How to Grow Vegetables in a Greenhouse: The Complete Guide

Growing vegetables in a greenhouse transforms your gardening experience, extending seasons, protecting crops from unpredictable weather, and delivering fresh produce year-round. Whether you’re a novice gardener, or an experienced grower, this comprehensive blog will walk you through every step of creating a thriving greenhouse vegetable garden.

What You Need Before You Start: Essential Tools and Supplies

Before beginning your greenhouse vegetable garden, gather these necessary items:

Item	Purpose
Greenhouse Structure	Main growing environment (6×4 to 10×12 feet recommended)
Foundation Materials	Concrete slabs, paving stones, or timber frame
Ventilation System	Roof vents or louvre windows
Heating System	Electric, paraffin, or gas heater
Staging/Shelving	Aluminum or wooden shelves for plants
Growing Containers	Pots (30-45cm deep) or raised bed materials
Seed Compost	For starting seeds
Multipurpose Compost	For growing containers
Garden Compost	Soil enrichment
Perlite or Vermiculite	Drainage improvement
Watering System	Hosepipe, spray wand, or drip irrigation
Thermometer	Temperature monitoring
Plant Labels	Seed and plant identification
Seed Trays/Modules	Starting seeds
Plant Ties and Canes	Supporting plants
Fertilizer	Liquid seaweed, tomato feed, or balanced fertilizer

Step by Step to Grow Vegetables in Your Greenhouse 

Step 1: Prepare and Reset the Greenhouse Interior

Before planting anything, the very first action is to clean, reset, and stabilise the greenhouse environment. This step determines whether plants thrive or struggle from day one.

What this includes:

• Clear out old pots, soil, plant debris, and tools
• Clean glazing, frames, and benches to remove algae, pests, and spores
• Disinfect surfaces using warm water and mild soap (or horticultural disinfectant)
• Flush drainage holes and pathways to prevent water pooling
• Check doors, vents, and seals for smooth operation

Why this must come first:

• Prevents disease carryover from previous seasons
• Removes hidden pest eggs and fungal spores
• Ensures light transmission is maximised before planting
• Creates a neutral, controlled baseline for all crops

Without this reset, every later step (watering, feeding, pest control) becomes reactive instead of preventive.

Step 2: Build Growing Infrastructure and Prepare Soil

• Install Sturdy Staging: Fit aluminum or wooden staging along one or both sides of the greenhouse, to maximize vertical growing space and keep plants organized at 75-90 cm height.
• Leave Clear Central Pathway: Maintain walkways at least 60 cm wide for comfortable movement, easy plant access, and safe maneuvering with tools and equipment.
• Create Multiple Growing Levels: Use tiered shelving or hanging systems to separate seedlings on lower levels, young plants in middle sections, and mature crops on upper shelves.
• Utilize Overhead Space: Install roof hooks for hanging baskets, ideal for trailing plants like tomatoes, strawberries, or cascading flowers that benefit from vertical growing.
• Add Wall-Mounted Shelves: Use vertical wall areas for compact plants, seed starting supplies, small tools, and fertilizers to keep items accessible and organized.
• Set Up Small Workbench: Dedicate a corner space for potting activities, seed sowing, transplanting work, and general plant maintenance tasks.
• Choose Growing System: Select between containers for flexibility, raised beds for permanent productive space, or in-ground borders based on your layout and preferences.

If Using Containers:

• Select Appropriately Sized Pots: Choose containers at least 30 cm deep for most vegetables like lettuce, beans, and herbs, to provide adequate root space.
• Use Larger Containers for Heavy Feeders: Opt for 40-45 cm deep containers or growing bags for tomatoes, peppers, cucumbers, and aubergines needing extensive root systems.
• Ensure Proper Drainage: Verify all containers have drainage holes at the bottom to prevent waterlogging and root rot.
• Fill with Quality Growing Media: Mix 40% peat-free compost, 30% garden compost, 20% perlite or vermiculite, and 10% coir for excellent drainage and nutrition.

