When to cover roses in Estonia: go by the thermometer

Roses are covered by the thermometer, not the calendar. Mound them up with the first steady frosts, and put the breathable winter cover on once nights hold at −5 to −7 °C and the ground starts to freeze. Inland Estonia usually gets there in the second half of November; the coast and the islands later, sometimes not until December. Covering too early kills more roses than frost does, because they rot underneath.

Two stages: mound first, cover later

The classic mistake is doing everything in one afternoon in mid-October. Split the job in two:

• Mounding – after the first frosts, once the leaves start to drop: usually late October or early November. A mound of soil does not stop the rose hardening off, and the graft union is already safe if a cold snap arrives early.
• Dry, airy cover (spruce boughs, or fleece over hoops or a frame) – when nights stay at −5 to −7 °C and the soil begins to freeze. A good sign: the frozen crust on the ground no longer thaws by midday, several days running.

Light frosts down to −5 °C do an uncovered rose no harm. They are its cue to stop growing and move sugars into the canes.

Why rushing does harm

Cover a rose in mild weather and it sits at +5 to +10 °C in damp air. Buds start to grow, mould spreads over the canes and the bark begins to rot. By spring the canes are brown, soft and blotched, and only the roots are still alive. An Estonian winter adds a second risk: December and January often bring several days above freezing in a row, and a tightly wrapped bush is back in a greenhouse.

What to do in September and October

• Stop nitrogen in July. Later feeding pushes soft growth that cannot ripen before winter.
• Feed with a phosphorus and potassium autumn fertiliser by the end of September. Potassium raises the concentration of cell sap and helps the canes turn woody. Use the rate on the pack (for ornamental shrubs usually about 40 g/m²), on moist soil, lightly worked in.
• Stop deadheading from late August. Let the hips form: that is another signal to go dormant.
• No hard pruning. In autumn, only trim soft tips and whatever gets in the way of the cover.
• Water if the autumn is dry: one deep soak in October. Moist soil freezes more slowly and the canes dry out less over winter. In a wet autumn, skip it.

Which roses need what

Hybrid teas, floribundas, grandifloras and miniatures

Always cover these: a soil mound plus dry, airy cover. The graft union is their weak point, and the buds kept under the mound will send up new canes even if everything above dies back.

Climbers

The most work. They flower on last year’s wood, so the canes have to come through winter whole. In October, while they still bend, untie them from the support and lower them gradually. Lay them on spruce boughs or boards, never on bare soil, pin them down with hoops and cover them like the bushes.

Standard (tree) roses

The graft sits at the top of the stem, so mounding does nothing for it. A young standard is bent to the ground and covered whole; an older one that no longer bends gets its head wrapped in two layers of fleece and its stem insulated.

Park roses, rugosas, Canadian roses and many shrub roses

Rosa rugosa and its hybrids, old park roses and the Canadian Explorer and Parkland series overwinter in Estonia without cover. The exception is their first winter after planting, when a 15–20 cm mound does no harm. If you do not know which group your rose belongs to, mound it: that never hurts any rose.

How to cover, step by step

1. Strip the remaining leaves and rake up fallen ones: black spot overwinters on them. Do not compost them.
2. If you like, spray the bare canes with a copper fungicide as a preventive, strictly following the label.
3. Shorten the canes to 30–40 cm so they fit under the cover. Do not cut climbers.
4. Mound the base 20–30 cm high. Bring the soil in from elsewhere: dry garden soil or a mix with compost. Do not scrape it up from around the bush, or you will expose the roots. Pure peat is a poor choice: it soaks up water and freezes into a block of ice.
5. Once −5 to −7 °C sets in, put up hoops or a frame and cover with spruce boughs or two layers of fleece of about 60 g/m². Leave an air gap between the cover and the canes.
6. For the first few weeks leave the ends open, and close them only when the frost is steady.

Spruce boughs also hold snow, and snow is the best insulation there is. Mice love to winter under thick mulch and hay, so if you have many, keep hay and straw out of the cover.

Thaws: how to stop roses rotting

If it stays above +3 to +5 °C for several days, open the ends of the cover, and close them again once the thaw is over. A cover that breathes (spruce boughs, fleece on a frame) copes with thaws far better than anything involving plastic sheeting. If you need plastic against rain, put it only on top of the frame and leave the sides open.

In spring

Remove the cover gradually, on overcast days, once the snow has gone and the ground starts to thaw: in Estonia usually in April. Open the ends first, then take the cover off completely a week later. Pull the mound back last, when the soil has thawed a spade’s depth: canes in warm air with roots in frozen soil will dry out. Prune only after that, back to live buds.

What not to do

• Do not cover in October just to get it done: that is the surest way to rot.
• No nitrogen or manure after midsummer.
• No plastic sheeting directly on the bush: condensation collects under it and mould follows.
• Do not mound with bagged peat alone, and do not scrape soil away from the roots.
• Do not leave leaves on the bush or beneath it.
• Do not uncover in one go on a sunny day: the canes will scorch.

Frequently asked questions

Can I plant roses in autumn?

Yes. Container roses can go in until early or mid-October: they need 3–4 weeks to root before the frosts. Set the graft union about 5 cm below the soil and mound the bush before winter.

The frost came before I covered my roses. What now?

Mound up the base straight away, with soil or compost brought in from elsewhere: that matters most. The airy cover can go on later, on a dry day.

Can I cover roses with plastic?

Only over a frame, as a rain shield, with the sides open. Plastic laid directly on the bush is the main cause of rotting.

Do park roses and rugosas need covering?

Established plants do not: they overwinter in Estonia uncovered. Young plants only need a soil mound in their first winter.

When should I uncover roses in spring?

Once the snow has gone and the ground begins to thaw, usually in April. Take the cover off in two or three stages in cloudy weather, and the mound last.

From our catalogue

More varieties in roses. For autumn feeding, see autumn fertilisers.