Lilac Colors: 7 Classes, and Why Soil pH Nudges the Shade Instead of Switching It Like Hydrangeas
Lilacs sort into 7 color classes. Get two well-regarded cultivars for each class, plus how sun, weather, rootstock and soil pH really shift a lilac’s shade.
Every lilac cultivar is filed in one of seven color classes — white, violet, blue, lilac, pink, magenta or purple — and the class travels with the plant. A bigleaf hydrangea works differently: aluminum from acidic soil flips its flowers from pink to blue. Nobody has documented a switch like that in lilac. The International Lilac Society’s registrar, the New York Botanical Garden and Montana State Extension all say soil chemistry can nudge a lilac’s shade, but I found no source showing soil moving a lilac from one class to another. Sun, weather, flower age and rootstock change a lilac’s color far more often than the soil does.
This guide covers what the seven classes mean, how single and double flowers fit in, two well-regarded cultivars per class, what really changes a lilac’s color, and how to choose by site. It’s a spoke of our lilac plant care guide, which covers planting, pruning and bloom troubleshooting.
What Are the Seven Lilac Color Classes?
The International Lilac Society’s register sorts lilacs into seven classes using the 1953 Wister color code: I White, II Violet, III Blue, IV Lilac, V Pink, VI Magenta and VII Purple, plus S or D for single or double flowers. A ‘Pocahontas’ is therefore “S II” — a single violet. Some European organizations add a VIII Creamy Yellow class; the register files ‘Primrose’, which Montana State calls the closest to yellow of all lilacs, as white. Montana State’s list of the seven groups swaps “lavender” in for “lilac”, so you’ll see that word for the same slot.
The Society grades a lilac’s class when one-third of the buds have opened, and says that check should happen in the shade before the bloom fades. A class label describes a lilac at its freshest, not at three o’clock on a hot afternoon.
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To see how the classes are really used, I ran the register’s March 2025 release through a script and counted the 1,770 entries that carry exactly one class (bicolors and range codes such as “S V-VII” left out). Pink is the largest class at 22.1%, purple is second at 18.1%, and the class literally called “lilac” holds only 15.1% of lilacs. Violet (7.5%) and blue (8.9%) are the smallest classes, so by count they are the scarcest colors in the register.
| Color class | Wister code | Share of the 1,770 entries | Share of the class that is double |
|---|---|---|---|
| White | I | 16.8% (297) | 30% |
| Violet | II | 7.5% (133) | 32% |
| Blue | III | 8.9% (157) | 32% |
| Lilac | IV | 15.1% (267) | 33% |
| Pink | V | 22.1% (391) | 29% |
| Magenta | VI | 11.5% (204) | 30% |
| Purple | VII | 18.1% (321) | 16% |
Treat those shares as approximate. The register itself warns that a cultivar’s color “is usually chosen by the originator and may not be accurate”, and that about 10% of entries list two or more colors.
Single vs Double Lilacs: What the S and D Mean
A single lilac floret has four petals (botanists call them lobes), and a double has more than four, usually looking like two to four stacked flowers, according to the New York Botanical Garden. Rarer “radial doubles” have five or more lobes, sometimes as many as 18, radiating from the center. The Society even files a few triples under D.
Doubles are the minority: 28% of the entries I counted carry a D. Purple is the odd class out, with only 16% double against 29–33% in every other class.
Does a double mean less scent? Montana State Extension says small, dark, single florets “generally are more fragrant than larger, lighter, double ones, although there are exceptions.” Iowa State Extension’s own ratings of 28 cultivars don’t bear that out: 7 of 11 doubles are rated “very fragrant” against 8 of 17 singles. The only three rated merely “mildly fragrant” are all pale — ‘Primrose’ and ‘Krasavitsa Moskvy’ (white) and ‘Nadezhda’ (blue). That’s a small sample from one state’s ratings, so the safer reading is Montana’s other line: fragrance “varies considerably with species and cultivar.” Even on one shrub it shifts with time of day and temperature, and the scent peaks on a warm, sunny afternoon with the florets fully open.
