The Public Herbarium

broad leaf plantain

Your Simple Guide to Preserving Herbal Medicine

Welcome! Drying herbs properly makes the difference between vibrant, potent medicine that lasts for months and moldy, flavorless plant material that ends up in the compost. This guide will teach you the simple principles that ensure your herbs dry quickly, stay colourful, and retain their medicinal power.

Why Proper Drying Matters

Fresh herbs are 70-90% water. If you don’t remove that moisture quickly and completely:

The goal: Remove water fast enough to stop mold and enzymes, but gently enough to preserve delicate medicinal compounds.

Why this matters: You’ve just spent time growing or foraging these herbs. Proper drying means your summer harvest of mint can soothe winter colds, and your spring calendula can heal summer sunburns. Poor drying means you’ve wasted all that effort.

The Four Pillars of Perfect Drying

1. Low Heat (or No Heat)

Ideal temperature: 35-43°C

Why: Higher temperatures destroy volatile oils (those aromatic compounds) and heat-sensitive vitamins. You want warmth to speed drying, not heat to cook the herbs.

How to tell if it’s too hot: If it feels hot to your hand, it’s too hot for herbs.

2. Good Airflow

This is the most important factor.

Stagnant air = moisture just sits there = mold. Moving air carries moisture away from the plant.

How to achieve it:

3. Darkness

Why: Light breaks down medicinal compounds, especially:

How to achieve it:

4. Low Humidity

Why: High humidity slows drying and promotes mold.

New Zealand consideration: Our climate is often humid, especially in North Island and coastal areas. This makes drying more challenging.

Solutions:

Drying Methods: Choose What Works for You

Method 1: Hanging Bundles (Best for: Sturdy-stemmed herbs)

Good for: Rosemary, thyme, sage, lavender, mint, oregano

How to:

  1. Gather small bunches of herbs (5-10 stems)
  2. Tie stems together tightly with string or elastic band (elastic tightens as stems shrink)
  3. Hang upside down in a dark, warm, well-ventilated space
  4. Optional: Cover with paper bag with holes punched in it (catches falling leaves, keeps dust off)
  5. Check daily; ready when leaves crumble easily (5-14 days depending on humidity)

Where to hang:

Not recommended: Kitchen (too much moisture from cooking), bathroom (humidity), closed cupboard (no airflow)

Method 2: Drying Screens/Racks (Best for: Flowers, leaves, petals)

Good for: Calendula flowers, chamomile, loose leaves, rose petals

How to:

  1. Make or buy drying screens (window screen stretched over frame works great)
  2. Spread herbs in single layer—don’t overlap
  3. Place in dark, warm, airy location
  4. Turn herbs daily for even drying (If daily turning is difficult, use a dehydrator with automated airflow or dry herbs in smaller, thinner batches to reduce turning frequency)
  5. Ready when completely crisp (3-10 days)

DIY screen options:

Method 3: Food Dehydrator (Best for: Everything, especially in humid climates)

Good for: All herbs; ESPECIALLY good if you live in humid areas

How to:

  1. Spread herbs in single layer on dehydrator trays
  2. Set temperature to 35-43°C — this is crucial!
  3. Check every 2-4 hours
  4. Ready when herbs crumble easily (3-8 hours typically)

Why dehydrators are worth it:

Cost: NZ$80-250 for a good dehydrator. Worth the investment if you dry herbs regularly.

Budget option: Look for second-hand dehydrators on Trade Me or in op shops. Many people buy them and rarely use them. A basic model is often enough for home herb drying.

Where to buy in NZ:

Temperature matters: Some cheaper dehydrators only have high-heat settings (60°C+). These are too hot for herbs, especially those rich in volatile oils (like mint, lavender, thyme). While some non-aromatic herbs can tolerate slightly higher temperatures, it’s best to choose a dehydrator with adjustable temperature control down to 35°C.

Method 4: Paper Bag Drying (Best for: Seedy herbs and flowers)

Good for: Elderflowers, herbs going to seed, delicate flowers

How to:

  1. Place herb stems or seed heads in paper bag
  2. Punch holes in bag for airflow
  3. Close top with rubber band
  4. Hang in warm, dry, dark place
  5. Shake periodically to redistribute
  6. Seeds will fall to bottom of bag as they dry

Why this works: Bag catches falling seeds/petals while allowing airflow

Drying Times by Plant Part

Leaves & Flowers: 3-14 days (depending on moisture content and method)

Roots & Bark: 1-3 weeks

Berries: 2-5 days

These are estimates. Your actual time depends on:

How to Tell When Herbs Are Completely Dry

The Tests:

1. Crumble Test (for leaves):

2. Snap Test (for stems):

3. Feel Test:

4. Jar Test (for confirmation):

Why complete dryness matters: Even 10-15% moisture left can cause mold in storage. Better to over-dry slightly than under-dry.

Common Drying Mistakes (and How to Fix Them)

✖ Mistake 1: Overcrowding

Problem: Herbs touching each other = trapped moisture = mold
Solution: Spread herbs out generously. It’s better to do multiple batches than cram everything together.

