Crown imperial ( Fritillaria imperialis )

Fritillaria imperialis, commonly known as crown imperial, is a bulb native to mountainous regions in Turkey, western Iran and eastwards to Kashmir. It is grown for its large and spectacular clusters of bell-shaped flowers in late-spring.

<EM>Fritillaria imperialis</EM> 'Garland Star'

Quick facts

Common name Crown imperial
Botanical name Fritillaria imperialis
Group Bulb
Flowering time Spring
Planting time Autumn
Height and spread 100cm (40in)
Aspect Sun
Hardiness Hardy
Difficulty Moderate

Cultivation notes

Crown imperials are strong-growing bulbous plants, making rapid growth in the spring, flowering during April/early May and dying down in early summer.

Planting

They need a deep, rich, well-drained loam soil, preferably alkaline, and a warm, sunny position where they can be left undisturbed for many years.

Where soil conditions are less than ideal it is advisable to thoroughly prepare the site before planting, digging in some well-rotted manure or rich leafmould and grit. Simply putting grit in the bottom of planting holes on heavy soils will achieve little. Add a dressing of Vitax Q4 Fertiliser at about 140g per sq m (4oz per sq yd) before planting in the early autumn.

Plant bulbs deeply at a depth of at least 30cms (1ft) and a similar distance apart. Shallow planting will lead to poor flowering after the first year. If the soil is too wet to allow planting at this depth then it is not a suitable site. Consider constructing a suitable raised bed.

It is claimed that planting the bulb on its side may prevent rot when the bulb is dormant during the summer. Over a season, however, bulbs tend to right themselves. 

Add a mulch of well decayed compost as the shoots emerge in the spring, after applying a general purpose fertiliser at the rates quoted above. Additional liquid feeding of high potassium (tomato) fertiliser during the growing season at fortnightly intervals is beneficial but start once bulbs have made a few inches of growth. Waiting until bulbs have flowered, as often recommended, is just too late as the new bulb for next year will have already formed.

Containers

Crown imperials rarely do well on heavy clay soils and, in such situations, are best grown in raised beds with good drainage or in containers. For the latter, use a mix of equal quantities of John Innes No.3 and multipurpose growing media with the addition of about 20 percent grit. Incorporate Vitax Q4 at 5g/litre. Do not use controlled release fertilisers which are unsuitable for spring flowering bulbs in containers due to excessive nutrient release.

Aftercare

In good growing conditions crown imperials will readily form large clumps. If a well-established colony begins to flower poorly then lifting in early autumn when dormant, thoroughly improving the soil and replanting, or moving to a new site may be sufficient to restore satisfactory flowering. The bulbs may take a year or two to re-establish.

Propagation

Fritillarias can be propagated by division or from seed.

Cultivar Selection

Fritillaria imperialis 'Aurora': Shorter than most at 60cm (2ft) with orange flowers veined red

F. imperialis 'Maxima Lutea' AGM: Tall, erect stems to 1.2m (48in) with half a dozen or more large nodding, bell-shaped bright yellow flowers

F. imperialis 'William Rex': Intense reddish orange flowers on dark bronze coloured stems to 90cm (3ft)

RHS Find a Plant

Problems

Pests: Commonly encountered pests include the red lily beetle, slugs and snails.
 
Non-flowering: Most gardeners manage to flower crown imperials in the first year but on less than ideal soils, such as heavy clays or infertile, sandy soils, or where bulbs are planted too shallowly, they rarely flower in subsequent years.
Ensure purchased bulbs are large - at least 8-10cm (3-4in) in diameter - and firm. Always purchase and plant crown imperial bulbs as early as possible in the autumn. It is important they produce strong roots before the onset of winter if they are to flower well.

Advertise here

Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Discuss this

for the site or to share your experiences on this topic and seek advice from our community of gardeners.

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.