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 under glass in the UK in early spring, for summer or autumn flowering in the same year. Many HHA are actually perennials in their native habitat (such as Antirrhinum) but are easily grown here as annuals and discarded at the end of the season. Read more about tender perennials.

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 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

Calibrachoa

Calibrachoa
Million Bells

Celosia argentea

Celosia
Cockscomb

Cleome Flowers

Cleome
Spider Flower

cosmos flower white

Cosmos
Cosmea

Diascia Pink Flowers

Diascia
 

Gaillardia

Gaillardia
Blanket Flower

Gazania

Gazania
 

Gypsophila

Gypsophila
 

Lobelia Cascade Mixed

Lobelia
Bedding Lobelia

Helianthus annuus

Helianthus
Sunflower

Helichrysum Bracteatum

Helichrysum (Xerochrysum)
Strawflower

Heliotrope

Heliotropium
Heliotrope

Mimulus

Mimulus
 

Nemesia

Nemesia
 

nicotiana flower pink

Nicotiana
Tobacco Plant

Petunia

Petunia
 

Salvia splendens flowers purple

Salvia
Annual Sage

Portulaca

Portulaca
 

Senecio Cineraria

Senecio Cineraria
 

tagetes flowers mixed

Tagetes
French Marigold

Zinnia

Zinnia
 


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 centres, 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.