When to plant out tender plants – avoiding late frosts

Tender and half-hardy plants are damaged or killed by frost. RHS hardiness ratings provide an overview of plant hardiness, indicating the lowest temperature range a plant is likely to withstand.

• H2 plants are considered tender, tolerating temperatures as low as 1 to 5 °C, but won’t survive freezing
• H3 plants are half-hardy, tolerating temperatures as low as −5 to 1 °C. They may be hardy in coastal, mild or sheltered areas, but are at risk from early frosts

In practice, both tender and half-hardy plants are planted out after frost risk has passed and once nights are reliably mild, so above at least 7 °C.  

Check individual plant pages and the RHS hardiness scale if you are unsure of the hardiness of your plants.

Use this rule of thumb guide to when to plant out in your area, then confirm with your 5–10-day weather forecast and your garden’s microclimate:

1. Timings by UK area

These timings reflect the typical first safe planting time in an average year. The pattern moves from earlier in the south-west to later in northern uplands.

• South-west tip and along the south coast of England: first to second half of May
• Southern England and south Wales: second half of May
• Midlands, north-west England, Yorkshire and north Wales: end of May
• North-east England, southern Scotland and Northern Ireland: early June
• The Highlands and northern Scotland: mid June
  

2. Adjust timing for your microclimate

• Sheltered by walls, fences or hedges, or in urban areas or coastal spots (e.g. city centres, Anglesey, coastal Ayrshire): you may be 1–2 weeks earlier
• Exposed, rural or higher elevation sites (e.g. Shropshire, Cotswolds, Pennines): delay 1–3 weeks
• Frost pockets/valley bottoms (e.g. Welsh borders, Vale of Worcester): plant later or avoid planting in the lowest, coldest areas of your garden
  

3. Harden off before planting 

Hardening off takes 2–3 weeks, gradually acclimatising plants raised indoors or in a heated greenhouse to outdoor light, wind and cooler nights. Place in a sheltered, dappled sunny spot, increasing time outdoors in the daytime (bring in at night). This is essential for tender summer plants such as dahlias in pots, coleus, salvias, tomatoes, basil, peppers and French beans. 

Young tomato plants are sensitive to low temperatures

4. Check temperatures and forecasts before planting 

After hardening off

Gradually acclimatising tender or indoor-raised plants to outdoor conditions, to toughen them up and prevent a check in growth. Place plants outside in a sheltered spot during the day then bring indoors at night for a couple of weeks. Or place in a coldframe, opening the lid during the day.

, plant out when nights are consistently above 7 °C. Some common heat‑loving edibles, including tomatoes, peppers, basil and cucurbits, do better if nights are above 10 °C. This avoids the risk of chilling injury that often affects tender and half-hardy plants at lower single-digit temperatures. 

5. Be ready to protect 

If an unexpected chill is forecast, cover with reused or biodegradable

Anything that can be decomposed by fungi, bacteria and micro-organisms, so it doesn’t persist indefinitely in the environment. Biodegradable plastics are usually made from plants, such as bamboo, rather than fossil fuels. Ideally, products that claim to be biodegradable should break down quickly and leave nothing harmful behind. However, they may need specific conditions in order to biodegrade successfully or may produce greenhouse gases such as methane in the process.

fleece

A soft, fibrous, translucent material laid over or around plants hastening their growth and protecting them against weather and pests. Heavier grades of fleece give about 2°C of protection from frost. It is usually used without supporting hoops.

. Use a double layer on the coldest nights.

Protect plants at night if low temperatures are forecast

• Bedding and baskets: don’t be swayed by shop displays or garden centres selling seedlings
  

  A seedling is a young plant grown from seed.

  and young bedding plants
  

  Bedding plants are usually colourful half-hardy, short-lived or annual plants, grown for displays in beds or containers. They may be changed seasonally, with spring, summer and winter bedding displays each using different plants of appropriate hardiness and flowering times.

  early in spring. Follow the timings above, harden off thoroughly, and have reused or biodegradable
  

  Anything that can be decomposed by fungi, bacteria and micro-organisms, so it doesn’t persist indefinitely in the environment. Biodegradable plastics are usually made from plants, such as bamboo, rather than fossil fuels. Ideally, products that claim to be biodegradable should break down quickly and leave nothing harmful behind. However, they may need specific conditions in order to biodegrade successfully or may produce greenhouse gases such as methane in the process.

  fleece
  

  A soft, fibrous, translucent material laid over or around plants hastening their growth and protecting them against weather and pests. Heavier grades of fleece give about 2°C of protection from frost. It is usually used without supporting hoops.

  to hand.
• Larger container plants (e.g. citrus, tender houseplants): introduce to strong sunshine gradually, starting in dappled shade; bring under cover on cool nights until temperatures are stable.
• Tree ferns and Japanese bananas: these are fairly hardy plants (RHS Hardiness Ratings: H3 and H2) so their winter wraps (fleece/hessian) are removed sooner – generally late April or early May in many areas, later in colder/northern locations. See our guides to growing tree ferns and bananas for more information. 

The term ‘last frost’ date is often used interchangeably for when to plant out. In fact, the timings of these two events are quite different, and here’s why:

• Last spring ‘air frost’ is the final night near or below 0 °C, which can scorch or kill tender growth through freezing. This typically occurs two to four weeks before it is safe to plant out.
• ‘Ground frost’ is still common after the last air frost. It occurs when the nights dip between 1 to 4 °C. Ground frost is a curious phenomenon: on clear calm nights, leaves and soil lose heat to the sky and can become colder than the air above them. In the early morning, you may see a light icy layer of frost on the grass – which gives rise to the alternative name – ‘grass frost’. It can sometimes kill tender and half-hardy plants, but will often cause them to grow slowly and poorly for many weeks.
• Plant out once the nights are consistently forecast to be above at least 7 °C. Waiting until the temperatures are milder helps tender plants grow away well, rather than stalling. This is the basis for the dates given in the When can tender plants go outside? section above.
• Don’t forget: harden off your tender plants to acclimatise them to outdoor conditions for maximum success.