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Cardiocrinum - Care Guide
Cardiocrinum bulbs have a monocarpic life history which means that they die after flowering.
When you buy a cardiocrinum bulb from Burncoose it will be in a 2.5-3L pot and roughly three to four years old already. It will normally send up a huge two to three meter flowering stalk in its fifth or sixth or even seventh season. However, in every batch of bulbs which we grow, there are always size irregularities and a few plants will flower (with perhaps somewhat smaller flowering spikes) in their fourth year. This uncertainty as to exactly when the bulb will flower is good news for growers who want to establish a clump of cardiocrinum plants which will produce some flowers every year after establishment in the garden.
When the flowering stalk dies off in the autumn the bulb, which produced this enormous flower, also dies. However, that is not the end of the story, because each bulb produces a number of ‘offset’ bulbs around the base of the old stem. These cloned bulbs will grow on to flower in three to five years although it may be necessary to move them a foot or more apart in the autumn so that they have enough space to grow on vigorously and flower more quickly.
Cardiocrinums produce their flowering spikes in June to August with 20 to 40 individual flowers on each stalk. The numerous creamy white individual flowers have a claret stripe in the throat. The flowers also have a strong vanilla scent.
Cardiocrinium giganteum - Video Tip
In the wild in China these giant lilies live in moist semi shaded wooded mountainsides often quite near streams or water.
This is exactly the sort of location which you need to identify in your own garden. Direct sunlight may well scorch the delicate heart shaped leaves as they develop. Water logged soil will rot the bulbs.
The soil needs to be well drained but moisture retentive. A slightly acidic, neutral or slightly alkaline pH is fine providing the soil is rich in nutrients which you can supplement when planting with well rotted dung or leaf mould.
Your cardiocrinum bulbs are perfectly hardy when dormant in the winter but a mulching with rotted leaves or some other mulch will help disguise and protect the bulbs from rodents and sharp frosts over winter as well as providing a feed for the bulbs in the next growing season.
Cardiocrinums dislike being moved so make sure you pick the very best location from the outset. When moved this can stunt bulb growth in the next season and delay flowering.
For best results plant three or five plants about 2-3ft apart in one newly dug bed in a woodland location. It is unlikely that all your plants will flower at once. More probably they will give you some flowers in the first three years after which the first offsets should be big enough to flower too thereby ensuring an ongoing continuity of flowers year on year which must be your objective.
The sort of position you should choose is the sort of woodland glade with dappled sunlight where you might well locate other ericaceous shrubs such as azaleas and rhododendrons. Wherever primulas, astilbes or rheums grow well with you should be the ideal spot.
Pests and diseases
When we first grew a clump of these amazing plants in a border at Caerhays Castle we made a huge mistake. The location was shady, protected from strong winds which might have blown the flowering stalks over and had a rich soil.
However, it was right beside two large walls. The walls were damp, covered in moss and built 200 years ago. A perfect haven for all sizes of slugs and snails who thought it was Christmas and Easter when presented with large clumps of tender and delicious green leaves.
While some of the more mature bulbs could withstand the onslaught, with many ragged holes in their leaves, the younger plants and the numerous tiny self sown seedlings with only one or a few leaves could not and were killed.
Slug traps, slug bait or perhaps a drench of garlic water to deter slugs is essential in April and May and on right through the summer. Choose a shady spot well away from a compost heap, walls or anything likely to harbour slugs and snails.
Mice can also nibble succulent young and immature cardiocrinum bulbs and you are just as likely to find these concentrated around an old wall as slugs and snails.
Squirrels and rats have been known to eat the bulbs in winter so covering the cardiocrinum bed with wire netting to keep them away may prove useful in avoiding another potential disaster.
However, once your clump of bulbs is growing well and expanding, a bit of slug damage here and there is not at all unusual and easily tolerated by the plants.
Growing from seed
The flowering stalks and individual flowering heads will produce copious amounts of seed by mid autumn. Wait until the stalk and seed pods are completely brown and the individual pods are just starting to split at the top before you collect the seed.
If you do not, and the location of your plants is dampish with clear weed free ground around them, you may well find that your plants produce a multitude of self sown seedlings all on their own.
You can sow cardiocrinum seed at any time of the year. The seed looks very like the ‘rabbits money’ seed on elm trees which you see in the spring. If you plan to sow in the spring keep the seed in the fridge over winter.
Sow the seeds in peaty compost with some grit just below the surface. There is no need for artificial heat which can be detrimental. Not all the seeds will necessarily germinate in the first year so patience is needed. However you will normally get a good crop in the first year.
Again slugs, snails and mice must be kept well away from the seeds when germinating and afterwards. The seedlings need to be grown in the shade or protected from direct sunlight at all times or they will literally scorch up and die.
Transplant the seedlings in the second year into pots just as they start to reshoot in spring. Equally you could grow them on in a nursery bed for three years or so before finally locating them in the garden.
When planting or potting on the small bulbs they should stand proud from the soil with the soil covering not much more than half of the bulb. Exactly how we will deliver the bulbs to you when you order them in fact.
We have a more detailed article about storing and growing seeds if you would like more information about this.
You will perhaps have seen cardiocrinums nearly or just in flower on our stands at the Chelsea Flower Show. These have been forced on by us to flower early in time for the show in late May. Customers are often scared of growing these odd but truly spectacular lilies. However, armed with this advice, we hope that you will have a go yourselves as it is not really that difficult to get a good clump started. After that, and by taking a few simple precautions, you can sit back and enjoy them flowering away for many years with very little effect.
We have more pictures and information about the cardiocrinums at Caerhays on the garden diary.