The Reiger Begonias

Shadow King® Rex Begonias

BEG Rex Shadow King Black Cherry
Begonia Rex 'Shadow King® Black Cherry’ PP24717

Although Rex Begonias are known as indoor plants, we use them successfully in containers and in shady landscape applications. They love low light, and come in bright colors and interesting textures, plus we sell cultivars that are not finicky. We find that the Rex fanbase is large and vocal, so there is a built-in audience that appreciates them. However, picking a good Rex beyond ‘Escargot’ is a tricky affair.

For this job, we turn to the Shadow King series. These Rex Begonias focus on the industry professional, but they are not magic bullets. Because we would rather design to a plant’s strengths, we try to understand the breeding under the hood. With that in mind, let’s dive into what makes this series tick.

BEG Shadow King Cool White
Begonia Rex ‘Shadow King® Cool White’ PP24738

Shadow Kings were introduced to the industry maybe seven years back, but their breeders have a long history with Begonias—we’re talking about Koppe in the Netherlands and GreenFuse in California. The series began with a private collection of Rex Begonias that showed promise. Several generations later—Luther Burbank-style—they developed into the Shadow Kings.

These Begonias were not an accident of history but rather were bred specifically for the horticultural channel, picked out from promising stock. They mature to about 8-12 inches in height, spread about 6 inches wide, and show a consistent shape among all the varieties. Disease resistance is stronger and their care needs are not as great.

BEG Shadow King Cherry Mint
Begonia Rex ‘Shadow King® Cherry Mint’ PPAF

Still, low-care is not no-care. For example, let’s look at the roots. Rex roots are very shallow, which explains why some cultivars tip or sprawl. Shadow Kings were bred for a deeper root system, which helps the plant sit upright and present better. However, deeper doesn’t mean tap root. They still grow horizontally along the soil surface, so you need to apply a layer of summer mulch over the top. There is a good chance the roots will grow into that mulch over the season, and the plants will be happier for the water the mulch conserves.

Roots of Shadow Kings require loose soil or a prepared bed. They can’t cover up construction scrapings and they won’t open up heavy clay soils. However, the roots are fibrous, so they do like a wet-to-dry cycle typical of commercial accounts. They are not finicky about their water, as long as they get some—less than Impatiens, but more than Lantanas. One warning: Shadow Kings respond directly to soil temperature, so plant them when the cold and frost are out of the soil; otherwise, they sit and do nothing until they feel the warmth.

BEG Shadow King Pink

Begonia Rex 'Shadow King® Pink’ PPAF

On our property we put Rex Begonias underneath the Magnolia tree where the shade is deep. Other situations where we use them include dark corners of a commercial plaza, a well-shaded porch or deck, or any area that has a canopy overhead.

You can do a mass planting with Shadow Kings, but they also mix well to create a full-rounded shade garden. We’ve seen them used with other types of Begonias, Streptocarpella, Hyperion, and low-growing Coleus—we’ve even seen them surrounding taller Colocasia and Alocasia.

BEG Shadow King Strawberry Sherbet
Begonia Rex 'Shadow King
® Strawberry Sherbet’ PPAF

These same plants also work in large urns, boxes, and planters. They play well with others, grow to their mature size, and then stay put for the entire season without overwhelming the other plants—and without underwhelming the viewer. Shadow Kings do their job well in that middle filler area. As long as we are looking at good shade, they work.

Sometimes we see Shadow Kings in places like lobbies, hotels, restaurants, and other areas where a business welcomes the public. Interior light is just the ticket. In fact, the low light helps the colors become more vivid. Strong light washes out the colors and eventually scorches the leaves.

In small containers, we often see Shadow Kings used as specimens in exotic pottery, where the leaves become a show set on a beautiful stage.

BEG Shadow King Wintergreen
Begonia Rex 'Shadow King
® Wintergreen’ PPAF

For a crop review we have said very little about the colors, but that’s what draws people to the Shadow Kings. Their photos speak for themselves. We would like to give a shout-out to ‘Black Cherry’, a personal favorite of the breeder and to ‘Cool White’ for its textured gray look. That medium tone is a hard color for a plant to nail—it looks fabulous as an accent.

We offer these cultivars in our 4.5-inch pot:

  • ‘Black Cherry’—ruffled deep red leaves are edged in black
  • ‘Cherry Mint’—heart-shaped leaves are rose red with cool gray-green splotches and black veining
  • ‘Cool White’—serrated leaves are steely white with faint green veining and hints of raspberry
  • ‘Pink’—solid pink leaves have serrated gray-green edges and occasional tinges of black
  • ‘Strawberry Sherbet’—multicolored leaves have red and green patterns
  • ‘Wintergreen’—pale green leaves have jagged edges and are tinged copper with black veining