How to Grow Bells of Ireland

Bells of Ireland plant with emerald green funnel-shaped flowers clustered

The Spruce / Evgeniya Vlasova

Before green flowers became a hot trend among plant breeders, there was bells of Ireland, an annual flowering plant that has been in cultivation since the 1500s. These plants produce spires with emerald green funnel-shaped flowers clustered along vertical stalks. The green bell is actually the calyx—outer sepals that surround the tiny white flower petals inside.

Florists love bells of Ireland for its availability and longevity, and you’ll see it used in wedding flower arrangements as often as in St. Patrick’s day bouquets. As a member of the Lamiaceae family, this plant is related to such ornamental and culinary plants as sage (Salvia), catmint (Nepeta), thyme (Thymus), and lavender (Lavandula).

Bells of Ireland is generally planted in the spring, from seeds either sown directly into the garden, or from seeds started indoors at least two months before the last expected frost of spring. It can take as much as a month for seeds to germinate and sprout, and another two months before they mature into flowering plants.

Botanical Name Moluccella laevis
Common Names  Bells of Ireland, shell flower
Plant Type Annual
Mature Size 2–3 feet, 10–12 inches wide
Sun Exposure Full sun to part shade
Soil Type Well-drained, evenly moist
Soil pH 6.5–7.5 (neutral)
Bloom Time July to September
Flower Color White, inside a bright green calyx
Hardiness Zones True annual, grown in zones 2 to 11
Native Area Turkey, western Asia

Bells of Ireland Care

Bells of Ireland is an annual that grows in all zones but fares poorly in areas with hot and humid summers. Shade cloth can go a long way towards prolonging the vigor of the plants when summer's heat kicks in.

If you are lucky enough to find a well-stocked nursery with plugs or young plants, it's worth the extra money to start with these the first season. Doing this allows you to see if bells of Ireland grow well in your area without a significant investment of time or effort. If they take off, you can plant a bigger patch the following season, using seeds saved from plants. 

Bells of Ireland are top-heavy, and they may topple over after heavy rain or in areas exposed to wind. Stake the blooming stalks, grow the compact variety, or grow them in a sheltered area to keep the spires upright.

Bells of Ireland don’t re-bloom, so you can remove plants past their prime without guilt. However, you may want to leave them in place long enough for the seeds to mature and scatter, as these annuals are self-sowing.

Bells of Ireland plant with emerald green funnel-shaped flowers and leaves clustered closeup

The Spruce / Evgeniya Vlasova

Bells of Ireland plant with emerald green funnel-shaped flowers clustered on stalks

The Spruce / Evgeniya Vlasova

Bells of Ireland plant with emerald green funnel-shaped flowers clustered on vertical stalks in sunlight

The Spruce / Evgeniya Vlasova

Light

Full sun is best for bells of Ireland. The plants need at least some morning sun to prevent them from growing too leggy, which makes them prone to flopping. Plants in shady locations will almost certainly need staking.

Soil

These plants like neutral soil that drains well and is kept evenly moist. It's best to blend in some compost to the planting area before sowing seeds.

Water

Keep bells of Ireland consistently moist during the vulnerable seedling and transplant stages. Soaker hoses are great for providing moisture without water-logging the plants. These plants will do well with about 1 inch of water per week.

Fertilizer

Bells of Ireland plants require little, if any feeding. Preparing the planting bed for them with compost should be enough.

Bells of Ireland Varieties

There are few cultivars of M. laevis available, but one very popular variety is 'Pixie Bells'. It is quite similar to the species, but with shorter, sturdier stems that are much less likely to topple over when the plants get wet. Most gardeners prefer it over the species plant.

Starting Bells of Ireland From Seed

Plant bells of Ireland in the garden after the last frost date in your area in average garden soil. Leave seeds uncovered, as they require light to germinate. The seeds are slow to germinate, taking up to a month to produce shoots, so for earlier blooms start them indoors two months before the average last frost date.

Stratification increases the germination rate of bells of Ireland seeds. You can expose them to cold by sowing them outdoors in the fall, or by refrigerating them for a week before starting them indoors. Don't just place the seed packet in the refrigerator; for best results, combine moist conditions with cold temperatures to mimic an outdoor experience. Sandwich the seeds between moist coffee filters or paper towels in the refrigerator, followed by planting in soil. This moist stratification results in a higher germination rate than simply exposing dry seeds to cold temperatures. 

When starting seeds indoors, it's best to plant seeds in 3-inch pots filled with seed starter mix or ordinary potting soil, and wait until the plant is of good size before planting it outdoors in the garden. These plants have a taproot that doesn't like to be disturbed, so try to avoid transplanting twice—from seed trays into pots, then from pots into the ground. While waiting for the seeds to germinate and sprout, keep the potting mix moist by misting with a spray bottle.

Propagating Bells of Ireland

The easiest way to propagate this plant is to collect seeds from the drying flower heads, saving them to plant the following spring (though they will need cold stratification for best results). You can also carefully transplant some of the self-seeded volunteers that spout up in the garden—they will be plentiful if you have left flowers on the plant to mature and dry.

Harvesting

Bells of Ireland flowers are easy to dry, and they add interest to fresh-cut flower arrangements. The lime green flowers make an attractive foil for wine or magenta-colored flowers, like Red Velvet celosia (Celosia argentea 'Red Velvet'), globe amaranth (Gomphrena globosa), or Purple Prince zinnia (Zinnia 'Purple Prince'). 

If you harvest bells of Ireland for fresh or dried bouquets, wear gloves to protect your hands from the small spiny thorns that grow along the stems. For fresh flower arrangements, cut the flowers when the bells are about half open. For dried flower arrangements, wait until the bells have become firm to the touch.

The stiff calyxes of bells of Ireland last up to two weeks in fresh arrangements, but the flowers don’t maintain their green tint as dried specimens. The bells will gradually turn tan as they dry. For a fun bouquet twist, spray paint dried stems gold or silver and pair with fresh green stems. 

Common Pests/ Diseases

Bells of Ireland can be subject to cerospora leaf blight, a disease that causes small fleck with yellowish halos to appear on the leaves. Crown rot can also cause the plants to wilt from the soil line up, eventually dying. Diseased plants should be removed and discarded.

There are few serious garden pests that threaten bells of Ireland plants, though aphids and spider mites are occasional problems.