Thank you for your question.  I have never grown lupines.  Are you sure that your seedlings are perennial?  If so, planting them now would be appropriate.I found this article especially interesting.
https://www.almanac.com/plant/lupines

Lupines

Botanical NameLupinus spp.Plant TypeFlowerSun ExposureFull SunPart SunSoil pHNeutralSlightly Acidic to NeutralBloom TimeSpringSummerFlower ColorBluePinkPurpleRedWhiteYellowHardiness Zone34567Special FeaturesAttracts SongbirdsAttracts ButterfliesSubhead

How to Plant, Grow, and Care for Lupine Flowers

Catherine BoeckmannJune 16, 2023

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Lupines, with their colorful flower spikes, are some of the most popular garden perennials of them all! Deer-resistant and low-maintenance, lupines attract pollinators and butterflies, too. See our complete guide to planting, growing, and caring for lupines.

All About Lupine

Lupinus includes hundreds of species, many native to North America! You’ll see them both in the wild and in gardens—from California to Maine. This hardy perennial blooms in late spring (April to June) and is a great addition to a low-maintenance meadowscape or cottage-style garden. Lupines were once thought to steal nutrients from the soil—hence their genus name, Lupinus, which is Latin for “wolf.” However, lupines are in the pea family and as nitrogen-fixers can actually improve soil.

The pea-like flowers are arranged on upright spikes varied in color from deep blue to purple shades. Growing 1 to 4 feet tall, the leaves of lupine are also beautiful with grey-green palmate foliage with silvery hairs. The seed pod looks like a hairy pea pod and contains up to 12 seeds. In fact, lupines are a legume, which means that they fix nitrogen in the soil and they enrich your soil health.

Note: Not all lupines are perennials; the potted plants are typically perennial cultivars but other lupines are annuals.

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PLANTING

Lupines prefer full sun; they’ll grow in light shade but won’t flower as profusely. They also prefer sandy, well-drained soil and can’t survive water-logged conditions. Also, they can not tolerate heavy soils so be sure to loosen the soil up before planting.

When to Plant Lupines

• Plant in cool temperatures; lupine can not tolerate heat, humidity, or drought.
• Lupine seeds are sown in early spring or in the fall. Many gardeners prefer to plant in fall to enjoy them mid-spring.
• If starting seedlings indoors, you can transplant them when they are about 4 to 6 weeks old. At this age, they haven’t developed the long tap root and will have a better chance to survive.

How to Plant Lupines

• First, just loosen soil for the lupines’ long tap roots to grow; loosen to a depth of about 1 to 1-1/2 foot; amend with organic matter and grit for good drainage.
• Before planting, soak seeds in a bowl of warm water 24 to 48 hours to soften the tough seed coat, and then you can “scarify” the seeds to allow moisture to reach the seed; this means roughening the seeds between two sheets of sandpaper before planting. Scarifying the seeds great improves the odds of germination.
• To sow seeds, dig a hole 1/2 inch deeper than the seedling pot and twice as wide. Space seedlings for smaller varieties about 1 foot apart and larger varieties about 2 to 3 feet apart.
• Tamp down the seeds, ensuring good soil contact. Water, and if the weather is dry, water lightly until germination, which can take up to 10 days.

GROWING

• Avoid fertilizing; if necessary, apply an acidifying agent to maintain slightly acidic pH in the soil.
• Taller varieties may need staking.
• Cut off faded flowers to promote more blooms.
• Save the seeds when the pods turn yellow.
• Don’t cut dead spikes in the fall, wait until spring.
• Harvest and save seeds then the pods turn yellow and seeds rattle inside.
• Add mulch around the plants to keep the roots cool (and for winter protection).
• Do not allow mulch or other organic matter to touch the crown of the plant, as it could introduce rot.

RECOMMENDED VARIETIES

There are over 200 wild species of lupine, and most are North American natives. These usually have blue, white, or yellow flowers.