Which Cultivars Represent Each Color Class?
Nine of the 14 picks below are rated “very fragrant” and the other five “fragrant” (Iowa State Extension’s ratings, plus Montana State’s for one), and none of them rebloom. I chose pairs where the register’s class code and Iowa State’s color label agree, so you aren’t relying on one source’s opinion. “Early” means the hyacinthiflora hybrids, which Montana State says bloom 7 to 14 days ahead of the French hybrids; “mid-season” is the common-lilac group.
| Color class | Cultivar (form) | Bloom slot | Fragrance | Worth knowing |
|---|---|---|---|---|
| I White | ‘Edith Cavell’ (double) | Mid-season | Very fragrant | Rated excellent in the Fiala ratings Montana State reprints; on its list of cultivars that may be less susceptible to bacterial blight. |
| I White | ‘Avalanche’ (single) | Mid-season | Fragrant | A Father Fiala hybrid, about 9 ft tall (Iowa State). |
| II Violet | ‘Pocahontas’ (single) | Early | Very fragrant | Hyacinthiflora hybrid; blooms mid to late April in Iowa. |
| II Violet | ‘Agincourt Beauty’ (single) | Mid to late | Fragrant | Very large violet-purple flowers that bloom well when young (Montana State). |
| III Blue | ‘Blanche Sweet’ (single) | Early | Very fragrant | Hyacinthiflora hybrid; registered as S III. |
| III Blue | ‘President Lincoln’ (single) | Mid-season | Very fragrant | Iowa State: “truest of the blues.” Montana State warns it becomes an enormous shrub (15–20 ft per Iowa State) whose leaves can hide the flowers. |
| IV Lilac | ‘Victor Lemoine’ (double) | Mid to late | Very fragrant | “One of the latest to bloom,” with rose-like florets in light pink and blue tints (Montana State). |
| IV Lilac | ‘Anna Nickles’ (single) | Mid-season | Very fragrant (Montana State) | Reddish-purple buds open to lilac-lavender; Montana spells it “Nickels.” |
| V Pink | ‘Charm’ (single) | Mid-season | Very fragrant | Large blue-pink florets (Iowa State). |
| V Pink | ‘Montaigne’ (double) | Mid-season | Very fragrant | The floret interior is lavender-blue, but the overall effect is still pink (Montana State). |
| VI Magenta | ‘Congo’ (single) | Mid-season | Fragrant | Wine-red flowers turning to purple; very old but rated excellent (Montana State). |
| VI Magenta | ‘Paul Thirion’ (double) | Mid-season | Fragrant | Red buds open to pink flowers; Montana State notes good cut flowers. |
| VII Purple | ‘Ludwig Spaeth’ (single) | Mid-season | Fragrant | Purple-red florets that “hold color in sun” (Montana State); registered as ‘Andenken an Ludwig Späth’. |
| VII Purple | ‘Adelaide Dunbar’ (double) | Mid-season | Very fragrant | Montana State calls it semi-double and “one of the richest of the bright reds” — class labels are loose. |
When the Sources Disagree About a Cultivar’s Class
A class label is an originator’s best description, not a measurement, and the three sources I checked disagree on several well-known cultivars:
| Cultivar | ILS register | Iowa State | Montana State |
|---|---|---|---|
| ‘Léon Gambetta’ | D IV (lilac) | Pink | Lilac |
| ‘Charles Joly’ | D VII (purple) | Magenta | Magenta |
| ‘Miss Kim’ | S II (violet) | “Lilac purple” | “Purple-blue” |
| ‘Sensation’ | S VII & I (purple, white edge) | Bi-color | Purple, single, with a “pure white border” |
Use the tables as a shortlist, then look at photos taken in a climate like yours, or buy a plant in bloom. ‘Sensation’ is the textbook bicolor: purple petals edged in white.
