Petunia Plant Care: How to Grow, Feed & Maintain Healthy, Long-Flowering Petunias

Petunias are among the most rewarding flowering plants, offering a cascade of colour through spring and summer. Whether grown in garden beds, hanging baskets, or pots, success comes down to sunlight, drainage, and steady feeding. With the right fertiliser routine, petunias can stay in bloom for months with lush, vibrant foliage.

Sunlight & Temperature

Petunias thrive in 6–8 hours of direct sunlight daily. In partial shade, they stretch and produce fewer blooms. While they tolerate warm days, they dislike excessive humidity or cold winds. Indoor or shaded petunias do well near bright windows or balconies with filtered light.

Soil & Potting Mix

Choose a light, well-draining soil rich in organic matter. Petunias are shallow-rooted and rely on consistent aeration. In containers, use a premium flowering plant mix and ensure pots have large drainage holes. For indoor or balcony pots, mix perlite or coarse sand to improve drainage and reduce sogginess.

Watering Routine

Petunias prefer even moisture but can’t tolerate standing water. Water when the top 3 cm of soil feels dry and let excess drain freely. Hanging baskets and balcony pots may need daily watering in warm weather, while garden beds can be watered twice a week. Always water at the base to prevent fungal leaf issues.

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Feeding for Strong Growth and Continuous Colour

Petunias are heavy feeders that quickly deplete nutrients—especially in pots. Regular fertilising is the key to keeping foliage full and blooms abundant. The best feeding schedule combines a balanced outdoor fertiliser with a gentle indoor option depending on where your petunias grow.

🌿 Outdoor & Container Petunias

Feed fortnightly with CompleteGrow All Purpose 20-20-20 Liquid Fertiliser. This balanced NPK blend delivers:

20% Nitrogen (N): Promotes lush, green leaves and vigorous stem growth.
20% Phosphorus (P): Strengthens root systems and boosts nutrient uptake.
20% Potassium (K): Drives flower production, colour intensity, and stress resistance.
Micronutrients: Iron, zinc, and magnesium enhance chlorophyll formation and colour vibrancy.

Mix 5 mL per litre of water and apply every two weeks. For hanging baskets or planter boxes that drain quickly, feed weekly at half strength.

🌱 Indoor or Balcony Petunias

For shaded patios, verandas, or indoor containers, use CompleteGrow Indoor Plant Food Concentrate. Its lower nitrogen strength supports gentle, controlled growth without excessive foliage stretch—ideal for decorative pots or smaller spaces. Apply every 3–4 weeks at the recommended dilution for compact, healthy plants that continue blooming even in filtered light.

Deadheading & Light Pruning

Regularly remove spent blooms to encourage new flowers. Every few weeks, trim back leggy stems by one-third to trigger fresh branching. Keep tools clean between cuts to prevent fungal spread. A light pruning after the main flush in mid-summer can spark a second flowering wave.

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Common Petunia Problems & Quick Fixes

Yellow Leaves: Often due to nutrient deficiency or poor drainage—feed with 20-20-20 and check soil aeration.
Leggy Growth: Not enough sun or excessive nitrogen. Move to full light and prune lightly.
No Blooms: Irregular feeding or high heat. Apply potassium-rich 20-20-20 or Indoor Plant Food every fortnight.
Root Rot: From overwatering—repot into fresh mix and water less frequently.

Frequently Asked Questions

How often should I fertilise petunias?
Outdoor plants: every two weeks with 20-20-20. Indoor or shaded plants: every 3–4 weeks with Indoor Plant Food.

Why are my petunias turning pale or yellow?
A sign of iron or magnesium deficiency. Use a balanced fertiliser containing micronutrients such as CompleteGrow 20-20-20 to restore green colour.

Can I grow petunias indoors?
Yes—place them in bright light and feed with CompleteGrow Indoor Plant Food to prevent leggy, weak growth.

How do I keep petunias flowering longer?
Maintain full sun, consistent watering, and regular feeding. Deadhead spent blooms weekly for continuous colour.

Final Recommendation

For lush, long-lasting blooms, combine sunlight, airflow, and regular feeding. Outdoor growers should feed fortnightly with CompleteGrow All Purpose 20-20-20 Liquid Fertiliser to fuel vigorous flowering. For indoor or balcony setups, use CompleteGrow Indoor Plant Food Concentrate for gentle, sustained nutrition that prevents stretch and keeps petunias compact, healthy, and colourful year-round.