Overrated perennials to skip in a cold-winter garden

Overrated perennials to skip are popular plants that cause more trouble than they are worth in a cold-climate bed. In my zone 5 garden the worst offenders are bishop’s weed (Aegopodium podagraria), obedient plant (Physostegia virginiana), hybrid fall mums (Chrysanthemum x morifolium florist types), delphinium (Delphinium elatum), and lupine (Lupinus polyphyllus). None of them are evil. Each just demands effort out of proportion to the reward, and there are better-behaved plants that do the same job.

I have grown all five over the years, and most earned their place on this list by failing me repeatedly. The bishop’s weed I planted as a ground cover took me six years and a tarp to remove. The fall mums I planted three Octobers in a row all died the same winter. Experience, not theory, put these plants on my skip list, and the right replacements have made my beds easier ever since.

What makes a perennial overrated

A perennial earns its keep by giving good value across the season for the space and effort it takes. The overrated ones fail that test in one of two ways. Either they spread so aggressively that they steal time and space from everything else, or they look glorious for a brief moment and then sulk, flop, or die, leaving you with a gap and a bill.

The garden-center photo never shows the trouble. A flopping delphinium looks magnificent in the catalog and pathetic in the bed after the first storm. A pot of fall mums looks like a bargain in October and a dead clump in April. The question to ask before buying is whether the plant earns its space all season or only at one short peak, and whether you can live with how it behaves.

I am not arguing these plants are bad everywhere. Lupine thrives in cool, sandy gardens. Delphinium is glorious where someone stakes it religiously. The point is that in an average zone 5 bed, tended by a gardener with limited time, each of these returns less than the effort it asks. Better plants exist for the same role.

The aggressive spreaders

Bishop’s weed (Aegopodium podagraria, USDA zones 3-9), also called goutweed, is the plant I warn people about most. Sold as a tough ground cover for difficult shade, it spreads by underground runners that are nearly impossible to dig out completely. Leave a fragment of root and it regrows. A small clump takes over a whole bed in a few seasons and chokes everything around it. I spent years and a smothering tarp removing mine. The variegated form ‘Variegatum’ is sometimes sold as ornamental, but it is just as invasive as the green species. The USDA NRCS Plants Database lists Aegopodium podagraria as an invasive species in several northeastern states.

Obedient plant (Physostegia virginiana, zones 3-9) carries an ironic name, because it is anything but obedient. The pink late-summer spikes look pretty, but the plant runs at the root and pops up several feet from where you planted it, weaving through and crowding its neighbors. In a small bed it becomes a constant editing job. In rich, moist soil it is even more aggressive. The straight species is the worst offender; the cultivar ‘Miss Manners’ (24 in / 60 cm) is a well-behaved, less-spreading form.

Both plants share the trait that makes a spreader dangerous: they expand faster than you can manage and they outcompete the plants you actually want. If you must grow an aggressive spreader, confine it to a buried container or a spot bounded by paving where it cannot escape. Better still, choose a well-behaved plant that stays where you put it.

The short-lived disappointments

Hybrid fall mums (Chrysanthemum x morifolium florist types) are the most expensive disappointment on the list. The potted mums sold in garden centers each autumn are florist types bred for one massive show, and most die over a zone 5 winter. The problem is timing as much as breeding: planted in October, they have no time to root before the freeze, so they heave out of the soil and die. People replant them every fall and treat a perennial like a costly annual. The University of Minnesota Extension notes that fall-planted mums in zone 4 and colder have less than a 50 percent survival rate even in mild winters.

Delphinium (Delphinium elatum, zones 3-7) gives two glorious weeks and then a season of trouble. The tall blue spires are striking in early summer, but they flop the moment a storm hits unless you staked them early, and after blooming the plant often sulks and looks ragged. The bloom-to-effort ratio is poor. I grow one or two for the spectacle and accept that they are high-effort, short-payoff plants.

Lupine (Lupinus polyphyllus, zones 4-7) fades fast in the heavy soil most gardens have. It wants cool, well-drained, slightly acidic ground, and in clay it blooms once, declines, and often dies within a few years. It also reseeds into colors and spots you did not plan, which some gardeners enjoy and others find messy. In the right soil it is a fine plant. In an average zone 5 bed it rarely lasts.

What to plant instead

For the role of a tough ground cover, skip bishop’s weed and plant well-behaved options like foamflower (Tiarella cordifolia, zones 4-9), hardy geranium (Geranium macrorrhizum, zones 3-8), or a clumping sedum. These cover ground and fill in without running rampant, and they stay where you put them. You get the coverage without the lifelong battle to keep the plant in bounds.

Instead of obedient plant for late-summer spikes, plant Russian sage (Perovskia atriplicifolia, zones 4-9) or hardy salvia (Salvia nemorosa, zones 3-8). Both give vertical color over a long season, stand on their own, and stay put. For the vertical drama of delphinium without the flopping, baptisia (Baptisia australis, zones 3-9) sends up blue-purple spikes in early summer on sturdy stems that never need staking and lives for years.

For the late color that fall mums promise but rarely deliver, plant hardy garden mums in spring so they root before winter, or grow asters like Symphyotrichum ‘Wood’s Blue’ (zones 4-8, 12-18 in / 30-45 cm), which return reliably and bloom hard into fall. Both give the autumn show without the annual replanting. The rule I follow is to choose the plant that does the job and stays put, rather than the one that flashes once and fails.

When a skip becomes a keep

Context changes the verdict, and it is worth saying which gardens can grow these plants well. If you have a large, contained area to fill and no precious neighbors to protect, an aggressive ground cover might be acceptable. If you garden in cool, sandy, acidic soil, lupine could thrive for you where it fails for me. The skip list is mine, shaped by my conditions and my patience.

Delphinium belongs in a garden where someone will stake it early and does not mind the post-bloom slump. Fall mums make sense if you treat them openly as seasonal decoration and replace them, the way you would a planter of annuals. The trouble comes from expecting a quick-fading or aggressive plant to behave like a reliable, well-mannered perennial.

The honest move before any purchase is to ask what the plant does across the whole season and how it behaves over years, not just how it looks in the photo. That single question has saved me more money and frustration than any other gardening habit. The flashy plant at the front of the garden center is often the one you will fight or replace.

A practical takeaway

Before you buy a popular perennial, ask whether it earns its space all season and whether it stays where you plant it. Skip the aggressive runners like bishop’s weed and obedient plant, the floppy delphinium, the soil-fussy lupine, and the late-planted fall mums. Reach instead for catmint, coreopsis, coneflower, baptisia, Russian sage, and hardy asters. Tougher, longer-lasting, and far less trouble, they make a zone 5 garden easier to live with.