The best soil for hostas and how to improve it

Hostas forgive a lot, but soil is where they show the difference most clearly. In rich, moist soil they grow into big, lush clumps; in dry sand or wet clay they stay small. Here is what hostas want from the ground, how to read your own soil and how to improve it before you plant.

What soil do hostas like?

• Rich in organic matter. Compost, leaf mould and well-rotted manure hold water and food and keep the soil crumbly.
• Moist. The RHS aims for hosta soil that stays at least slightly damp 15 cm down, even in summer.
• Well drained. Moist is not the same as wet: hosta crowns can rot in soil that stays waterlogged.
• Not fussy about pH. Hostas grow in slightly acidic to neutral soil and cope with most ordinary garden soils; structure and moisture matter far more than pH.

How to read your soil

Improving clay soil

Clay holds plenty of water and food, which hostas like, but it can stay wet and cold in winter and set hard in summer.

1. Dig in a generous layer of compost or leaf mould over the whole bed, not just the planting hole, so the hole does not become a sump.
2. Work the soil only when it is not sticky; digging wet clay ruins its structure.
3. Where water stands for days, plant on a gentle mound or in a slightly raised bed so the crown sits above the wettest layer.
4. Mulch every spring; worms carry the organic matter down and open the soil over time.

Improving sandy soil

Sand drains fast and dries out quickly, so the aim is to help it hold water.

1. Dig in plenty of compost or well-rotted manure before planting.
2. Choose thick-leaved varieties, which the RHS recommends for drier soils, such as Big Daddy or Devon Green.
3. Mulch 5–10 cm deep and top it up each spring.
4. Water deeply in dry spells, especially in the first summer.

Soil under trees

The ground under trees is often dry and full of roots. Improve small planting pockets between the roots rather than the whole area, and never pile new soil over a tree's roots: Nebraska Extension warns that even a thin layer can harm the tree. Our guide to hostas under trees covers this in detail.

Compost for hostas in pots

In containers you choose the soil. The RHS suggests a peat-free multipurpose compost or a loam-based one such as John Innes No. 3, which is heavier and steadies a tall pot. For free drainage, BBC Gardeners' World mixes peat-free multipurpose compost with an equal volume of fine grit for new divisions. More in our guide to hostas in pots.

Feeding the soil

On fertile ground, a yearly mulch of compost is all a hosta needs, according to the RHS; on poor soil it suggests a general fertiliser in early spring. Wait about four weeks after planting before feeding a new division, as Iowa State advises, and do not overdo it: soft, overfed growth attracts slugs and can make roots rot.

Preparing a new bed, step by step

1. Remove perennial weeds and their roots.
2. Spread 5–10 cm of compost or well-rotted manure over the whole area.
3. Dig or fork it into the top spade's depth.
4. Let the soil settle for a week or two if you can, then plant.
5. Plant the crowns at soil level, water in and mulch.

Our planting and care guide covers depth and spacing, and when to plant hostas covers timing.

Common mistakes

• Improving only the planting hole in heavy clay, so that it fills with water like a pot.
• Adding sand to clay in small amounts, which can make it set harder.
• Piling topsoil over tree roots to make a bed.
• Feeding heavily instead of improving the soil itself.

In short

• Hostas want moist, well-drained soil rich in organic matter.
• Improve clay and sand alike with plenty of compost over the whole bed.
• Raise the crown slightly where water stands; mulch every spring.
• Feed lightly: a yearly compost mulch is enough on fertile ground.