UD Botanic Gardens Annual Spring Benefit Plant Sale 2025

By Andrew Adams, UDBG Horticulture Manager 

Housed in the Ericaceae family with over 123 other genera, Rhododendron  is one of the genera you can point at, and you can find a species to fit  most any environment or cultural condition. The name Rhododendron comes from the Greek terms rhodon meaning rose and dendron meaning tree. This genus is comprehensive with over 900 species including deciduous, evergreen, tropical, temperate and any condition in between. Because these species hybridize easily, new cultivars and species have been popping up at a rate comparable to that of Hydrangea. There are believed to be about 50 deciduous species and of those, 18 are native to our region here in the Mid-Atlantic. 

A note for all  gardeners: this genus includes Azaleas, and much like the finger and thumb rule, all Azaleas are Rhododendrons, but not all Rhododendrons are Azaleas! There are a few ways botanists and gardeners alike can tell the difference between the two, but take note, there are exceptions throughout the genus. Though these rules will work for most of the plants grown in this region, a true Rhododendron will typically be evergreen and have bell-shaped flowers with 10 stamens and scaled leaves, (meaning upon close inspection, you will see what appears to be small leaves layered on top of one another) with small dots on the undersides. Azaleas typically are deciduous with funnel-shaped flowers containing five stamens. 

While species of this genus are found worldwide, mainly the United States and Southeastern Asia, they all originate from regions with similar climates. If you head to more mountainous terrain, you will find Rhodies which love well-draining soil due to their shallow roots. While water will not directly kill the plant, it leads to easy entry for root rot or cankers and then they will sadly decline. So, if you are planting, be sure to take that into account! Many of our native deciduous species prefer to be tucked away in the understory and are not fond of the blaring summer sun. If these plants are sited for morning sun and afternoon shade, our native species will thrive.

While fall color can range from fairly insignificant to yellows, reds, and burgundy, the real reason we all love Rhodies and Azaleas is the flower. Looking for warm colors? There’s reds, yellows, oranges. How about cool colors?  There are whites, purples, pinks. I’m not sure where salmon’s fit in that range, but there’s those as well. Flowers can have different colored throats, with some  edged in different colors as well, and in the future, I’m sure there will be more combinations than we can count. Right after flower, seed can be collected  in May or June in our area and many come true to seed.  However, some hybrids are less reliable in that ability, which has led to countless new cultivars and hybrids; maybe you could do the same!

Some favorites from UDBG staff include Rhododendron calendulaceum, the Flame Azalea. Maturing to about 4 to 8 feet tall and roughly 6 to 8 feet wide with deep orange flowers (hence the common name). These plants bloom later in the spring, typically mid May to early June in our area. 

Another favorite you will see at the sale is Rhododendron viscosum, the Swamp Azalea. It fits a niche that is a bit harder to fill for many gardeners! This azalea can take shade, and stays on the shorter side, topping out typically at 3 to 5 feet. The best part: it can take wet feet for prolonged periods, hence its common name. White blooms in Mid Spring are notably fragrant and can bring a pop to otherwise slightly annoying areas to garden! 

Last, but certainly not least, is Rhododendron canescens. Getting to a nice 6 to 8 foot tall and about the same width with showy light pink flowers that emerge to lighten an area dappled in shade. Their spring bloom is followed by thicker and velvety leaves. At maturity, even the bark is an interesting gray to reddish brown display! 

We will have a ton of Azaleas and Rhodies down at the sale this year. Between our native species types and some very cool hybrids, you’ll be sure to find something to scratch that gardening itch! 

UD Botanic Gardens Annual Spring Benefit Plant Sale 2025

By Andrew Adams, UDBG Horticulture Manager

Within the family Lamiaceae, commonly known as the mint family, you will find the genus Salvia, and its associated 900+ species, the common name for this genus is sage. In our area, Salvias can be annuals, biennials, perennials and even some shrubby forms! First described by (surprise, surprise) a Roman, Pliny the Elder, in roughly 50AD, Salvia is derived from the Latin term “salvo” meaning healthy or safe, referring to its previous use as a medicinal herb. Gardener or not, you have probably interacted with these plants before, mainly in cooking! Both the herbs sage and rosemary, common ingredients in the culinary world, are members of the Salvia club.  

This genus is primarily native to three regions of the world. Those that have traveled to South America, the Mediterranean, and Eastern Asia have probably run into some species of Salvia in their native habitat. Salvia has served many purposes throughout history including culinary, medicinal, and ornamental purposes. And for those naughty folks out there, hallucinogenic purposes.  

Some key characteristics in identifying this genus are as follows: stems are always square; a  characteristic shared with all other members of the Lamiaceae family. The foliage is typically entire but sometimes appears toothed or pinnately divided. Most of these species will be pubescent to some degree, and many species share flowers of similar shape. From a side profile, the flowers are produced in racemes or panicles, and because of the petals being “two-lipped”, you get an appearance of a lobster or crab claw from a side profile. 

Many pollinators flock to these flowers, and because of their specific shape, they have become a favorite for our native pollinators and hummingbirds. Between varying species, cultivars, and hybrids, flowers of Salvia can fit most any design, and run the full gambit of blues, pinks, purples and whites in addition to reds, yellows, oranges.  

In  Mid-Atlantic gardens, you will typically see S. nemorosa and its associated cultivars, or hybrids containing parentage of that species. While that is not the only perennial species you will find, it is by far the most common. If you jump into the world of annuals, the amount of species and hybrids grows immensely and includes all shapes and sizes to fill pots, or run in your annuals edges! 

A few favorites are S. nemorosa ‘Caradonna’, a tried-and-true performer with ultra purple flowers that bloom at the end of May. Then there is Salvia koyomae, a relatively underused species that lends a coarse texture and amazing yellow flowers to a shady area. One last underused and underappreciated species is Salvia uliginosa, with its true bright blue flower color (not botanic blue which actually just turns out to be purple most of the time). Despite the common name of Bog Sage, this plant grows well in average garden soil in addition to wet areas. With its abnormally quick growth rate, this species can make an impact in your garden in a hurry!