Half Hardy Annuals for UK Gardens

Half Hardy Annuals (HHA) are not native to the UK, so they are unable to survive our cold frosty weather in autumn and winter. However, they have a long and prolific flowering period (usually from June to October) which more than makes up for this. HHAs are normally raised undercover in the UK in early spring for summer or autumn flowering in the same year.

Sowing Half Hardy Annuals

Seed is usually sown undercover (in warm conditions) between January to April (depending on the variety). The plants are then hardened-off and planted-out once all danger of frost has passed. Certain fast growing varieties of HHAs can be also be sown outside in May for flowering in late summer/autumn.

The following selection of half hardy (frost tender) flowering plants are suitable for domestic gardens in Great Britain (England/Scotland/Ireland).

Ageratum houstonianum

Ageratum
Floss Flower

yellow snap dragon flower

Antirrhinum
Snap Dragon

begonia red leaves

Begonia (fibrous rooted)
Bedding Begonia

canna red flowers

Canna
Indian Shot

Celosia argentea

Celosia
Cockscomb

dahlia flower

Dahlia
Bedding Dahlia

nicotiana flower pink

Nicotiana
Tobacco Plant

coleus red flame

Solenostemon
Flame Nettle

Salvia splendens flowers purple

Salvia
Annual Sage

tagetes flowers mixed

Tagetes
French Marigold


Buying Half Hardy Annual Plants

Many of the most popular Half Hardy Annual varieties can be purchased as small plug plants or in bedding trays from DIY stores and garden centers, usually from March to May. Remember when buying HHAs plants that they can still be damaged or killed by cold weather, so you will need protection them undercover until all frosty weather has past in your area.

A great advantage of Half Hardy Annuals, is that they usually flower over a much longer period, especially if regularly dead-headed. Whereas perennials, shrubs, bulbs, and even many hardy annuals, bloom from just a few weeks to a month or more, depending on the variety. So if you want long lasting colour in the garden, HHAs are the ideal choice, especially in baskets and containers.