The Spruce / Adrienne Legault
Sea hollyis a low-maintenance, long-lived flowering perennial.
Its dark green leaves produce taller flower stems with striking purple-blue flowers.
The flowers look like small glowing thistles and often bloom from midsummer until fall.
The Spruce / Adrienne Legault
This perennial grows best in dry to medium sandy soil in a location that boasts full sun.
It’s hardy down to -20 degrees.
Once established, sea holly only needs water when it’s dry, thanks to a long taproot.
The Spruce / Adrienne Legault
Sea holly is self-sowing but non-invasive since it can be easily removed.
Despite its name, sea holly is not a true holly.
Once planted, it will require little tending.
The Spruce / Adrienne Legault
Flowering usually starts in midsummer and will continue well into the fall.
It has a good tolerance for salty soil and does well in coastal gardens.
Soil that is too rich can make sea hollies sprawl.
Good drainage is a must, so amend compact soil with compost.
Sea holly is not particular about itssoil pHanything around the neutral range is sufficient (pH 6.17.8).
However, the plants need good drainage or will be susceptible to root rot and can die off.
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Fertilizer
Sea holly plants are not heavy feeders.
Too much fertilizer will make the plants sprawl.
Plant these where you have poor, moderately fertile soil in your garden.
All have similar metallic blue flowers, though the size of the blossoms varies somewhat.
Some common species include:
Pruning
Sea holly will bloom longer if you deadhead the spent flowers.
Prune the plants off near ground level at the end of the growing season with sharppruners.
Sow seeds in late summer or fall, and they’ll germinate in spring.
The seeds will do best ifstratified(chilled to stimulate the growth cycle) first.
you’ve got the option to start sea holly seeds indoors if you want a head start.
It does much better in dry, sandy, even barren soils.
Do not overwater potted plants; ensure they get as much direct sunlight as possible.
Overwintering
Provide protection against winter cold to allow the rosettes to overwinter successfully.
Otherwise, the plant will use all of its energy to make new foliage in the spring.
Lay evergreen branches over the plants or mulch with pine needles.
Withhold water in the fall, as it does not care for damp winter soil.
After flowering is complete, cut the flower stalks and foliage back to just above ground level.
you’ve got the option to also leave the flowers for winter interest.
Moist conditions may also encourageaphids, slugs, and snails to feed on the foliage.
Fungicides can help control serious leaf spot disease.
Aphids can usually be easily controlled with horticultural oil (or ignored since the damage is rarely severe).
Slugs and snails can be removed by hand or controlled with baits.
What Do Sea Holly Flowers Look and Smell Like?
The dark green sea holly leaves form a rosette at or near the plant’s base.
They are long and narrow, slightly heart-shaped with toothed edges, and spiny.
Ensure it has full sun for at least eight hours to encourage more blooms.
Also, avoid giving fertilizer or planting it in an area with rich, fertile soil.
Poor soil usually yields better flowering.
Also,remove dead flower headsto encourage more blooms.
Plant these plants in dry, sandy soil where other plants won’t grow.
Such sprawling may also occur if the sea holly doesn’t get enough sun or if you overwater it.
They can be planted individually or in small groups.
Paradoxically, plants growing in rich, fertile soil are often more short-lived.
Sea holly self-seeds in the garden if you don’t deadhead the spent flowers.
Resulting seedlings are rarely a problem.
When you notice them, carefully transplant them to propagate new plants.
Do it quickly since sea holly develops a relatively long taproot that doesn’t handle transplantation well once formed.
Sea holly usually blooms from mid-summer to fall.
To prolong blooms or encourage more blooms, deadhead spent flowers.
