Getting it to bloom
Why won't my Melancholy Thistle bloom? (and how to make it flower)
Also called Melancholy Thistle, Melancholy Plume Thistle (Cirsium heterophyllum).
More about melancholy thistle
About Melancholy Thistle
Cirsium heterophyllum · also called Melancholy Thistle, Melancholy Plume Thistle · flowering
Melancholy thistle is a stately native British perennial of upland hay meadows, road verges, and open woodland in Scotland, northern England, and Wales, producing solitary nodding purple-pink flower heads 3–5 cm across on tall, woolly, unwinged stems from June to August. Unlike most thistles its leaves are not truly spiny — the margins are softly toothed with weak prickles — and the leaf undersides are distinctively white-felted. The most important care fact is that it prefers moist, moderately fertile neutral to slightly acidic soils and is not suited to dry chalk conditions. Cirsium heterophyllum is not listed on the ASPCA Toxic and Non-Toxic Plant database; it is classified as mildly-toxic here as a precaution.
Plant type: flowering
Watch for — Aphid colonies on flower stems: Dense colonies of thistle aphids (Aphis fabae and related species) can infest the woolly stems in summer; treat with insecticidal soap or encourage natural predators such as ladybirds and lacewings.
The reasons melancholy thistle isn't blooming
Almost every non-blooming melancholy thistle 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 melancholy thistle 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 melancholy thistle to flower
- Maximise sun. Give melancholy thistle 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 melancholy thistle and get the feeding right with the melancholy thistle 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
Melancholy Thistle 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 melancholy thistle care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.
Melancholy Thistle blooming — frequently asked questions
Why won't my melancholy thistle flower?
Melancholy Thistle 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 melancholy thistle bloom?
Give melancholy thistle 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 melancholy thistle normally bloom?
Melancholy Thistle 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 melancholy thistle 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 melancholy thistle flowering?
Feeding melancholy thistle a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.
Keep reading
- Melancholy Thistle care — the full brief (light, water, humidity, problems, pet safety)
- Melancholy Thistle light needs — usually the first thing to fix for flowers
- Melancholy Thistle 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