Q: I have always loved the look of blue spruce, and I see many Maryland nurseries stocking them. I’ve heard that I should consider alternatives. Why?
A: Every plant has something it can be vulnerable to — pests, diseases, environmental stress — and nothing is risk-free. Colorado spruce (Picea pungens), the species with the popular blue-needled cultivars, struggles in Maryland growing conditions. As such, it is at risk for several problems that cause dieback and significant aesthetic damage. Overall, spruces as a group are not well-adapted to high summer heat and humidity, or compacted or clay-dominated soils common to urban or suburban landscaping.
Spruces are not native in the state except for the tip of Western Maryland, where the rare red spruce grows in the mountains. (Maryland Biodiversity Project notes that prior logging and wildfires reduced this already limited population.) You can see from the spruce species range maps on the Biota of North America Program website that no other spruce species grows wild anywhere near Maryland.
Due to the particularly damaging nature of the issues spruces can develop here, primarily from fungal infections – drastic needle browning and shedding, plus branch dieback – I suggest using alternatives if you want a large-statured, pyramidal, and/or blue-leaved evergreen specimen tree. This spruce decline issue is prevalent enough that it has its own UMD Extension web page, “What’s Wrong with my Colorado Blue Spruce Tree?”
Few local native species are evergreen and large-statured, but they include American holly (Ilex opaca), Eastern redcedar (Juniperus virginiana), and Atlantic whitecedar (Chamaecyparis thyoides), the latter of which is rare, unfortunately hard to find for purchase, and limited to the Coastal Plain in the wild. Several species of pine grow wild throughout Maryland, but their mature habit is quite different from spruce.
Non-native candidates include other holly species or hybrids, Japanese cedar (Cryptomeria japonica), true cedars (Atlas Cedar, Cedrus atlantica, and Deodar Cedar, Cedrus deodara), and Western arborvitae (Thuja plicata). Arizona cypress (Cupressus glabra) and Atlas cedar come in silvery-blue forms if you want a foliage color similar to blue spruce. While Leyland Cypress (Cupressocyparis leylandii) is commonly planted, it suffers from some serious shortcomings that can make it short-lived and prone to fungal branch dieback.
Whichever plants you try, use a mix of species if you’re growing them in a group, like a screen or living fence, rather than mass-planting of only one variety. This helps to resist future pest, disease or weather stress problems, since different species have different tolerances and vulnerabilities. That way, a future issue won’t be likely to impact them all equally, like a fungal needle cast infection wiping-out a row of blue spruce.
Q: My perennial sedum has been floppy the past year. It used to stay upright while it flowered. It still blooms okay, but I’d rather it look nicer. Will I have to stake it each spring?
A: The flopping that sedum (stonecrop) and some other perennials can exhibit with age is mainly caused by environmental conditions, so that suggests something in its growing conditions changed over the years. Certain cultivars of plants are more prone to flopping or lodging than other cultivars of the same species, but when an individual plant flops when it didn’t use to, then genetics isn’t as much of a contributing factor.
Is the plant getting more shade than it used to? For example, maybe nearby trees or shrubs have matured enough to cast some shade on the sedum. It might not take much – maybe just a couple hours less of direct summer sun – to make a sun-loving perennial weaker and more likely to arch over under its own weight.
Excesses of nutrients (like from applying too much fertilizer or compost) and water (over-irrigation) can also contribute to floppy stems. Make sure any nearby lawn or garden irrigation doesn’t water the sedum if the soil around its roots isn’t getting dry several inches below the surface.
If the problem doesn’t lie with inadequate sun or too much water or fertilizer, then you can either use a ring stake around the plant in spring, which it will grow through and be supported by, or you can try pinching it next year. When pinching, take off no more than the top third of the plant’s total height around early June.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.