Gloxinia Care: How to Grow, Propagate, and Cultivate Tubers Indoors

Gloxinia is a greenhouse tuberous plant and one of the finest representatives of the Gesneriaceae family. Known botanically as Sinningia speciosa and often called florist's gloxinia, it produces velvety green leaves and large, rounded, bell-shaped flowers — single or double — in white, pink, red and deep blue, frequently edged with a contrasting white border. A well-grown plant can carry 50 to 100 open blooms at once.

Gloxinia: a general plant overview

Gloxinia (Sinningia speciosa) is a compact tuberous perennial grown indoors and in greenhouses for its showy, trumpet-shaped flowers and soft, downy foliage. It originates from the tropical regions of the Americas and belongs to the Gesneriad family, the same group that includes the African Violet. Many cultivated varieties exist, ranging from solid colours to bicolours with picotee edging.

Origin and botanical characteristics

The florist's gloxinia traces its native habitat to Brazil, where wild Sinningia species grow on shaded rocky slopes and forest floors. The plant was named after Wilhelm Sinning, a gardener at the University of Bonn in Germany, who developed many of the early hybrids; the older common name "gloxinia" honours P.B. Gloxin, an early botanist. Most modern garden plants are forms of Sinningia speciosa or the hybrid group Sinningia x hybrida, with Sinningia maxima among the related wild species. The plant grows from a tuber (technically functioning much like a corm), produces a rosette of oval, velvety leaves, and reaches 25–30 cm in height.

Cultivars and varieties of gloxinia

Gloxinia cultivars are grouped mainly by flower form, colour and whether the blooms are single or double. Popular seed strains include the Empress Mix, the Double Brocade Mix and selections sometimes sold under names such as Kaiser Wilhelm. When choosing a variety, gardeners consider:

• Flower form — single bell-shaped blooms or fully double, ruffled types.
• Colour — pure white, pink, red, violet and deep blue, often with a white picotee margin.
• Plant habit — compact rosettes suited to windowsills versus larger display plants.
• Flowering season — strains bred for early bloom versus those timed for summer display.

Methods of propagating gloxinia

Gloxinia is propagated by seed, by careful division of the tuber, by small tubercles, and by green stem or leaf cuttings. Each method suits a different goal: seed for large numbers and healthier plants, division and cuttings for reproducing a favourite named variety true to type.

Propagation by seed

Seed is sown in spring into trays filled with a peat-and-sand mixture (2:1), scattered very thinly on the surface, covered with glass and lightly shaded. The seed is extremely fine and must not be buried. Germination follows in 2–3 weeks. Seedlings are pricked out into trays of the same mix at a spacing of 2×3 or 3×3 cm and fed regularly with weak solutions of complete fertilizer. Plants raised from seed generally grow more vigorously, flower more profusely and resist disease better than those grown from old tubers.

Dividing the tuber

Tuber division reproduces an established plant when the tuber has grown large and developed several growth buds. The dormant or just-sprouting tuber is cut into sections with a clean, sharp knife so that each piece carries at least one healthy shoot or eye. Dusting the cut surfaces with a fungicide such as Captan and letting them dry briefly reduces the risk of rot from Pythium and Phytophthora before each division is potted up.

Propagation by tubercles

Small tubercles formed by seedlings or leaf cuttings are stored over winter and used for early flowering the following season. They are kept in a dry room at 10–15 °C in dry sand. From January they are started into growth in a propagation tray at about 25 °C with adequate humidity; after 3–4 weeks the young plants are potted individually, held first at 18–22 °C and, after rooting, at 15–18 °C.

Green and leaf cuttings

Leaf and stem cuttings let you multiply a chosen cultivar without losing its characteristics. A healthy leaf with a short length of stalk, or a young shoot, is inserted into a moist peat-and-sand mix and kept warm and humid. New tubercles form at the base of the cutting, much as with related gesneriads such as Streptocarpus and Achimenes, and these in turn produce flowering plants the next season.

Growing gloxinia step by step

Growing gloxinia successfully comes down to a free-draining acidic mix, steady warmth, even soil moisture without wetting the leaves, bright but filtered light, and regular feeding through the growing season. The stages below follow the plant from potting through to a flowering specimen by midsummer.

Preparing the potting mix and choosing a pot

Established plants are moved into 9–11 cm pots filled with a blend of peat, leaf mould and sand in a ratio of 4:2:1, which holds moisture yet drains freely. Gloxinia prefers a slightly acidic medium, roughly pH 5.5–6.5. Choose a pot only slightly wider than the tuber, since an oversized container holds excess wet soil around the roots. Sterilising or using fresh, clean medium reduces soil-borne fungal problems. A slow-release feed such as Osmocote 14-14-14 can be incorporated at potting for steady nutrition.

Pricking out and transplanting seedlings

Seedlings are pricked out into trays of peat-and-sand mix once large enough to handle, spaced 2×3 or 3×3 cm, and fed with dilute complete fertilizer. As they fill the space they are transplanted into 9–11 cm pots and placed in a lightly shaded greenhouse, watered well and fed regularly. Tubers carried over from the previous year give plants ready in June, while seed-raised plants come into production in August.

