Half Hardy Annual Flowers

By
Jamie McIntosh
Jamie McIntosh
Jamie McIntosh
Jamie McIntosh has written about gardening and special occasion flowers for the Spruce since 2011. She has more than 20 years of experience caring for flowers and plants. She was a feature writer for Organic Gardening at Suite101, where she won awards for her writing.
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Updated on 11/02/21
Love in a most plant with fine ferny foliage around white flowers on thin stems

The Spruce / Evgeniya Vlasova

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 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 eight 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 08

    Bells of Ireland

    Bells of Ireland

    Guillermo Lecuona / Moment / Getty Images

    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, but they also 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. Direct sowing also preserves the delicate taproot of the plant, preventing transplant shock.

  • 02 of 08

    Calendula

    Pot Marigold

    Maria Mosolova / Photographer's Choice / Getty Images

    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 'Bonbon' for fluffy cut flowers, but plant single-petaled heirloom types for eating.

  • 03 of 08

    Dianthus

    Annual Dianthus chinensis

    tc397 / E+ / Getty Images

    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 (rock gardens are ideal), or enjoy in containers.

  • 04 of 08

    Snapdragon

    Snapdragon Arrow Orange

    Photos Lamontagne / Photolibrary / Getty Images

    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.

    Continue to 5 of 8 below.
  • 05 of 08

    Stock

    Scented Stock

    James A. Guilliam / Photolibrary / Getty Images

    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 08

    Sweet Pea

    Sweet Peas

    David Q. Cavagnaro / Photolibrary / Getty Images

    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. 

  • 07 of 08

    Love in a Mist

    Love in a mist plant with fennel-like foliage around light blue flower closeup

    The Spruce / Evgeniya Vlasova

    The blue flowers of Nigella damascena nestled among fine ferny foliage give the impression of a delicate specimen, but old-fashioned love-in-a-mist plants need little beyond what nature provides in the garden. Plant the black seeds directly in the soil in the winter where you want them to grow, as they don't like the stress of transplanting. The frost-tolerant plants will germinate and bloom early, and then fade as the weather heats up. Leave spent blooms in place both for the interesting seed capsules, and to ensure the next generation of volunteer plants.

  • 08 of 08

    Larkspur

    Annual Larkspur Flowers

    Mohan Singh / Getty Images

    Unlike the perennial delphinium that shares the common larkspur nickname, the plants that grow from Consolida ajacis seeds don't require staking, as the bloom spikes are smaller than its perennial cousin. Sow the seeds of annual larkspur in the fall to allow the natural chilling period that triggers growth when temperatures warm in the spring. Seed mixtures that include plants in shades of purple, pink, and white will give you a predesigned flower bed from one packet of seeds. Plant in full sun, and provide rich soil and consistent moisture.