Garden lupine (Lupinus polyphyllus), aka big-leaved lupine: blue, pink, and purple flowers; native to much of western North America; prefers moist environments.

Wild Lupine (Lupinus perennis) is a blue perennial plant that grows in the eastern half of North America.

Texas Bluebonnet (L. texensis) is an annual plant with dark blue flowers with white markings that cover fields and roadsides in Texas every April.

Russell hybrid lupines (L. polyphyllus) also called garden lupines have been the basic perennial group from which all new hybrids are created. Be patient; it can take a year to begin its abundant blooms.

The Russell Lupine Mix seeds are easy to grow and the tall flowers bloom in a variety of colors.

Lupine Woodfield Hybrids are perennial plants that come in deeper shades and beautiful bi-colored blooms.

Dwarf hybrids ‘Dwarf Lulu’ and ‘Minarette’ grow only to 1 ½ to 2 feet tall. Excellent for small gardens, containers, or the front of beds and borders. Plants grow to 20 inches tall. Winter hardy to zone 4.

WIT AND WISDOM

• Lupines are nitrogen-fixing and can improve your soil!
• Many species of lupine are poisonous to livestock.
• Lupines are deer-resistant.
• The lupine flowers are not edible, but the seeds are. The nut-like seeds were once a favorite food for traveling troops in ancient Europe.
• Lupine seeds can be ground into flour. In Europe this flour is used in baking.

PESTS/DISEASES

Lupine is deer-resistant.

Diseases: anthracnose; blight, Botrytis; blight, southern; brown spot; leaf spots, fungal; mildew, downy; mildew, powdery; rot, Phytophthora crown and root; rot, Rhizoctonia root and stem; rust; viruses; wilt, Fusarium.

Pests: aphids; slugs/snails; thrips.

Here is another source with lots of good info.


https://www.thespruce.com/growing-lupine-flowers-1316034
The lupine flower, also known as bluebonnet, may look like a
wildflower, but it is a fast-growing legume in the pea family that just happens to have a tall, showy spire of colorful blooms that are typically purple, but can also be blue, white, or yellow. You can expect flowers for about 3 months, from spring through mid summer and, while individual lupine plants do not spread, you can expect flower pods to disperse up to a dozen seeds from each pod.

Lupine is available as both an annual and a perennial flower and grows best in northern climates with cooler summers, requires full sunlight of at least 6 hours a day, weekly watering, and soil on the acidic side. These brilliant flowers are also deer-resistant and beneficial to pollinators like bees and butterflies. Keep in mind that the plant is toxic to both humans and animals.12

***Pay special attention to this as you choose where to plant your seedlings!***

WARNING

According to the National Park Service, wild lupine flower is an invasive plant that can crowd out native species. Additionally, because its seeds are toxic, it can threaten herbivores that are native to the area.

https://www.nps.gov/articles/000/lupine.htm#:~:text=In%20a%20nutshell%2C%20it%20is,farm%20animals%20and%20native%20herbivores.

Common Names	Lupine, bluebonnet
Botanical Name	Lupinus x hybrida
Family	Fabaceae
Plant Type	Herbaceous, perennial, annual
Mature Size	3–4 ft. tall, 1–1.5 ft. wide
Sun Exposure	Full
Soil Type	Moist, well-drained
Soil pH	Acidic, neutral
Bloom Time	Spring, summer
Flower Color	White, pink, red, yellow, blue, purple
Hardiness Zones	4–8 (USDA)
Native Area	North America
Toxicity	Toxic to humans and animals12

Lupine Care

Here are the main care requirements for growing lupine:

• Plant during cooler early spring or fall temperatures.
• Offer more sun and minimum shade.
• Stake taller varieties using grow-through grid stakes to prevent them from flopping over.
• Water during periods of dry weather.
• Use an acidifying, phosphorous-heavy fertilizer.
• Deadhead to encourage continuous flowering.

Sounds like a plan, good luck!