Season extension with fleece and polytunnel — 4 to 8 weeks more harvest

In Central Europe the gardening season feels like it ends with the first night frosts in October. In fact it can — with simple tools — reach into winter. And on the other side: start as early as February/March instead of May. Here are the tools, ordered by effort and effect.

What you gain

Depending on the protective measure, your growing season is extended by:

• Fleece: +36 °F → 4–6 weeks extension
• Small polytunnel: +39 °F → 6–8 weeks
• Large (walk-in) polytunnel: +41 °F → 8–10 weeks
• Cold frame: +41 °F–46 °F → 8–12 weeks, with a solar store even usable year-round
• Heated greenhouse: year-round (but energy costs)

Fleece — the beginner's tool

Horticultural fleece (PP fleece, 17–30 g/m²) is the simplest and cheapest season extension. A 16.4 × 32.8 ft piece costs €10–15 and lasts 3–5 seasons.

How it works: the fleece holds warmth near the ground, protects against wind and reduces evaporation. Frost is buffered by 36 °F–39 °F. Light and rain come through, while insects and birds are kept out.

When to use it:

• Late summer/autumn: over winter salads, spinach, Asian greens for harvest until December
• Spring: over direct sowings of carrots, radishes, peas from February/March
• Season: against carrot fly, cabbage white — as insect protection

Securing it: with sandbags, stones or fleece pegs. In a lot of wind: stretch the fleece over small hoops (bent wires) instead of directly onto the plants.

Polytunnel — the all-rounder

A polytunnel is essentially a long, low mini-greenhouse without heating. Classic construction:

• 9.8 ft–19.7 ft long, 3.9 ft–6.6 ft wide, 2.6 ft–4.9 ft high
• PE film (UV-stabilised) over steel or plastic hoops
• Cost: €50–200 ready-made, or from ~€30 self-built

Advantages over fleece:

• Higher temperature gain (+39 °F–41 °F at night, +50 °F during the day)
• Controlled watering (rain is kept out — good for fungus-sensitive plants like tomatoes in autumn)
• More room — several rows fit inside

When to ventilate: During the day it quickly gets hot in the tunnel — open the ends from 68 °F outside temperature. Otherwise salads turn bitter, plants sweat.

Cold frame — the solar heavyweight

A cold frame (also "cold box" or "hotbed") is a wooden box with a glass or acrylic lid, about 19.7 in × 39.4 in and 11.8 in–19.7 in high. It stands directly on the ground, gathering solar warmth passively.

• +41 °F to +46 °F, ideally usable year-round
• With a solar store (black water-filled stones or dark soil inside): warmer still at night
• Building it: 1 weekend, ~€50–100 in materials

Classic uses:

• February/March: raising salad, kohlrabi, broccoli, herbs
• April: first direct sowing of carrots and radishes under the glass
• October–February: winter salad, spinach, lamb's lettuce, Asian greens — continuous harvest

What you DON'T need (but is often sold)

• Heated greenhouses for the hobby garden. Energy costs eat up any extra yield. Better 2 polytunnels than 1 heated greenhouse.
• Pro films rated for 3 seasons. Hobby-market film for €15 lasts 2 years — enough for most.
• A complicated watering system in the tunnel. A watering can and 5 minutes a day are enough.

Practical tip: combination

The pros combine: fleece inside the polytunnel. That gives another +36 °F — frost-free salads down to −50 °F outside are possible. In summer remove the fleece, carry on in the tunnel with ventilation.

In the Garden Planner you can enter the greenhouse and raised beds as infrastructure — the plan generation automatically accounts for the extended growing possibilities under glass/film.