Begonia plants, with their diverse foliage and vibrant blooms, are cherished additions to many indoor and outdoor gardens. The color blue holds a particular fascination for many gardeners, leading them to seek out plants displaying this elusive hue.
The Elusive True Blue Begonia
A genuine blue pigment is remarkably uncommon in nature, with less than 10% of flowering plants producing blue flowers. The blue color in many plants typically results from complex interactions involving anthocyanins, which are red pigments, modified by factors like pH levels, metal ions, or co-pigments. For instance, a single anthocyanin can appear red, purple, or blue depending on the acidity of its environment.
True blue pigments are almost nonexistent in the plant world. What often appears blue is a trick of light or a specific shade of violet or purple. This phenomenon, known as structural coloration, involves microscopic structures on the plant’s surface manipulating light to reflect blue wavelengths, rather than the plant synthesizing a blue pigment. To date, no true blue begonias that produce their color through a blue pigment have been identified.
Begonias with Blue Hues and Iridescence
While a begonia with true blue pigment remains elusive, some species exhibit stunning blue-ish tones or iridescence, particularly under specific lighting conditions. Begonia pavonina, often called the Peacock Begonia, is a notable example, displaying a shimmering metallic blue iridescence. This captivating appearance is an evolutionary adaptation, allowing the plant to thrive in the dim light of its native Malaysian rainforest understory.
The blue sheen of Begonia pavonina comes from specialized chloroplasts within its epidermal cells, known as iridoplasts. These iridoplasts contain precisely arranged stacks of thylakoids that function like photonic crystals. This unique structure causes blue wavelengths of light to be reflected, creating the iridescent effect that is most visible in low light or when light hits the leaves at a specific angle. This mechanism also enables the plant to slow down light, thereby increasing its photosynthetic efficiency in its perpetually dim habitat. Other begonias, such as Begonia ‘Old Blue’, feature leaves with a grey and silver base that carries a blue tinge. Begonia ‘Salsa’ also demonstrates this capacity for blue iridescence.
Caring for Begonias
For those cultivating begonias, understanding their care requirements is essential for healthy growth. Most begonias thrive in bright, indirect light, mimicking their natural habitat beneath a forest canopy. Direct sunlight, especially in hot climates, can scorch their delicate leaves and cause colors to fade. Indoor begonias benefit from a position near a window that receives filtered sunlight.
Consistent moisture is preferred by begonias, but they are susceptible to root rot if overwatered. Water thoroughly when the top inch of soil feels dry to the touch, ensuring the soil remains moist but never soggy. Watering at the base of the plant helps prevent fungal diseases on the foliage. A well-draining, rich potting mix is ideal, with slightly acidic or humusy soil providing optimal conditions. Potting mixes formulated for African violets can be a convenient choice.
Begonias are tropical plants that flourish in warm temperatures, typically between 60 to 75 degrees Fahrenheit (15-24°C). They also appreciate moderate to high humidity, ideally around 50% or higher. Protecting them from drafts and sudden temperature fluctuations is important for their well-being. During their active growing season, from spring through summer, begonias benefit from regular fertilization. A high-phosphorus fertilizer, such as a 15-30-15 or 5-10-5 NPK ratio, applied every two to four weeks, promotes robust growth and flowering. Diluting liquid fertilizers to half-strength is often recommended to prevent over-fertilization. Pruning is also beneficial for begonias, helping to maintain their shape, encourage bushier growth, and promote continuous blooming. Removing dead or diseased leaves and spent flowers is a key part of this maintenance.
Achieving a Blue Garden Aesthetic
For those captivated by the color blue in gardening, many other plant species offer genuine blue flowers or foliage, providing alternatives to begonias. To achieve a blue garden aesthetic, consider:
Flowering Plants
Delphiniums, known for their blue blooms. Hydrangeas can also produce beautiful blue flowers, with their hue often influenced by soil pH. Salvia varieties like Salvia azurea or S. patens offer true blue flowers, while others provide lovely violet-blue shades. Additional flowering plants include gentians, morning glories, borage, forget-me-nots, lupines, Lord Nelson Sweet Peas, baptisias, and Virginia bluebells.
Foliage Plants
Blue hostas, blue chalksticks (Senecio serpens), and certain echeverias, like ‘Imbricata’, feature attractive blue leaves. Other plants with blue foliage include agaves, yuccas, and sedums, some of which develop their blue color from a protective waxy coating.