The Best Summer Flowers for a Greenhouse: A Guide to Vibrant Blooms

Greenhouses offer the perfect environment to cultivate stunning flowers, especially during the summer months. With controlled temperatures, humidity, and protection from pests, a greenhouse allows gardeners to extend the growing season and nurture plants that might struggle outdoors. If you’re wondering which summer flowers thrive best in a greenhouse, this guide will introduce you to some of the most beautiful and rewarding blooms to grow. Here, we explore fifteen exceptional summer flowers, along with the best ways to cultivate them for maximum health and vibrancy.

1. Petunias (Petunia spp.)

Petunias are a classic choice for greenhouse cultivation due to their striking colours and long-lasting blooms. They come in various shades, including pink, purple, red, white, and yellow, making them a perfect addition to any greenhouse display.

Growing Tips:

• Petunias thrive in well-draining soil with moderate moisture.
• They prefer full sunlight, so ensure they receive at least 6 hours of light daily.
• Regular deadheading (removing spent blooms) encourages continuous flowering throughout summer.
• Feed with a balanced liquid fertilizer every two weeks for optimal growth.

2. Geraniums (Pelargonium spp.)

Geraniums are another greenhouse favourite, known for their vibrant flowers and attractive foliage. These hardy plants can flourish in pots or hanging baskets, making them versatile for any greenhouse setup.

Growing Tips:

• Use a well-draining potting mix and water when the top inch of soil feels dry.
• Position them in a location with plenty of light, ideally 6-8 hours of sunlight per day.
• Pinch off dead flowers to encourage new blooms.
• Geraniums benefit from a slow-release fertilizer to support healthy growth.

3. Begonias (Begonia spp.)

Begonias are prized for their lush, colourful flowers and ability to thrive in partial shade, making them ideal for greenhouse conditions. They are particularly popular in hanging baskets and containers.

Growing Tips:

• Plant begonias in a well-draining, peat-based potting mix.
• Keep humidity levels moderate but avoid excessive watering, as begonias are prone to root rot.
• Indirect sunlight or dappled shade works best to prevent leaf scorching.
• Regularly remove wilted flowers to keep plants healthy and blooming.

4. Fuchsias (Fuchsia spp.)

Fuchsias are a stunning addition to any greenhouse, with their pendulous flowers that attract pollinators such as bees and butterflies. They come in an array of colours, including pink, red, purple, and white.

Growing Tips:

• Fuchsias prefer rich, well-drained soil with a slightly acidic pH.
• Maintain a consistent watering schedule, ensuring the soil remains moist but not soggy.
• Position in partial shade to prevent leaf burn.
• Feed with a high-potassium fertilizer every two weeks to promote abundant flowering.

5. Orchids (Orchidaceae family)

Orchids are an exotic and elegant choice for greenhouse cultivation, thriving in the controlled environment that prevents temperature fluctuations. While they require a bit more care, their stunning blooms make the effort worthwhile.

Growing Tips:

• Use an orchid-specific potting mix, such as one made of bark, sphagnum moss, or perlite.
• Maintain high humidity levels, ideally between 50-70%.
• Provide indirect light, as direct sun can scorch their delicate petals.
• Water sparingly but consistently, allowing roots to dry out between waterings.

6. Lantanas (Lantana camara)

Lantanas are excellent greenhouse plants known for their vibrant clusters of flowers that bloom continuously throughout the summer. They are particularly attractive to butterflies and hummingbirds.

Growing Tips:

• Plant in well-draining soil with a slightly acidic to neutral pH.
• Position in full sun for at least 6-8 hours a day.
• Water moderately, allowing the soil to dry out slightly between watering sessions.
• Prune regularly to encourage bushy growth and prevent legginess.

7. Marigolds (Tagetes spp.)

Marigolds are a fantastic addition to any greenhouse, not only for their cheerful blooms but also for their natural ability to deter pests. These flowers range in colour from bright yellow to deep orange.

Growing Tips:

• Use well-drained soil with a neutral to slightly acidic pH.
• Water moderately, allowing the soil to dry between watering.
• Ensure full sun exposure to encourage prolific flowering.
• Deadhead spent flowers to extend the blooming period.

8. Zinnias (Zinnia elegans)

Zinnias are a great choice for greenhouse cultivation, offering a wide array of colours and long-lasting blooms. They are easy to grow and provide excellent cut flowers for arrangements.

Growing Tips:

• Use rich, well-drained soil with good air circulation.
• Ensure full sun exposure for at least 6 hours daily.
• Avoid overhead watering to reduce the risk of powdery mildew.
• Regular deadheading promotes continuous flowering throughout summer.

9. Sunflowers (Helianthus annuus)

Sunflowers may not be the first choice for greenhouse growing, but dwarf varieties thrive well in controlled conditions. Their bright, cheerful blooms add height and interest to any greenhouse.

Growing Tips:

• Plant in deep, well-drained soil with plenty of organic matter.
• Provide full sun and maintain temperatures around 70-80°F.
• Water consistently, ensuring the soil stays moist but not waterlogged.
• Support taller varieties with stakes if needed.

10. Impatiens (Impatiens walleriana)

Impatiens are a greenhouse favourite, known for their ability to produce abundant, colourful flowers in shaded conditions. They work well in pots, hanging baskets, or bedding displays.

Growing Tips:

• Use a moisture-retentive, well-draining potting mix.
• Water regularly, keeping the soil evenly moist but not soggy.
• Provide filtered or indirect light to prevent leaf burn.
• Fertilize with a balanced liquid fertilizer every two weeks.

Additional Flowers and Their Growing Tips:

11. Dahlias (Dahlia spp.) – Grow in rich, well-draining soil with full sun exposure. Water deeply but infrequently and stake taller varieties for support.
12. Snapdragons (Antirrhinum majus) – Prefers well-drained, nutrient-rich soil. Keep in full sun to partial shade and deadhead spent blooms to encourage continuous flowering.
13. Cosmos (Cosmos bipinnatus) – Thrives in light, well-drained soil and full sun. Water sparingly and avoid over-fertilizing to prevent excessive foliage growth.
14. Lilies (Lilium spp.) – Plant in well-draining soil with good air circulation. Ensure they receive at least 6 hours of sunlight daily and keep the soil evenly moist.
15. Salvia (Salvia spp.) – Requires well-drained soil and full sun. Water moderately and trim back spent flowers to encourage new growth.

Conclusion

In this ‘Best Summer Flowers for a Greenhouse guide, we have seen that growing summer flowers in a greenhouse allows you to cultivate a vibrant, colourful display while protecting plants from unpredictable weather and pests. By selecting flowers that thrive in greenhouse conditions—such as petunias, geraniums, begonias, and orchids—you can enjoy continuous blooms throughout the season. Remember to tailor your care routine to each plant’s specific needs regarding sunlight, watering, and fertilization. With proper attention and maintenance, your greenhouse can become a floral paradise filled with radiant summer blossoms.