What a day in the greenhouse looks like

A greenhouse day starts with a look at the thermometer. On a sunny morning you open the door and vents before the heat builds, water anything that has dried out, and check the trays for new sprouts or trouble. In the evening you close up to hold the day's warmth overnight. Around that routine sits the actual gardening: sowing, moving seedlings into bigger pots, tying in tomatoes, picking. A weekday visit takes ten minutes. The real sessions are an hour or two on a spring weekend, when everything needs sowing or repotting at once.

Trays of young green seedlings lined up along a wooden bench inside a film-covered greenhouse — Seedling trays on the bench

Your first month, step by step

What you can grow in your first month

A tray of baby salad leaves

Loose-leaf lettuce sown thickly is ready for a first cut in three to four weeks, and regrows for a second.

Radishes in a grow bag

The fastest root crop there is, ready to pull about four weeks after sowing.

Tomato and pepper seedlings

By week four they have true leaves and are ready to move into bigger pots, weeks ahead of anything sown outdoors.

Stocky lettuce transplants

Sown in cells in week one, they are ready to plant into a grow bag or an outdoor bed by week four.

Find your zone and frost dates

USDA Plant Hardiness Zone Map Free lookup by ZIP code. Use it with your local last frost date to time sowing.

How to choose a first greenhouse

Size

Buy the largest one that fits the spot and the budget. A bigger volume of air heats and cools more slowly, so it is easier to manage, and almost everyone runs out of room in the first spring.

Covering

Zip-up plastic film is the cheapest and fine for a first season or two, but the cover wears out in the sun. Twin-wall polycarbonate panels cost more, hold heat better overnight and last for years.

Ventilation

Look for a roof vent or roll-up side windows as well as the door. A greenhouse with only a door is hard to keep cool in May.

Frame and anchoring

Check that it comes with ground stakes, guy lines or a base you can bolt down. Thin steel tube frames need extra weight on the base rails in a windy yard.

Headroom

If you plan to grow tomatoes or cucumbers, you want at least six feet at the ridge so the plants and you can both stand up.

Local rules

Before you buy a rigid one, check for a homeowners association rule or a building permit threshold. Many towns exempt small sheds and greenhouses under a set floor area, but the number varies.

A small polycarbonate greenhouse standing on a lawn beside a white wall, with a clay pot inside the door — A small polycarbonate greenhouse in a yard

Running the climate inside

Heat

Most crops are happy between 60 and 80°F. Above 85°F growth stalls and above 95°F seedlings can die in an afternoon, even when it is only 60°F outside.

Venting

Open up early on any sunny day, before the temperature climbs, and close an hour before sunset to trap warmth for the night.

Shade

From late spring, hang shade cloth over the sunny side and leave it up until early fall.

Air movement

Still, damp air is what brings gray mold and weak stems. A small fan on low and a cracked door do more for plant health than any spray.

Watering

Water in the morning so leaves are dry by night. Pots can need water daily in June and only once a week in January.

Cold nights

An unheated greenhouse only runs a few degrees above the outside low. When frost is forecast, drape frost cloth over the plants inside for extra protection.

Four ways to use the space

Seed starting and transplantsRaise your own vegetable and flower seedlings in late winter and plant them outside in spring. This is where most people begin and it pays for the seed trays in one season.

Start here

Look up your average last frost date, count back six to eight weeks, and sow a tray of tomatoes or peppers on that day. Sow lettuce and other hardy greens two weeks earlier.

USDA Plant Hardiness Zone Map

Summer heat cropsGrow tomatoes, peppers and cucumbers inside all summer for earlier, heavier harvests, especially where summers are short or cool.

Start here

Once nights inside stay above 50°F, move two or three young tomato plants into grow bags along the sunniest side, and pinch out the side shoots every week.

Fall and winter greensKeep spinach, lettuce, kale and arugula cropping through the cold months, when the greenhouse would otherwise stand empty.

Start here

In late summer, sow spinach, lettuce and arugula in trays, then plant them in grow bags inside by early fall so they are nearly full size before the days get short.

Cold Frame GardeningA low, lidded box that works like a knee-high greenhouse. It costs far less, fits a small yard, and is ideal for hardy greens and for toughening up seedlings.