Soil Preparation:

• Test Soil pH: Use a simple pH test kit and aim for 6.0-7.0 range, which suits most vegetables and ensures optimal nutrient availability.
• Adjust pH as Needed: Add garden lime to raise pH levels in acidic soil or sulfur to lower pH in alkaline soil, following product instructions carefully.
• Mix in Slow-Release Fertiliser: Incorporate slow-release organic fertilizer according to packet instructions to provide steady nutrition throughout the growing season.

Step 3: Install Watering Systems and Select Vegetables

• Prepare Basic Hand Watering: Connect a hosepipe with an adjustable spray wand attachment that allows controlled, targeted watering for individual plants without waste.
• Run Main Supply Line (For Drip Irrigation): Position a primary water line along the length of beds, or staging where plants will be located for easy connection access.
• Connect Drip Lines to Plants: Attach individual drip emitters or soaker lines to each plant location to deliver steady, root-level watering without wetting foliage.
• Add Timer for Efficiency: Install a battery-powered or electric timer set to water once or twice daily, adjusting frequency as temperatures and plant sizes change.
• Group Plants by Water Needs: Place moisture-loving crops like cucumbers together and drought-tolerant herbs separately to avoid overwatering or underwatering.
• Collect Rainwater: Install a water butt outside connected to greenhouse roof gutters to harvest roof runoff, providing chlorine-free water that plants prefer.

Watering System Comparison

System	Maintenance	Water Efficiency	Best For
Hand Watering	Low	Moderate	Small greenhouses
Drip Irrigation	Moderate	Excellent	All sizes
Soaker Hoses	Low	Very Good	Bed systems
Capillary Matting	Low	Good	Container staging

Select Your First Vegetables:

• Choose Tomatoes: Select indeterminate (cordon) varieties for continuous production, or try determinate (bush) types for containers that require less maintenance.
• Plant Cucumbers: Grow varieties that thrive in warmth, preferring all-female types that eliminate bitter fruits and don’t require pollination.
• Grow Peppers and Chillies: Start with sweet pepper varieties that mature reliably, or explore different heat levels from mild to fiery options.
• Sow Salad Leaves: Plant lettuce, rocket, mizuna, and pak choi every two weeks for constant supplies, utilizing space between larger summer crops.
• Try Aubergines: Grow varieties that produce glossy fruits with adequate heat and consistent feeding for optimal growth.
• Add Climbing Beans: Plant French beans or runner beans trained up canes, to provide heavy crops from small ground footprints with minimal care.

Performance Expectations for Common Greenhouse Vegetables

Vegetable	Days to Harvest	Yield per Plant	Growing Difficulty	Space Required
Tomatoes (cordon)	70-85	4-8kg	Easy	45cm spacing
Cucumbers	55-70	15-25 fruits	Easy	60cm spacing
Peppers	80-100	8-12 fruits	Moderate	40cm spacing
Aubergines	85-100	6-10 fruits	Moderate	50cm spacing
Lettuce	30-50	1 head	Very Easy	20cm spacing
French Beans	55-65	1-2kg	Easy	15cm spacing

Step 4: Plan Your Growing Calendar and Start Seeds

Create Strategic Planting Schedule:

• January-February: Start early crops like tomatoes, peppers, and aubergines in heated propagators at 18-24°C, and plant hardy varieties like overwintered onions and early salads.
• March-April: Begin main sowing period for cucumbers, courgettes, and squashes, continue fortnightly succession sowings of salads, and start brassicas for autumn outdoor transplanting.
• May-June: Transplant summer crops into final positions, maintain succession sowings of quick crops, and start planning autumn harvests with appropriate varieties.
• July-August: Focus on maintenance including watering, feeding, and harvesting, while sowing winter crops like salads and oriental vegetables for late-season production.
• September-October: Clear spent summer plants, plant autumn crops including winter lettuce and hardy greens, and perform deep greenhouse cleaning between seasons.
• November-December: Grow cold-tolerant crops like winter lettuce, spinach, and lamb’s lettuce, perform maintenance and repairs, and plan next season’s planting.

