Getting it to bloom
Why won't my Slim-leaved Biarum bloom? (and how to make it flower)
Also called Slim-leaved biarum, Slender-leaved biarum, Narrow-leaved biarum (Biarum tenuifolium).
More about slim-leaved biarum
About Slim-leaved Biarum
Biarum tenuifolium · also called Slim-leaved biarum, Slender-leaved biarum · flowering
Biarum tenuifolium is a tuberous aroid native to rocky scrubland and open hillsides across the eastern Mediterranean, from Greece and Turkey to Cyprus. It produces a small, pungent, dark spathe in late summer or autumn — before the narrow, slightly wavy leaves emerge in winter — making it a curiosity for a warm, sheltered rock garden or alpine house. The key care requirement is a dry summer dormancy in well-drained, alkaline soil; any summer moisture will rot the tuber. All parts contain insoluble calcium oxalate crystals and are toxic to pets and humans.
Plant type: flowering
Watch for — Failure to flower: Usually a result of insufficient summer heat and drought; in cool or damp UK summers, growing in a clay pot in an alpine house and baking the pot dry on a south-facing bench greatly improves flower production.
The reasons slim-leaved biarum isn't blooming
Almost every non-blooming slim-leaved biarum traces back to one of these, roughly in order of how common they are:
- Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
- Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
- The plant has not been deadheaded, so it stops flowering once it sets seed.
- Irregular watering — drought or waterlogging at the budding stage makes buds abort.
- It is still too young or was checked by a transplant and is rebuilding before flowering.
Feeding slim-leaved biarum a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.
The fix — how to get slim-leaved biarum to flower
- Maximise sun. Give slim-leaved biarum the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
- Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
- Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
- Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.
Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for slim-leaved biarum and get the feeding right with the slim-leaved biarum fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.
Bloom season and what to expect
Slim-leaved Biarum flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.
Post-bloom care so it flowers again
Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.
For everything else this plant needs day to day, see the full slim-leaved biarum care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.
Slim-leaved Biarum blooming — frequently asked questions
Why won't my slim-leaved biarum flower?
Slim-leaved Biarum blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
How do I make slim-leaved biarum bloom?
Give slim-leaved biarum the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
When does slim-leaved biarum normally bloom?
Slim-leaved Biarum flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.
What should I do with slim-leaved biarum after it flowers?
Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.
What is the single biggest mistake stopping slim-leaved biarum flowering?
Feeding slim-leaved biarum a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.
Keep reading
- Slim-leaved Biarum care — the full brief (light, water, humidity, problems, pet safety)
- Slim-leaved Biarum light needs — usually the first thing to fix for flowers
- Slim-leaved Biarum fertilising — the right feed for buds, not just leaves
- Should I water my plant? The simple check
- Why is my plant wilting? Wet vs dry
- Underwatered plant — signs and rehydration
- Why won't my peace lily bloom?
- Why won't my jade plant bloom?
- Why won't my tomato bloom?
- All 4114 bloom guides in the Growli library