Overwintering Hosta and other Perennials

Step-by-Step guide to overwintering hostas and other perennial plants.

University studies show that hostas need at least 30 days of temperatures about 42 degrees or lower AND the longer the cold dormancy the better.  (See this study from Auburn University). If they don’t get a cold treatment, they will lose vigor year after year and eventually die out.

overwintering hostas house in winter gardenDifferent regions of the country have different growing characteristics (soil pH and type, temperature and temperature extremes, wind, sun). Check for information online or contact your local hosta society, extension agent or university if you have more specific concerns about plant overwintering needs in your area. Here is our Hosta Society Links Page – find your local society here!

What to do when overwintering perennials

Observe “microclimates”

Specific areas of your garden may have different “microclimates” that vary from the rest of your garden because of sun, soil, moisture, freezing, wind, temperature, and competition from roots from other plants.

Please carefully observe the different areas in your garden for yearly trends – some places can get warmer or colder faster than others, or perhaps you know there is a prevailing wind usually coming from one direction that could dry out plants.  If you’ve had renovation/construction done and added soil fill, that area may react differently than your surrounding soils.

Watch out for pests

Certain regions of the country have area-specific pests – voles, moles, gophers, etc. that can eat your plants and their roots during the winter.  There are traps, baits, and sonic or other disruptors to discourage predation by rodents and other pests. Learn more about Hosta Pests.

Plan for unpredictability

The climate seems to be more unpredictable in recent years – not only from season to season but within the same season.  Try to prepare for the worst extremes of temperature and precipitation/snow.

Pots are not containers

Pots and containers often require different overwintering.  See our Info Page on Containers for more information on overwintering pots and containers – there are a few different ways to try for the best outcome.

Consider each plant’s genetics

WaltersGardens Geranium sanguineum New Hampshire Purple
Geranium ‘New Hampshire Purple’

Based upon the genetics of the plant, the needs of the plant can vary.  We try to offer the most comprehensive information we can; if you are worried about a particular plant, do some research into its history, area of origin, and species lineage – this will help you to predict how it will react to environmental changes.

Hostas with plantaginea and lancifolia lineage are more sensitive to cold. Growing zone and species lineage are big factors in determining the needs of your plant – see our Additional Information tab on our individual products’ Buy Pages and Plant Information Pages for information on growing zone and species lineage.

Snow is good!

Remember that snow is a good insulator.  More plants die in the winter when there isn’t enough snow. So if you see snow cover your plants entirely, don’t worry – think of them as hiding in protective snow forts for the winter!

What NOT to do when overwintering perennials

Be careful what you use for mulch and how much!

As an example, do not put a foot of wood chips over plants and in particular new plants.  This is heavy, will compact, and will trap moisture and make it hard for the plants to ‘breathe’.  The roots can and will rot in a wet, low air-flow environment.

The best mulches are leaves, straw and other easily biodegradable materials

They’re light and breathable while offering protection from temperature fluctuations; they provide air pockets that insulate your plants.

Wood chips are more suitable for around trees and established woody perennials

They are also heavy and difficult to move each spring; it’s a better idea to use them in a more permanent way as weed control around (not over!) established plants instead of seasonal winter protection.  It’s very difficult for any plant to force its way up through wood chips every year – your plants might come up warped or not at all.  Plants that don’t die back to the ground every year and keep some woody stems above ground are not as bothered by wood chips.

Do not leave plants in containers outside standing alone

They might dry out, freeze and die.  Huddle them up and tuck them in! See our Info Page on Containers for help overwintering container plants.

Heucheras and Heucherellas are evergreen

heuchera forever purple 1b
Heuchera ‘Forever Purple’

This means they keep their foliage through the winter.  You can leave their foliage alone, though they will still need some winter protection, particularly the species that are adapted for more southern and warmer climates – the Heuchera hybrids with sanguinea and villosa species in their lineage. The species lineage information for each variety can be found on their pages on our website.

Don’t underestimate the pests

Do not underestimate the damage voles, moles, etc. can do, even to pots in your garage!  Covering your containers with hardware cloth, cage-like mesh tops, etc can help keep them out of your pots.  Traps, baits, and disruptors are also available to discourage them.  For more information on voles and other pest problems see our Hosta Pests Page.

Don’t uncover your plants too early in the spring

Late frosts and freezes can do significant cold damage! Plants that thaw and refreeze and thaw again are likely to have the most problems. Beware of areas that get quite a bit of sun in the winter- they may especially need mulch.

What you should do for most of your perennials

Preferably wait until a hard freeze to cut back MOST of your perennial plants.  Although gardeners may rightfully disagree, we believe it is best to remove dead foliage from the ground in the fall as it eliminate places for slugs, voles and moles to hide, reduces the chance of plant diseases and fungi and prevents raking in the spring when tender plants might be coming out.

Mark your plants with markers that stay in the ground and together. Remember the polystyrene plant tags you get with our plant or through other sellers can become brittle and break due to cold temperatures or come out of the ground.   Make a map of where your plants are located or get better markers. If you’re looking for sturdy markers that stay in place, why not try our Ideal Garden Markers?

If you use a powerblower or rake, remember you might remove your plant markers and lose the identity of your plants.

Make sure plants have been watered in the fall.

Cover first year plants with one or a combination of the following:

  • 6″ to 1 foot of straw.
  • 6″ to 1 foot of leaves.   Oak leaves are preferred as they are curled and thus do not lay as flat as other leaves and don’t break down as quickly.  The air pockets serve as insulation.
  • Leaves in a plastic bag.  Place bag directly over the plant(s).  The bag will keep the wind from blowing the mulch around AND make it easier to clean in the spring.
  • As the picture below shows, a bag laid sideways with a thick but not excessively heavy layer of leaves works best.  Stake and/or tie down to keep in place.

Leaf Bag Mulch Pic

Remove bags/mulch once all danger of a hard frost is past, ideally before their leaves unfurl in the spring.

What you should do for your tools, etc.

Drain irrigation systems, hoses, power washers, sprayers as the moisture can freeze, expand and break them.
If you have an older house, your outdoor faucets/spigots may not be ‘frost-free’ and will need the shutoff valve closed inside the house and then the faucet/spigot opened and drained.Clean your tools and oil them to prevent rust.

Bring chemicals or liquids inside where they won’t freeze or have their chemistry altered/spoiled. Make sure all containers are sealed or placed into plastic bags and sealed.

Update any written notes you have made – about what you did well last season, what you can do better, (fertilizer, water, etc) specific plant needs, what new varieties, colors, textures or heights you may wish to add to the garden next year.

Purchasing

To purchase perennial plants:  HostasHeucherasHeucherellasPeoniesAstilbeTiarella, and other Shade Companion Plants and Sun Companion Plants