November Greenhouse Gardening for Mediterranean Winters

Our greenhouse on the second terrace, soaking up the last warm days before winter’s slow rhythm settles in.

November on a Mediterranean homestead can feel like a season of contrasts. Sunlight still warms the afternoons, but nights drop fast. Air stays humid longer. Condensation gathers on greenhouse walls. Tender greens grow one moment and stall the next. This is the month where careful greenhouse management makes all the difference between strong winter crops and a disappointing cold-season slump.

Inside our own greenhouse on the second terrace, November is when the seasonal dance begins. Doors open wide on warm days to release trapped humidity. At night, we plug the bottom gaps around the greenhouse doors with leftover wood fibre insulation from our stone house renovation. It is not pretty, but it keeps the first frosty nights out. Eggplants still hang on from summer, greens take over the lower beds, and the ridgeline breeze needs to be managed daily. It is not complicated, but it does require attention.

If you want to step into winter with confidence, this guide will walk you through each November task clearly and simply. At the end, check out Herman’s Tough Kraut Fixes for troubleshooting and FAQ help.

Why November Greenhouse Gardening Matters in Mediterranean Zones 8 to 11

Mediterranean climates are defined by dry summers and mild winters, but November is the turning point. Days shrink. Light intensity drops. Nights cool quickly. Soil stays warmer than the air, and this creates the perfect chance for crops to establish strong roots before mid-winter.

Greenhouses in Zones 8 to 11 keep the cold at a distance but not completely. They soften frost, reduce stress on young crops, and extend harvests into the dull months when garden beds outside slow down. November is your last window to prepare the structure, balance humidity, and plan for winter growth.

In our greenhouse, set above a steep terrace and close to the river, night air slides down the slope and pools around the base. This small detail shapes how we manage ventilation and insulation. Every greenhouse has its own quirks. Understanding these quirks now leads to stronger winter crops later.

A quiet November morning inside the greenhouse. Summer vines fading, winter greens rising, and plenty of work tucked between the rows.

Manage Ventilation Carefully

Ventilation is the foundation of November greenhouse gardening. Days can still reach comfortable temperatures, but nights bring cold snaps. That warm-cold cycle creates condensation, and condensation is what encourages fungal problems like botrytis, rust, and powdery mildew.

What to do now:

• Ventilate on warm or dry days.

• Open doors or windows for cross-flow.

• Close up late afternoon as soon as temperatures begin dropping.

• Avoid trapping warm, wet air overnight.

Humidity out, fresh air in. November greenhouse gardening starts with simple daily habits like this.

What to avoid:

Over-sealing the greenhouse too early. A fully closed greenhouse in November traps moisture, not heat.

Tough Tip: If the nights are mild, leave a small gap open for passive ventilation. Even a 2 cm crack reduces humidity more than you think.

Monitor and Harvest Root Crops

Root crops love the steady soil temperature under cover. These beets are almost ready for the winter kitchen.

Greenhouses often host late carrots, radishes, beets, and baby turnips. These roots love the stable soil temperatures inside.

Your November root crop checklist:

• Thin crowded carrots and beets so roots develop properly.

• Harvest radishes on time before they turn woody.

• Pull out any diseased or misshapen roots to prevent pests from hiding in the soil.

• Inspect for slug activity around root shoulders and mulch edges.

How to store your roots:

• Carrots: keep in slightly damp sand or soil-filled buckets in a cool space.

• Beets: trim leaves and store in crates with good airflow.

• Radishes: best eaten fresh but can be kept in airtight containers in the fridge.

Tough Tip: A narrow, clean greenhouse bed is perfect for overwintering a late carrot patch for slow, sweet harvests in January.

Protect Tender Crops Before Hard Frosts Hit

Mediterranean winters are gentle, but not frost-free. Greenhouses buffer the cold, yet tender crops like lettuce, pak choi, parsley, basil cuttings, and young seedlings still need extra protection when temperatures dip near freezing.

Here is what to keep ready:

• Double fleece layers to place loosely over beds during cold nights.

• Bubble wrap to protect pots and trays near the edges of the structure.

• Watering cans filled by evening because frost-damaged hoses are no fun.

For container-grown plants, wrap the outside of pots with bubble wrap or old blankets. Roots freeze faster in containers than in the ground.

Tough Tip: Always remove fleece in the morning. Leaving it on during sunny hours can trap too much heat and moisture.

Check and Repair Greenhouse Infrastructure

Wind, moisture, and ultraviolet exposure weaken greenhouse materials over time. November is the month to inspect everything before winter storms arrive.

Leaf debris gathering on the glazing — a November reminder to clean panels and check seals before winter storms.

Key areas to inspect:

• Door seals and hinge areas.

• Polycarbonate panels, screws, and clips.

• Any loose joints in the frame.

• Gutter channels above and beside the greenhouse. Clear out leaves and debris.

• Ground anchors or tie-down points on polytunnels if you use both structures.

Inside, check for:

• Cracked seed trays.

• Mouldy wooden shelves.

• Leaking irrigation fittings.

A few minutes spent tightening and cleaning saves hours of frustration later.

Tough Tip: Use straw bales to block draughts around the base of the greenhouse. After winter, the straw becomes mulch or compost.

Balance Light and Moisture for steady winter growth

November light levels drop sharply in Zones 8 to 11. Even small reductions in sunlight have a big effect on leafy greens, herbs, and winter seedlings.

