Bulb Planting Depth Guidelines: How Deep Should I Plant Bulbs

(Image credit: LianeM)

Bulbs always seem a bit like magic. Each dry, round, papery bulb contains a plant and everything it will need to grow. Planting bulbs is a wonderful, easy way to add enchantment to your spring or summer garden. If you are considering adding bulb plants to your beds this year, you’ll want to get the how-to info well in advance, including site preparation and bulb planting depth. Read on for tips on planting bulbs, including how deep to plant bulbs of different sizes.

About Planting Bulbs

Most bulbs are either spring flowering or summer flowering. You can plant spring bulbs in autumn, then summer bulbs in spring. The preliminary steps for planting bulbs are very much the same as for garden plants. You need to cultivate the soil down to a depth of 12 to 14 inches (31-35 cm.) and be sure that the soil drains well. Organic compost can be added to clay soil to increase drainage.

Next, it’s time to blend in required nutrients to help your bulbs bloom well. To do this, you must first figure out the planting depth for bulbs you have chosen. Then work nutrients, like phosphorus, into the soil at that depth before putting in the bulbs. You might also mix in a general bulb fertilizer. All nutrients should be placed at the appropriate bulb planting depth – that is, the level where the bottom of the bulb will sit in the soil.

How Deep Should I Plant Bulbs?

So, you’ve worked the soil and are ready to begin. Now is the time to ask: how deep should I plant bulbs? The key to figuring out how deep to plant bulbs is the size of the bulb.

The general rule is that bulb planting depth should be between two to three times the length of the bulb. That means that a small bulb like a grape hyacinth will be planted closer to the surface of the soil than a large bulb like a tulip.

If your bulb is an inch (2.5 cm) long, you will plant it about 3 inches (8 cm.) deep. That is, measure from the bottom of the bulb to the surface of the soil.

Do not make the mistake of planting too deep or you are unlikely to see flowers. However, you can dig up the bulbs and replant them at the appropriate depth the following year.

Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.