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It is really starting to feel like winter will never end, isn’t it? I bet you wish you could predict exactly when the cold nights would finally be over. Well good news, you can learn all about your last frost date her in my UK frost dates guide, and the implications of frost dates for your garden.
If you do any gardening, mark first and last frost dates in your calendar. Knowing these dates is essential for planning a productive cut flower garden. These dates guide you when planning your flower patch, and deciding when to start seeds, transplant out seedlings, and whether to protect your flowers.
Now you have decided which cut flowers you want to grow, you need to know when to grow them! Here’s everything you need to know to be confident that frosts won’t result in any nasty surprises in your growing season this year!
What is a frost date and why do they matter for UK gardeners?
Frost dates are days when temperatures fall below 00C (or 32F). On these days, plants that aren’t hardy may be damaged or killed so it is important to understand these timescales when planning your garden.
First and last frost dates define the average times of year when temperatures dip below 00C, whether for occasional nights, or consistent chilly weather for weeks on end (Does anyone else remember the Beast from the East?) In the UK this period is usually between October and June depending on your altitude, latitude, hills/valleys, distance to the sea and whether you are in an urban or rural location.
Last Frost Date: The average date of the final frost in spring. It marks the safe time to plant frost-sensitive flowers outdoors. The average last frost date in the UK ranges from early March to the end of June. That variation will have a huge impact on when you can plant flowers for gardening success!
First Frost Date: The average date of the first frost in autumn. It signals the end of the growing season for tender plants.
A side note about hardiness zones
Hardiness zones indicate typical climates of geographic areas. There are 13 zones based on the average extreme minimum winter temperature during the year, and you can use this information to determine which perennial plants are most likely to thrive where you are. UK zones range from zone 6 – 10. For example, in York we are in hardiness zone 8b, with minimums of -9.4°C to -6.7°C.
While zones focus on winter lows, frost dates provide more specific planting guidance. Combine both for smarter planning.
When is my last frost?
There are numerous online resources that will predict the first and last frost dates for your area of the UK. There can be variations in the predicted date depending what data they use to determine it, and as a disclaimer, weather is unpredictable so the actual date could (will probably) be different! My poor zinnias had a shock when I thought they would be safe from the cold last year: always keep an eye out on local weather forecasts in real time!
Why can’t I grow cut flowers whenever I want?
Sowing seeds and growing plants too early can cause them to rot from cold and wet weather conditions, go dormant in the cool soil, suffer because of the cool weather, get leggy from too little daylight and generally become week, unhealthy plants. Additionally, repeated freezing and defrosting can destroy plants.
Hardy annuals can withstand light frosts and be sown and planted out earlier, while tender annuals must wait until after the last frost to be planted out.
How do frost dates impact seed sowing?
You will see phrases like “Sow 4-6 weeks before last frost date” and “plant out after all risk of frosts has passed”, but what does this actually mean for your garden?
The last UK frost date guides when you sow flower seeds because it depends on the type of flower and how it can tolerate frost. I am always jealous of fellow UK growers who see their last frost down South much earlier than I do in the North. I used to follow their lead with sowing planting dates leading to reduced success owing to these differences in temperatures.
Use YOUR frost dates as your planting guide.
It’s easy to get sucked in when seed packets say you can sow them from Feb – June. I am the keenest bean around so if it says February, historically I would be sowing in February! But the reality is that this is only appropriate in certain areas and my plants suffered and seeds were wasted. I should have waited until April.
Use your last frost date as a guide for all sowing plans! Start achillea 8 weeks before your last frost, start cosmos 4 weeks before, do sunflowers just a few weeks before. Don’t get sucked into packets date ranges. Make an individual sowing plan for your climate and area.
Can I utilise frost dates to grow more flowers?
You can also use the knowledge of last frost dates to guide you in staggering sowing for continuous blooms. When you sow the same flower multiple times at various intervals is called succession sowing. This can help spread out your blooms, so they don’t come all at once, and is particularly useful for plants that produce a single flower.
For example, starting a few weeks before my last frost, I will sow sunflowers every 2-3 weeks. Using my first frost date in autumn, the days to maturity for sunflowers, and a buffer of a few weeks to account for cooler shorter autumn days, I know my last sowing has to be in midsummer to ensure these have enough time to flower before the forsts.
Protecting Your Plants before and after frost dates
Knowing your local frost dates can help you protect your plants from frost damage. Keep an eye on the weather forecast to figure out how to best protect your plants and delicate new Spring growth.
You can utilise the following gardening frost protection tips when temperatures fall below freezing:
- Cover plants with frost fleece, or other suitable protection. Make sure to pin the fleece down and cover the plants all the way to the ground
- Move pots to a sheltered location like a porch, greenhouse or cold frame.
- Mulch around plants to insulate the soil and prevent frost reaching the roots
- Water your plants in the morning before a frost to help protect the roots. Moist soil retains heat better than dry soil
Note that younger plants can be more susceptible to frost damage than mature established plants, so even hardier varieties may need additional protection when seedlings or small plants.
At the other end of the season, you can take these steps to extend to growing season around the first frost. Harvest tender blooms or cover plants to protect in cooler temperatures.
Understanding frost dates is key to a thriving cut flower garden. By timing your sowing, planting, and harvesting around these dates, you will enjoy maximum blooms from your garden. Unfortunately its easy to be caught out by unexpected frosts, but by reading this blog and arming yourself with the knowledge and techniques to support your plants in cooler weather, you have a reduced risk of frost damage.
Do you have questions about your local frost dates? Comment below and let us know how you’re gardening by frost dates this year.
