Cold protection

FIRST/LAST FROST DATES in NORTHERN ENGLAND AND SCOTLAND

snow-ravensworth-est-silverhills-jan-29-15
Snowfall over the Ravensworth Estate, Gateshead, January 2015.

Just when you think summer’s round the corner, a blast of Arctic air can ruin a gardener’s plans.

Get the fleece ready for any fruit trees in blossom; take in any plants you’re hardening off and anything slightly tender.

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 frosts will be, so you can plant out tender annuals and veg – and gather in your harvest – without your efforts coming to nothing.

Snow December 2012
Our last meaningful snow that lasted more than a day, December 2012

Of course, it’s not just how far North you are, but your altitude (the higher, the greater the risk).

Rural areas cool faster than cities, as the concrete in built-up areas releases heat stored during the day slowly – 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.

Here’s a list of Northern English and Scottish towns and cities and their expected first/last frost dates.

I was very surprised when I read it and of course, this is only a guideline – I watch Countryfile’s weekly weather round-up and check the Met Office daily.

You never know… I remember it snowing in June once.

Snow gryphon
A rare fall of snow, starring Kenneth the gryphon
  • 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

RHS HARDINESS CLASSIFICATIONS

Echium
Echium pininana in fleece bags, January 2015. They survived the winter

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 areas or coastal areas. Can be grown outside once risk of frost is over. (Most succulents, subtropical plants, bedding plants, spring-sown vegetables.)

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.)

Leeks
Leeks can stand all winter as they are hardy

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) in 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) in 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.


TOP 10 TIPS ON WINTER PROTECTION

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

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

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

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

Rheum palmatum
Rheum palmatum – keep the crown clear or it may 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 the 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.