Complete Flower Bulb Planting Guide


Some of our most spectacular color displays come from bulbs. Whether you are interested in spring flowers or an outstanding summer scheme, starting bulbs during fall is a great start for healthy blooming plants.

Planting time, type of soil, light exposure and fertilization all contribute to successful bulb growth.

Bulbs are storage units for the embryonic plant as well as the fuel that will help it get started and, as such, they must gather energy for the next season's flowers after they have bloomed.

To advance this situation, it is wise to leave the foliage intact once flowers are spent, to allow leaves to photosynthesize and turn sunlight into plant starches that are stored in the bulb.


2 main types of bulbs: spring or summer blooming

  • The best time to plant spring bulbs is in fall. This is because most spring flowering bulbs require a chilling period. This varies dependent upon species but, generally, three months is sufficient for most varieties. You can also force bulbs by mimicking the chilling period in your refrigerator.
  • Summer bloomers should be planted in spring. The time to plant depends upon your zone. For the most part, the upper regions of North America should plant in April to June, the middle regions in March to May and the southern stretch in February to April. A good rule of thumb is to wait until all danger of frost has passed in your area.


What soil and how much light?

Fat, healthy bulbs with no signs of insect damage or rot will start your garden off right. Most bulbs do best in at least 6 hours of sunlight daily, so site choice is important for beautiful blooms. Well-draining soil is the next requirement.

Loosen soil to a depth of at least 12 inches (31 cm). If soil has a high clay content or is compacted, it may be amended with generous amounts of compost, peat, leaf litter or other organic material.

While the soil is being amended, mix in superphosphate or bone meal to enhance the fertility of the planting bed. A recommended amount is 5 tablespoons (74 mL) of water soluble 10-10-10 and 2 cups (474 mL) of bone meal per 10 square feet (1 square meter).


Planting depth requirements

Planting depth can make or break a color display. Bulbs have different depth requirements for their installation. The general rule of thumb is to plant bulbs 2 to 3 times as deep as the bulb is tall. The larger bulbs should be 8 inches (20 cm) deep. These might be tulips or daffodils.

The smaller bulbs go in ground at a depth of 3 to 4 inches (7.6 to 10 cm) deep. Summer blooming bulbs have more particular depth requirements, which can be found on the packaging. Iris and lilies, for example, require a slightly deeper hole than gladiolus or liatris.

Bulbs need to be planted right side up. Some bulbs are easy to identify the top because there is a root plate at the base and a pronounced peak at the top. If there is no pointed top, look for where the roots come out and use that as the base.


How to water bulbs?

Summer blooming plants especially need watering at installation, but in arid regions, watering the spring bloomers is recommended. When flower buds appear, plants need even more water. An inch of water per week should be sufficient to soak down to the roots.

Some bulbs are quite top heavy and will require staking as they bear heavy flowers. Apply mulch around the bulb bed to prevent weeds and conserve moisture. Once flowers are spent, cut them off but leave that foliage for continued bulb health.