Medicinal plant harvest calendar: when to pick to preserve actives

Month by month, which plants to harvest, at what stage, at what time of day, and how to dry them to preserve their active compounds.

Harvesting your own medicinal plants deeply reconnects you with the living world and guarantees optimal quality — provided you respect the right harvest moments. A plant picked at the wrong stage or poorly dried can lose up to 80% of its active compounds.

Golden rules for the gatherer

• Harvest in dry weather, after dew evaporation (10am-12pm) and before peak heat
• Avoid roadsides, treated fields and polluted areas (at least 100 m from a road)
• Identify with certainty (in the slightest doubt, abstain) — a botanical guide is essential
• Never take more than a third of a station, never protected species
• Prefer waxing Moon days (active growth, herbalist tradition)

Month by month

March-April

Buds (blackcurrant, birch, pine), tender nettle leaves, dandelion (young leaves, flowers and roots), violet, primrose, daisy.

May

Hawthorn in bloom (flowering tops), meadowsweet in buds, black elderberry flowers, lemon balm in early flowering, plantain.

June

Linden (bracts at the beginning of flowering, over only 3-5 days a year), Roman chamomile, Provins rose, raspberry (leaves), yarrow.

July

Lavender (just before full flowering), thyme, rosemary, savory, hyssop, St. John's Wort (June 24 traditionally, St. John's Day), common verbena.

August

Sage, lemon balm in second cut, basil, peppermint, calendula.

September

Elderberry (berries at full ripeness), hawthorn (haws), wild rose (rosehips), hops (female cones), angelica.

October-November

Roots: dandelion, valerian, burdock, gentian, marshmallow. Cold concentrates actives toward the root.

At what stage to harvest each part?

• Buds: before bursting, late winter
• Leaves: just before flowering (maximum active concentration)
• Flowers: at the beginning of flowering, early morning
• Flowering tops: full bloom, tender part only
• Fruits/berries: at full ripeness
• Roots: autumn or very early spring, outside vegetative period

How to dry properly

Drying is the most critical step. Bad drying = mold or essential oil loss.

• In the shade, in a ventilated, dry room, at 25-35 °C maximum
• Spread on a muslin-covered frame, or in small bunches hung upside down
• Never in direct sun (destroys pigments and essential oils)
• Never in the oven except at very low temperature (35 °C max)
• Plant is dry when it snaps cleanly between fingers (5-15 days depending on part)

Storage

Store in opaque glass jars (or sheltered from light), labeled with date and harvest location, in a dry, cool place. Average shelf life: 1 year for leaves and flowers, 2-3 years for roots. Beyond that, actives degrade.

Frequently asked questions

Should one really account for the moon?

It's an ancestral herbalist tradition, partially validated by some modern studies on compound content variations. If it speaks to you, follow it; otherwise, time of day is more decisive.

Can fresh plants be frozen?

Yes for some (lemon balm, basil, parsley), often in oil or water ice cubes. Not ideal for medicinal plants because thawing alters many actives: prefer drying.