Above and Beyond: Best Annuals for High-Altitude Gardening

Mountain gardeners know that everything is a little bit different up high: light level, flower colors, rate of growth, and additional challenges with overwintering all make mountain gardening an adventure. Selecting annuals that will tolerate cooler evening temperatures can help to extend that short gardening season and keep the color rolling all summer long. In order to choose wisely, it’s important to know which annuals are very-hardy, hardy, half-hardy, and tender.

You will also need to know your hardiness zone. Here at Echter’s, our lowest evening temps are between -20 and -10, which puts us in Zone 5. Evening temperatures from -30 to -20 are Zone 4, and if you are way, way up, you might be Zone 3 (-40 to -30).
Very-Hardy annuals are unfazed by early frosts and night temperatures of 25 degrees. These plants will continue to grow at the same rate in cool weather and they will flower on their normal schedule. These are the first annuals you will see out on the benches here at Echter’s. Very-hardy annual plants include:

• Alyssum
• Pansies
• Snapdragons
• Dusty Miller
• Ornamental Cabbage/Kalekale

Hardy annuals can take night temperatures of 28, but may experience slower growth and flowering. In the big picture, that’s not a problem— just a delay. Waiting a week or two to plant this group will prevent freezing and let them get started.

• Bacopa
• Calendula
• Carnation
• LobeliaLobelia_026
• Nemesia
• Osteospermum

Half-Hardy annuals

• Angelonia
• Calibrachoa
• California Poppy
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• Datura
• Dichondra
• Gazania
• Gerbera
• Gomphrena
• Lotus VineLotus_berthelotii_IMGP5869

• Pennisetum
• Petunia
• Regal geranium
• Sanvitalia
• Stock
• Strawflower
• Trifolium

Tender annuals essentially includes everything else you may find in the annuals house. In the Metro Denver area, tender annuals would be planted around Mother’s day. At higher elevation