Larkspur Growing Success: A UK Cottage Garden Essential

The Complete Larkspur Growing Guide for UK Gardens

If delphiniums set your heart racing but their perennial temperament leaves you frustrated, larkspur is your perfect solution. Often called "annual delphiniums," these magnificent hardy annuals deliver all the vertical drama and stately elegance of their perennial cousins with none of the fuss. With towering spires of densely packed flowers in jewel-like shades of blue, pink, white, and purple, larkspur (Consolida ajacis) brings architectural beauty and old-fashioned romance to British cottage gardens.

Best of all, larkspur is supremely well-suited to UK growing conditions. As hardy annuals, they thrive in our cool climate and reward gardeners with months of spectacular blooms that make outstanding cut flowers. Whether you're planning a traditional cottage border, a productive cutting patch, or simply want to add vertical interest to your plantings, this comprehensive guide will show you how to grow larkspur that reaches for the sky.

Understanding Larkspur: The Annual Delphinium

Larkspur belongs to the same botanical family as delphiniums (Ranunculaceae) and the family resemblance is striking. Both produce tall spires of flowers in similar colour ranges, but there are crucial differences that make larkspur far easier to grow in many situations.

As hardy annuals, larkspur completes its entire life cycle in one season but possesses remarkable cold tolerance. This hardiness allows autumn sowing—the secret weapon for achieving truly impressive plants. Unlike perennial delphiniums that require staking, slug protection, and careful overwintering year after year, larkspur simply grows, flowers magnificently, sets seed, and finishes—leaving you free to grow it again exactly where you want it the following year.

The flowers are slightly smaller and more delicate than delphiniums, but what larkspur lacks in individual flower size, it more than compensates for with sheer abundance. A well-grown larkspur plant produces multiple flowering spires that keep coming throughout summer, especially if you practice regular cutting.

The Autumn Sowing Advantage

Autumn sowing is the insider secret to growing larkspur that truly impresses. The difference between autumn and spring-sown plants is so dramatic that once you've experienced it, you'll never return to spring sowing alone.

Why Autumn Sowing Produces Superior Plants

When larkspur seeds are sown in September or early October, they germinate quickly in soil that's still warm from summer. The young seedlings establish modest rosettes of finely cut, feathery foliage before winter arrives. Then, throughout the cold months, whilst visible growth appears minimal, the plants invest all their energy into developing extensive, deep root systems.

By the time spring warmth returns, autumn-sown larkspur plants possess underground networks that spring-sown seedlings won't achieve until mid-summer. This root advantage translates to:

• Dramatically taller plants: Autumn-sown larkspur regularly reaches 120-150cm compared to 60-90cm for spring-sown plants
• Earlier flowering: Blooms appear 4-6 weeks earlier than spring-sown equivalents
• More flower spires per plant: The robust root system supports multiple flowering stems
• Longer flowering season: Early start means prolonged display into autumn
• Better drought tolerance: Deep roots access moisture spring-sown plants can't reach
• Sturdier stems: Less likely to require staking despite greater height

Larkspur 'Giant Imperial Mix' is particularly spectacular when autumn-sown, producing towering columns of colour that dominate the summer border.

Spring Sowing Still Works

If you've missed the autumn window or simply prefer a more straightforward approach, spring sowing from March to early May delivers perfectly respectable results. Spring-sown larkspur will flower later (typically July onwards) and won't achieve the statuesque heights of autumn-sown plants, but they'll still provide beautiful vertical interest and excellent cut flowers.

For beginners or those with limited space to dedicate over winter, spring sowing offers a simpler route to success. The plants require less management and still reward you with gorgeous blooms throughout summer.

Direct Sowing: The Larkspur Preference

Larkspur, like cornflowers, develops a long tap root that penetrates deep into the soil. Plants with tap roots strongly dislike root disturbance, which means larkspur performs best when sown directly where it's to flower rather than raised in pots and transplanted.

Site Selection and Soil Preparation

Choose your location carefully as larkspur will occupy the space for the entire growing season:

Light requirements: Full sun is essential. Larkspur needs at least 6 hours of direct sunlight daily to produce strong stems and abundant flowers. In shade, plants become leggy and flower poorly.

