When to Plant Lupin Seedlings in an Outdoor Garden in Plant Zone 5B?

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Seeing a field of lupin swaying in an early summer breeze is enough to make anyone want the plant. But you don't need a field to grow this herbaceous perennial. With a bit of knowledge, most northern gardeners can start their own lupins indoors, and transplant them outside in spring.

Seeds and Seedlings

Lupin is easy to start from seed. In U.S. Department of Agriculture plant hardiness zone 5b, it is possible simply to scatter the seed onto the ground in the fall. A more reliable method, however, is to start them indoors in March. Chill the seed in your refrigerator for a week. Nick the tough outer seed coat with a file and soak the seed overnight before planting. Use a lightweight, professional potting mix and start the seeds in small peat pots. Within several weeks, young seedlings will emerge and your lupins are on their way.

Planting Seedlings Outdoors

Although mature lupin prefer cool temperatures, seedlings started indoors have been spoiled by growing in a warm house and are too tender to be planted outside in early spring. Using a cold frame in early April will quickly accustom the young plants to outdoor conditions. Otherwise, in zone 5b, temperatures are conducive for the young seedlings by late April or early May. Keep them evenly moist, but never wet, in this early stage of growth.


Lupin require slightly acidic, well-drained soil and cooler summers. They suffer in heavy clay and in soils that are overly alkaline. Avoid disturbing the roots once the plant is established. Transplanting seedlings is easier if they have been grown in peat pots that can go directly into the ground.

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