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Is Alyssum a Perennial? It Depends Which One You Bought

Sweet alyssum is a short-lived perennial grown as an annual in most gardens. Basket-of-gold is a true perennial. The label rarely says which.

By Zakaria 2 min read Save to Pinterest — opens Pinterest in a new tab
A tight rounded cluster of sweet alyssum flowers, each with four small white petals and a yellow-green centre
Photo: Martina Vella 2002, CC BY-SA 4.0, via Wikimedia Commons
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Two different plants are sold as “alyssum”, and the answer flips depending which one is in your pot. Sweet alyssum is a tender short-lived perennial grown as an annual. Basket-of-gold is a genuine hardy perennial.

Which one do you have?

Two plants, one name
Sweet alyssum (Lobularia maritima)Basket-of-gold (Aurinia saxatilis)
Perennial?Tender, short-lived — grown as an annualYes, hardy to ~zone 4
HabitLow spreading carpetMounding, rock garden
FlowersTiny white, pink, purple. Honey-scentedBright yellow
WhenSpring to frostSpring only
FoliageGreen, fineGrey

If it flowered all summer, it is sweet alyssum. That single question settles it in almost every case.

“Mine comes back every year”

It is probably seedlings, not the same plant

Sweet alyssum self-seeds prolifically, and the seedlings come up in the same spot the following spring — which looks exactly like a plant returning.

In zone 9 and warmer the original really can overwinter and carry on for two or three years, though it goes woody and flowers less each season.

To encourage it: leave the last flush to set seed rather than deadheading into autumn. Seedlings turn up the next spring, often in paving cracks and gravel, which it likes. They pull out easily where you do not want them.

Modern sterile hybrids sold for hanging baskets will not do this at all.

Winter

  • Sweet alyssum — survives light frost, killed somewhere around the low 20s°F
  • Basket-of-gold — hardy to about zone 4, but wet winter soil kills it far more often than cold does

Neither will tolerate sitting in waterlogged ground through winter.

Another plant whose name misleads people about how it grows is mother of thousands, which propagates from the leaf edge.

The one piece of maintenance that matters

Shear it in midsummer, or it stops

Sweet alyssum reliably slows in heat, goes leggy and often does not recover on its own.

Cut the whole plant back by about a third when flowering slows. It looks drastic and it rebounds within two weeks with a fresh flush that carries to frost.

Keep it watered through the shear and feed lightly afterwards.

Common questions

Is alyssum a perennial?

It depends which plant you have, and two different ones are sold as alyssum. Sweet alyssum, Lobularia maritima, is botanically a short-lived tender perennial but is grown as an annual almost everywhere, because it is killed by hard frost and is cheap to replace. Basket-of-gold, Aurinia saxatilis, is a genuine hardy perennial that comes back for years. The label usually just says alyssum, which is why the question keeps coming up.

Does sweet alyssum come back every year?

Often it appears to, but usually through self-seeding rather than the same plant surviving. Sweet alyssum seeds prolifically and the seedlings come up in the same spot the following spring, which reads as a plant returning. In zone 9 and warmer the original plant genuinely can overwinter and carry on, sometimes for two or three years, though it gets woody and flowers less each season.

What is the difference between sweet alyssum and basket-of-gold?

They are different genera that share a common name. Sweet alyssum is a low spreading carpet of tiny white, pink or purple flowers with a honey scent, flowering from spring until frost, and it is what goes in hanging baskets and path edges. Basket-of-gold is a mounding rock-garden perennial with grey foliage and bright yellow flowers that bloom in spring only. If yours flowered all summer, it is sweet alyssum.

Will alyssum survive winter?

Sweet alyssum survives a mild winter and light frost, and is reliably killed somewhere around the low 20s°F, so in zone 9 and warmer it often persists while in zone 7 and colder it does not. Basket-of-gold is hardy to about zone 4 and needs nothing beyond sharp drainage — wet winter soil kills it far more often than cold does. Neither wants to sit in waterlogged ground through winter.

Does alyssum self-seed?

Sweet alyssum self-seeds freely, and in most gardens that is how it persists. Leave the last flush of flowers to set seed rather than deadheading into autumn, and seedlings appear the following spring — often in paving cracks and gravel, which it rather likes. It is not aggressive enough to be a problem, and unwanted seedlings pull out easily. Modern sterile hybrids sold for baskets will not do this.

How do you keep sweet alyssum flowering all season?

Shear the whole plant back by about a third when flowering slows in midsummer, which it reliably does in heat. It looks drastic and the plant rebounds within two weeks with a fresh flush that carries to frost. Without that cut it goes leggy, stops flowering and often does not recover. Keep it watered through the shear and feed lightly afterwards.

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