How to Grow St. John's Wort
St. John's Wort At a Glance
Difficulty
Easy
Category
Herb
Sun Exposure
Full Sun
Frost Tolerance
Frost Hardy
Cold Hardiness
Survives to -29°C
Plant Family
Hypericaceae
Growing Season
Warm Season
Plant Lifecycle
Perennial
How to Start It
★ Recommended for beginners
St John's wort handles frost, so sow it about 2 weeks before your last spring frost, or in late fall and let winter do the work. Press the tiny seeds onto the soil surface without covering them, since they need light to sprout, and keep the spot damp. They are slow and uneven, taking 14 to 28 days, so be patient and thin the seedlings to 45 cm apart. Plants from seed usually flower in their second summer.
St John's wort is a tough, sunny perennial with bright yellow flowers in midsummer that comes back every year. It spreads by underground stems and by seed, and it is treated as a weed in some parts of Canada, so grow it in a contained spot and cut the flowers before they set seed if it starts to wander.
When To Start
St. John's Wort needs warmth. Wait until your last frost has passed and the soil has warmed before sowing.
We do not have exact sowing dates for this one yet.
When should you plant St. John's Wort?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your St. John's Wort Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
Your St. John's Wort Calendar
Set your location to turn these into exact dates and reminders.
Sow St John's wort seeds on the soil surface outdoors now
2 weeks before your last frost
Optional: start St John's wort indoors on the soil surface
8 weeks before your last frost· optional
Optional: plant St John's wort seedlings or divisions out
Around your last frost· optional
Cut St John's wort tops when half the flowers are open
90 days after your last frost· every year
Cut back St John's wort to stop it spreading
30 days before your first frost· every year· optional
Did you water your st. john's wort seedlings today? Keep the top of the soil damp until they are up and growing.
About 1 days after you plant it
How is your St. John's wort coming along? Keep the soil lightly moist while the young plants settle in.
About 30 days after you plant it
Checking in on your St. John's wort. Pull weeds around it so the young plants are not crowded.
About 90 days after you plant it
The Journey Ahead
St. John's Wort's Lifecycle
Seedling
Mature Plant
Seed Production
Step 1
Prepare Your Space
0.1 cm
Seeding Depth
45 cm
Plant Spacing
60 cm
Row Spacing
1
Plants / Sq Ft
Vertical Growing
No.
Succession Planting
No.
Good Companions
Bad Companions
Step 2
Planting & Sprouting
Expect sprouts in 14–28 days
Growing Tips
- 1Grow St John's wort in full sun, though it handles a little shade.
- 2It thrives in poor soil that drains well, so a little compost at planting is all it needs.
- 3Water seedlings until they settle in, then only in long dry spells.
- 4It needs no feeding, and rich soil just makes it spread faster.
- 5Cut off faded flowers before they form seed, and divide the clump every few years to keep it in bounds.
- 6It is toxic to grazing animals, can harm cats and dogs, and reacts with many medicines, so keep it away from pets and ask a doctor or pharmacist before using it.
Seedling Phase
Step 3
Growth & Maturity
70 cm
Mature Height
60 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
Harvest Window
30 days
When to Pick
Harvest the flowering tops at peak bloom in midsummer
How to Harvest
- 1Cut the flowering tops of the stems in midsummer, when about half the flowers are open and the rest are still in bud.
- 2Crush a bud between your fingers: if it stains them red, it is ready.
- 3Tie small bunches and hang them upside down in a dark, airy spot for 1 to 2 weeks to dry.
- 4Store the dry tops in a sealed jar away from light, or soak fresh flowers in oil to make the red oil traditionally used on skin.
Step 5
Saving Seeds
How to Save Seeds
St John's wort usually comes true from seed, since it can make seed without being pollinated. Leave a few flower heads on the plant until the small seed capsules turn brown and dry in late summer. Cut them into a paper bag, let them dry for another week, then shake out the very fine seeds. Store them labelled in a cool, dark, dry place, where they keep for several years.
Seed Production
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