The bulbs are bought, the bed is cleared, and the trowel is in your hand. The only decision left is the hole itself — how deep to set each bulb, and how far apart — and the answer changes with the bulb.
This table gives the answer for seven bulbs, from the first flowers of spring to the garlic you will harvest next summer. The numbers come from two university Extension guides — Iowa State University Extension and University of Minnesota Extension — and every depth is measured from the base of the bulb to the soil surface, which matters if your bulb packet measures from a different point.
The table
A rough rule of thumb puts planting depth at two to four times the bulb’s width, measured from the base of the bulb. The table below gives the exact figure for each bulb, so that is the number to plant by. Spacing is measured center to center, and a dash in the Blooms column means neither guide states a bloom window for that bulb.
| Bulb | Planting depth | Spacing | Blooms |
|---|---|---|---|
| Glory-of-the-Snow (Chionodoxa) | 3–4 in | 3 in * | Mar–Apr |
| Crocus | 3–4 in | 3 in | Mar–Apr |
| Grape hyacinth (Muscari) | 3–4 in | 3 in | — |
| Daffodil (Narcissus hybrids) | 6–8 in | 6 in | Apr–May |
| Tulip | 6–8 in | 6 in | Apr–May |
| Allium (ornamental onion) | 4–8 in (by bulb size) | 6 in * | May–Jun |
| Hardneck garlic (cloves) | 2 in | 4–6 in | Harvest Jul–Aug |
* Spacing by the Extension size-class rule — three inches for small bulbs, six for large — rather than a figure stated for that bulb by name. Depths and bloom windows are the per-bulb figures from the two Extension guides behind this table, and spacing follows Iowa State University Extension’s large- and small-bulb rules.
How to plant them
Set each bulb with the pointed end up and the base resting at the depth in the table, then water the bed well. Cover the surface with two to three inches of leaf mulch, wood mulch, or clean straw, which holds moisture in and keeps the soil temperature steady as the seasons turn.
Plant in clusters of five to fifteen, since odd-numbered groups and mass plantings look the most natural. A drift of one kind beats a single bulb standing alone. In light, sandy soil, set each bulb an inch or two deeper than the table says; in heavy clay, set it an inch or two shallower.
Fall-planted bulbs need cool soil to grow roots before winter, and the window stays open as long as the ground can still be dug. In cold-climate areas the usual window runs from mid-September to mid-October, though tulips can go in as late as you can get them into the ground. If the calendar has you wondering whether the window is already shut, Is November Too Late to Plant Bulbs? takes up exactly that question. This weekend’s yard list carries the bulb jobs still open for the days ahead.
Daffodils are deer- and rodent-resistant, so they suit an open bed, but tulips belong in a protected spot where deer cannot browse them. The bloom windows in the table are northern ones that shift with the weather, so southern gardens will see the same flowers earlier.
Hyacinth, snowdrop, and lily do not appear in this table, because no planting depth for them could be found in the Extension guides behind it — so they are left out rather than guessed at.
Bottom line
Follow the table’s depths — three to four inches for Glory-of-the-Snow and crocus, six to eight for tulips and daffodils — set the bulbs in clusters of five to fifteen, and lay a light mulch over the bed once the ground freezes. If you can still dig a hole, you can still plant a bulb, and the table above tells you exactly how deep to dig it. When spring turns to seed-sowing, our vegetable seed spacing, sowing depth, and days to maturity table picks up where this one leaves off.
Sources
Iowa State University Extension and Outreach, “How deep should I plant tulips?” (Yard and Garden FAQ; page updated December 3, 2024) — https://yardandgarden.extension.iastate.edu/faq/how-deep-should-i-plant-tulips — fetched November 10, 2026.
University of Minnesota Extension, “Plant bulbs now; you’ll be thankful later” (Yard and Garden News, November 2, 2026) — https://extension.umn.edu/about/our-stories/news/yard-and-garden-news/plant-bulbs-now-youll-be-thankful-later — fetched November 10, 2026.
University of Minnesota Extension, “Planting bulbs, tubers and rhizomes” — https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/planting-bulbs-tubers-and-rhizomes — fetched November 10, 2026.
