When to Plant Petunia 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, November 6, 2025

Transplant Outdoors

Thursday, January 29, 2026

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

Pro tip: Start Petunia seeds indoors 10 weeks before your last frost date, then transplant outdoors around Thursday, January 29, 2026.

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🌿 Plant Details

Scientific Name Petunia × hybrida

Days to Maturity 75 days

Mature Height 6-18"

Spread 18"

Type Annual

☀️ Growing Requirements

☀️

Sun

Full Sun (6-8 hours)

💧

Water

Moderate (1 inch/week)

↔️

Spacing

12" apart

🌱

Planting Depth

0.13" deep

Seeds typically germinate in 7-14 days

Ready to Plant Petunia in Saint Petersburg?

Get your seeds now so they're ready by Thursday, November 6, 2025.

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🤝 Good Companions

TomatoBasilMarigold

⚠️ Avoid Planting Near

Fennel

🤝

Full Companion Planting Guide for Petunia

See which plants help Petunia 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

* Affiliate links — we may earn a small commission at no extra cost to you.

🌾 Seed Saving Guide

🟡 Moderate

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

When to Harvest Seed

Allow seed pods to form after flowers fade. Harvest when the small pod turns tan and begins to split.

Processing

Collect tiny seeds in a bowl when pod splits, dry 1 week before storing.

Seed Viability

Up to 3 years when stored cool, dark, and dry.

Pro Tip

Most petunias are F1 hybrids — seedlings will not match the parent. Look for OP/heirloom varieties for reliable seed.

🪴

Raised Bed Planting Guides

A 4×8 bed fits 32 plants of Petunia. See plant counts, spacing grids, and companion pairings for every bed size →

Frequently Asked Questions

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

In Saint Petersburg (Zone 10b), start Petunia seeds indoors around Thursday, November 6, 2025 and transplant outdoors around Thursday, January 29, 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 Petunia take to grow? +

Petunia typically matures in about 75 days from transplanting. In Saint Petersburg, that means you can expect harvest around Thursday, January 29, 2026 plus 75 days.

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

Petunia should be started indoors 10 weeks before your last frost date. In Saint Petersburg, that means starting around Thursday, November 6, 2025.

📚 More Petunia Planting Guides

🗺️

Petunia in Florida

Zone-by-zone breakdown · Full state guide

→ 🌡️

Zone 10b Petunia Guide

All cities in your zone · Avg dates

→

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Growing Petunia in Zone 10b

Petunia (Petunia × hybrida) is a popular garden vegetable. In Saint Petersburg, Florida, which is in USDA Hardiness Zone 10b, you should start seeds indoors around Thursday, November 6, 2025.

Your average last frost date is Thursday, January 15, 2026. Plan to transplant your Petunia seedlings outdoors around Thursday, January 29, 2026, about 2 weeks after your last frost date.