Persicarias Deserve Your Love—Trial Results

This controversial genus features more beautiful garden assets than thuggish liabilities

For many geezerhood , persicarias — also known as knotweeds — live the outer boundary for me . I saw them but mostly looked past them , thinking of them as makeweight more than thriller . My first genuine perceptiveness come almost 20 age ago after spotting a commanding swath of deep red - spired ‘ Firetail ’ nestled in a ocean of palm sedge ( Carex muskingumensis , Zones 4–9 ) in a new display garden at the Chicago Botanic Garden . Stylized meadows of this form , championed by the landscape architect at Oehme van Sweden , are the perfect vitrine for sheer yet simple perennials like persicaria . With my sake offend and eyes now wide assailable , my persicaria sightings became more frequent and satisfying . A trial to get to know them well was on my creative thinker for years , but it strike one infamous persicaria to finally make it take place .

Persicarias At a Glance:

Persicariaspp . and cvs .

Zones:4–9Conditions : Full Sunday to partial shade ; moist soilBloom time : belated spring through fallPests : graze deer ; Japanese beetles may do foliar damageTroubles : Certain specific species can be fast-growing

Reasonable concern over the likely unruly nature of persicarias is justifiable , but a move to ban all persicarias from our garden was worrisome . Yes , the garden value of persicarias stacked against their potential invasiveness is a “ tortuous ” subject . A closer feeling , though , show that they ’re not all thuggish ; in fact , there are many garden - desirable persicarias .

Top performers worth planting

‘Firetail’ mountain persicaria

‘ Firetail ’ mess persicaria(P. amplexicaulis‘Firetail ’ ) is pretty light to like : a apparently endless bloom of vivid crimson spike sit atop shaggy works from previous bounce to early fall . The flower colouring material is particularly vibrant on crisp fall days . A flair of red accents appears in midsummer , and the average jet , arrowlike leaf lighten a bit as summertime wanes . ‘ Firetail ’ prove similar to ‘ Atrosanguineum ’ in its bushy riding habit and size of it , but I liked the full-bodied peak colour of ‘ Firetail ’ more . All things being equal , ‘ Firetail ’ would have been top rated , but a turn of crest accidental injury in multiple wintertime cost it a champion .

‘Rosea’ mountain persicaria

The sick pinkish efflorescence of long - blooming‘Rosea ’ passel persicaria(P. amplexicaulis‘Rosea ’ ) arise generously above dark-skinned green leaves from midsummer to late midfall . While ‘ Rosea ’ present quite a good flower show , I never found the lenient pink as hearty as the bright red of ‘ Firetail ’ or ‘ Summer Dance ’ . The tiny flowers opened randomly along taper spike up to 7 inch prospicient and were busy with bees for weeks on closing . Stout ‘ Rosea ’ formed braggart shaggy-haired mounds accomplish nigh 5 feet tall and panoptic by the ending of summertime . Unlike a few similar persicaria , ‘ Rosea ’ was full wintertime hardy but was not aggressive or scraggy .

‘Summer Dance’ mountain persicaria

deal persicaria tends to be a rounded clumping flora with big pointed leaves and slender floral spires in shades of reddened , pink , purple , or white . ‘Summer Dance ’ mountain persicaria(P. amplexicaulis‘Summer Dance ’ ) embody all the best attributes of this metal money and was the measure whereby others were judged . you may gestate a beautiful profusion of uniquely bright coral - red flowers that dance above basswood - unripened leaves for three full month . At 5 feet tall and wide , ‘ Summer Dance ’ has bragging right for being the largest and most vigorous of the mountain persicarias in the trial . If you ’ve got the elbow room , give ‘ Summer dancing ’ a whirl .

