Getting it to bloom

Why won't my Reed Sweetgrass bloom? (and how to make it flower)

Also called Reed Sweetgrass, Great Water Grass, Reed Mannagrass (Glyceria maxima).

More about reed sweetgrass

About Reed Sweetgrass

Glyceria maxima · also called Reed Sweetgrass, Great Water Grass · flowering

Reed Sweetgrass is one of Britain's most vigorous native aquatic grasses, forming dense stands along rivers, canals, lakes, and drainage ditches where it can reach head height. Its broad, bright-green leaves and large, branching flower panicles are architecturally striking, and the variegated cultivar 'Variegata' is widely grown as a pond ornamental. It spreads aggressively by rhizomes and should always be contained in baskets. Wilted foliage can contain cyanogenic glucosides that are mildly toxic to livestock; treat as mildly-toxic around pets as a precaution.

Plant type: flowering

The reasons reed sweetgrass isn't blooming

Almost every non-blooming reed sweetgrass 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 reed sweetgrass 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 reed sweetgrass to flower

Maximise sun. Give reed sweetgrass 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 reed sweetgrass and get the feeding right with the reed sweetgrass 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

Reed Sweetgrass 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 reed sweetgrass care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Reed Sweetgrass blooming — frequently asked questions

Why won't my reed sweetgrass flower?

Reed Sweetgrass 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 reed sweetgrass bloom?

Give reed sweetgrass 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 reed sweetgrass normally bloom?