Start Seeds Properly:

• Gather Essential Supplies: Collect clean seed trays or modules, fresh seed compost, plant labels, watering can with fine rose, and propagator or clear plastic covers.
• Fill Containers Correctly: Add slightly moist seed compost to trays or modules, firming gently to eliminate large air pockets without compacting the surface.
• Sow at Proper Depth: Plant seeds at roughly twice their diameter depth scatter very small seeds on the surface and press larger seeds 1-2 cm deep.
• Space Seeds Appropriately: Avoid overcrowding by spacing seeds evenly in trays or sowing individually in modules to prevent weak, leggy seedlings.
• Label Immediately: Mark each container clearly with variety name and sowing date to avoid confusion, especially when growing multiple similar varieties.
• Cover for Warmth: Place propagator lids or clear plastic bags over containers to maintain moisture and warmth at 18-24°C essential for germination.
• Check Moisture Daily: Keep compost evenly moist by misting or bottom-watering without saturating, which causes seeds to rot before germinating.
• Remove Covers Promptly: Take off propagator lids or plastic as soon as seedlings emerge to improve airflow and prevent fungal diseases.
• Provide Bright Light: Move young seedlings to strong natural light or under grow lights positioned 15-30 cm above to prevent weak, stretched growth.
• Transplant at Right Stage: Move seedlings to individual pots once two true leaves develop, handled gently by leaves rather than fragile stems.
• Keep a Growing Journal: Record sowing dates, varieties, performance, pest issues, and harvest dates to improve planning and refine strategies each season.

Step 5: Transplant, Train, and Support Plants

Transplant Seedlings:

• Harden Off Gradually: Begin acclimatization 10-14 days before transplanting by gradually reducing heat levels, increasing ventilation, and exposing plants to cooler conditions.
• Water Soil Thoroughly: Ensure growing beds or containers are adequately moist before transplanting to reduce transplant shock and encourage immediate root growth.
• Dig Proper Planting Holes: Make holes slightly larger than each root ball and mix compost or slow-release fertilizer into the bottom.
• Remove from Pots Gently: Ease seedlings out carefully, loosening tightly bound roots by gently teasing them apart without breaking major roots.
• Plant at Correct Depth: Set most vegetables at the same depth they grew in pots; tomatoes can be planted deeper to develop extra roots along buried stems.
• Firm and Water: Press soil gently but firmly around transplants to eliminate air gaps, then water thoroughly to settle soil around roots.

Train and Support Plants:

• Install Support Systems Early: Set up canes, strings, trellises, or frames while plants are still small to avoid disturbing established root systems later.
• Train Tomatoes Vertically: Secure sturdy canes or strings to roof supports, guide main stems upward, remove side shoots weekly, and pinch growing tips after six or seven fruit trusses.
• Train Cucumbers Correctly: Remove early side shoots until plants reach 60 cm height, allow two or three strong laterals to develop, and remove male flowers from traditional varieties.
• Support Peppers and Aubergines: Tie main stems to individual canes as plants grow, pinch growing tips at 30 cm height to encourage bushier growth and increased yields.
• Use Proper Plant Ties: Choose soft garden twine or plant clips, tie in figure-eight pattern around stake and stem, check weekly, and leave room for stem expansion.

