Great Blue Lobelia (Lobelia siphilitica)

Great Blue Lobelia | Lobelia siphilitica

Vibrant blue flowering marginal plant for late season colour and wildlife ponds

Great Blue Lobelia is a fantastic choice if you are looking to extend colour in your pond well into late summer and early autumn. Lobelia siphilitica produces striking upright spikes of rich blue flowers that stand tall above its neat green foliage, creating a bold and elegant display at a time when many other pond plants have finished flowering.

Blooming from August through to October, this plant provides valuable late season interest, making it a key addition to any well planned pond planting scheme. The vivid blue flowers create a beautiful contrast against surrounding greenery and work particularly well when combined with softer, earlier flowering plants such as marsh marigold or water hawthorn.

This clump forming perennial is ideal for pond margins, damp borders, and bog gardens. It thrives in consistently moist to wet soil and can also be placed in very shallow water, making it highly versatile around the pond edge. Its upright growth habit adds vertical structure, helping to break up lower growing planting and giving a more layered, natural look.

Beyond its visual appeal, Great Blue Lobelia is highly beneficial for wildlife. The flowers are extremely attractive to bees and other pollinators, providing an important food source later in the season. Its dense foliage also offers shelter for amphibians such as frogs and toads, as well as a safe resting place for insects around the pond.

This plant performs best in full sun, where flowering will be at its most abundant, although it will tolerate partial shade without issue. It has a relatively slow and controlled growth habit, making it easy to manage and suitable for both small and larger ponds.

Fully hardy in most UK conditions, Great Blue Lobelia is reliable year after year with minimal maintenance required. It is particularly effective when planted in small groups to create a strong visual impact, or mixed into wildlife planting schemes for added diversity.

Please note that all parts of the plant are harmful if ingested and may cause skin irritation when handled.

🇬🇧 UK-grown aquatic plant: Grown at a dedicated aquatic plant nursery in the South of England and carefully prepared for delivery across the UK.

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Key Benefits

• Striking blue flower spikes for late season colour
• Excellent for extending interest into autumn
• Highly attractive to bees and pollinators
• Adds vertical structure to pond planting
• Provides shelter for amphibians and pond life
• Fully hardy and easy to maintain

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Reasons to Buy

• Perfect for adding colour when other plants fade
• Ideal for wildlife friendly ponds and gardens
• Works well in both modern and natural planting schemes
• Compact and easy to manage growth habit
• Pairs beautifully with early and mid season plants

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Care Instructions

• Place on a marginal shelf at a depth of 0 cm to 5 cm, measured from the top of the basket to the water surface, or plant into consistently moist soil.
• Position in full sun for best flowering, although partial shade is tolerated.
• Deadhead spent flowers to encourage continued blooming. Cut back foliage in autumn once it has died back. Divide clumps every few years in spring to maintain healthy growth.

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Flowering Period

August to October

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Size and Growing Conditions

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Dispatching Your Pond Plants

Your Great Blue Lobelia will be carefully packed to protect the foliage and roots during transit.

Orders received by 11am Monday to Wednesday are normally dispatched on the following working day using a next working day courier service. During busy periods, dispatch may occasionally take an extra day.

To avoid plants being held in depots over a weekend, we do not usually dispatch on Fridays. Highlands and Islands orders using a two day service are not normally dispatched on Thursdays.

Available basket sizes:

• 1 Litre Basket – usually 11 × 11 × 11cm square; some varieties may be supplied in a 14cm diameter × 10cm round basket
• Pack of 3 × 1 Litre Baskets – each usually 11 × 11 × 11cm square

Planting depth is measured from the top of the aquatic basket to the water surface.

Finofil baskets are manufactured in the UK from 100% recycled plastic and are fully recyclable. Their fine dual-mesh construction helps retain aquatic soil while allowing water and nutrients to reach the roots. Basket shape may vary slightly depending on the plant and supplier availability.

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Similar pond plants

For another pond-edge planting option, compare Cardinal Flower (Lobelia cardinalis) and Greater Pond Sedge (Carex riparia). Explore the Lobelia pond plant group to compare the whole collection.

Explore more marginal pond plants or browse our complete pond plants range. Need baskets, aquatic soil or planting essentials? Browse our pond plant baskets and aquatic planting supplies.