‘Golden Arrow’ mountain persicaria

Golden - yellow leave-taking can be a knotty sell — some gardener have belike already tune up out — but‘Golden Arrow ’ mountain persicaria(P. amplexicaulis‘Golden Arrow ’ ) is deserving a tightlipped look . Radiant gold in bounce , the leave-taking cool to soft yellow - leafy vegetable for the summer , although they are still vibrant enough to glow under the rosy-cheeked pink prime . This dramatic color combination is so arresting that you might not observe that the flower spike are only 3 inches long . ‘ Golden Arrow ’ is midget compared to other cultivars , have smaller , exquisitely - textured arrow - shaped leaves and a low , mounded habit just 26 inch marvelous . Too much sun bleaches the leaves white , so ‘ Golden Arrow ’ is well grown in partial shade .

‘Border Jewel’

There is no mistaking the kinship of‘Border Jewel’(P. affinis‘Border Jewel ’ ) to other persicarias , but rather than being mound and bushy , it is a ground - squeeze broadcaster . petite pink blossoms split from vibrant pinkish buds , then years to pinky orange before finally turning burnt orange to russet . Due to the farseeing bloom menstruation , all efflorescence stages and colors are present at the same time . Green leave accented with cherry-red and orangish add together to the kaleidoscopic event throughout the season ; leaves withstand russet for the wintertime , so fussy gardeners may want to do some springtime cleanup . ‘ Border Jewel ’ can broadcast wide but was not aggressive — it move into ‘ Dimity ’ but did n’t seem uncoerced or able to vie with larger neighbors .

Giant fleeceflower

Giant fleeceflower(P. polymorpha ) is a gentle goliath — bluff enough to knock your socks off in bloom but soft - mannered enough to shake the brand of being thuggish . Even before the flower appeared , I loved the uniformity and uprightness of its clumping habit : it formed decent out of the solid ground in give as arrant testis . Its hulking shrublike habit may give pause , but its sizing is only a problem in modest garden . You do n’t have to wait long for the big show , because the teeny white blossoms gather in magnanimous frothy plumes open in tardy spring and go on for weeks . My evaluator differed greatly in describing the bouquet : from a lighting , pleasant scent to a disagreeable odor . I ’ll let you break the tie . Shear it when the first blooms go past for a 2d efflorescence presentation .

Uncommon gems to search out

‘Fat Domino’ mountain persicaria

A number of tremendous persicarias have come from Belgian plantsperson Chris Ghyselen , and while not exactly young , they are n’t as well known . Among them is‘Fat Domino ’ mountain persicaria(P. amplexicaulis‘Fat Domino ’ ) , which was outstanding in its first year . describe the vividness of the flower color is slick — it ’s dark orange - purpleness up close but sultry scarlet - purple a forgetful distance away . ‘ Fat Domino ’ was not shy to flower , pushing up chubby spikes one after another well into late dusk . This plant ’s striking color delighted me , as did its muscularity . From midget plant in recent spring , ‘ Fat Domino ’ flourished , reaching 30 inches improbable and wide by early fall , and 20 column inch to the top of the gullible leaves . It looks like it will be brawny , more akin to ‘ Firetail ’ . The fact that it thrived despite reprise deer surf all summertime is a will to an unsubduable look .

‘Orangefield’ mountain persicaria

‘ Orangefield ’ slew persicaria(P. amplexicaulis ‘ Orangefield ’ ) has a unique chameleonlike flower color — paradoxically , the two - chant reddish and very pale pink ( almost lily-white ) flowers count pink in fly-by-night ignitor but decidedly orange in full sun . Its green leafage are narrow than those of other cultivars , giving it a more svelte look , and are ringed in moody burgundy in drop . ‘ Orangefield ’ reached half its ultimate sizing of 3 feet tall and wide the first twelvemonth in the trial , which reflects its vigour .

‘Blackfield’ mountain persicaria

‘ Blackfield ’ mountain persicaria(P. amplexicaulis‘Blackfield ’ ) is a dusky beauty , with drear purple - crimson flowers that fascinate and held my aid at first glance . The about smutty buds and profoundly hued flowers were the black in the trial , although there is one out there called ‘ Black Adder ’ that allegedly is even gloomy . The fine - textured , lance - shaped leaf were importantly small in scale than those of other persicarias , but perhaps this was just a first - year thing . ‘ Blackfield ’ was 18 inches tall and 20 inches wide last summer , and like ‘ Orangefield ’ , it palpate lilliputian compared to other cultivar , although it too is expected to be 3 feet hearty . Truth be told , I acquire ‘ Blackfield ’ several years ago , but it did n’t make it through a wintertime . I definitely waited too prospicient to try it again .

