The biggest question that runs through every gardener’s mind during winter and spring comes down to when to sow. Some plants will succumb to frosts, others will not. Some need heat to get started, while others thrive when planted directly outdoors.
Knowing when to plant hardy annuals and the difference between hardy annuals and half-hardy annuals will give you a really good headstart. It will help you avoid weather-related disasters and grow healthy, happy seedlings.
So, what is a hardy annual plant, what is a half-hardy annual, and when should I be sowing new flower seeds? Here we look at some definitions and general rules to help you get it right this season.
What is a Hardy Annual Plant? The Tough Guys
A hardy annual plant completes its life cycle within one year. However, unlike half-hardy annuals, it can tolerate frost; therefore, it can be sown outside in spring between March and April or in autumn around September.
Hardy annuals are straightforward to grow and often do better in rougher seed beds rather than the well-prepared beds needed for half-hardy annuals. They don't require protection and will recover after a hard frost. Their only requirement is that the soil is workable at planting, meaning it is not waterlogged or frozen. As slow-growing plants, they need a long season to get established so that they can flower in the summer.
Even though hardy annuals are generally pretty tough, they are not invincible. They can still rot in heavy wet clay soils, or become victim to hungry slugs or birds, so it's worth sowing a few more seeds than you think you might need and thinning them out later.
2026’s Must-Try Hardy Annuals
In 2026, we are seeing a real shift towards more pollinator-friendly mixes and softer colour palettes. Peach-fuzz tones and muted pinks are becoming increasingly popular alongside the classics that remain in stock every year. Here are some annual plants that are expected to be popular in 2026.
The ever-popular cornflower will be taking centre stage in many gardens this year, with varieties such as Cornflower Blue Ball flower seeds being beloved for their ability to add height and deep blue tones. Poppy seeds will also add a splash of colour to beds and borders with their blooms, with wide varieties such as Poppy Amazing Grey seeds now offering more muted and dramatic tones. Then the classic Love in a Mist Nigella Persian Jewels flower seeds, with their exquisite texture and charm, will help to add softer tones to our gardens too.
What is a Half-Hardy Annual? The Sun Lovers
Just like hardy annuals, half-hardy annuals also complete their life cycle within one year. However, unlike hardy annuals, half-hardy annuals cannot withstand frost. Planting them too early can result in them all being killed by an overnight frost, which is devastating when you've taken so much time and care to grow them.
As half-hardy annuals still require a long growing season to get going, we should start these off indoors using a heated garden propagator. A small amount of additional heat will help the seeds germinate and the plants grow. Once the risk of frost has passed, they can be hardened off and then planted outdoors. Don’t be tempted by a few warm days in April, as frosts are still a regular occurrence for most of the country until mid-May and later in some areas.
Half-hardy annuals are usually plants that originate in warmer places like Mexico and South America, where the growing seasons are long, and frosts are not a concern. We need to replicate these conditions at the start of our growing seasons to support them. Ensure they have warmth and plenty of light to help them feel at home.
If you don’t have a greenhouse and are starting your half-hardy annuals off indoors on a windowsill, make sure that it receives plenty of bright, indirect sun. Direct sun can scorch young seedlings, and if the area is not bright enough, they will grow thin and leggy. If your seedlings become leggy, pinch out the tops to promote lateral growth and make them stouter.
2026’s Must Try Hardy Annuals
Popular half-hardy choices for new flower seeds in 2026 will include rich colour contrasts, improved branching, and longer-flowering varieties. There is a growing interest in flower seed mixes that work well in community spaces and shared gardens. These spaces favour long flowering periods and resilient plants.
Expect cosmos to remain popular, with exciting colours and flower varieties such as fizzy purple and sensation mixed, taking centre stage. Zinnias seeds will also be seen quite a lot, with the more subtle and interesting colour palettes of their blooms gaining in popularity. Also, Nicotiana seeds, with their deep colours and beautiful tubular flowers, will see a resurgence, with gardeners falling in love with them all over again.
The Harden-off Cheat Sheet
The process of hardening off involves taking plants outside during the day and then back indoors at night. It should be done over 7 to 10 days to acclimatise plants to outdoor conditions. This will help prevent shock during transplantation. We can’t expect them to move from the warm, comfortable indoor conditions to the cold outdoors without prior warning.
If plants are shocked, it can inhibit their growth and increase their susceptibility to pest damage. While this job can seem a little draining, it's worth the extra time in spring to help nurture your seedlings.
A Wide Range of Quality Flower Seeds at D.T. Brown
Sowing annuals outdoors in the UK is fine, as long as they are hardy annuals. Hardy annuals require a long growing season and can withstand frosts. Half-hardy annuals also require a long growing season but are very susceptible to frosts, so will need to be started off indoors and planted outdoors after the risk of frost has passed.
Using annual wildflower seeds and looking out for RHS Plants for Pollinators logos will help if you want to create a natural look, or start your own wild-flower meadow.
When it comes to sowing, timing is everything, so make sure you know if your seeds are hardy or half-hardy, and whether they should be protected from the frost or not.
Shop our full range of high-quality, reliable flower seeds at D.T. Brown. All varieties are tried, tested, and handpicked by our experts to deliver 100% satisfaction, guaranteed. Order now for fast UK delivery.
