How to Plant Spring Bulbs in Fall (Depth, Spacing, Drainage)
I plant bulbs every October in Melville. My current mix is daffodils ('Ice Follies', 'Thalia', 'February Gold'), ornamental alliums ('Purple Sensation', 'Globemaster'), and grape hyacinths through the lawn edge. Tulips I have mostly given up on in open beds because of deer -- they will eat them.
I plant bulbs every October in Melville. My current mix is daffodils ('Ice Follies', 'Thalia', 'February Gold'), ornamental alliums ('Purple Sensation', 'Globemaster'), and grape hyacinths through the lawn edge. Tulips I have mostly given up on in open beds because of deer — they will eat them regardless of repellent if the pressure is high enough in late April.
Spring bulbs need to go in the ground in fall because they require a cold period of 12–16 weeks to develop properly. Per Penn State Extension, most spring-flowering bulbs need a minimum of 12–16 weeks at temperatures below 48°F to complete the physiological process that enables flower development. In zones 7 and warmer, planting in October is later than zones 5–6 (which can plant in September) because you need the soil to cool first.
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When to Plant
Per Penn State Extension, the planting window for spring bulbs is when soil temperature at 6-inch depth falls to 40–50°F. For most zones:
| Zone | Typical Planting Window |
|---|---|
| Zone 4–5 | September 15–October 15 |
| Zone 6–7 | October 1–November 15 |
| Zone 7b–8 | October 15–December 1 |
| Zone 9–10 | Pre-chill bulbs required (see below) |
Upper limit: Per Penn State, do not plant bulbs after the ground freezes. Bulbs planted in frozen soil will not establish properly.
Lower limit: In zones 9–10, spring-flowering bulbs require artificial pre-chilling. Per Clemson HGIC, refrigerate tulips and hyacinths at 40–48°F in a paper bag (not the crisper drawer with fruit — ethylene from fruit damages bulbs) for 8–12 weeks before planting in December–January.
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