Start here

Set a cold frame against a south-facing wall, fill it with trays of hardy greens, and prop the lid open a few inches on any sunny day above 45°F.

MU Extension: Building and Using Hotbeds and Cold Frames

Open a card for the first thing to do. The cold frame card has a button that adds a cold frame to the kit list.

A long row of white-framed cold frames with their lids propped open against a brick garden wall — Cold frames along a south-facing wall

Cold frames in depth

MU Extension: Building and Using Hotbeds and Cold Frames Free guide to siting, building and managing a cold frame.

Expect overheating to be the main problem, not cold.

One sunny morning with the door shut can cook a whole tray of seedlings before lunch.

Expect an unheated greenhouse to add weeks, not a tropical winter.

It keeps frost off and stretches both ends of the season, but tomatoes in January need heat and light you are not paying for yet.

Expect pests to like it as much as the plants do.

Whiteflies, aphids and fungus gnats breed fast in the warmth. Hang sticky traps from day one so you spot them early.

Stop sowing everything at once.

Twelve tomato plants need far more room in June than twelve seedlings do in March. Sow a few of each and repeat every two weeks.

Stop watering on a schedule.

Lift the pot or touch the mix first. Overwatering in cool, dull weather kills more seedlings than drought does.

Stop using garden soil in trays and pots.

It packs down, drains badly and brings in disease. Use fresh seed starting mix for seeds.

Stop skipping the fall cleanup.

Wash the cover and sweep out dead leaves before winter, so more light gets in and fewer pests carry over.

Wind, power and heat safety

Wind

Zip or latch the greenhouse fully shut when a storm is forecast. A half-open door lets gusts get under the cover and lift the whole structure.

Electricity

A heat mat and a fan mean running power into a damp space. Plug them into an outdoor-rated extension cord on a GFCI outlet, and keep every connection off the floor.

Your own heat

In summer the inside can be 20°F hotter than the yard. Do the long jobs early or late in the day and bring water with you.

Your state's cooperative extension service is the best free source: most publish greenhouse and season-extension guides written for your climate, and the Master Gardener volunteers answer questions by phone or email. The Hobby Greenhouse Association is a nonprofit for home growers with free starter articles. For running the climate through the year, the Royal Horticultural Society's greenhouse pages are clear and practical, though the calendar assumes a mild, damp climate.

Free greenhouse guides

Why the kit looks like this

The greenhouse itself is most of the bill, and its price range is wide: a zip-up film walk-in costs about as much as a nice dinner out, while a rigid polycarbonate one runs several hundred dollars. Everything else is small. The essentials are what you need to raise a first round of seedlings and know what the temperature is doing. The recommended lines solve the problems that show up in the first season: heat, still air, cold nights and pests. If a greenhouse is more than you want to spend or have room for, switch on Cold Frame Gardening and take the greenhouse out of the cart. The rest of the kit works the same in a cold frame.

Compare the options on each line, then set your tiers and check out from the kit list. Clicking a card selects it there, and clicking the selected card again takes that line out. The cold frame stays out of the total until you switch on Cold Frame Gardening.

Walk-in hobby greenhouse

Essential · Structure

This is the hobby's one big purchase: the covered space that traps heat and keeps frost and wind off your plants.

budget

Greenhouse for Outdoors with Screen Windows, Ohuhu Upgraded 4 Tiers 11 Shelves Walk-in Greenhouses with Durable PE Cover, Outside Garden Plastic Green House with Ground Pegs & Ropes for Stability

4.4(652)

$71.99

Greenhouse Gardening

What a day in the greenhouse looks like

Your first month, step by step

How to choose a first greenhouse

Running the climate inside

Four ways to use the space

What trips beginners up

Wind, power and heat safety

Where to learn more

Why the kit looks like this

Stock the greenhouse

Walk-in hobby greenhouse

Min-max thermometer and hygrometer

Seed starting trays with humidity domes

Seed starting mix

Vegetable seed variety pack

Watering can with a fine rose

Seedling heat mat

Clip-on circulation fan

Greenhouse shade cloth

Frost cloth plant cover

Fabric grow bags

Potting mix

Liquid vegetable fertilizer

Yellow sticky traps

Cold frame