Learning how to garden in dry shade is like becoming a mediator; you need to consider the needs of all the plants involved and the challenges each one faces. Then, you make a decision based on compromises.
Dry shade is abundant under trees, because trees consume lots of water. Fortunately, Salvias are an adaptable lot. They include numerous drought-resistant species that can handle, and sometimes prefer, life in dry, partial shade. Before considering what Salvias to select for your shady areas, it's necessary to consider some gardening basics that aid success in shade gardening.
Perennials Under Trees
Relying on bedding plants to provide color means disruption of soil each growing season. While this usually isn't a problem along a shady foundation wall, it can be hazardous to the survival of a tree.
The majority of a tree's roots are hair-like structures that grow within the first 6 to 24 inches of soil and transport water and nutrients to the heavy, woody anchor roots. Repeatedly digging up the ground under and near the canopy of a tree can lead to its early death.
Low-water perennials, such as shade-tolerant Salvias, are a better choice for planting under trees. Plants in 4-inch pots or smaller are a good choice, because they don't require large planting holes.
Whatever perennials you plant, don't build raised beds under trees. The extra layer of soil decreases oxygen to tree roots, which smothers them.
Soil underneath trees often becomes compacted. To insure adequate room for Salvias to stretch their roots and to avoid drowning them, it's necessary to loosen soil in the planting holes by adding plenty of organic matter. This is especially true for clay soils, which are rich in nutrients but tightly packed. Organic matter, such as compost and leaf mold increases the space between soil particles for better penetration of water and air.
Once you've planted your Salvias, you can further increase humus in the soil by allowing some leaf litter and pine needles to accumulate. Eventually, these materials decompose and become part of the soil, especially with the help of hungry earthworms.
Soil Chemistry Considerations
Gardeners also need to determine whether the chemical balance, or pH, of their soil in any dry shade situation -- whether under a tree or in another part of the yard -- is appropriate for the Salvias and other perennials to be planted.
It's important to note yet again that Salvias are adaptable. Many do well whether in soil that is extremely acidic, heavily alkaline or well balanced between the two extremes. The best way to judge soil pH is to obtain a soil test from a private lab or the local office of your state's agricultural extension service. Soil testing can help you to avoid growing an acid-loving plant, such as Salvia splendens, in an overly alkaline soil.
Soil pH measurements range from 0 to 14, with 7 indicating a neutral or balanced combination of acidity and alkalinity. Soils less than 5.5 are extremely acidic. Ones that are greater than 7.5 are too alkaline for many plants. Ultimately, the acidity or alkalinity level of a soil affects what nutrients are dangerously abundant or difficult for plants to access.
In general, decision-making about what Salvias to plant is easier if you consider their native lands. Ones that come from woodland settings, such as many Asian Salvias, likely will thrive in acidic soils. Those that are native to the desert lands of the Southwest and Northern Mexico do just fine with alkaline 'sweet' soils, which are heavy on lime.
Soil chemistry is something we'll dig into further at a future date. Right now, it's time for our suggestions concerning low-water sages that can help you dress up your dry shade.
The plants listed here are among the most drought-tolerant selections from our partial shade list, which notes Salvias that can thrive in the dappled or 'broken' sunshine of a leafy canopy that doesn't heavily block light. A number of partial-shade Salvias also do well in full shade under dense foliage; we've noted these. Also, some of these Salvias may grow a bit taller than the average mature heights stated here.
On with the show! We've organized this bouquet of suggestions into warm and cool color groups, but feel free to mix them up in your landscape.
Golden Pineapple Sage (Salvia elegans 'Golden Delicious') Zones 9 to 11.
All varieties of Pineapple Sage are well known for their cheerful crimson flowers, which cooks sometimes use in baking along with the species' flavorful leaves. They're also renowned for attracting butterflies, honeybees and hummingbirds. This variety is the best at handling shade whether partial, full or in locations where morning sun is balanced by afternoon shade.
Variegated Mirto de Montes Sage (Salvia microphylla 'Variegata') Zones 7 to 9.