Watering and the bottom-watering technique

Water gloxinia evenly so the medium stays moist but never waterlogged, and keep water off the velvety leaves and crown, where droplets cause spotting and rot. Soft water — rainwater or river water — is best. Bottom watering suits gloxinia particularly well: stand the pot in a tray of tepid water for 15–30 minutes, let the mix draw moisture up from below, then drain off any surplus. This keeps the foliage dry and delivers moisture directly to the roots.

Feeding and fertilizing

Gloxinia is a hungry plant and rewards frequent, light feeding through active growth and flowering. Feed regularly with liquid fertilizer at a weak concentration, leaning toward higher phosphorus and potassium as flower buds form to support abundant bloom. Frequent repotting combined with generous feeding can noticeably extend the flowering period. Stop feeding as the plant begins to die back in autumn.

Light and temperature

Flowering gloxinias love a well-lit position but dislike scorching direct sun and draughts, so an east- or west-facing window with filtered light is ideal. As plants approach flowering they need progressively more light, yet they must be shaded from the harsh midday sun to prevent leaf burn. Warm, even temperatures suit them: around 20–22 °C while starting tubers into growth, easing to 18–22 °C for young plants and 15–18 °C after rooting. Keep the air humid to discourage Thrips and mites.

Care during flowering

During flowering, gloxinia needs bright filtered light, steady warmth, humid air and consistent feeding to keep producing its large bell-shaped blooms. Remove spent flowers promptly so the plant directs energy into fresh buds rather than seed set, unless you intend to collect seed.

How to prolong the flowering period

The flowering period is extended by repotting often, feeding generously, and protecting plants from midday sun. By July, plants raised this way are in full, healthy bloom. Pinching off the very first buds early in the season encourages a fuller plant that later flowers more heavily, and disbudding — removing some buds — can produce larger, better-presented individual blooms for display.

Dormancy and overwintering the tubers

Gloxinia enters a natural rest period after flowering, when the top growth dies back and the tuber must be kept cool and dry until spring. Managing this dormancy correctly is what allows the same tuber to flower year after year.

Care after flowering

When gloxinias finish flowering in late autumn, watering is gradually reduced and the plants dry off. The tubers that have formed are then lifted, or the pots holding old tubers are laid on their side and stored in a dry room until March.

Storing tubers over winter

The tubers are overwintered in dry peat packed into boxes, kept in a cool, dry place. This keeps them firm and dormant without rotting or sprouting prematurely. Check stored tubers occasionally and discard any that turn soft or show mould.

Waking the tubers in spring

In early March the tubers are cleaned of old roots and planted shallowly and closely together in boxes of peat-and-sand mix (2:1), then placed in a warm greenhouse at 20–22 °C. When the young shoots reach about 5 cm, each tuber is potted up with its root ball into individual pots, exactly as for seedlings.

Diseases and pests of gloxinia

The most common threats to gloxinia are fungal rots in cold, wet conditions and sap-sucking pests such as thrips and mites in warm, dry air. Prevention through clean medium, careful watering and humidity control is far more effective than treating an established outbreak.

Preventing fungal disease

Fungal problems — leaf rot, crown rot and the root rots caused by Pythium and Phytophthora — are best prevented by using sterile, free-draining medium, watering from below to keep foliage dry, and avoiding waterlogging. Spacing plants for airflow lowers humidity around the leaves, and a protective fungicide such as Captan can be used on cut surfaces during division or as a preventive treatment when conditions favour disease.

Controlling thrips and other pests

Keeping the air humid is the simplest way to discourage thrips, which thrive in dry conditions, while regular liquid feeding keeps plants vigorous and more resistant. Watch also for sap-sucking mites:

• Thrips — cause silvery streaking and distorted buds; raise humidity and remove affected flowers.
• Cyclamen mites — produce stunted, deformed new growth at the crown.
• Red spider mites — appear in hot, dry air, causing fine stippling and webbing on leaves.

Isolate affected plants, improve humidity, and treat with an appropriate miticide or insecticide where infestation is confirmed.

Common growing problems and their solutions

Most gloxinia problems trace back to watering, light or temperature, and they resolve once the cause is corrected. Use the points below to diagnose and fix the usual cultural issues:

• Leaf rot or spotting — caused by water sitting on the foliage; switch to bottom watering and keep the crown dry.
• Light burn — pale, scorched patches from direct midday sun; move to filtered light or shade at noon.
• Few or no flowers — usually too little light or under-feeding; increase brightness and feed regularly.
• Soft, collapsing tuber — root rot from overwatering or cold, wet soil; improve drainage and reduce watering.
• Leggy, weak growth — insufficient light; move closer to a bright window or add supplemental lighting.

Gloxinia as a houseplant in summer

In summer, gloxinia is best grown indoors as a houseplant, where it enjoys bright, filtered light at a window away from harsh sun and draughts. It is not suited to open-garden planting in cool climates, since it needs warmth, shelter and protection from heavy rain on its velvety leaves. A bright windowsill, a warm room and the watering and feeding routine described above keep it flowering through the warm months.

Comparing gloxinia with the African Violet

Gloxinia and the African Violet both belong to the Gesneriaceae family but differ in habit, size and life cycle. The table below sets out the practical differences for indoor growers:

Both share a preference for warmth, soft water, even moisture without wetting the crown, and bright filtered light, so the care skills learned on one transfer readily to the other. For more practical horticulture guides, see our Agriculture section.

Give gloxinia your time and patience, and these splendid plants will reward you with their unusual, exotic beauty.