Protecting tender plants over winter

Protecting Tender Plants Over Winter

Preparing your tender plants for winter is an important late autumn task. In this lesson, we'll look at how to protect plants left in the ground and how to decide whether to leave a plant in or lift it to bring indoors.

If you have half-hardy or tender plants, it's really important to do one of the following before you get hard frosts.

1. Protect them.
2. Take cuttings.
3. Lift them and bring them indoors.

Dahlias we lift as we'll see later, and that's sensible as they often need dividing too.

How to Protect a Plant Left in the Ground

An example is Hedychium (ginger lily) - if I lifted them, they'd be set back next year as they resent disturbance, so it's best to leave them in.

• The tops are fine to be frosted, but we don't want hard frost penetrating the roots over successive weeks.
• Protecting tender herbaceous plants is all about protecting the roots.

1. Cut the stems down.
2. Protect the crown of the plant. We use fern (e.g. Dryopteris, Polystichum) and bracken fronds from the garden.

• This gives some insulation and stops the crown from sitting wet, reducing risk of rot and winter damage.
• Fern fronds need to be cut off in winter anyway to allow new fronds to emerge, and it's good to do so before there's any risk of cutting the shoots of the new fronds.

1. Lay fronds over the crown in one direction, and then more at 90 degrees.
2. To stop wind or animals moving the bracken, use short pea sticks stuck into the soil - put four around the edge and bend them over to form a bit of a low cage over the fronds.

Other Materials You Can Use

If you don't have fern or bracken fronds, you can mulch with homemade garden compost or other organic matter to insulate the plant.

• Be aware that mulch speeds up growth of new shoots (through warmth and feeding), so these can be vulnerable to late frosts when the mulch is removed.
• The fronds provide protection without bringing on the plants underneath, so they are my preferred material.

If you don't have bracken or ferns and don't want to use mulch, have a look round your garden to see if there's anything else you can use that's bulky and can add a layer of cover on top.

• Try some kind of foliage or ornamental grasses such as Miscanthus.

Leaving in or Lifting Out

As well as Hedychium, other plants you might choose to leave in, often because they resent disturbance, include:

• cannas
• Melianthus major
• some of the tender salvias that don't really have top growth in winter but whose roots need protection.

It's common practice to lift dahlias; you can leave them in and protect them as above, but lifting is a useful opportunity to be able to divide them.

You might also choose to lift because you want to use that space in spring.

• Hedychium don't start coming into growth until quite late - perhaps the second or third week of May - so the space is a bit wasted until then.
• You could sow some very light annuals to colonise the top inch or so of soil and not be affected by the ginger lilies underneath.
• If you want anything of more substance, you'd need to lift the Hedychium so you can plant biennials such as wallflowers and bulbs such as tulips.

It's not an obvious decision - you have to think about the implications.

• For plants that need winter protection but don't like disturbance, and you're happy not to free up the space, it's a very good idea to use bracken or another leaf material as a winter duvet.

Further Resources

Further detailed information on how to protect plants over winter, the different methods you can use and the plants they're suitable for can be found on the RHS website:

• RHS guide to preventing winter damage
• How to overwinter tender plants by wrapping
• How to overwinter tender plants by lifting or mulching

Plant Directory

Canna species and cultivars

Cannas, canna lilies

Tender rhizomatous perennials

Cannaceae

Dahlia species, hybrids and cultivars

Dahlias

Tender or half-hardy tuberous or herbaceous perennials

Asteraceae

Dryopteris species and cultivars

Male fern, shield fern, wood fern, buckler fern and more

Hardy herbaceous, semi-evergreen or evergreen ferns

Dryopteridaceae

Hedychium species and cultivars

Ginger lilies

Half-hardy or tender rhizomatous perennials

Zingiberaceae

Melianthus major

Great honey flower

Half-hardy evergreen subshrub

Francoaceae

Miscanthus species and cultivars

Eulalia grasses

Hardy deciduous or evergreen grasses

Poaceae

Polystichum species and cultivars

Shield fern, holly fern and more

Hardy evergreen or semi-evergreen ferns

Dryopteridaceae

Pteridium aquilinum

Bracken

Hardy herbaceous perennial

Dennstaedtiaceae

Salvia species and cultivars

Sages

Hardy, half-hardy or tender annuals, biennials, herbaceous or evergreen perennials or shrubs

Lamiaceae