Does Soil pH Change Lilac Flower Color Like It Does for Hydrangeas?
Three sources say soil can shift a lilac’s shade within its class, but none I found shows it moving a lilac from one class to another, which is the difference from hydrangea. Hydrangea behaves like a switch because of chemistry. Its blue is a metal-complex pigment: 3-O-glucosyldelphinidin, an aluminum ion and an acylquinic-acid co-pigment, bound 1:1:1, as Ito, Oyama and Yoshida showed in 2018. The aluminum comes up from the soil, where it dissolves more readily in acid ground; University of Georgia Extension puts the split at pH 5.5 or lower for blue and 7.0 or higher for pink. No aluminum, no blue complex, pink sepals. Our guide on how to change hydrangea colour has the full recipe.
Lilac petals run on a different system. A 2022 genome paper in Communications Biology (Ma and colleagues) found that two pigments, delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside, make up about 98% of the anthocyanin in Syringa oblata petals. The shift from red-purple bud to violet flower to near-white fade tracks which of the two pigments the petal is making at each stage. I found no mention of a metal complex or of petal pH in that paper, which is the part hydrangea needs soil for.
Here’s where the sources get interesting, because three of them say soil does move the hue. The register’s notes say “soil pH influences floral color which can differ from the description given by the hybridizer or Registry. Blue is more pronounced in alkaline soil while violet and purple are more pronounced in acidic soil.” The New York Botanical Garden says “variations in the environment such as soil chemistry can also change flower hues,” and Montana State says “soil type sometimes alters flower colors so arboretum specimens may not look the same in your garden.” That direction is the reverse of hydrangea, where acid soil makes blue. Against all that, an Ask Extension expert wrote in 2019 that changing flower color by changing soil pH is “a proven fact” for hydrangea, “which is not true of lilacs.”
Those statements fit together if “change” means two different things: a nudge versus a switch. The registrar, NYBG and Montana State describe a nudge within a class. The Ask Extension reply is about the switch, the hydrangea trick. One caveat matters: each of those lines is an observation with no data shown, and I found no controlled trial measuring how far soil pH shifts a lilac’s petals. So don’t amend soil for color. Soil that’s too acidic costs you flowers, which is the bigger problem (why acidic soil stops lilacs blooming), and Montana State says lilacs tolerate a pH of 6.5 to 8.5 in well-drained ground.
Why Did My Lilac Change Color? A Diagnostic Table
Most color changes on a lilac come from flower age, heat, weather or rootstock rather than from soil. Find your symptom:
| Symptom | Likely cause | What to do |
|---|---|---|
| Buds are deeper than the open flowers, and the panicle pales over the bloom period | Normal development: petals go from red-purple bud to violet to near-white as pigment production falls (Ma 2022; Wang 2024). Montana State calls it the “unfolding of the colors.” | Nothing. Judge a cultivar’s color when a third of the buds are open, in shade. |
| Panicles open pale pink, yellowish or white after a hot spell | Heat breaks down the anthocyanin pigment (Iowa State Extension). | Nothing to fix, and the shrub isn’t harmed. Expect its normal color next spring if the weather differs. |
| Paler than last year with no heat wave | Weather: cool, damp springs keep color intense and hot sun fades it (NYBG; Montana State). | Nothing this year. |
| A dark purple or magenta lilac fades within days | Montana State: hot afternoon sun “fades the flowers quickly” on dark-flowered lilacs. | For new plantings, choose a spot with dappled afternoon sun, but keep at least six hours of sun a day because shade greatly reduces flowering. |
| One branch, or the whole shrub, flowers a different color than the cultivar you planted | Suckers from the rootstock or a failed graft. The rootstock is commonly privet, sometimes common lilac, and its suckers can overtake the cultivar, “resulting in an entirely different shrub” (Montana State). A branch below the graft gives “whatever flower color that the rootstock has” (Ask Extension). | Cut suckers off at their base (see our guide to lilac suckers). If the grafted top has died, the plant that’s left is the rootstock. |
