Bulb Spacing Calculator — How Many Flower Bulbs Do I Need?

A Bit About Garden Bulbs

Bulbs are a common sight in gardens around the world. Many plant species use them as winter energy stores. As winter approaches and days grow shorter, plants have less sunlight for photosynthesis. To prevent dying off, some plants store energy in specially adapted stem sections surrounded by leaf layers — this is a garden bulb. Like an onion, it has distinct layers.

All that stored energy is very attractive to animals (especially squirrels), so plants hide their winter lifeline underground. Since the plant grows from the bulb the next season, most bulbs are perennial — they come back year after year.

It is also possible to propagate bulbs to get more plants. Sometimes the plant grows new bulbs next to the original one automatically. Gardeners can also propagate plants from cuttings or by "chipping" a bulb into several pieces, all of which can sprout new plants.

How to Use the Bulb Spacing Calculator

1. Choose your unit system — Metric (meters / centimeters) or American (feet / inches).
2. Select the planting grid — Rectangular for rows and columns (square or oblong), or Triangular for a denser, offset pattern that fits more plants in the same area.
3. Enter your garden bed dimensions — length and width. You may also enter a border gap between the bed edge and the first plant.
4. Pick your bulb type from the drop-down menu (e.g., Tulip, Crocus, Daffodil). The plant spacing field will auto-fill. You can still edit it manually. For rectangular grids you may also set the row spacing independently.
5. Optional: enter the cost per bulb and choose a currency to see the total planting cost.
6. Click Calculate — the tool shows the total number of bulbs needed, number of rows, plants per row, effective planting area, and recommended planting depth.

🔎 If you wish to plan spacing for non-bulb plants in hedgerows, try our dedicated plant spacing calculator.

What Bulbs to Plant in Fall?

The following bulbs are planted in fall (typically September–November, before the ground freezes) to bloom in spring:

• Alliums — tall, globe-shaped purple flowers, great for back borders. Spacing: 20 cm / 8 in.
• Anemone — delicate, daisy-like blooms in blue, white, and pink. Spacing: 10 cm / 4 in.
• Bluebells — classic spring woodland flowers with a gentle fragrance. Spacing: 10 cm / 4 in.
• Crocus — one of the earliest spring flowers, great for naturalizing in lawns. Spacing: 7–8 cm / 3 in.
• Cyclamen — low-growing, swept-back petals, ideal for shady spots. Spacing: 15 cm / 6 in.
• Daffodil — classic yellow trumpets, very easy to grow and deer-resistant. Spacing: 15 cm / 6 in.
• Fritillaria — exotic bell-shaped flowers, including the chess-pattern fritillary. Spacing: 15 cm / 6 in.
• Hyacinths — intensely fragrant spikes in pink, blue, white, and purple. Spacing: 15 cm / 6 in.
• Iris — elegant, orchid-like blooms in a wide range of colors. Spacing: 10 cm / 4 in.
• Muscari (Grape Hyacinth) — small, deep-blue clusters, perfect for edging. Spacing: 7–8 cm / 3 in.
• Tulips — the iconic spring bulb, available in hundreds of varieties. Spacing: 15 cm / 6 in.

What Bulbs to Plant in Spring?

A smaller selection of bulbs prefers spring planting (March–May) for summer or fall blooming:

• Anemone (some varieties) — can be soaked overnight and planted in spring for summer blooms.
• Cyclamen (some varieties) — hardy corms that can also be planted in spring for fall color.
• Snowdrops — although technically fall-planted, "in the green" snowdrop divisions are often planted in late winter / early spring.

Planting Depth Reference

FAQs

What are some easy-to-grow bulbs?

The easiest bulbs for beginners are:

• Daffodils — virtually pest-proof, they naturalize and multiply on their own.
• Hyacinths — reliable bloomers with a strong, sweet scent.
• Tulips — wide variety, easy to plant, stunning results in spring.
• Muscari — tiny, tough, and perfect for filling gaps between larger bulbs.
• Crocus — among the first to bloom in spring, very low maintenance.

What flower bulbs can be planted in January?

Outdoors in January, only tulip bulbs can still be planted — but only if the ground is not yet frozen. Most other fall bulbs should have been planted by November. However, you can start bulbs indoors in January by placing them in a cool (1–9 °C / 34–48 °F), dark, dry location to simulate winter dormancy. This technique, called forcing, is commonly used for tulips, hyacinths, and crocuses to bring them to bloom indoors during winter months.

What is the difference between rectangular and triangular planting grids?

In a rectangular grid, each plant is directly across from the one in the next row — forming a regular checkerboard pattern. It is easy to plan and works well for formal, structured gardens.

In a triangular (offset) grid, every other row is shifted by half the spacing, so each plant sits in the gap between two plants in the adjacent rows. This mimics how plants grow in nature and fits approximately 15% more plants in the same area — making it ideal for a lush, full-coverage look.

How deep should I plant flower bulbs?

A common rule of thumb is to plant bulbs at a depth equal to 2–3 times the bulb's diameter. Large bulbs like tulips and daffodils go in at 15–20 cm (6–8 in), while small bulbs like crocuses and snowdrops go in at just 7–10 cm (3–4 in). See the planting depth table above for specific guidance.