Soil preferences: Unlike many plants, larkspur actually prefers relatively lean, well-drained soil. Rich, heavily manured ground encourages excessive leafy growth at the expense of flowers. The ideal is ordinary garden soil that's been improved with compost for structure but not over-fed with nitrogen-rich fertilisers.

Drainage: This is crucial. Larkspur will not tolerate waterlogged conditions, particularly during winter when autumn-sown seedlings are establishing. If your soil is heavy clay that sits wet, consider growing larkspur in a different area, improving drainage with grit, or creating raised beds.

Preparing the Seed Bed

• Remove all weeds and their roots thoroughly
• Break up any compacted soil to create a fine, crumbly texture
• Rake the surface smooth, removing stones and debris
• If soil is very dry, water thoroughly and allow to drain before sowing
• Resist the temptation to add manure or high-nitrogen fertiliser

The Direct Sowing Process

Autumn Sowing (September to early October):

• Create shallow drills approximately 0.5-1cm deep using a cane or hoe handle
• Space drills 30cm apart to allow for mature plant width
• Sprinkle seeds thinly along each drill—larkspur seeds are small and black
• Cover lightly with soil and gently firm with the back of a rake
• Water gently using a fine rose on your watering can
• Mark rows clearly with labels and short canes

Spring Sowing (March to early May):

Follow exactly the same process. Later spring sowings extend the flowering season but will bloom progressively later.

Seed Stratification: The Germination Booster

Here's a technique that can dramatically improve germination rates, especially for spring sowings: cold stratification. Larkspur seeds actually benefit from a period of cold, which mimics the natural winter conditions they'd experience if they fell to the ground in autumn.

What is stratification? Stratification is the process of exposing seeds to cold temperatures (around 1-5°C) for a period of time before sowing. This breaks down germination inhibitors within the seed coat and primes the seed for growth. In nature, autumn-sown seeds undergo this process naturally over winter, which is partly why they germinate so reliably.

Benefits of stratification:

• Significantly improved germination rates (often 20-30% better)
• More uniform germination—seedlings emerge together rather than sporadically
• Stronger, more vigorous seedlings
• Particularly beneficial for spring sowings which miss the natural winter chilling
• Can rejuvenate older seeds with declining viability

How to stratify larkspur seeds:

• The refrigerator method (easiest): Place seeds in a small plastic bag or container with barely damp (not wet) kitchen paper or vermiculite Seal and label with variety and date Place in the refrigerator (not freezer) for 2-4 weeks Check weekly—if mould appears, the medium is too wet Sow immediately after stratification period
• The outdoor method (for spring sowings): In January or February, sow seeds in modules or pots as described Place containers in an unheated greenhouse, cold frame, or sheltered spot outdoors Leave for 4-6 weeks in cold conditions Bring into slightly warmer conditions (10-15°C) to trigger germination This method mimics natural conditions perfectly

Do you need to stratify?

• Autumn sowings: No—nature does it for you over winter
• Spring sowings: Highly beneficial but not essential—stratification can turn "reasonable" germination into "excellent" germination
• Older seeds: Definitely worthwhile—can make the difference between poor and good germination
• Problem batches: If you've had poor germination in the past, try stratification

Many experienced growers swear by stratification for spring sowings, claiming it produces seedlings as vigorous as autumn-sown plants (though they'll still flower later). It's a simple extra step that can significantly improve results.

Germination and Early Growth

Larkspur seeds germinate within 14-21 days in suitable conditions (or 7-14 days if stratified). The tiny seedlings emerge with narrow, grass-like seed leaves followed quickly by the characteristic finely divided, feathery true leaves. These delicate leaves give larkspur its distinctive texture in the garden.

Cool conditions suit germination best—larkspur doesn't require heat. In fact, excessive warmth can inhibit germination or produce weak seedlings. Autumn germination is often more reliable than spring precisely because temperatures are naturally optimal and seeds receive natural stratification over winter.

Thinning Seedlings

Once seedlings have developed several true leaves and are large enough to handle, thin them ruthlessly to 25-30cm apart. This seems extreme when they're tiny, but larkspur needs this space to develop properly. Crowded plants produce weak, spindly stems and are more susceptible to mildew.

You can attempt to transplant thinned seedlings to fill gaps elsewhere, though success is variable due to the tap root. If you try, water transplants thoroughly and provide temporary shade for a day or two whilst they recover from the move.

