When to Plant Dahlia in Saint Petersburg, Florida (33708)

Location

Saint Petersburg, Florida

ZIP Code

33708

USDA Zone

10b

Last Frost

Thursday, January 15, 2026

📅 Your 2026 Planting Dates

Start Seeds Indoors

Thursday, December 4, 2025

Transplant Outdoors

Thursday, January 22, 2026

Based on last frost Thursday, January 15, 2026 · Zone 10b

Pro tip: Start Dahlia seeds indoors 6 weeks before your last frost date, then transplant outdoors around Thursday, January 22, 2026.

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🌿 Plant Details

Scientific Name Dahlia pinnata

Days to Maturity 90 days

Mature Height 18-60"

Spread 18"

☀️ Growing Requirements

☀️

Sun

Full Sun (6-8 hours)

💧

Water

Regular (1-2 inches/week)

↔️

Spacing

18" apart

🌱

Planting Depth

4" deep

Seeds typically germinate in 7-14 days

Ready to Plant Dahlia in Saint Petersburg?

Get your seeds now so they're ready by Thursday, December 4, 2025.

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🤝 Good Companions

MarigoldBasilCosmos

🤝

Full Companion Planting Guide for Dahlia

See which plants help Dahlia thrive, which to keep away, and raised bed layout tips →

🛠️ Supplies You'll Need

🌱 Seed Starting Trays 🪴 Seed Starting Mix 💡 Grow Lights 🌡️ Heat Mat 🌍 Flower Garden Soil ✂️ Pruning Shears 🚿 Watering Can

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🌾 Seed Saving Guide

🟡 Moderate

⚠️ Many varieties are F1 hybrid — look for OP/heirloom types

When to Harvest Seed

Allow seed pods (behind the flower) to dry on the plant in fall.

Processing

Remove dried seed pods, extract flat seeds, dry 1 week in an open envelope.

Seed Viability

Up to 2 years when stored cool, dark, and dry.

Pro Tip

Dahlia seeds do not grow true to the parent — each seedling is a unique hybrid. Propagate named varieties by tuber division.

🪴

Raised Bed Planting Guides

A 4×8 bed fits 14 plants of Dahlia. See plant counts, spacing grids, and companion pairings for every bed size →

Frequently Asked Questions

When should I plant Dahlia in Saint Petersburg, Florida? +

In Saint Petersburg (Zone 10b), start Dahlia seeds indoors around Thursday, December 4, 2025 and transplant outdoors around Thursday, January 22, 2026.

What is the last frost date for Saint Petersburg, Florida? +

The average last spring frost date for Saint Petersburg, Florida (ZIP 33708) is around Thursday, January 15, 2026. This is based on NOAA climate normals for USDA Zone 10b.

How long does Dahlia take to grow? +

Dahlia typically matures in about 90 days from transplanting. In Saint Petersburg, that means you can expect harvest around Thursday, January 22, 2026 plus 90 days.

Should I start Dahlia indoors or direct sow in Florida? +

Dahlia should be started indoors 6 weeks before your last frost date. In Saint Petersburg, that means starting around Thursday, December 4, 2025.

📚 More Dahlia Planting Guides

🗺️

Dahlia in Florida

Zone-by-zone breakdown · Full state guide

→ 🌡️

Zone 10b Dahlia Guide

All cities in your zone · Avg dates

→

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Growing Dahlia in Zone 10b

Dahlia (Dahlia pinnata) is a popular garden vegetable. In Saint Petersburg, Florida, which is in USDA Hardiness Zone 10b, you should start seeds indoors around Thursday, December 4, 2025.

Your average last frost date is Thursday, January 15, 2026. Plan to transplant your Dahlia seedlings outdoors around Thursday, January 22, 2026, about 1 weeks after your last frost date.