My first try with Alyssum was a McKenzie Seeds package picked up on a whim at a big box store – Carpet of Snow. I quickly fell in love, except Carpet of Snow is leggy, so needs frequent shearing if grown in a container. I’ve since switched to shorter varieties which will bloom longer without shearing or cutting back.
This is my personal growing guide. I use it to track seed sources, when to start seeds and if I should adjust growing conditions in my own greenhouse and garden. Please don’t consider this professional grower’s advice. I like the plant card information from Ball Seed Company. You can find an alyssum growing card here.
CURRENT VARIETIES AND SOURCES
I’ve grown both the Wonderland and Clear Crystal series. For a home garden I see little difference so I’m choosing just one this year.
Swallowtail Garden Seeds
- Clear Crystal Purple
- Clear Crystal Lavender
I also like Wonderland Blue – I sourced this via Stokes in 2023, but I’m not ordering one seed packet online. Swallowtail now carries it but I forgot to add it to my 2026 order, so next year.
| Hardiness | tolerates light frost so it keeps going from spring to late fall |
| Exposure | full sun, some shade tolerance |
| Deer resistant | yes |
| Bloom time & length | early spring to late fall, past frost |
| Deadheading, care | shorter varieties only needed one shearing in mid-summer and then not all pots |
| Water & soil conditions | medium |
| Height | I prefer shorter varieties, see my note on Carpet of Snow below |
| Spacing | 12-14 inches |
My notes:
In 2023 I tried several shorter varieties – both Clear Crystal and Wonderland were only 6 inches tall or so. They bloomed nonstop and worked extremely well in my annual planters. I put what seed of Carpet of Snow I had left in the vegetable garden for the pollinators.
I’m sticking with Alyssum over Bacopa as a small flowered spiller in containers. Bacopa looks great when it’s blooming but often stops blooming during mid-summer here.
I used Alyssum as a stand-alone in small 8-inch containers and as a spiller in larger containers. This is Clear Crystal Lavender in the left planter.
For 2024:
- trying more Wonderland colours (an update: I found little difference between the Wonderland and Crystal Clear series in terms of colour or growth habit)
- test out how early you can transplant in the spring since cold-tolerant
Seed Starting Guide
I notoriously start too early. Our last frost date is around May 13 according to the almanac however it’s rare for us not to have a cold snap before the May 24 weekend. So for 2026, this is my new schedule:
Start Date
- March 30–April 5 (7–8 weeks before May 24)
- Germination temp: 18-21°C
- Days to germination: 5-10
Sowing Method
- Can sow thinly directly in cell packs You can multi-sow and transplant but the seedlings are very small and you get a lot of seeds per package so this is easier. I cut out the smaller seedlings and leave 3-4 per cell.
- Press into soil, barely cover (very fine dusting optional). Needs light to germinate. Barely cover with vermiculite if pelleted.
- If sowing in cell pack, thin to 1-2 seedlings per cell
- Does not need heat mat to germinate. Will germinate 55-70°F / 13-21°C in 2 to 10 days but the cooler the temps, the longer to germinate.
Growing On
- If sowing in cell pack, thin to 1-2 seedlings per cell
- If using germination trays, transplant when 1-2 sets of leaves appear
- Temp: 13-18°C (likes it cool)
- Light: 14–16 hours
- Fertilize when 3 to 4 weeks old.
Planting Out
- Tolerates light frost
- Harden off outside early
- Can plant out mid-May
- Will bloom better in cooler weather