Step 6: Feed Plants and Monitor for Pests

Establish Fertilizing Routine:

• Understand Nutrient Demands: Recognize that warm greenhouse conditions accelerate plant growth, significantly increasing nutrient requirements compared to outdoor growing.
• Choose Appropriate Fertilizers: Use liquid seaweed for trace minerals, fish emulsion for balanced nutrition, tomato feed for fruiting crops, or slow-release granular fertilizers.
• Water Before Feeding: Always moisten soil thoroughly first to prevent concentrated fertilizer from burning delicate feeder roots.
• Feed Little and Often: Apply fertilizer at half recommended strength twice weekly rather than full strength once weekly for more consistent nutrition.
• Identify Heavy Feeders: Tomatoes, peppers, cucumbers, and aubergines need weekly high-potassium feeding once flowering begins to support fruit development.
• Feed According to Crop Type: Apply high-potassium feed weekly for fruiting crops, balanced feed fortnightly for cucumbers, nitrogen-rich feed monthly for leafy vegetables, and minimal feeding for beans.
• Watch for Deficiencies: Yellowing lower leaves indicate nitrogen shortage, purple leaf undersides suggest phosphorus deficiency, and browning leaf edges point to potassium lack.

Monitor and Control Pests:

• Inspect Plants Daily: Walk through the greenhouse each day checking for pest activity, disease symptoms, or nutrient deficiency signs requiring immediate attention.
• Control Aphids: Squash small infestations by hand, spray with insecticidal soap, or introduce ladybirds for severe problems caught early.
• Manage Whitefly: Hang yellow sticky traps near affected plants, apply neem oil or insecticidal soap weekly covering leaf undersides, or release Encarsia parasitic wasps.
• Control Red Spider Mites: Increase humidity by misting paths and using damp gravel trays, blast leaf undersides with water spray, or introduce predatory Phytoseiulus mites.
• Prevent Fungal Diseases: Ensure adequate plant spacing for airflow, improve ventilation by opening vents daily, avoid overhead watering, and remove affected leaves promptly.
• Practice Integrated Pest Management: Maintain plant health through proper care, monitor daily for early detection, use physical controls first, employ biological controls when available, and resort to pesticides only when necessary.

Step 7: Manage Pollination and Daily Maintenance

Ensure Proper Pollination:

• Understand Greenhouse Limitations: Recognize that limited natural pollinators in enclosed greenhouses mean fruiting crops like tomatoes, peppers, and aubergines require assistance for fruit set.
• Tap Flower Trusses Daily: Gently tap or shake flowering stems once each day during mid-morning to release pollen and encourage successful fruit development.
• Use Vibration Method: Hold an electric toothbrush against flower stems for 2-3 seconds per truss to mimic natural bee vibration effectively.
• Hand-Pollinate with Brush: Transfer pollen between flowers using a small, soft paintbrush, especially useful for peppers with less accessible flowers.
• Pollinate at Optimal Time: Work during mid-morning hours when pollen is dry, loose, and most viable for successful fertilization between 20-25°C.
• Manage Cucumber Pollination: Choose all-female parthenocarpic varieties that set fruit without pollination, or remove male flowers from traditional types to prevent bitter fruits.
• Watch for Success Signs: Properly pollinated flowers remain attached with petals withering naturally, small fruits begin swelling behind flowers, and no premature flower drop occurs.

Follow Daily Maintenance Routine:

• Morning Tasks: Check greenhouse temperature first thing, open vents if mild weather predicted, and water plants if compost feels dry 5 cm below surface.
• Midday Inspection: Walk through greenhouse inspecting plants for pest activity, disease symptoms, nutrient deficiency signs, and provide shade if temperatures exceed 28°C.
• Afternoon Checks: Monitor water requirements again during hot weather, harvest ripe produce to encourage continued production, and remove any yellowing leaves or spent flowers.
• Evening Tasks: Close vents to retain warmth overnight, check heating settings for cooler periods, and tidy walkways by clearing debris and fallen leaves.
• Manage Ventilation Proactively: Open vents on mild mornings and close in evening to retain warmth, or install automatic vent openers for adjustments without manual intervention.
• Monitor Moisture Levels: Check compost moisture by testing 5 cm below surface, water when barely moist especially for container plants, and increase frequency in hot weather.
• Maintain Balanced Humidity: Use damp gravel trays or light path misting to maintain 50-70% humidity, but improve airflow immediately if condensation forms on glazing.

