In the wild Epimediums generally occupy niches with some shade and adequate moisture. Having not seen their natural habitats, we have relied on the guidance of others coupled with our own ongoing experience, to try to suit them in our garden. We are currently experimenting with the degree of shade, having seen some, stood out in a nursery in full sun, not appearing to be suffering in any way. We think, in the past, we have tried some in too much shade for the deciduous species and their varieties and hybrids.
The standard recommendation would be for planting in light to medium shade and for adequate moisture for the roots with good drainage. The shade can be provided by trees or shrubs or planting on the North side of your house, a wall or a fence. The soil’s moisture retaining ability may be improved by adding organic matter. We make beautiful garden compost by combining shredded shrub and tree prunings, with grass mowings. When composted for six months to a year it turns into friable garden compost. If you have no objection to using peat it will last rather longer in the ground, we suspect. You can use your grow-bags and hanging basket compost after its previous use, as the nutrient content is less important than its moisture holding capacity. I wouldn’t use spent mushroom compost as at least E. grandiflorum is known to object to limey soil. Lime is used as a ‘capping’ material with mushroom culture to induce fruiting-body production. On our heavy London clay soil we often incorporate sharp sand when preparing beds for Epimediums to improve the drainage in the top spit.
Epimediums are self-sterile. They tend to cross freely between species, even those from widely different geographical sources. Therefore if you wished to propagate a particular species from seed you would need to have two different clones of the species in a situation where insects couldn’t bring pollen from other sources. The seed capsules look like miniature pea pods and shed the seed while it and they are still green. This can happen quite suddenly and it is all too easy to lose the seed for a season, if you don’t check the plants regularly. I would recommend sowing the seed immediately after collection. It should germinate the following spring after receiving the cold temperatures of the winter season. Experiments with seed placed in a refrigerator seem to indicate three months in normal fridge temperatures breaks the dormancy in the seeds. I made the mistake once of leaving sown pots for too long in the fridge and they had already germinated and become thoroughly etiolated, when discovered. Although some American Epimedium growers say they can get flowers in the year of sowing, my experience is that with our climate it often takes up to three years from the initial germination. Some dedicated growers have made deliberate crosses with a particular aim in mind. We have just collected open pollinated seed and sown a random portion of it just for fun.Propagation by division is the only way to increase your named species or varieties so the results remain true to the original plants. Larger plants in the ground can have a section carefully cut through and levered out with a spade, or the whole plant may be dug up and split with two garden forks back to back. Potted plants can be split with two hand forks back to back possibly assisted with an old knife or secateurs to cut through the woody rhizomes. Different growers recommend various times of the year to carry out division. Some say early March and others, August or September. Commercial growers may do it in early spring in order to get a well rooted out plant for flowering time the following year. You have to be very careful in early spring as the new flowering shoots develop very quickly and once the leaves and flowers are starting to unfurl they are very easily broken. The truth is that if you only want to propagate the odd extra plant and you do it carefully any time will work except perhaps for the coldest periods of winter.