Half Hardy Annual Flowers

Annual flowers provide so much instant color in our flower gardens, but it seems to be a matter of "easy come, easy go" when fall approaches: Many annuals turn brown, mushy, and hideous at the first whiff of frost on the lawn. However, not all annuals are created equally in this respect. A number of annuals, referred to as half-hardy annuals, can tolerate several light frosts in the garden, potentially extending the beauty in your landscape for an additional month or longer.  

Why are...MORE some annual flowers more tolerant of frost and cold weather than others? Part of the answer lies in the plant's metabolism. The proteins, sugars, and moisture content of the plant affect its ability to withstand cold weather without demonstrating symptoms of cold injury, such as white or brown blistering or dead, water-soaked tissue. Eventually, most annuals succumb to damage caused by ice crystals, which form and puncture cell membranes at temperatures below freezing. Only truly cold-hardy annuals, like pansies and violas, can bounce back after a hard freeze. However, these six annual flowers can form the foundation of your early spring and late fall flower garden, as they will tolerate light frosts without damage.

  • 01 of 06
    Bells of Ireland
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    Bells of Ireland are underrepresented in the garden, but the unusual green hue and fabulous shape of these spring blossoms make any cut flower arrangement look special. Not only are bells of Ireland tolerant of cold temperatures and light frosts, they require a cold dormancy to germinate, called stratification. The easiest way to achieve this is to sow bells of Ireland seeds directly in the garden as soon as the soil can be worked, allowing Mother Nature to tell the seeds when to germinate....MORE Direct sowing also preserves the delicate tap root of the plant, preventing transplant shock.

  • 02 of 06

    Calendula

    Pot Marigold
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     Calendula, also known as pot marigold for its culinary value, is an easy annual for the kitchen garden in early spring or late fall. In fact, the flower might be too easy, for it can self-seed aggressively, guaranteeing that one packet of seeds will provide you with zesty salad toppings for many seasons to come. Ideal germination temperatures fall between 55 and 60 degrees F, and you must cover the seeds to exclude germination-inhibiting light. Choose double-petaled varieties like...MORE 'Bonbon' for fluffy cut flowers, but plant single-petaled heirloom types for eating.

  • 03 of 06

    Dianthus

    Annual Dianthus chinensis
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     The spicy clove scent of dianthus is a welcome wake up call in the garden after a dreary winter. Plants can be slow to get going from seed, but transplants are common in garden centers in early spring. Give dianthus the best drainage you can, or enjoy in containers.

  • 04 of 06
    Snapdragon Arrow Orange
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    Snapdragon flowers are so winter hardy they may come back in the garden after exposure to temperatures as low as zero degrees F, given a sheltered spot in the garden and some protective mulch.  The plants are easy to grow from seed, so start them indoors at least eight weeks before your last frost date so the transplants can get growing in the cool temperatures they enjoy. Try the 'Rocket' series for great cut flowers.

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  • 05 of 06
    Scented Stock
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     Scented stock flowers aren't the showiest, but a small container by the front door will provide a natural aromatherapy boost on grey spring days. Direct seed in full sun, and provide plenty of moisture. The plants will wither when summer approaches, but you can tuck them around emerging perennials, which will hide plants past their prime.

  • 06 of 06

    Sweet Pea

    Sweet Peas
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     Sweet pea vines will be scrambling for the sun before some perennials have even peeked through the soil's surface in the spring. Sow seeds outdoors as soon as the soil can be worked; raised beds are best to encourage good drainage. In areas with warm winters, sow in the fall for late winter blooms. If hungry birds pluck seedlings before they get established, cover with plastic netting or floating row covers to protect young plants.