Step 8: Harvest Vegetables Properly

• Pick Tomatoes When Ready: Harvest when fully colored and slightly soft to gentle pressure, twist or cut stems rather than pulling, and pick regularly to stimulate further production.
• Cut Cucumbers at Optimal Size: Harvest when 15-20 cm long for best flavor and texture, avoiding overmaturity that causes bitterness and tough seeds.
• Harvest Peppers Strategically: Pick green for higher overall yields or wait for full color development (red, yellow, orange) for sweeter flavor but reduced productivity.
• Pick Aubergines at Peak Quality: Harvest when skin is glossy and fruit feels firm, avoiding overmaturity indicated by dull, soft fruits past their prime.
• Cut Salad Leaves Regularly: Harvest just above soil level for varieties that resprout for multiple harvests, or pick outer leaves from loose-leaf types leaving centers growing.
• Harvest Beans Frequently: Pick every 2-3 days once production begins since regular harvesting prevents over-mature pods and triggers further flower formation.
• Time Harvests Appropriately: Pick vegetables in cool morning hours when produce is crisp and fully hydrated for best flavor, texture, and storage quality.

Store Harvests Correctly:

• Store Tomatoes at Room Temperature: Keep harvested tomatoes on countertop rather than refrigerating to preserve best flavor and texture.
• Refrigerate Cucumbers and Peppers: Place in plastic bags in refrigerator crisper drawer where they stay fresh for 7-10 days.
• Handle Salad Leaves Properly: Wash thoroughly, spin or pat dry, and store in sealed containers with paper towels absorbing excess moisture for up to 5 days.
• Use Produce Promptly: Harvest only what you need for immediate use when possible, as vegetables taste best and contain maximum nutrition when freshly picked.

Troubleshoot Problems and Maintain Your Greenhouse

Issue	Symptoms / Cause	Recommended Solution
Temperature Fluctuations	Uneven growth, stressed plants	Install automatic thermostatic controls, add water-filled containers for thermal mass, and improve insulation during extreme weather
Excessive Humidity	Condensation, mould, fungal disease	Increase ventilation by opening vents more often, water earlier in the day, and space plants further apart
Nutrient Deficiencies	Yellow, purple, or scorched leaves	Use nitrogen fertilizer for yellowing, phosphorus for purple tones, potassium-rich feed for brown edges, or balanced feed for weak growth
Poor Fruit Set	Flowers drop, low yields	Improve pollination methods, maintain temperatures between 15–30°C, and ensure consistent watering
Leggy Seedlings	Tall, weak stems	Move seedlings closer to light, add grow lights, or slightly reduce temperatures to slow stretching
Blossom End Rot	Dark, sunken patches on fruit bases	Maintain steady watering; avoid calcium supplements as the issue is caused by irregular moisture uptake

The real advantage of a Greenhouse lies in control and predictability. When plants receive stable care and attention, problems reduce and output improves naturally. Each season then becomes easier, more efficient, and more rewarding.

FAQs

1. How do I stop a greenhouse from overheating?

Open the vents and doors early in the day to let hot air escape and encourage airflow. Using shade cloth or whitewash on the roof helps reduce direct sunlight and lower temperatures. A fan or automatic vent opener can also keep the greenhouse cool on very warm days.

2. Is a plastic or glass greenhouse better?

Plastic greenhouses are generally cheaper, lighter and retain heat well, making them great for most gardeners. Glass greenhouses look more attractive and last longer but can be more expensive and lose heat faster. The best choice depends on your budget, style preference, and how much insulation you need.

3. Do greenhouses increase plant growth speed?

Yes, greenhouses create a warm, stable environment that helps plants grow faster. They protect plants from harsh weather and pests, allowing longer growing seasons. This usually results in quicker and healthier growth than outdoors.