Petunias are among the easiest and most colorful annuals for beds, borders, containers and hanging baskets. They bloom from late spring until frost when they get plenty of sun, steady water and regular feeding. The type you choose matters: upright petunias suit beds, while spreading wave types trail from baskets. This page covers the types, planting time, spacing, watering, feeding, deadheading and starting petunias from seed.
Petunia at a glance
| Type | Flower |
|---|---|
| Season | Warm-season |
| Sun | Full sun |
| Plant spacing | 12 in |
| Row spacing | 12 in |
| Per square foot | 1 |
| Seed depth | At surface |
| Days to maturity | Seedlings need 10–12 weeks indoors |
| How to start | Petunias are tender annuals. |
| Water | 1 in per week |
These are the same numbers our plant spacing, square foot and harvest date calculators use. See every crop in the plant database.
When to plant petunia
Petunias are tender annuals. Transplant them outdoors when the soil reaches about 60°F (16°C) and the danger of frost has passed, as University of Minnesota Extension advises. Starting from seed indoors takes patience: sow around ten to twelve weeks before you plan to plant out. Check your last spring frost with the frost dates by ZIP code tool and plan dates with the planting calendar.
How to plant petunia
- Choose the right type. Grandiflora has the largest flowers (3 to 4 inches or more) on plants 12 to 15 inches tall. Multiflora is more compact with many smaller blooms. Milliflora is miniature, with 1 to 1.5 inch flowers for edging. Spreading wave types are about 6 inches tall and trail 2 to 3 feet or more.
- Give at least 5 to 6 hours of sun. Full sun all day gives the most flowers.
- Prepare the soil. It does not need to be rich, but it must drain decently. Work 2 to 3 inches of organic matter into the top 8 to 10 inches.
- Space by type. Grandiflora and multiflora about 12 inches apart, milliflora 4 to 6 inches, and spreading types at least 18 inches. Use the plant spacing calculator.
- Pot them up closely. In containers, plant more closely for a full look.
Caring for petunia
Water thoroughly about once a week, soaking 6 to 8 inches deep. Spreading types, hanging baskets and containers need more water, sometimes daily in hot weather. Use the garden watering calculator for beds.
Feed regularly. In beds, mix a balanced fertilizer into the soil at planting, then give liquid feed every three weeks from early to mid-summer. In containers, use timed-release fertilizer at planting and liquid feed every two weeks. Spreading types need feeding weekly.
Deadhead by removing faded flowers along with the seed-forming part just below them. This prolongs blooming, and is essential in containers. Pinch grandiflora and multiflora back when about 6 inches tall to encourage side shoots, but do not pinch milliflora or spreading types.
Companion plants
| Grow nearby | Marigolds, alyssum, lobelia, geraniums and ornamental grasses |
|---|---|
| Keep apart | Shade-lovers like hostas and ferns, which need very different light and moisture |
Petunias combine well with other sun-loving annuals that share their need for steady water and feeding, and with trailing plants in mixed containers. Check other pairings with the companion plant finder.
Common problems
| Problem | What you see | What to do |
|---|---|---|
| Leggy, few flowers | Long stems with sparse blooms in midsummer | Usually too little sun, missed deadheading or too little feeding. Move to full sun, deadhead and feed on schedule. |
| Yellow leaves | Lower leaves turning yellow | Often overwatering or poor drainage, though low nutrients can also cause it. Use the yellow leaf identifier and the overwatering checker. |
| Wilting in heat | Droopy plants and baskets that dry out fast | Containers and baskets can need water daily. Soak deeply and check the soil rather than the leaves. |
| Aphids and other sap-suckers | Sticky leaves, curled new growth | Rinse with a strong spray of water, then use insecticidal soap if needed. See the pest identifier. |
Not sure what you are looking at? The plant problem identifier ranks likely causes from the symptoms you see.
When and how to harvest
Petunias are grown for color rather than harvest. Deadheading keeps them blooming until frost. Most garden petunias are treated as annuals, so remove them after frost or pot up cuttings to overwinter indoors.
To start from seed, sow indoors about 10 to 12 weeks before planting out. Press seed onto the surface of the mix without covering it, because it needs light to germinate.
Plan your petunia
- Plant spacing calculator: how many plants fit your bed
- Planting calendar: sowing and transplant dates for your frost dates
- Frost dates by ZIP code: your last spring and first fall frost
- Harvest date calculator: when your crop will be ready
Frequently asked questions
How far apart should I plant petunias?
Space petunias 12 inches apart in rows 12 inches apart. In a square foot garden, plant 1 per square foot.
How deep do I plant petunia seeds?
Do not bury petunia seeds: press them onto the soil surface because they need light to germinate. Plant transplants at the depth of their pots.
How long do petunias take to grow?
Seedlings need about 10 to 12 weeks indoors before they are ready to plant out; flowers follow once they are established in the garden.
How much water do petunias need?
About 1 inch of water a week, from rain and watering combined. Water thoroughly about once a week, soaking 6 to 8 inches deep; containers, baskets and spreading types need much more.
How far apart should I plant petunias?
Plant grandiflora and multiflora about 12 inches apart, milliflora 4 to 6 inches apart, and spreading wave types at least 18 inches apart. Containers can be planted more closely.
Why are my petunias not flowering?
The usual causes are too little sun (they need at least 5 to 6 hours), too little feeding and not removing faded flowers. Fix these and pinch back leggy stems.
Should I pinch petunias?
Pinch grandiflora and multiflora back at about 6 inches tall to get side shoots. Do not pinch milliflora or spreading types.