Module Sowing: When Container Starting is Necessary

If direct sowing isn't possible—perhaps because the intended space is occupied by other plants, or you want larkspur for containers—module sowing offers a workable alternative, though results never quite match direct-sown plants.

Container Sowing Technique

• Use deep modules (minimum 5cm) or root trainers that accommodate the developing tap root
• Fill with peat-free seed compost
• Sow 2-3 seeds per module, covering lightly with compost
• Germinate in an unheated greenhouse, cold frame, or cool porch
• Thin to the strongest seedling per module once germinated
• Transplant whilst still young (4-6 weeks old maximum)
• Handle very carefully, disturbing roots as little as possible
• Water in thoroughly after planting

The key is transplanting whilst plants are genuinely young, before the tap root develops extensively. Even with careful handling, module-raised larkspur typically grows shorter and bushier than direct-sown plants.

Overwintering Autumn-Sown Larkspur

Autumn-sown larkspur seedlings will spend winter as small rosettes of ferny foliage sitting at soil level. They're remarkably tough, but a few considerations help them through the cold months successfully.

Winter Protection and Care

Drainage is critical: Larkspur is genuinely hardy and can withstand British winter cold, but it cannot tolerate sitting in waterlogged soil. Seedlings may rot if drainage is poor. If you have heavy clay or any doubt about winter drainage, create raised beds or grow larkspur elsewhere.

Minimal intervention: Resist the urge to fuss over winter seedlings. They're semi-dormant and need very little attention. Don't feed, don't water unless conditions are exceptionally dry, and leave them undisturbed.

Mark their positions: The ferny foliage is delicate and easily overlooked during winter weeding. Mark rows or individual plants with short canes or labels so you don't accidentally hoe them out.

Pest watch: Slugs and snails can damage young seedlings during mild, wet spells. Check periodically and remove any pests found. Mice occasionally nibble seedlings but aren't usually a major problem with larkspur.

Pigeons: In hard winters when food is scarce, pigeons sometimes peck at young larkspur foliage. If this becomes problematic, cover with netting or fleece until spring.

Spring Growth and Care

As temperatures rise in March and April, larkspur seedlings—whether autumn or spring sown—begin their spectacular growth phase. This is when autumn-sown plants demonstrate their superiority, shooting upwards rapidly whilst spring-sown seedlings are just getting established.

Support Requirements

Larkspur's greatest weakness is its tendency to flop, particularly in exposed gardens or if plants are grown too closely together. The Giant Imperial and Giant Hyacinth varieties can easily reach 120-150cm when autumn-sown, and these tall stems benefit from support.

Install support early: The crucial mistake is waiting until plants start flopping. By then, stems have already grown at an angle and can't be properly corrected. Install support in April when plants are 20-30cm tall, well before they need it.

Support methods that work:

• Twiggy branches (pea sticks): Push sturdy, branching twigs into the ground around young plants. As larkspur grows, stems push up through the branches and are naturally supported. This creates the most natural look.
• Horizontal netting: Stretch pea and bean netting horizontally across the planting area, supported on short canes at 40-50cm height. Larkspur stems grow up through the mesh and are held upright. This works brilliantly for cutting rows.
• Ring stakes: Individual circular supports work well for specimen plants or border positions. Place them early and raise them as plants grow.
• Bamboo canes and twine: For cutting rows, push canes in at intervals and run horizontal lines of garden twine between them at 30cm and 60cm heights, creating a corral that keeps stems upright.

Whatever method you choose, ensure supports are secure. Larkspur foliage hides them quickly, creating an apparently unsupported column of flowers.

Watering

Established larkspur is relatively drought-tolerant thanks to its deep tap root, but consistent moisture during the growing and flowering period produces the best results. In dry weather, water deeply once or twice weekly rather than lightly every day. Deep watering encourages roots to penetrate further, increasing drought resilience.

During the critical flowering period (June-August), don't let plants become water-stressed. Moisture stress reduces flowering and encourages the plant to set seed prematurely, ending the display.

Feeding

Like cornflowers, larkspur prefers lean conditions and doesn't require feeding. In fact, nitrogen-rich feeding produces lush foliage at the expense of flowers. If you've prepared the soil properly before sowing, larkspur has everything it needs.

