As a plant, our relationship with the sun is fundamental; it is the engine of our existence. Through the process of photosynthesis, we convert sunlight, water, and carbon dioxide into the energy (sugars) we need to grow, produce our iconic flower spikes, and develop strong roots. For lupines (Lupinus spp.), we are classified as full sun to partial shade plants. This means we require a minimum of six hours of direct, unfiltered sunlight each day to truly thrive and perform at our best. In optimal light conditions, our stems grow strong and avoid becoming leggy, our foliage remains dense and healthy, and our flower production is maximized, resulting in those stunning, colorful spires gardeners cherish.
Our ideal location is in a garden bed that receives full sun for most of the day. In this environment, especially in the cooler climates of the northern US or at higher elevations, we can easily tolerate and even crave eight or more hours of sun. The abundant energy allows us to support a prolific and long-lasting bloom period. Ample sunlight also helps keep our foliage dry, which is a crucial defense against fungal diseases like powdery mildew that can thrive in damp, stagnant air. The heat that accompanies full sun is generally not an issue for us in these regions, as many species are naturally adapted to well-drained, sometimes even challenging, soils.
We can adapt to partial shade, which is typically defined as four to six hours of sunlight, preferably the gentle morning sun. This is a necessary adaptation for our survival in warmer regions of the US, such as the South or parts of the Midwest. In these areas, the intense, scorching afternoon sun can be too stressful, causing our leaves to wilt, scorch, or fade. The shade during the hottest part of the day acts as a protective barrier, reducing heat stress and conserving precious water. However, it is critical to understand that "shade" does not mean "deep shade." Without the requisite minimum of direct sunlight, our growth will become weak and spindly as we stretch desperately for light, and our flowering will be significantly reduced or may not occur at all.
Your local climate dramatically influences our sun preferences. In cool-summer regions like the Pacific Northwest, New England, and the Upper Midwest, we enthusiastically welcome all-day full sun. It provides the energy we need without the associated heat stress. Conversely, in hot-summer regions like the Southeast, Southwest, and Deep South, providing us with afternoon shade is not just beneficial—it is often essential for our survival. The combination of intense solar radiation and high humidity in these areas can be overwhelming. Therefore, a planting site with bright morning sun and dappled or partial afternoon shade represents the perfect compromise, allowing us to photosynthesize effectively while avoiding the most damaging heat of the day.
You can learn a great deal about our needs by observing our foliage. If we are receiving too much sun, especially the harsh afternoon variety, our leaves may appear bleached, develop brown, crispy edges, or wilt consistently even when the soil is moist. This is a clear sign of heat and light stress. Conversely, if we are not receiving enough sun, you will notice our growth is stunted, our stems are weak and floppy, our leaves are sparse, and most tellingly, our flower production is poor or non-existent. We will direct all our limited energy simply toward survival rather than reproduction. Adjusting our location or providing temporary shade cloth during heatwaves can rectify these issues.
