Certified Professional Horticulturist (CPH) Practice Exam

How deep should you plant bulbs?

1. Halfway leaving part exposed

2. Depth should equal the width of the bulb

3. 2 to 3 times the width of the bulb

4. No set rule on planting depth

The correct answer is: 2 to 3 times the width of the bulb

The depth at which bulbs should be planted is typically recommended to be 2 to 3 times the width of the bulb. This guideline helps ensure that the bulb is adequately buried to provide stability and protection from temperature fluctuations, while also allowing for proper drainage and aeration. Planting at this depth supports the bulb's development and encourages healthy growth, as it places the bulb at an optimal depth for moisture retention without risking rot. If bulbs are planted too shallowly, they may be more prone to drying out, being disturbed by animals, or being exposed to surface freeze/thaw cycles, which can damage their growth. Conversely, if they are planted too deeply, it can hinder their ability to emerge properly when the time comes for them to sprout. Thus, planting bulbs at a depth of 2 to 3 times their width provides a good balance for their health and flowering potential.