| Flowers don’t match the tag or catalog photo | Class labels are the originator’s description and “may not be accurate” (ILS register); weather and soil shift the hue. | Compare photos from your own climate, or buy a plant in bloom. |
| Slightly bluer or redder than the nursery or arboretum plant | Soil chemistry or soil type nudging the hue (ILS register, NYBG, Montana State). | Don’t amend for color. Soil-test only if the shrub isn’t blooming. |
| One side of each petal looks darker than the other | Normal two-toned petals (NYBG). | Nothing; it’s part of the look. |
Heat bleaching has two parts that stack. Wang and colleagues found that lilac petals fade as flowers age because the genes that build pigment switch down (SoNAC72 and SobHLH130, which feed SoMYB44 and then SoUFGT1), and that the rate of pigment breakdown matters too. Iowa State’s Aaron Steil adds that the pigment is easily broken down by heat. Put together — my reading, not a finding from either source — a flower that’s already running out of pigment loses it faster in strong sun. It also fits why the same cultivar looks richer in a cool, damp spring.
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→ View My Garden CalendarBloom Time, Fragrance and Rebloomers by Color
Color class doesn’t decide when a lilac blooms; species and hybrid group do. Montana State’s sequence runs early (hyacinthiflora), mid-season (Meyer, common and French hybrid lilacs, Chinese lilac and ‘Miss Kim’), late (Hers, Preston hybrids and late lilac) and very late (Japanese tree and Pekin lilacs). Iowa State’s dates for its climate are mid to late April, early to mid-May, late May to June and early to mid-June. A common lilac stays in bloom 16 to 20 days from first bud color to fade, so planting one cultivar from each group can stretch the show to at least six weeks.
Rebloom is a separate trait, and none of the 14 cultivars above have it. The reblooming lilacs are the Bloomerang line. Proven Winners says Bloomerang Purple blooms in spring with other lilacs, “takes a brief rest to put on new growth, then blooms again from mid-summer through fall,” on a 4–5 ft shrub for zones 3a–7b. It describes the color as “classic lilac purple,” and the line also includes Dark Purple, Dwarf Pink and Dwarf Purple. Every Bloomerang name I found is a purple or pink; I couldn’t confirm a reblooming white or blue. That’s breeder information rather than independent trial data, so treat the second flush as a bonus, not a promise.
How Should You Choose a Lilac Color?
Choose by site and bloom window first and color second, because sun and weather move a lilac’s color more than soil does. This table matches common situations to cultivars from the sources above.
| If you have… | Consider | Why |
|---|---|---|
| Hot, reflective afternoon sun | ‘Ami Schott’ (blue, very double) or ‘Ludwig Spaeth’ (purple) | Montana State’s table says Ami Schott’s flowers “tolerate heat well” and Ludwig Spaeth’s florets “hold color in sun.” |
| A small yard | ‘Miss Kim’, Meyer lilac or a Bloomerang | ‘Miss Kim’ grows 5–6 ft per Iowa State and resists powdery mildew per Montana State. Bloomerang Purple stays 4–5 ft. Meyer lilac tops out around 4–8 ft but spreads 6–12 ft (Iowa State), so check our lilac spacing formula first. |
| A wish for cut flowers | ‘Paul Thirion’ (magenta, double) | Montana State notes it makes good cut flowers; our guide to cutting lilacs for a vase covers the technique. |
| A worry about disease | ‘Edith Cavell’ or ‘Ludwig Spaeth’ | Montana State says “some experts say that white-flowered lilacs are most susceptible” to bacterial blight and names ‘Edith Cavell’, ‘Glory’ and ‘Ludwig Spaeth’ as possibly less susceptible. See how to identify lilac diseases. |
| Mild winters | Choose for chill hours first, color second | Color doesn’t matter if the buds don’t set; our zone 9 lilac guide covers low-chill varieties. |
| A wish for a long bloom season | One cultivar from each bloom group | An early ‘Pocahontas’ or ‘Blanche Sweet’, then a French hybrid, then a Preston hybrid or Japanese tree lilac (Montana State’s sequence). |
Whatever color you pick, prune right after bloom: lilacs set next year’s flower buds in June and July. Our guide to when to prune lilacs has the two-week deadline.
