Planting Hostas in soil:Preparation is the key to success. If you can double dig your hosta or flower bed in early autumn and leave the sods of soil intact do not walk over what you dig. Allow the frost in the winter months to break the sods down. Then in Early Spring fork over the soil and rake to the required level. At this stage I would apply an organic slow release fertiliser and rake it in. When digging your planting holes allow at least twice the size of the hosta clump you are going to plant. So if the clump is 10cm wide dig your hole 20cm wide and twice the depth of the clump. Add leaf mould or similar organic compost to the base of the planting hole and lightly fork in. Mound the soil up like a cone shape in the centre of the hole. Make sure your hosta division the roots are not tangled up tease the roots out like a fan shape and spread the roots over the cone making sure the eyes (growing points) are at the same level as planted at before. Now gently fill in around the roots with a good mix of garden soil, grit and garden compost. Do not firm too much you need to allow air pockets to promote good growth. Now water the plant in with a fine rose watercan always start watering away from the spot you want to water first then move your watercan over the planted hosta this stops the soil getting compacted. If you just tip your watercan out right away over your hosta plant this puts out a heavy spray of water usually washes the soil away from the centre of the plant.
Planting Hostas in Containers:You can make your own potting compost or buy in a good proprietor brand of soil based compost. You can use peat based compost provided it has slow release fertiliser added to sustain the plant growth.
Making your own potting compost:- Good top soil that has been riddled and if you can sterilised to this add 10% 4mm washed grit, organic matter like leaf mould or composted shredded waste paper or composted seaweed. Add dolomite (magnesium) lime at the rate of 3kg to 1000 Litres of compost mix. Mix the ingredients well and add water as required. When you lift the compost up in your hand it should be moist when you squeeze the comopost in your hand no water should come out just leave your hand feeling wet.
Buying in a potting compost:- Always go for a soil based compost if possible and add extra 4mm grit at 10% per volume more for using to plant up mini hostas. Bought compost make sure the bags look like new avoid bags that have been sitting for a long time in the garden centres or diy store. When compost sits too long the nutrients get leached out of the compost and become concentrated at the bottom of the bag this causes root scorch.
When you made your choice for potting compost soak your hosta division for a minute before potting up to allow the roots get adjusted to shock of moving. Place your compost straight into the container if the container is less than 20cm wide over this add broken crocks or packaging chips at the base then a couple sheets of newspaper over this and some compost. Hold the hosta division by the eye(s) and fill in the compost around the plant overfilling the pot then gently with your 2 index fingers push the cmpost down lightly and give the container a gentle tap this will settle the compost enough without over compacting it. Fill the compost up to about 2.5cm from the rim with the eye(s) of the division level with the top of the pot then fill with 10mm size or bigger grit to mulch the container. The stones on the top of the pot help to keep moisture in the container and stop moss growing on the surface of the pot. Now you can water your pots and leave to drain.