# When to Plant Flowers: Complete Calendar by Zone
Timing is everything. Plant too early and frost kills your investment. Plant too late and summer heat stresses transplants. This guide gives you exact windows by zone.
The Two Rules
Rule 1: Know your last frost date. This is the single most important date in gardening. Everything else is calculated from it.
| Zone | Avg Last Spring Frost | Avg First Fall Frost |
|---|---|---|
| 3 | May 15–30 | Sep 15–30 |
| 4 | May 1–15 | Oct 1–15 |
| 5 | Apr 15–30 | Oct 15–30 |
| 6 | Apr 1–15 | Oct 15–Nov 1 |
| 7 | Mar 15–Apr 1 | Nov 1–15 |
| 8 | Mar 1–15 | Nov 15–30 |
| 9 | Feb 15–Mar 1 | Dec 1–15 |
| 10 | Jan 31 or earlier | Dec 15 or later |
Rule 2: Soil temperature matters more than air temperature. Seeds and roots respond to soil temp, not what the thermometer on your porch reads. Buy a $10 soil thermometer.
Annual Flowers
Warm-Season Annuals (Need warm soil 60°F+)
Plant 1–2 weeks AFTER last frost
Marigold, zinnia, petunia, impatiens, begonia, vinca, celosia, cosmos, sunflower, lantana, calibrachoa.
| Zone | Plant Transplants | Direct Sow Seeds |
|---|---|---|
| 3–4 | Late May–early June | June |
| 5–6 | Mid-May | Late May |
| 7 | Late April | Early May |
| 8 | Early April | Mid-April |
| 9–10 | March | March |
Cool-Season Annuals (Prefer cool temps 40–65°F)
Plant 4–6 weeks BEFORE last frost
Pansy, viola, snapdragon, sweet pea, stock, larkspur, sweet alyssum, calendula, dianthus.
| Zone | Spring Planting | Fall Planting |
|---|---|---|
| 3–4 | April (short window) | Not practical |
| 5–6 | March–early April | September |
| 7 | February–March | October |
| 8–9 | January–February | October–November |
| 10 | November–February | October–December |
In Zones 8–10, cool-season annuals are your winter flowers. Plant them in fall and enjoy through spring.
Perennial Flowers
Spring Planting (Most Common)
Plant after soil is workable but before summer heat
Best for: Most perennials, ornamental grasses, groundcovers.
| Zone | Ideal Window |
|---|---|
| 3–4 | May–early June |
| 5–6 | April–May |
| 7 | March–April |
| 8–9 | February–March |
| 10 | January–February |
Fall Planting (Often Better)
Plant 6–8 weeks before first hard freeze
Why fall is often BETTER than spring:
- Soil is warm (roots establish immediately)
- Air is cool (less stress on foliage)
- Fall/winter rain provides natural irrigation
- Roots grow all winter (in mild zones)
- Plants emerge stronger the following spring
| Zone | Ideal Fall Window |
|---|---|
| 3–4 | August–September |
| 5–6 | September–October |
| 7 | October–November |
| 8–9 | November–December |
| 10 | December–January |
Best perennials for fall planting: Hosta, daylily, coneflower, black-eyed Susan, ornamental grasses, sedum, catmint, Russian sage, peonies.
Bulbs
Spring-Blooming Bulbs (Plant in Fall)
Tulips, daffodils, crocus, hyacinth, allium, grape hyacinth, snowdrops.
Rule: Plant when soil temperature drops below 55°F (usually 6–8 weeks before ground freezes).
| Zone | Plant Window |
|---|---|
| 3–4 | September–October |
| 5–6 | October–November |
| 7 | November–December |
| 8–9 | December–January (refrigerate tulips/hyacinths 6–8 weeks first) |
| 10 | Not practical for most spring bulbs (insufficient chill) |
Planting depth: 3× the height of the bulb. A 2" tall tulip bulb goes 6" deep.
Summer-Blooming Bulbs (Plant in Spring)
Dahlia, gladiolus, canna, lily, caladium, crocosmia, tuberous begonia.
Rule: Plant after last frost when soil is 60°F+.
| Zone | Plant Window |
|---|---|
| 3–4 | Late May–June |
| 5–6 | May |
| 7 | April |
| 8–9 | March–April |
| 10 | February–March |
Trees and Shrubs
Best time: Fall (after leaf drop) through early spring (before bud break).
Fall planting is preferred in Zones 6–10. Spring planting is safer in Zones 3–5 (gives roots a full season before harsh winter).
Container plants can technically be planted anytime the ground isn't frozen, but avoid planting in the heat of summer unless you can water daily.
Balled-and-burlapped (B&B) trees: Plant in spring or fall only. The root ball dries out quickly in summer heat.
Seed Starting Indoors
| Plant Type | Start Indoors Before Transplant Date |
|---|---|
| Tomatoes, peppers | 6–8 weeks |
| Marigolds, zinnias | 4–6 weeks |
| Petunias, snapdragons | 8–10 weeks |
| Perennial seeds | 8–12 weeks (many need cold stratification first) |
Hardening off: 7–10 days before transplanting, move seedlings outdoors for increasing hours each day. Day 1: 2 hours in shade. Day 7: all day in sun. Then transplant.
Your Yardcast design comes with a region-specific planting timeline so you know exactly when to install every plant in your plan.