hollow stems and distorted growth in asparagus. Boron is a trace element needed for cell wall development. If your spears are consistently hollow across multiple seasons and the soil is light and sandy or the pH is high, a small application of borax (a boron source) to the bed may help. However, boron is toxic in excess — do not apply it without a genuine deficiency and do so sparingly. Most hollow spear issues are water-related rather than nutrient-related.

Thick varieties are more prone

Larger, thicker spear varieties are more prone to hollow centres than thin varieties, simply because the inner tissue has more space to form a cavity when conditions trigger it. If hollowness is a recurring problem and you grow one of the thicker commercial varieties, it may just be a trait of that cultivar under your conditions rather than a fixable problem.

What you can do

Maintain consistent soil moisture throughout the spear-production season with regular watering, especially in dry springs. Mulching the bed well in spring helps retain moisture and moderates soil temperature swings. If hollow spears are rare and the season has been dry then wet, that is the likely cause and no action is needed. If they are consistent year after year, check soil pH (aim for 6.5–7.5) and consider a trace element test to rule out boron deficiency.