Wintersweets need a lot of sun and water to bloom. Make sure they have an abundance of both.

Add potassium.
Potassium is considered the big booster for plant blooms. Potassium regulates water levels within the flower plant, affecting the color and size of the flower. Potassium also acts as an overall plant strengthener. This nutrient, for fertilizers, is formed from a compound known as potash, taken from natural ore deposits.


Alkaline or acid soils make little difference but some Bloom Buster(TM) from Miracle Grow ( potassium) in the watering can may help.
The Wintersweet will naturally grow to a small tree as that is their normal pattern habit. Just keep trimming them to shrub size.

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