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Cold protection

The first and last frost dates in Northern England and Scotland

Just when you think summer’s around the corner, a blast of Arctic air can ruin your plans, so it’s important to know about cold protection in gardening,

I never miss Countryfile’s weather forecast on Sunday evenings. However you get your weather information, make sure that you do. That way, you can plan for any weather surprises. Always have horticultural fleece ready for early fruit trees in blossom; take in any plants you’re hardening off and anything slightly tender.

Cold protection
Snowy view from my window over the Ravensworth Estate and woods

At 55°N, where I live, we’re on the same latitude as Newfoundland and Alaska. We should thank our lucky stars for the Gulf Stream keeping us relatively temperate.

To plan your garden successfully, you need to know approximately when your first and last frost will be. This will determine when you can plant out tender annuals and veg, without your efforts coming to nothing. As the weather gets colder, spiders try to get into your home – here’s how to keep them out.

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  • Snow blocking the office door - there's a step under there!
  • Korean fir
  • Holly in snow
  • There's a path under there...
  • Drifting snow on stairs
  • Arty trellis on black wall
  • It's bin day tomorrow...

The Beast from the East 2018 and worse

I took these pictures on February 28, during the Beast from the East, the worst winter we’ve had for years. The lowest temperature I recorded was -7°C on two consecutive nights. We had a similar event in February 2021 – beware of the east wind! The snow wasn’t as heavy but the temperatures were lower for longer – between -5°C and -7°C for five consecutive nights. Read more about the Beast from the East.

This proved a breaking point for many plants, especially the Echiums, despite cold protection. The Tetrapanax rex (Chinese rice paper plant) last all its leaves for the first time. Many plants, even the Fatsias, have frost burn on their leaves.

  • Snowy garden, February 10 2021
  • Tropical bed, February 10
  • Frozen pond, February 25
  • Snowy garden and euphorbia, February 25
  • Cornus Midwinter Fire and Chinese witch hazel, February 10
  • Echium in fleece covered with snow, February 10
  • Long border, February 10
  • Photinia Pink Crispy, February 10
  • Fatsia japonica variegata, February 10

Cold protection – How high’s your garden?

Of course, it’s not just how far north you are, but the altitude of your plot. The higher you are, the greater the risk of frost, and the more cold protection you’ll need. My garden lies at 114m (375ft) above sea level, luckily facing west.

Rural areas cool faster than cities, as concrete in built-up areas releases heat stored during the day slowly. This can really make a difference of a few degrees. Coastal areas also benefit in winter. The sea is warmer than the land in the colder months, the opposite of summer.

  • Not-so-tropical bed - Echium pininana and windmill palm
  • Cold damage on the Echium, February 25
  • A cluster of Echiums under netting
  • Echiums fleeced against bitterly cold weather
  • Excessive winter wet and cold was too much for this Echium

Frost dates

Here’s a list of Northern English and Scottish towns and cities and expected first and last frost dates. You never know… I remember it snowing in June more than once. Get your cold protection ready…

  • Bradford: Mid-October/Mid-May
  • Hull: Mid-October/Early May
  • Leeds: Late-September/Mid-May
  • Liverpool: Mid-October/Early May
  • Manchester: Mid-October/Early May
  • Middlesbrough: Mid-October/Early May
  • Newcastle-upon-Tyne/Gateshead: Early October/Late-May
  • Sheffield: Mid-October/Mid-May
  • York: Mid-October/Mid-May
  • Aberdeen: Early October/Late-May
  • Ayr: Mid-October/Mid-May
  • Dundee: Mid-October/Early May
  • Edinburgh: Early October/Mid-May
  • Glasgow: Mid-October/Mid-May
Cold protection
Bananas, ginger, yucca, Washingtonia and cacti, December

Cold protection – RHS hardiness classifications

The RHS hardiness classifications are in Centigrade and refer to the LOWEST temperature a plant will normally survive.

H1a:  Greater than 15°C – heated greenhouse all year.

H1b: 10 to 15°C – heated greenhouse. Can be grown outside in summer in hotter, sunny and subtropical sheltered locations, but performs better under glass all year.

H1c: 5 to 10°C – heated greenhouse. Can be grown outside in summer in most of the UK. (Most bedding plants, tomatoes and cucumbers.)

H2: 1 to 5°C – tender. Tolerant of low temperatures, but not surviving frost, except in frost-free southern inner-city or coastal areas. Can be grown outside once the risk of frost is over. (Most succulents, subtropical plants, bedding plants, spring-sown vegetables.)

Plants getting hardier

H3: 1 to -5°C – half-hardy. Hardy in coastal and mild parts of the UK except in severe winters. At risk from sudden (early) frosts. May be hardy with wall shelter or microclimate. Likely to be damaged or killed in cold winters, particularly with no snow cover or if pot grown. (Many Mediterranean plants, spring-sown vegetables.)

H4: -5 to -10°C – hardy (average winter). In most of the UK apart from inland valleys, at altitude and central/northerly locations. May suffer foliage damage and stem dieback in harsh winters. Some normally hardy plants may not survive wet winters in heavy soils. Plants in pots are more vulnerable, particularly evergreens and bulbs. (Many herbaceous and woody plants.)

H5: -10C to -15°C – hardy (cold winter). Most places in the UK even in severe winters. May not withstand open/exposed sites or central/northern locations. Many evergreens will suffer foliage damage; plants in pots at increased risk. (Many herbaceous and woody plants, brassicas, leeks.)

H6: -15C to -20°C – hardy (very cold winter). All of the UK and northern Europe. Plants grown in containers will be damaged unless given protection. (Herbaceous and woody plants from continental climates.)

H7: Less than -20°C – very hardy in the severest European continental climates.

Cold protection
Euphorbia wulfenii under a fleece bag after planting – however, this hasn’t been necessary since

Top 10 tips on cold protection

Here are my top 10 tips for helping borderline plants survive the winter:

1. Gunnera: Cover the crown with its own huge leaves to stop it from rotting.

2. Euphorbia wulfenii, lavender, rosemary: Hardy down to -5°C; good drainage is the key – add grit when planting.

3. Red hot pokers: Tie foliage in a top knot to protect the crown. Good drainage is essential.

4. Mulching: A 2″ mulch of compost acts as an insulating blanket and smothers weeds.

5. Giant mullein (Verbascum bombyciferum): Mulch heavily and watch out for rot.

Cold protection
Rheum palmatum – keep the crown clear or it may rot

6. Ornamental rhubarb (Rheum palmatum) and Rodgersia: Cut back. Don’t mulch over the crowns as they can rot.

7. Herbaceous perennials: Leave dead stems to give protection for the crowns.

8. Conifers: Gently knock heavy snow off branches, which can be broken by weight.

9: Snow: A covering provides an insulating ‘blanket’ to bare soil, so let it melt naturally.

10. Grass: Don’t walk on a frosted lawn – it damages the turf.

Cold protection updated 2023