How To Winter Sow Lupine: 5 Pro Tips
Lupine brings distinctive bloom spikes in a sweep of color in spring and summer. Sowing them in winter is an easy way to give seeds the conditions they need to germinate. Gardening expert Katherine Rowe explores how to winter sow lupine for a successful show of warm-season blooms.
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Lupine enchants in spring and summer with bell blooms in blues, purples, pinks, yellows, and bicolors. The ornamental wildflowers grow in various conditions, from hot to cold, dry to moist, and in lean soils. As legumes, they fix nitrogen in the soil and improve surrounding nutrition.
The durable wildflowers reseed after flowering, with seeds holding over the winter until the time is right for germination. Their seeds benefit from cold stratification, where they spend weeks in cool temperatures. As temperatures warm, their outer seed coat and inner tissues give way to sprouting. The freeze and thaw cycles naturally weaken their tough shell.
Winter sowing is ideal for seed-starting lupine, whether direct sowing or through the simple method of repurposing plastic containers into mini-greenhouses. Winter sowing lets us start ahead of spring and provides a foundation for sturdy seedlings.
In the winter sowing container method, seeds overwinter in homemade “greenhouses” with outdoor exposure to natural elements. When conditions are favorable, the seedlings sprout, developing strong taproots for vigorous growth and early blooming with no hardening-off period. Winter sowing lupine is straightforward, budget-friendly, and works with the seed’s needs to promote sprouting.
About Lupines
The Lupinus genus holds over 300 species, many of them native to North America and the western region, in particular. Meadow lupine (Lupinus polyphyllus) is one of the showiest species, with dense violet bloom spikes and a cushion of blue-green leaves. It’s a vigorous grower at three to five feet tall and plays a vital role in ecosystem management for erosion control, soil improvement, and pollinator food sources.
Silky lupine, Lupinus sericeus, grows across a range of elevations and habitats, including grasslands, sagebrush meadows, forests, and steep slopes. Flowers are rich purple – a sweet pea bloom with attractive gray-green palmate leaves.
Lupinus perennis, or wild lupine, is native to eastern North America. Sky-blue flowers line multiple spikes up to eight inches long. Flowers are often two tones of purple and blue or blue and white. Wild lupine is a wonderful choice for the eastern gardener to attract pollinators and bring beauty to the wildflower garden.
In addition to the species are ornamental hybrids tailored to the home garden for striking displays and good performance. Lupines are usually hardy in USDA growing zones 3-8, where they do well in cool climates in full sun to partial shade. Whether short-lived perennials or annuals, the beauties may take time to establish but often reseed once they do.
How to Winter Sow Lupine
Winter sowing relates to direct sowing and also using insulative mini-greenhouses to foster germination. Direct sowing is the easiest way to sow lupine seeds in winter. With scattering them in place in cold weather, they germinate in spring’s mild conditions after exposure to natural freeze and thaw cycles. Lupines develop strong taproots sensitive to disturbance at transplanting, and sowing seeds in their permanent location avoids potential damage.
Lupines also show high success rates with winter sowing in protective containers to expose seeds to natural conditions while warming the ambient air. In the outdoor containers, the seeds receive all they need to germinate (light, water, oxygen, and temperature variation). With a headstart on growth, the seedlings are ready to take off at planting and flower earlier than direct sown seedlings.
The Method
When winter sowing in containers, the vessels become upcycled mini-greenhouses. The streamlined seed-starting method uses basic household supplies, making it easy to accomplish and budget-friendly. It saves indoor growing space and lessens the time spent managing seedlings. Mid to late winter is the time to winter sow, ideal for cold climates.
To winter sow, the “greenhouses” are repurposed plastic containers. Transparent containers like milk jugs and plastic bottles become growing vessels with a few simple modifications. The little greenhouses sit outside in a sunny location, exposed to elements like snow and rain. The seeds benefit, and seedlings harden off naturally as they sprout later in the season.
Advantages
Winter sowing has a lot of advantages, especially in being easy to accomplish with high germination rates and working with seasonal conditions to promote seedling development.
The resourceful method:
- Uses supplies on hand; doesn’t require expensive materials
- Doesn’t use indoor growing space
- Allows early seeding and a jumpstart on growth
- Provides cold stratification
- Needs no hardening off period before transplanting
- Lessens intensive oversight
When to Winter Sow
As early as December, you can winter sow lupine, either directly on the ground or in protective containers. In cold climates, this extends into March. Climate and temperature affect germination, and starting in freezing conditions ensures seeds get their cold stratification. They also won’t sprout too early and risk freezing again later.
Direct Sowing
Sow lupine seeds by scattering them in fall or winter. Snowfall helps by providing insulation until seeds germinate in the spring. If you miss a winter sow, you can broadcast in cold weather, or wait until one to weeks after your final frost in spring to seed outside.
When starting lupine indoors or outside post-frost, seeds benefit from scarification. Scarifying accelerates what naturally occurs during cold stratification by softening the seed coat. To scarify lupine, make a small nick in the coat or rub lightly with medium-grit sandpaper. Soak seeds to soften before planting. With winter sowing, there’s no need for the extra scarifying due to seasonal exposure.
In Repurposed Containers
Aim to winter sow lupine about six to eight weeks before you plan to transplant them to the garden bed or outdoor container. In warm zones, the seeds germinate faster. Provide at least several weeks of cool temperatures for cold stratification.