S. microphylla is native to Mexico where it often is called Mirto de Montes (Myrtle of the Mountains). Brent Barnes of Southern California's Rancho Santa Ana Botanic Garden developed this variety, which is well loved by hummingbirds.
Cedar Sage (Salvia roemeriana) Zones 7 to 9.
Due to self-seeding, this Salvia is an economical groundcover. It is native to the cedar, juniper and oak forests of Arizona, Texas and Northern Mexico. Consequently, it thrives when mulched with leaf litter from these types of trees. Expect it to attract butterflies and hummingbirds.
Hummingbird Sage (Salvia spathacea) Zones 8 to 11.
Sticky and richly scented, this sage's large clusters of leaves are as attractive as its rosy flowers. Plus, it grows in all types of shade. As its common name indicates, hummingbirds love it.
Jupiter's Distaff Sage (Salvia glutinosa) Zones 5 to 9.
The common name of this sage likens the plant's upright flower spikes to wool spindles. Honeybees and butterflies love Jupiter's Distaff, which is native to Europe and Asia. It also does well in full shade.
Wild Rose Lemmon's Sage (Salvia lemmonii 'Wild Rose') Zones 6 to10.
Cold tolerant and tough, Lemmon's Sage is native to the rocky canyons of Arizona, New Mexico and Northern Mexico. Butterflies, hummingbirds and honeybees love the pink lemonade blossoms of this close relative of S. microphylla.
Oaxaca Orange Wooly Sage (Salvia lineata) Zones 7 to 11.
Truly orange flowers aren't common among Salvias. This one is heat tolerant and also survives at 0 degrees F. Oaxaca Orange is a native of Southern Mexico's cloud forests where it likes growing in rich soil.
Arizona Blue Sage (Salvia arizonica) Zones 6 to 11.
Arizona Blue is an excellent groundcover for all kinds of shade. Heat- and cold-tolerant, it is native to the shaded areas of canyons in Arizona, New Mexico and Texas.
Snowflake Sage (Salvia chionophylla ) Zones 7b to 11.
In full desert sun, the whitish foliage of this groundcover sage creates the illusion of snow. Snowflake is native to the Chihuahua Desert of North Central Mexico.
Blue Ecuadorian Sage (Salvia flocculosa) Zones 9 to 11.
Although it loves water, this tough Andean species does fine in dry shade. But watch out for surprises. The warmer your climate, the taller it grows. Butterflies, honeybees and hummingbirds all enjoy it.
West Texas Grass Sage (Salvia reptans) Zones 9 to 11.
True blue flowers top grass-like stems in this willowy West Texas sage.
Balkan Sage (Salvia forsskaolii) Zones 4 to 9.
Bring on the snow. This Balkan Peninsula native survives winter temperatures as low as -30 degrees F. Hummingbirds aren't strongly drawn to Eastern Hemisphere species, but they adore S. forsskaolii's lavender cloud of blooms that seem to float atop its basal foliage.
Lavender Leaf Sage (Salvia lavanduloides) Zones 8 to 11.
The flowers and small, gray-green foliage of this fragrant sage make it look like its cousin, Lavender. However, this plant's bloom season is the opposite of a Lavandula species. Expect honeybee and butterfly visitors.
Variegated Mexican Bush Sage (Salvia leucantha 'Variegata') Zones 8 to 11.
Although the tiny flowers are pretty, it's the quirky foliage of this sage that catches the eye. The stems twist slightly and the velvety leaves have irregularly shaped margins. This species does well in all kinds of shade.
Wand Sage (Salvia cadmica) Zones 7 to 10.
This one has whorls of deep violet blossoms supported by dark bracts. The foliage is bright green, corrugated and fragrant.
Questions? Give Us a Buzz
We think we've given you enough information about shade-loving Salvias to consume at the moment. However, if you haven't quite had your fill of this nectar-rich subject, more information is available at our previous blog post 6 Salvias for Shade. If you have more questions, you're always welcome to give us a buzz by email or telephone.