Plant Spacing & Layout

Flower Bulb Spacing Calculator

Pick a bulb type and enter your bed size to get the exact number of bulbs to buy, plus how far apart and how deep to plant them, which way up they go, and the best planting season.

Planting pattern

How to use the flower bulb calculator

Choose your bulb type, type in the length and width of your bed in feet, and pick a planting pattern. Press Calculate Bulb Count and you will see how many bulbs to buy (with a 10% cushion built in), how many you actually need to fill the bed, how far apart and how deep to plant them, which way up they go, and the best season to get them in the ground. Change any input and the result updates instantly.

How bulb spacing is calculated

Bulbs are spaced on a simple grid. We convert the recommended spacing for your chosen bulb from inches to feet, then work out how many fit along the length of the bed and how many fit across the width. Multiplying those two numbers gives the total for a standard grid. The "dense display" option adds about 20% more bulbs by tightening the gaps, which gives a fuller first-season show. Finally, we add roughly 10% on top of whichever pattern you choose so you have spares for gaps and losses.

Recommended spacing and depth by bulb

Spacing and depth vary a lot between bulb types. As a quick reference, small bulbs are planted shallow and close together while large bulbs need room and depth:

  • Crocus and muscari: about 3 inches apart and 3 inches deep.
  • Tulip: about 5 inches apart and 6 inches deep.
  • Daffodil and hyacinth: about 6 inches apart and 6 inches deep.
  • Gladiolus: about 6 inches apart and 4 inches deep.
  • Allium: about 8 inches apart and 4 inches deep.
  • Iris and lily: about 12 inches apart; iris 4 inches deep, lily 6 inches deep.
  • Dahlia: about 18 inches apart and 4 inches deep, laid on its side.

Planting depth and orientation tips

A reliable guideline is to plant a bulb two to three times as deep as the bulb is tall, measuring to the base. Plant most bulbs with the pointed end up and the rounded, root end down. Crocus and gladiolus corms go pointed side up, while dahlia tubers are laid on their side with the eye facing up. Good drainage matters more than perfect depth: bulbs sitting in soggy soil are prone to rot, so loosen heavy ground and add grit or compost before planting.

When to plant for the best display

Timing is what separates a great spring show from a disappointing one. Hardy spring-flowering bulbs need a cold period over winter, so plant them in fall once the soil has cooled but before it freezes hard. Tender summer-flowering types such as dahlias and gladiolus have no frost tolerance, so wait until spring once the danger of frost has passed. Whatever you grow, plant bulbs promptly after buying them, water them in, and let nature handle the rest.

Frequently Asked Questions

How many flower bulbs do I need per square foot?

It depends entirely on spacing. Small bulbs like crocus and muscari sit about 3 inches apart, so you can fit roughly 16 per square foot. Tulips at 5 inches give about 5 to 6 per square foot, daffodils and hyacinths at 6 inches give about 4, and large bulbs like alliums or dahlias need far fewer. The calculator does this math for your exact bed size and chosen bulb.

How deep should I plant flower bulbs?

A common rule is to plant a bulb two to three times as deep as it is tall, measuring to the base of the bulb. In practice that means about 6 inches for tulips, daffodils, hyacinths, and lilies, 3 inches for crocus and muscari, and roughly 4 inches for alliums, irises, gladiolus, and dahlia tubers. The calculator shows the recommended depth for the bulb you select.

Which way up do bulbs go?

Most bulbs are planted with the pointed tip facing up and the flatter, root end facing down. Crocus and gladiolus corms go pointed (sprout) side up. Dahlia tubers are the exception: lay them on their side with the growing point, or "eye", facing upward. If you genuinely cannot tell, plant the bulb on its side — the stem will still find its way up.

When is the best time to plant bulbs?

Spring-blooming bulbs such as tulips, daffodils, crocus, hyacinths, alliums, irises, and muscari are planted in fall, a few weeks before the ground freezes, so they get the winter chill they need. Tender summer bloomers like dahlias and gladiolus are planted in spring after the last frost. Lilies can go in during fall or early spring.

Why does the calculator tell me to buy 10% extra?

Some bulbs arrive damaged, fail to sprout, rot in wet soil, or get dug up by squirrels and other animals. Buying about 10% more than the bed strictly needs covers these losses and lets you fill any gaps for an even, full display. If you garden somewhere with heavy pest pressure, you may want an even bigger cushion.

What is the difference between standard grid and dense display?

Standard grid spaces bulbs at the recommended distance for healthy, long-term growth, which is best if you want the planting to come back year after year. Dense display packs in about 20% more bulbs for a fuller, more dramatic first-season show, which is popular for tulips and other bulbs that many gardeners treat as annuals.

More Tools to Explore

Plant Spacing Calculator How many plants fit in your bed Open tool → Square Foot Garden Planner Plants per square foot, any bed size Open tool → Planting Calendar When to plant by ZIP code Open tool →

GardenCalc Editorial Team

Horticulture Writers & Master Gardeners

Our calculators and guides are written and fact-checked by gardeners with hands-on experience in vegetable production, soil management, and home landscaping.