Select Your Containers
Options for repurposed plastic containers are numerous – get creative with what you have access to. Start with clear or mostly transparent containers like milk jugs, two-liter bottles, bins, or freezer bags. They need to allow plenty of light infiltration and have the capacity for drainage, ventilation, several inches of soil, and room for seedling growth. Start by washing the containers in warm, soapy water to sanitize them.
Next, they need simple modifications to account for temperature regulation and airflow. We’ll cover a few basic options (milk jugs, bottles, freezer bags, bins) that allow easy setup.
Stored outside, the vessels collect seasonal moisture from snow and rainfall. Drainage holes are essential in preventing rot and other fungal problems. Make four to six holes in the base of the container with a screwdriver or drill. Label the date and variety on each with a permanent marker for easy identification.
Other creative containers for winter sowing include:
- Salad greens packaging
- Deli cake/cookie container or clamshell
- Large takeout containers
Milk Jugs
Transparent jugs are one of the easiest to adapt.
- Remove the cap and poke drainage holes in the bottom.
- Cut the jug nearly in half just below the handle, almost all the way around (about three-quarters). Leave the handle portion attached to lift the lid during the season for ventilation.
- Add three to four inches of potting mix to the base.
- Sow seeds ⅛” deep according to spacing guidelines, covering them only lightly with soil.
- Water them in, and tape the jug’s cut seam.
Plastic Bottles
Two-liter water or soda bottles make protective little greenhouses.
- Remove the cap
- Make a cut three-quarters of the way around. Leave four inches of space at the bottom of the bottle for soil and seedling growth.
- With drainage holes in place, add three to four inches of soil.
- Sow the seeds and moisten the media.
- Tape the cut seam and place the bottle outside, cap off.
Freezer Bags
Gallon-sized resealable freezer bags become easy seedling pouches.
- Clip the bottom corners and cut slits or holes for drainage.
- Add several inches of potting mix and sow accordingly.
- Water for even moisture.
- Leave an inch or so of the bag’s seal open for ventilation. To adjust airflow and regulate temperature on warm days, open the seam more. In spring, roll the seal down like a cuff for full exposure, closing it if necessary on chilly nights.
- Stabilize the bags upright by stringing them along a skewer. The bottom should rest on a crate or bin.
Bins
Clear plastic bins are handy to hold the other vessels for support or become seedling trays themselves.
- Add a few inches of soil to the base.
- For lupine, experiment with paper towel tubes cut into sections to house the individual seedlings (see below).
- Make holes in the lid to allow moisture and ventilation, popping it off to vent on warm days.
Seeding
No special seed-starting mixes are necessary to winter sow lupine. Use a high-quality, regular potting mix. Avoid garden soil or straight compost, which are too heavy for young roots and stems.
Because lupine have sensitive taproots, you may experiment with scattering seeds on the soil surface in containers or sowing them in cardboard tubes. Cut paper towel or toilet paper tubes to fit and nestle them into the soil. Sow a single seed or two per tube. When ready to transplant, cut the tube on one side to peel it away, ease the roots out, or plant the tube with the lupine to biodegrade.
Sow the seeds according to varietal guidelines and spacing recommendations. Lupine seeds are large and easy to work with.
Situating Outdoors
Once prepped and seeded, place the containers in a sunny location outside with access to natural moisture. Expose them to the elements. A southeast exposure works well for sunlight and warmth. If this becomes too intense or warm for seedlings toward spring or in warmer climates, move them to an east-facing spot with good morning exposure.
In windy areas, secure the vessels to keep them from blowing over. Nestle them against a foundation or wall, or place them in a milk crate, tray, or tub. Breezes help develop strong stems, but toppling over can disrupt the roots. Ensure the site is well-draining so the containers aren’t sitting in pooling water or puddles.
Tend and Maintain
Precipitation from snow, rain, and condensation is usually enough to maintain soil moisture early on. Check containers once a week, especially as conditions become drier or warmer as the season progresses. With regular rain or snow, they need only supplemental water or misting every few weeks. Watering needs may increase as temperatures warm and seedlings sprout. If the soil surface shows signs of drying, mist or sprinkle with water to prevent seeds or shallow roots from drying out.
Condensation is a sign that moisture is available. If it lessens, make sure soil moisture is adequate and that rain can enter the top. If not, add more openings. Keep tape in place at cut seams to prevent evaporation early in the process.
Vent the lid on warm days to allow transpiration and airflow to stave off diseases and to keep seedlings from getting too hot. Close the lid again before temperatures drop late in the day. As seedlings develop, this allows natural hardening-off that makes for easy transplanting without shock.
Transplant Seedlings
Seedlings are ready to transplant after exposure to warm days in their open containers. Look for true leaves (fully developed leaves after the cotyledons) and a few inches of height as indicators of readiness.
With winter sowing lupines, take care during transplanting to avoid root disturbance. Capture as much soil and roots as possible for each seedling to minimize disruption.
Follow regular transplant guidelines to meet the best air and soil temperatures. To transplant, gently divide the seedlings. Reach into the open container or cut side flaps for access to slide them out. Use varietal spacing guidelines to position the lupines. Small varieties benefit from a 12-18-inch spacing, while larger ones need two to three feet apart. Enjoy the floriferous wildflowers as they establish for a show of recurrent color.