The one exception is container-grown larkspur, which benefits from diluted liquid tomato feed every 2-3 weeks once flowering begins, as nutrients leach from compost quickly.

Deadheading and Harvesting for Prolonged Flowering

The difference between mediocre larkspur and spectacular, long-flowering larkspur often comes down to one factor: regular cutting and deadheading. Larkspur is excellent as a cut-and-come-again flower, producing multiple side shoots after the main spike is cut.

Cutting Technique

• Cut main spikes when half to two-thirds of flowers are open: This is the perfect stage for cutting. The remaining buds will open in the vase over several days.
• Cut long stems: Take stems as long as possible, cutting just above a leaf joint. This encourages the plant to produce more long-stemmed side shoots.
• Harvest regularly: Check plants every 3-4 days throughout the flowering period. Regular cutting keeps plants productive.
• Remove spent blooms immediately: If you're not cutting for display, deadhead religiously. The moment a flower spike finishes, cut it off. If allowed to set seed, larkspur interprets this as job done and stops flowering.

Vase Life and Conditioning

Larkspur makes an outstanding cut flower, lasting 7-10 days with proper care:

• Cut in the morning when stems are fully hydrated
• Strip lower foliage that would sit below water
• Re-cut stems at an angle under water
• Use flower food in the vase water
• Change water every 2-3 days
• Keep away from fruit bowls (ethylene gas shortens vase life)

The vertical spires add wonderful height and structure to arrangements, working beautifully with roses, sweet peas, cornflowers, and virtually any other cottage garden flower.

Stunning Larkspur Varieties for UK Gardens

Giant Imperial Mix

Larkspur 'Giant Imperial Mix' is the classic choice for cutting gardens and cottage borders. This tall variety produces spectacular flower spires in an artist's palette of colours including deep blue, pink, lilac, white, and rose. The double flowers are densely packed along strong stems that can reach 120cm or more when autumn-sown.

This is the workhorse variety for serious cut flower production. The colour mix ensures you have a range for creating varied arrangements, and the prolific flowering means one small patch keeps you supplied with cut flowers throughout summer.

Giant Hyacinth Mixed

Larkspur 'Giant Hyacinth' takes larkspur to another level of sophistication. The flowers are even more densely double than Imperial types, creating spires that resemble clustered hyacinth blooms. Colours span pink, lilac, blue, cream, and white.

The 'Hyacinth' types are particularly stunning in borders where they create bold vertical statements. The extra-full flowers make them special for weddings and formal arrangements. If you adore delphiniums, you'll be utterly captivated by Giant Hyacinth larkspur.

Limelight

Larkspur 'Limelight' offers something truly unique—soft, luminous lime-green flowers that seem to glow in the garden. This unusual colour brings a fresh, contemporary feel to plantings whilst maintaining larkspur's classic vertical elegance. The tall spires reach 90-120cm and work brilliantly as a bridge colour in arrangements, softening bold contrasts and adding sophistication.

In the garden, Limelight's chartreuse tones create stunning combinations with purples, blues, and pinks. It's particularly effective in white gardens where it adds subtle colour variation, or paired with deep blue varieties for striking contrast. This is a must-grow for flower arrangers seeking something beyond the traditional larkspur palette.

Purple Picotee

Larkspur 'Purple Picotee' is a true showstopper with exquisite bicolour blooms. Each white flower is delicately edged with deep purple-violet, creating an elegant picotee effect that's absolutely captivating up close. The double flowers are densely packed along tall stems, making this variety outstanding for both garden display and cutting.

The sophisticated colour combination works beautifully in romantic, cottage-style arrangements and adds refinement to border plantings. Purple Picotee pairs wonderfully with pure whites, soft pinks, and other purple-toned flowers. This variety often elicits admiring comments from visitors—the bicolour effect is simply stunning.

Companion Planting with Larkspur

Larkspur's vertical spires provide wonderful contrast in mixed plantings. The feathery foliage adds texture even before flowering begins.

Cottage Garden Combinations

With Sweet Peas: A classic pairing that works brilliantly. The vertical spikes of larkspur contrast beautifully with the more informal sweet pea blooms. Both enjoy similar growing conditions and excel as cut flowers.

