How to Grow Petunia
Petunia At a Glance
Difficulty
Easy
Category
Flower
Sun Exposure
Full Sun
Frost Tolerance
Frost Tender
Cold Hardiness
Survives to 2°C
Plant Family
Solanaceae
Growing Season
Warm Season
Plant Lifecycle
Annual
How to Start It
★ Recommended for beginners
Young petunias from a garden centre are the easiest start and give you flowers right away. Plant them out about 1 week after your last frost, 25 cm apart in beds, or a little closer in pots and baskets.
Petunias flower nonstop from late spring until frost, which makes them one of the best flowers for pots, window boxes and hanging baskets. Trailing types spill over the edges of baskets, while mounding types fill beds.
When To Start
Petunia needs warmth. Wait until your last frost has passed and the soil has warmed before sowing.
We do not have exact sowing dates for this one yet.
When should you plant Petunia?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your Petunia Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
Your Petunia Calendar
Set your location to turn these into exact dates and reminders.
Optional: start petunia seeds indoors on the surface, they need light
10 weeks before your last frost· every year· optional
Plant petunias out in full sun now that frost is past
1 week after your last frost· every year
Cut long, straggly petunias back by half and feed them
60 days after your last frost· every year· optional
Did you water your petunia seedlings today? Keep the top of the soil damp until they are up and growing.
About 1 days after you plant it
Your petunias are settling in! Water when the top of the soil dries, and pinch the tips to make the plants bushier.
About 30 days after you plant it
Look at your petunias go! Pinch off faded flowers and feed them every couple of weeks to keep the colour coming.
About 90 days after you plant it
The Journey Ahead
Petunia's Lifecycle
Seedling
Mature Plant
Seed Production
Step 1
Prepare Your Space
25 cm
Plant Spacing
30 cm
Row Spacing
Vertical Growing
No.
Succession Planting
No.
Good Companions
Bad Companions
Step 2
Planting & Sprouting
Expect sprouts in 7–14 days
Growing Tips
- 1Give petunias full sun, at least 6 hours a day, for the most flowers.
- 2Plant them in rich soil or potting mix with plenty of compost mixed in.
- 3Water when the top 2 to 3 cm of soil are dry, at the base rather than over the flowers, and check pots daily in hot weather.
- 4Feed every 1 to 2 weeks with compost tea or worm castings, especially in pots and baskets, where the food washes out fast.
- 5If plants get long and bare in midsummer, cut them back by about half, and they come back bushier within a couple of weeks.
- 6Wash aphids off with a spray of water, and pick off any green caterpillars hiding in the flower buds.
Seedling Phase
Step 3
Growth & Maturity
30 cm
Mature Height
40 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
When to Pick
Blooms late spring to frost; feed and trim for a non-stop display
How to Harvest
- 1Pinch off faded flowers, including the little green seed pod behind each one, to keep new flowers coming.
- 2Many newer spreading types drop their old flowers on their own and need little of this care.
- 3Trim back long, straggly stems whenever the plant starts to look tired.
- 4Feed and water well after each trim to help the plant bounce back.
- 5Pull the plants out after the first hard frost in fall, since they do not survive winter outdoors.
Step 5
Saving Seeds
How to Save Seeds
Most petunias sold today are hybrid F1 types, so their seeds will not grow true, and many give plants with different colours or fewer flowers. If you want to try, leave a few faded flowers on a plant until the small pods behind them turn brown and dry. Snip them into a paper bag and gently crush them to free the tiny seeds. Store them labelled somewhere cool, dark and dry, where they keep about 2 to 3 years.
Seed Production
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