Getting it to bloom

Why won't my Sea Knotgrass bloom? (and how to make it flower)

Also called Sea Knotgrass, Coast Knotgrass, Sea Knotweed (Polygonum maritimum).

More about sea knotgrass

About Sea Knotgrass

Polygonum maritimum · also called Sea Knotgrass, Coast Knotgrass · flowering

Polygonum maritimum is a woody-based perennial herb in the Polygonaceae family, native to the sandy and shingle beaches of the Mediterranean, Atlantic Europe, and Black Sea coasts, with rare populations on a few south-west English beaches. It forms sprawling, grey-green mats of small elliptic leaves with distinctive silvery ochrea (papery sheaths at each leaf node) and produces tiny pinkish-white flowers from June to October. Its key requirement is non-compacted, freely draining coastal sand or fine shingle; it is a specialist of very open, disturbed beach environments. This species is not listed by the ASPCA and is classified mildly-toxic as a precaution.

Plant type: flowering

The reasons sea knotgrass isn't blooming

Almost every non-blooming sea knotgrass 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 sea knotgrass 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 sea knotgrass to flower

Maximise sun. Give sea knotgrass 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 sea knotgrass and get the feeding right with the sea knotgrass 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

Sea Knotgrass 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 sea knotgrass care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Sea Knotgrass blooming — frequently asked questions

Why won't my sea knotgrass flower?

Sea Knotgrass 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 sea knotgrass bloom?

Give sea knotgrass 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 sea knotgrass normally bloom?