Frequently Asked Questions
How many lilac colors are there?
The International Lilac Society recognizes seven color classes: white, violet, blue, lilac, pink, magenta and purple. Some European organizations add creamy yellow as an eighth, and bicolors such as ‘Sensation’ are coded as two colors.
Do lilacs come in yellow?
Not a true yellow. ‘Primrose’ is the closest, a creamy, yellowish white that Montana State calls the closest to yellow of all lilacs. The register files it as white (S I), while some European organizations recognize a separate creamy yellow class.
Can you change a lilac’s color with soil?
You can’t switch it the way you switch a hydrangea. The Lilac Society’s register says blue is more pronounced in alkaline soil and violet and purple in acidic soil, so soil can nudge the shade, but I found no source showing a lilac changing class. Don’t amend soil for color.
Why did my lilac bloom a different color this year?
Heat, weather and flower age are the usual causes, and rootstock suckers are the cause when a whole branch is a different color. Hot sun bleaches pink and purple flowers, while a cool, damp spring keeps color intense.
What is the rarest lilac color?
By count of the register, violet (7.5% of entries) and blue (8.9%) are the smallest classes. That measures how many cultivars exist, not how easy they are to buy.
Which lilac color is the most fragrant?
None of them. In Iowa State’s ratings each of the seven class colors includes at least one “very fragrant” cultivar, and the only “mildly fragrant” ones are pale. Fragrance varies by cultivar and by weather, and it’s strongest on a warm, sunny afternoon.
Sources
- International Lilac Society. Lilacs — Lilac Color and Classifications. International Lilac Society
- DeBard, M.L. International Register and Checklist of Cultivar names in the Genus Syringa L. (Oleaceae), update of March 6, 2025. International Lilac Society
- New York Botanical Garden. Lilac Diversity. NYBG Lilac Collection
- New York Botanical Garden. Growing Lilacs. NYBG Lilac Collection
- Mikkelson, M., Maatta, J. and Gough, B. Growing Lilacs in Montana (MontGuide MT199805AG, reviewed 2/11). Montana State University Extension
- Haynes, C. Lilacs Species for Iowa Gardens. Iowa State University Extension and Outreach
- Steil, A. Bleached Flowers on Lilac, May 20, 2022. Iowa State University Extension and Outreach
- Ma, K. et al. Lilac (Syringa oblata) genome provides insights into its evolution and molecular mechanism of petal color change. Communications Biology 5:686 (2022)
- Wang, Y. et al. SoNAC72-SoMYB44/SobHLH130 module contributes to flower color fading via regulating anthocyanin biosynthesis in lilac (Syringa oblata). Horticulture Research 12(3): uhae326 (2024)
- Ito, T., Oyama, K. and Yoshida, K. Direct Observation of Hydrangea Blue-Complex Composed of 3-O-Glucosyldelphinidin, Al3+ and 5-O-Acylquinic Acid by ESI-Mass Spectrometry. Molecules 23(6):1424 (2018)
- Williams, T. Hydrangea blooms turn colors based on soil pH levels, September 20, 2012. University of Georgia Cooperative Extension
- Ask Extension. My lilac bush changed colors (answered May 19, 2019). eXtension Foundation
- Ask Extension. My lilac was light purple and change to white. Why? (answered June 6, 2016). eXtension Foundation
- Proven Winners. Bloomerang Purple Reblooming Lilac (Syringa x). Proven Winners North America