✖ Mistake 2: Too Much Heat

Problem: High temperatures = loss of volatile oils and vitamins
Solution: Keep temperature under 43°C. If using oven, use lowest setting (usually too hot for herbs) with door ajar.

✖ Mistake 3: Drying in Light

Problem: Light degrades medicinal compounds and causes colour loss
Solution: Choose a dark location or cover herbs

✖ Mistake 4: Not Enough Airflow

Problem: Stagnant air = slow drying = mold risk
Solution: Use a fan, choose an airy location, don’t seal herbs in enclosed spaces

✖ Mistake 5: Storing Before Completely Dry

Problem: Any moisture left = mold in jars
Solution: Do the jar test. Be patient. Extra day of drying is better than a moldy batch.

✖ Mistake 6: Leaving Herbs to Dry Too Long

Problem: Collecting dust, losing potency, taking up space
Solution: Check daily. Process as soon as fully dry.

Special Considerations for NZ Conditions

High Humidity Regions (Auckland, Northland, Coastal Areas)

Challenges:

Solutions:

  1. Invest in a dehydrator: This is genuinely the best solution for humid climates
  2. Use a dehumidifier in your drying room
  3. Dry in smaller batches: Less risk of mold
  4. Check more frequently: Catch any mold early
  5. Choose drier times of year: Autumn is often drier than summer in humid regions

Can’t afford a dehydrator? Try these free or low-cost options:

Drier Regions (Central Otago, Canterbury)

Advantage: Faster, easier drying
Still need: Darkness and good airflow (don’t skip these!)

Seasonal Considerations

Summer (December-February): Generally easier drying due to warmth, but can be humid
Autumn (March-May): Often ideal (drier air, still warm)
Winter (June-August): Slower drying due to cold; may need gentle heat source
Spring (September-November): Variable—often humid

What to dry when in NZ:

After Drying: Next Steps

1. Strip Leaves from Stems (if applicable)

Once fully dry, remove leaves from stems by running your hand down the stem. Stems don’t add medicinal value for most uses.

Exception: If you want to make herb bundles for aesthetic reasons, leave on stems.

2. Crumble or Leave Whole?

Whole leaves: Last longer (12-18 months), retain potency better
Crumbled: Easier to use, measure, and make tea, but degrades faster (6-12 months)

Best practice: Store whole, crumble as needed for use.

Pro tip: Store in portions you’ll use within 2 weeks. Opening jars repeatedly exposes herbs to air and light, degrading them faster.

3. Check for Any Mold

Inspect carefully. If you see ANY mold (fuzzy white, grey, or green growth), discard entire batch. Mold is not safe.

4. Storage (Covered in detail in the Storage Guide)

Quick version:

Drying NZ Native Herbs

NZ Native Herbs: Kawakawa, horopito, and other native plants can be dried using these same methods.

Important cultural and sustainability considerations:

Kawakawa drying notes:

Quick Reference: Drying Methods by Herb Type

Herb TypeBest MethodTemperatureTime
Leafy herbs (mint, basil, lemon balm)Hanging bundles or dehydrator35-40°C3-7 days
Woody herbs (rosemary, thyme, sage)Hanging bundles35-43°C5-10 days
Flowers (calendula, chamomile)Screens or dehydrator35-38°C5-10 days
Roots (dandelion, burdock)Dehydrator (sliced thin)38-43°C1-3 weeks
Berries (elderberry, rose hips)Dehydrator38-43°C2-5 days
NZ natives (kawakawa, horopito)Air-drying or dehydrator35-38°C3-7 days

Quality Check: Good vs Poor Dried Herbs

Examples of what to look for:

✅ Good quality dried mint:

❌ Poor quality dried mint:

✅ Good quality dried calendula:

❌ Poor quality dried calendula:

If your herbs look like the “poor quality” examples: They may have been dried incorrectly (too slow, too hot, or in light) or stored improperly. They’ll have reduced potency and may not be safe if mold is present.

First-Timer Success Path

New to herb drying? Start here:

Week 1: Try mint or rosemary (easiest, most forgiving)

Week 2-3: Try calendula or chamomile flowers

Month 2: Experiment with roots or berries

Month 3: Try native herbs

Final Thoughts

Drying herbs is straightforward once you understand the principles:

Start with an easy herb like mint or rosemary. Master the process. Then expand to more delicate herbs.

Your dried herbs should:

If they meet these criteria, you’ve succeeded. You now have shelf-stable medicine that will last 6-18 months.

Happy drying!

Sources & Further Reading

Books:

Extension Services:

Scientific Articles:

Disclaimer: This guide is for educational purposes only. Properly dried herbs are essential for safe herbal preparations. Moldy herbs should be discarded completely. Always use clean equipment and practice good hygiene throughout the drying process. When in doubt about herb quality, err on the side of caution and discard.

Note on Pricing: All prices mentioned in this guide are approximate and based on New Zealand suppliers as of December 2025. Prices vary by supplier, season, and market conditions. We recommend checking current prices with your local suppliers.

The Public Herbarium is built on a foundation of scientific integrity, transparency, and care. Research sources are referenced throughout the site wherever possible. Content creation is assisted by AI tools and carefully reviewed for accuracy.