Trial parameters

The Chicago Botanic Garden is evaluating 30 different persicarias in on-going comparative trial . In 2011 , a previous test ran afoul of an errant bulldozer during garden renovations , so we started over again in 2012 . Participants primarily include natural selection ofPersicariaspp . andFallopia japonica ; numerous nomenclatural changes over the years have elaborate the classification of these two grouping .

Duration:7 age

Zone:5b

Conditions : Full Dominicus ; well - drained , alkaline , clay - loam soil

Care : We provided minimum care , allowing the plant to flourish or fail under natural conditions . Besides observing their ornamental traits , we monitored the plants to see how well they grow and adapted to environmental and soil conditions while retain a close center on any disease or pest problems and assessing flora injury or loss over wintertime .

Persicaria: Friend or foe?

You might be asking yourself at this period , “ Is n’t the horribly invading Japanese knotweed a persicaria ? ” The solvent is yes — and no . Although formerly point to the genusPersicaria , Japanese knotweed is nowFallopia japonica . Nipponese knotweed is perhaps the archetype of an trespassing plant , and its status as a noxious weed is universally make out : it ’s on the lean of the earthly concern ’s bad 100 invasive mintage . Despite all this , a few “ cosmetic ” varieties of Japanese knotweed are readily sold to the gardening public . know this , we adjudicate to do a test of Nipponese knotweeds at the same time as our persicaria run .

notice : The square mintage is not a want works , so it was n’t obtain for the study .

Characteristics

Japanese knotweed is an upright shrubby perennial with stout bamboolike stems attain to 15 foot tall . The large light-green leaf — to 6 inches long — are broadly egg - mould with pointed tips . spray of white flower crown the plant in belated summer . Variegated and shorter mutation also survive .

How they spread

As startling as knotweeds are above ground , it ’s what ’s going on underground that is more troublesome . A immense connection of fatheaded rhizomes can go up to 60 feet from the industrial plant ’s link . Japanese knotweed spread chop-chop , work dense thickets that shade and crowd out native plants , thus threatening natural ecosystems , mintage diverseness , and wildlife habitat . Once established , it is extremely persistent and difficult to carry off . Shoots can sprout from modest rhizome shard swallow up to several feet abstruse and can punch through mineral pitch .

Reports from other sources note that seed are produced but are seldom viable , yet come dispersed by wind , water , animals , mankind , or in soil is cited as a primary mode of spreading .

Trial participants

Length of trial:6 years

Hardiness

While listed as cold Oliver Hardy to USDA Zone 5 , the fact that it has naturalized in northern state , Alaska , and most of Canada implies its adaptability to utmost climates . In other words , no space is safe .

Names

Nipponese knotweed may be labeled asPolygonum cuspidatumorReynoutria japonica . In fact , the many names and synonyms of knotweeds — Polygonum , Reynoutria , Tovara , Fallopia , andPersicaria — muddy up the water and may call into query what industrial plant you ’re actually get .

Trial findings

Potential invasiveness was measured by the vigorous rhizomatous habit rather than seedling , which were never discovered . The vigor of these selection was obvious from the start , and none carry themselves to their leave place after several years . ‘ Devon Cream ’ was by far the scarey of the Japanese knotweeds , spreading over 20 feet in all directions and into the turf by the fourth twelvemonth . And its vigor and flower production only increased when the taupe - stippled diversification began to be overrun by reverted green - leaved theme .

Mitigation

With the trial now over , I venerate the titan we ’ve unleashed . The question stay how long it will take to remove these plants from our garden . We ’ve begun by manually digging out rhizomes , but we will likely have to pair this practice with some chemical treatment . Nipponese knotweed and all its selections have been firmly placed on our “ Do not found ” list .

Richard Hawke is plant life evaluation manager for the Chicago Botanic Garden in Glencoe , Illinois .

Sources :

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