Soil preparation and planting out.
Hostas may be planted out at any time between the appearance of the new shoots in spring through to late summer while the soil is still warm thus enabling them to establish quickly before the onset of autumn. Whilst they can be moved successfully at the height of summer it is advisable to keep them well watered and to remove 80% of the leaves to prevent excessive loss of water. Never plant out hostas when they are dormant as there is a significant chance of the roots rotting.
Hostas are very tolerant plants and will prosper in a wide range of soils, however, one which is rich in organic matter, well drained and slightly acidic is ideal. The planting hole should be at least a foot deep and a mixture of grit and well rotted manure added will get the hosta off to an excellent start.
When planting out pot grown plants it is best to untangle and spread out the roots, shake off excess soil and plant at the same level as it grew in the container.
Hostas thrive particularly well in pots but they do require adequate drainage particularly small or miniature varieties. For miniature varieties we find a 5 : 1 mix of soiless compost to sharp grit to be ideal but for large hostas a John Innes No 2 mix with 10% added grit tends to work better and is less prone to drying out.