Growing hostas

Hostas are some of the best foliage plants for shade, and among the most frustrating. Most of the damage people blame on “slug season” happens in a few weeks each spring, when soft new leaves unfurl into mild, damp weather. Plan for those weeks and hostas become far easier to grow.

There is no slug-free planting month

We are often asked when to plant hostas to avoid slugs. The honest answer is that planting time makes little difference. Whenever you plant, the risk point is the same: the next flush of new shoots in spring, when the leaves are thin and tender.

What does make a difference is the variety you choose, where you plant it, and what you do while the shoots are coming through.

Choose varieties slugs like less

Leaf thickness makes the biggest difference. Slugs prefer soft, thin leaves and usually do less damage to thick, waxy ones. Many blue-leaved hostas have a waxy bloom that makes the leaves tougher and less palatable.

Varieties with a good reputation include Hosta ‘Devon Green’ (glossy, dark green leaves), H. ‘Blue Elf’, H. ‘Autumn Frost’ and H. ‘Sum and Substance’, along with the blue H. Tardiana Group. “Resistant” is not the same as immune, but you should usually see fewer holes.

The varieties to avoid if slugs are a problem are thin-leaved ones, especially those with a lot of white in the leaf.

Where to plant them

Hostas grow best in part shade, in fertile soil that stays moist but drains well, with shelter from cold, drying winds. Gold and yellow-leaved hostas colour best with some sun. Blue-leaved hostas need light shade: strong sun strips the waxy bloom and the leaves turn green. White-variegated types need some light to grow well, but not hot afternoon sun.

Our London Clay holds moisture well, which hostas like, but crowns sitting in winter wet can rot. Dig in plenty of organic matter before planting. See improving clay soil.

Not sure how much shade you have? The Flourish Sun Planner will show you, and our shade plants guide explains the difference between part, full, dry and wet shade.

When to plant and divide

Pot-grown hostas can be planted in spring or autumn. We prefer early autumn, while the soil is still warm, so the roots establish before winter. Spring planting works well too.

Buy the largest, healthiest plants you can. A big, established clump produces new leaves faster and recovers from damage better than a small plant.

Divide congested clumps in early spring as the shoots appear, or in early autumn while the soil is still warm.

Protecting new growth in spring

In our area the shoots usually come through from March to May. These are the weeks that matter.

• Clear hiding places around the crowns in late winter: old leaves, debris and loose mulch.
• Check on mild, damp evenings. Picking slugs off by torchlight after rain is one of the most effective things you can do.
• Don’t rely on barriers. In an RHS trial, copper tape, grit, eggshells, wool pellets and bark mulch made no real difference to slug damage.
• Consider biological control. Nematodes watered into moist soil can work well once the soil has warmed in spring. Follow the timing and soil temperature on the pack.
• Use pellets sparingly, if at all. Only ferric phosphate pellets are now sold in the UK. Follow the pack instructions and scatter thinly, never in heaps.
• Grow in pots. Pots are easier to check and protect, although slugs can still climb them. Watch for vine weevil in containers.
• Welcome predators. Frogs, toads, thrushes, hedgehogs and ground beetles all eat slugs.

Once the leaves have firmed up and fully opened, damage usually slows right down. For more on pests in our area, see garden pests and diseases.

Care through the year

Water in dry spells, especially hostas in pots. Feed in spring as growth starts. Cut the leaves down in autumn once they collapse, which also removes slug shelter. Lift and divide every few years if the clump becomes congested.

Good partners in shade include ferns, Brunnera, Epimedium and hardy Geraniums (Geranium).

Your hosta calendar

Make your own plan

Add shade plants to your free planting calendar for seasonal reminders, and use this guide for when to watch for slugs on new growth.

Related pages

• Shade plants: what to grow in part, full, dry and wet shade
• Flourish Sun Planner: see where sun and shade fall in your garden
• Garden pests and diseases: the problems we see most in local gardens
• Winter flowers and colour: hardy cyclamen and hellebores for the same shady spots

Let’s create your perfect garden

Planning a shady border? Our planting design and installation service matches plants to your aspect and soil, then supplies, plants and looks after them.

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