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Fertilising guide

How to fertilise Begonia 'Looking Glass' (Begonia rex-cultorum 'Looking Glass')— schedule & NPK

Also called looking glass begonia, silver rex begonia.

More about begonia 'looking glass'

About Begonia 'Looking Glass'

Begonia rex-cultorum 'Looking Glass' · also called looking glass begonia, silver rex begonia · houseplant

Begonia 'Looking Glass' is a rex-cultorum hybrid grown for its dramatic foliage: large, asymmetric leaves washed in metallic silver with olive-green veins and deep red undersides. A rhizomatous houseplant, it demands bright indirect light and steady humidity but resents soggy roots. Flowers are insignificant; the shimmering leaves are the entire point of growing it.

Growth habit: Rhizomatous foliage houseplant with a low, spreading habit; creeping surface rhizomes produce a mound of large, painted leaves. Often goes semi-dormant in winter, dropping leaves before reflushing.

What fertiliser begonia 'looking glass' actually wants — and why

Begonia 'Looking Glass' is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for begonia 'looking glass': match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed begonia 'looking glass', and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For begonia 'looking glass':

Feed every 2-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rex begonias are light feeders, so avoid overfeeding; stop in winter. Treat that as every 2-4 weeks between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

The dormant-season rule matters more than the exact interval: skip feeding entirely when begonia 'looking glass' is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for begonia 'looking glass'

Half strength is the safe default for begonia 'looking glass' — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

Feeding always goes onto already-damp soil, never dry roots — water begonia 'looking glass' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the begonia 'looking glass' watering schedule.

Signs you are over-feeding begonia 'looking glass'

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for begonia 'looking glass':

Signs you are under-feeding begonia 'looking glass'

If the symptoms point at watering, light or roots rather than nutrition, the full begonia 'looking glass' care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush the pot of begonia 'looking glass' with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

Organic vs synthetic feeds for begonia 'looking glass'

Organic options

A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.

Synthetic / liquid feeds

A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising begonia 'looking glass' — frequently asked questions

What fertiliser does begonia 'looking glass' need?

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Begonia 'Looking Glass' is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

How often should I feed begonia 'looking glass'?

Feed every 2-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rex begonias are light feeders, so avoid overfeeding; stop in winter. Feed every 2-4 weeks in spring and summer with a balanced liquid fertiliser at half strength. Rex begonias are light feeders, so avoid overfeeding; stop in winter. Treat that as every 2-4 weeks between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

What strength of feed for begonia 'looking glass'?

Half strength is the safe default for begonia 'looking glass' — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

What does over-feeding begonia 'looking glass' look like?

Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding begonia 'looking glass' year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.

Should I flush the soil of begonia 'looking glass'?

Flush the pot of begonia 'looking glass' with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

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