Creeping Sedums to Cover Large Sunny Areas
In my search for groundcovers that can replace lawn, I’ve discarded some failures but, like most plant addicts, I’m excited about my newest love – creeping sedums, the dominant plant used on green roofs because they do so well in that harsh environment. Here’s how they perform as lawn replacement – meaning, covering large areas in the sun, in ground – followed by some that I’m growing and others that are recommended by the experts. And those experts are: Ed Snodgrass of Green Roof Plants in Maryland, Sandy McDougal of Sandy’s Plants in Virginia (both in actual visits to their nurseries) and Paul Mancuso at Mahoney’s in Boston.
Where Sedums Perform the Best
Sedums do their best in lean soils and not much water – because in those conditions the weeds DON’T do well. In other words, in the world of groundcovers it’s all about the competition – can a plant out-compete the weeds or not? So first, making your site inhospitable to weeds before planting gives sedums greatly reduces the long-term maintenance from then on (less weeding).
Greenroof plant supplier to the world Ed Snodgrass taught me this, first introducing the notion that on a hillside, the sedums will perform better. That surprised me because some sources say that sedum does NOT do well on an incline, because those short roots supposedly don’t prevent erosion. Total bull, says Ed. It’s on flat surfaces that sedums struggle – because flat surfaces hold water, which the sedums don’t need but competing weeds love (especially in good soil). On flat surfaces, Ed actually thinks lawns are probably less work than sedums. (Hmm, this is the situation I have in my front yard, where I’ve recently added a bunch of new sedums to replace an assortment of thymes. Time will tell, and I’ll report the results.)
The other factor determining whether a groundcover can out-compete weeds or not is how quickly it spreads to fill in, covering those open spots that are invitations to weeds. So, vigor is required!
A crucial advantage that sedums have going for them as groundcovers is their diminutive stature – 6 inches or shorter. This matters if you’re worried about walking through and brushing up against taller plants where ticks are lying in wait – ticks that carry Lyme Disease especially. And design-wise, these creeping sedums will stay close to the height of mowed grass, and may even approximate the look of lawn, especially if an all-green one is used (like S. sarmentosum, the dominant sedum in my back yard.)
But the huuuuuge advantage sedums have – any sedum – is how little water they need – because they’re succulent, like cactus. Most of them I water maybe twice, then never again.
Sedums are found everywhere in the Northern Hemisphere, but mainly in Asia and Europe. I’m told there are two that are native to eastern North America, and both prefer shade.
Ed thinks that if you grow sedums in the conditions they like they are indeed less work to maintain than lawns, and it’s a different kind of work. While there’s no watering or mowing needed, there will be weeds, and here’s how Ed zaps them – with a gas torch tool. He attached a 3-foot extension, which eliminates the need to bend over. And the amazing thing about using a torch around sedums is that the flame kills weeds but NOT the sedums, because as succulents, they contain water and are naturally resistant to fire. (That makes them a great choice out West where fires are a real threat.)
Preparation and Planting
The growing medium that Ed uses at Great Roof Plants is 90 percent pea gravel and 10 percent compost, and he doesn’t irrigate at all – no wonder the weeds don’t love it. For converting from lawn to sedums he recommends killing all the weeds somehow (by spraying or solarizing), then putting 2” of pea gravel mulch on top, and planting in the pea gravel.
S. spuriums, grow to 6″ max (though they’re normally 3″). Ed calls them the best “persistent groundcover”, and cites the common ‘Dragon’s Blood’ that turns green in the summer as probably the most successful of them all. Another popular spurium is ‘Fuldaglut’. Sandy also likes spuriums and says they’re the most heat-tolerant of the bunch. (Here’s her info about spuriums.)
S. albums are really short, like 2″ and shorter, and I’m trying some ‘Coral Carpet’, shown here. It’s one of the hardier ones, to Zone 3. Here’s Sandy’s description of it and this photo is from her catalog.
S. rupestre is a particularly gorgeous group of Sedums that includes two of the most popular - ‘Angelina’ and ‘Blue Spruce’. Our Boston source says they’re most likely to be evergreen in New England, but Ed tells me the other side of that is that they don’t like our heat. He adds that they’re evergreen for just some of the winter, but not for about 2 and a half months of it. They’re hardy to Zone 4. Here’s Sandy’s info on Angelina and on ‘Blue Spruce’.
S. acre is another short one (to 2″) and also hardy to Zone 4. This photo is from her catalog. Though Paul in New England likes it, Ed doesn’t like it for the Mid-Atlantic because it “melts in our heat”. Here are the details.
S. kamtschaticum variegatum are so gorgeous I grabbed some when I spotted them at a Home Depot. Here’s Sandy’s information about it, and this is her photo.
S. floriferum ‘Weihnstephaner Gold’ is one that Sandy chose for my lawn replacement project, and then gave me some to try out. Hardy to Zone 3. This photo is from Green Roof Plants.