With Roses: Larkspur fills the awkward period between rose flushes, providing continuous colour and vertical interest amongst rose bushes.

With Cornflowers: The rounded cornflower blooms and upright larkspur spires create perfect textural contrast. Blue cornflowers with pink larkspur is particularly lovely.

With Cosmos: Both bloom prolifically through summer, creating abundant cutting material. The feathery foliage of cosmos complements larkspur's ferny leaves.

Cutting Garden Partners

Ammi majus (Bishop's Flower): White lacy umbels provide the perfect foil for coloured larkspur in arrangements.

Calendula: Orange and yellow calendula adds warm tones that complement blue and pink larkspur beautifully.

Nigella (Love-in-a-Mist): The feathery foliage and star-shaped flowers create romantic combinations with larkspur's spires.

Cerinthe (Honeywort): Dusky purple-blue bracts look stunning with pink or white larkspur.

Border Planting Ideas

Use larkspur to create vertical rhythm in borders. Plant in groups of 3-5 for impact rather than single specimens. The vertical spires draw the eye upward and break up solid masses of mounded plants.

Particularly effective planted behind:

• Lower-growing roses
• Geraniums (hardy cranesbills)
• Nepeta (catmint)
• Lavender

The contrast between horizontal and vertical plant forms creates dynamic, visually interesting plantings.

Encouraging Self-Seeding

One of larkspur's most endearing qualities is its willingness to self-seed, creating spontaneous displays year after year. To encourage this beneficial behaviour:

• Allow some late-summer flowers to remain on plants until seed pods form and ripen
• Let seed pods dry completely on the plant (they turn brown and papery)
• Avoid heavy mulching in areas where you want self-seeding
• When weeding in spring, learn to recognise larkspur seedlings (ferny, finely cut foliage) and leave them
• Let a few seed pods shatter naturally over the soil rather than deadheading everything

Self-sown seedlings often appear in unexpected locations, creating charming surprises and naturalistic effects. Simply thin them to appropriate spacing or transplant very young seedlings to more desirable positions.

Pest and Disease Management

Larkspur is generally robust, but a few problems occasionally occur.

Aphids

The soft new growth is attractive to aphids, particularly in late spring. Check growing tips and flower buds regularly. Squash small colonies by hand or spray with soapy water. Encouraging natural predators (ladybirds, lacewings, hoverflies) by growing diverse plantings helps keep aphids under control naturally.

Slugs and Snails

Young seedlings are vulnerable, especially during autumn establishment and early spring growth. Use organic slug pellets, copper tape around young plants, or beer traps. Check regularly during damp weather and remove any slugs or snails found.

Powdery Mildew

This fungal disease appears as white powder on leaves and stems, particularly in dry conditions or when plants are overcrowded. Prevention is better than cure:

• Ensure adequate spacing (25-30cm minimum)
• Water at soil level rather than overhead
• Ensure good air circulation
• Remove badly affected leaves

Mildew rarely impacts flowering significantly but can look unsightly. Well-spaced plants with consistent moisture rarely suffer serious mildew problems.

Flea Beetles

Tiny jumping beetles sometimes create small holes in young foliage. This is rarely serious and plants grow through it. Keeping soil moist helps as flea beetles prefer dry conditions.

Growing Larkspur in Containers

Whilst larkspur prefers open ground, it adapts reasonably well to container cultivation, particularly shorter varieties or spring-sown plants that naturally stay more compact.

Container Requirements

• Use large containers (minimum 40cm diameter and 40cm deep)
• Ensure excellent drainage with crocks or gravel in the base
• Use peat-free multipurpose compost mixed with 20% horticultural grit
• Provide support stakes or canes from early on

Container Care

Containers dry out quickly, requiring daily watering in hot weather. Feed weekly with diluted liquid tomato feed once flowering begins. Container-grown larkspur won't achieve the height of border-grown plants but still provides worthwhile vertical interest for patios and balconies.

Important Safety Warning

Larkspur is toxic: All parts of larkspur plants are poisonous if ingested, particularly the seeds. Symptoms of poisoning include nausea, vomiting, and in severe cases, cardiovascular effects. While handling plants poses no risk, always:

• Keep seeds away from children and pets
• Wash hands after handling, especially before eating
• Never confuse larkspur with edible plants
• Educate family members about which plants are ornamental only

Exercise the same basic caution you would with any ornamental plant. The toxicity shouldn't deter you from growing these beautiful flowers—just be sensible and aware.