Do this now:

• Wash the greenhouse glazing inside and out to increase light penetration.

• Remove algae and dust from hard-to-reach corners.

• Reduce watering frequency to avoid waterlogging.

• Water only in the morning so leaves dry before sunset.

Why it matters:

Plants grow slower now. They drink less. Watering on autopilot often leads to soggy roots and fungal issues.

Tough Tip: If you grow in raised greenhouse beds, rake the surface lightly after watering to improve aeration and slow down algae growth.

Plan Your Winter Crop Layout

Greenhouses offer precious warm space in winter, so plan plant placement with intention.

Ideal crops for greenhouse production in November:

• Lettuce mixes

• Spinach

• Pak choi

• Mustards

• Rocket

• Coriander

• Chard

• Spring onions

• Winter radishes

• Asian greens

• Mizuna and mibuna

• Early peas for shoots

• Herbs like parsley and winter-hardy dill

Place fast growers near the edges for easy harvesting. Keep slower crops like chard and carrots toward the back.

Winter crops settling into their November beds. A simple layout keeps the greenhouse productive all season.

Rotate crops if summer fruiting crops were in the greenhouse. Tomatoes, peppers, and cucumbers create soil imbalance that leafy greens help restore.

Tough Tip: Do not plant the entire greenhouse at once. Stagger small sowings over two or three weeks to avoid a mid-winter harvest gap.

Small November Habits Shape Strong Winter Crops

November is not the end of the gardening year. It is the quiet beginning of your winter greenhouse season. With a little preparation, steady habits, and a bit of observation, your greenhouse becomes a warm refuge where greens and root crops thrive long after the outdoor beds slow down.

On our land in Central Portugal, this month brings a calmer rhythm. Morning ventilation. Afternoon light checks. Evenings with fleece ready on standby. These small routines build resilience and keep fresh food growing right through winter.

If you are ready for more November guides, explore the other posts in this mini-series. Let’s grow smarter together, one season at a time.

Herman’s Tough Kraut Fixes: Common November Greenhouse Gardening Challenges

This troubleshooting FAQ tackles the most common November greenhouse problems, from humidity headaches to frost damage. These are the issues growers across Mediterranean Zones 8 to 11 face year after year.

Q: My greenhouse fogs up every morning. Is this normal?

A: Yes, but it should clear quickly. If condensation stays until midday, you need more morning ventilation. Wipe down heavy droplets to prevent fungal spread.

Q: Why are my lettuce seedlings stretching and leaning?

A: Low light. Wash your glazing and widen spacing between trays so each one gets more direct sun.

Q: My greenhouse smells earthy and damp. Should I worry?

A: A small earthy smell is normal, but a strong, sour odour means overwatering. Let the soil dry slightly and open vents during the warmest hour of the day.

Q: My radishes are all leaves and no roots. What went wrong?

A: Too much nitrogen or not enough light. Thin seedlings early and avoid adding fresh manure to root crop beds.

Q: How do I protect the greenhouse from sudden frost?

A: Use double fleece over tender crops, seal gaps with straw bales, and place bubble wrap around the lower frame. Even small changes help reduce heat loss.

Q: When do I stop watering completely?

A: Never stop completely. Reduce frequency but always check soil moisture with your fingers. Dry soil stresses winter crops more than cool temperatures do.

Recommended Books and Resources

Books

• The Winter Harvest Handbook by Eliot Coleman

  A foundational guide to growing vegetables through cold months using simple, unheated structures and climate-smart planning. Ideal for anyone wanting steady winter harvests without relying on electric heat.

• The Greenhouse Gardener’s Manual by Roger Marshall

  A comprehensive manual on building, managing, and troubleshooting greenhouses in all climates, with strong sections on humidity control, insulation, and winter protection. Great for growers who want to fine-tune their structure for year-round use.

• The Year-Round Vegetable Gardener by Niki Jabbour

  A practical, highly visual guide to extending the growing season using cold frames, row covers, and unheated greenhouses. Perfect for beginners building confidence with winter greens and slow-season crops.

• Mediterranean Gardening: A Waterwise Approach by Heidi Gildemeister

  A valuable reference for gardeners in warm, dry climates, teaching how to design resilient Mediterranean gardens with smart water use and climate-adapted plants. Excellent for readers balancing greenhouse production with outdoor drought-aware gardening.

Resources

• Bluetooth Greenhouse Thermometer & Hygrometer (ThermoPro TP50)

  A wireless thermometer–hygrometer with Bluetooth and an app lets growers track temperature and humidity trends from inside the house. Some models store up to 2 years of data and show min/max values, which is incredibly useful for understanding how a greenhouse behaves on frosty nights and damp mornings.

• Automatic Greenhouse Vent Opener (Bayliss XL Autovent)

  These mechanical vent openers use a wax-filled piston that expands with heat to open greenhouse windows and contracts as it cools to close them. No electricity needed, and they are designed for standard greenhouse roof vents.

• Solar-Powered Greenhouse Fan Kit

  Solar exhaust fan kits combine a small solar panel with one or more DC fans designed for sheds, coops, and greenhouses. During sunny hours they actively pull hot, humid air out and draw fresh air in, reducing condensation and mould risk without wiring or grid power.

• Tough Kraut Resources

  Our curated list of tested greenhouse tools and garden gear is available on the Tough Kraut Resources page.