For plants: Upon delivery in early spring, plant immediately in a hole that has been amended with organic matter and grit for good drainage. Do not allow mulch or other organic matter to touch the crown of the plant and induce rot. Water in thoroughly.
For seeds: Lupine seeds can be planted in very early spring, but tend to do better if planted in late spring and allowed to overwinter, blooming in the following spring like foxgloves. They have a very tough seed coat, and it’s a good idea to either soak seeds for 24-48 hours, or roughen them between two sheets of sandpaper before planting. Cover lightly with soil (1/8”) and tamp down the seeds well – making sure they make good soil to seed contact. Water in, and if the weather is dry, water lightly until germination which can take up to 10 days.
How to Grow Lupine Throughout the Season
Growth Habit: Lupine has a rounded shrub-like habit and grows from 12-48” high depending on species or variety. Individual flowers resemble those of peas and are densely packed on several spikes above the foliage.
Staking: For Russell hybrids and taller species, it is wise to stake flower spikes if you have the time. Though they stand very straight on their own, high winds can blow the flower spikes over and create a curve in the flower as it attempts to grow back towards the sun. Smaller wildflower species do not need staking.
Watering: For the first few months in your garden, make sure that lupine plants are getting adequate water for good root development (they are deeply rooted), but let the soil dry out between waterings. After that, water only during periods of drought or very dry spells.
Fertilizing: Extra fertilizing is not necessary, but a top dressing of compost is appreciated, as long as it isn’t placed close to the crown of the plant.
Mulching: A light dressing of mulch is not a bad idea, particularly in hotter climates, but it is crucial that mulch is not allowed to touch the crown of the plant and induce stem rot.
Trimming & Pruning: Lupine can bloom again lightly on side shoots if immediately deadheaded. If seeds have begun to form in the lower parts of the flower however, they are unlikely to repeat their bloom.
After blooming, the foliage is not as attractive in the garden and can often suffer from mildew. As cutting it back completely can kill or weaken the plant, many gardeners choose to remove the plants completely and grow lupine as biennials, placing out new spring-grown plants in the fall for the next season. This is especially true in the southern limits of its heat hardiness where humidity is punishing.
Lupine: End of Season Care
If you are growing lupines for blooming the following spring, it’s wise to make sure that they are sited where you eventually want them. Lupines have deep roots and do not transplant well as they get bigger. Moreover, they start growing very early in the spring when digging and transplanting might not be advisable.
Make sure that lupine is not situated somewhere that will suffer from wet soil during the winter months which is a difficult situation for the plant to recover from.
Dividing and Transplanting: Lupine does not need to be divided and is actually difficult to divide due to its deep tap root.
Pests & Disease: Lupine can suffer from powdery mildew, particularly in hot and humid climates for which it is not suited. There are no other major pests for this plant besides pill-bugs (roly-polys, sow bugs) which like to eat the seeds and seedlings. Birds can be a problem if seeds are not lightly covered with soil at planting time.
Additional Concerns: Lupine seeds are actually cultivated as a food crop in some areas of the world, and therefore people assume that all lupine seeds are edible. However, these are specific species – some of the cultivated varieties and hybrids are toxic. Therefore, it’s best not to use the seeds in any culinary way, and to instruct children not to put the pea-like seeds into their mouths.
Lupine: Extra Info