Saving Larkspur Seeds

Larkspur seeds are straightforward to save, allowing you to grow your favourite colours year after year.

Seed Saving Process

• Allow some flower spikes to fade completely on the plant in late summer
• Seed pods will develop—they look like small clusters of pointed pods
• Leave on the plant until pods turn brown and papery (August-September)
• Cut entire seed heads and place in a paper bag
• Hang bags in a warm, dry location for 2-3 weeks
• Shake bags vigorously—seeds will fall out as dry black specks
• Separate seeds from chaff by gentle winnowing
• Store in labelled paper envelopes in a cool, dark, dry place

Larkspur seeds remain viable for 2-3 years when stored properly. Always save from your best plants with the strongest stems, truest colours, and most abundant flowers.

Troubleshooting Common Problems

Seeds Not Germinating

• Temperature too warm—larkspur prefers cool conditions (10-15°C)
• Sown too deeply—cover very lightly, 0.5-1cm maximum
• Soil waterlogged—improve drainage before resowing
• Old seeds—larkspur seed viability declines after 2-3 years

Weak, Floppy Stems

• Insufficient sun—needs full sun minimum 6 hours daily
• Planted too closely—thin to 25-30cm spacing
• Support installed too late or inadequate
• Soil too rich—avoid nitrogen-rich feeding

Short Flowering Season

• Inadequate deadheading—must remove spent flowers constantly
• Water stress—ensure consistent moisture during flowering
• Allowed to set seed—deadhead religiously

Plants Very Short

• Spring sowing rather than autumn—this is normal
• Too much shade—move to sunnier position next year
• Poor soil—although larkspur likes lean soil, extreme poverty limits growth

Seedlings Disappearing

• Slug and snail damage—protect young plants
• Poor drainage causing rot—improve drainage
• Accidental hoeing—mark positions clearly

Monthly Larkspur Care Calendar

September-October: Prime time for sowing seeds directly outdoors. Prepare soil but don't over-feed. Mark rows clearly.

November-February: Leave autumn-sown seedlings undisturbed through winter. They'll sit as small rosettes requiring no attention. Check occasionally for slug damage.

March: Thin autumn-sown seedlings to 25-30cm apart. Install support frameworks whilst plants are still small. Spring sowing possible from mid-March onwards.

April-May: Vigorous growth phase for autumn-sown plants. Continue spring sowings until early May. Support structures should be in place. Water during dry spells.

June-August: Peak flowering period. Cut stems regularly for indoor display. Deadhead religiously. Water consistently, especially during dry weather.

September-October: Late flowers on well-maintained plants. Collect seed from selected plants. Pull up spent plants or allow some to self-seed. Sow next year's crop!

Final Thoughts

Larkspur embodies vertical grace and old-fashioned cottage garden charm. These annual delphiniums deliver all the drama of their perennial cousins with far less fuss, rewarding you with months of spectacular flowers perfect for cutting. The stately spires add architectural beauty to borders and provide invaluable height and structure to flower arrangements.

The autumn sowing secret—whilst requiring slightly more planning—is absolutely worth embracing if you want truly impressive plants. The extra height, earlier flowering, and prolonged season make autumn-sown larkspur incomparably superior to spring-sown equivalents. However, even spring-sown larkspur performs admirably, so don't let timing prevent you from experiencing these magnificent plants.

Whether you choose the classic Giant Imperial Mix for maximum cutting material or the extra-full Giant Hyacinth for showstopping garden display, larkspur will become an indispensable part of your summer garden. Just remember the golden rules: sow directly where they're to flower, provide support early, and deadhead religiously.

Most importantly, cut armfuls to enjoy indoors—larkspur's whole purpose is to provide you with beauty, and it performs this task magnificently. Fill vases with those towering spires, marvel at how they transform simple arrangements into something special, and enjoy the cottage garden romance these elegant flowers bring to your home and garden.

For the complete range of larkspur varieties and everything else you need to create your perfect cottage garden, visit Bishy Barnabees Cottage Garden.

Written with love from our Norfolk flower farm, where larkspur spires have graced our cutting garden for generations.