Small Greenhouse – How it Works + How to Make One for $50

A small greenhouse, also known as a cold box or portable greenhouse, is perfect for home gardeners who want to start their seeds in containers and get a 6-week head start on the growing season. This is especially nice if you live in a colder climate with a shorter growing season. 

You may be wondering, how effective are mini-greenhouses? 

Which is an excellent question. Before you DIY or purchase a small greenhouse, make sure you know what conditions they are best used for. 

A small greenhouse is usually a portable structure or tent that will keep your plants and soil about 10 degrees warmer than the outside temperatures. This can give people a 6-week head start on the spring growing season, by starting seeds in containers, hardening them off, and then transplanting them to raised beds or an in-ground garden. You’ll want to find out your region’s frost dates and start seeds in your small greenhouse six weeks before your last frost date. 

When it comes time to transplant your baby plants, my grandpa taught me to get a simple ground thermometer so you can make sure your ground temps are at least 45 degrees or above, and plant your cold weather-friendly crops first. Dates can give you a general guideline for your area, but nothing can beat real-time ground temperature readings. 

If your small greenhouse is portable, you can also move it to cover fall crops in your garden to protect them from frost. This can effectively extend your growing season an additional six weeks in the fall. Using row covers is also another option that gives you a mini-greenhouse effect. 

You can get an extra 12 weeks of growing time using a small greenhouse, which is an incredible three months! If you live in a moderate climate that doesn’t get freezing temperatures, you can also use a small greenhouse to grow fresh garden vegetables in the winter. 

Do greenhouses work in winter?  

If you are looking for a small greenhouse to work in the winter, you might be disappointed. Unless you live in a very moderate climate that hardly freezes. If you’d like your small greenhouse to allow you to grow vegetables through the winter, you’ll need to add a greenhouse heater with an automatic thermometer to keep your plants warm enough to grow. We also recommend using raised beds or containers inside your small greenhouse so the soil stays warm in winter too. 

A true greenhouse is a permanent structure with heating, and sometimes even AC as well. They often have plumbing run to them, and act as garden storage along with a cozy place to start seeds, and allow plants to grow in the winter. Radishes and salad greens do especially well in greenhouses through the winter. Wouldn’t it be wonderful to have fresh salad through the cold winter months!? 

What are tiny greenhouses called?

Tiny greenhouses are actually not usually referred to as greenhouses, but rather as cold boxes. Cold boxes are very simple to make yourself and can be used to start seeds 6-weeks before your last frost date or to cover fall crops from frost. 

Portable greenhouses that are not permanently attached to a foundation, are also called cold frames or hoop houses. These are typically what is used for commercial farming because of their large size, but you can get them small and they will work great for backyard gardeners too.

If you’re looking for a very tiny greenhouse that can cover an individual plant, you may be thinking of garden cloches. Cloches are usually made from glass or plastic and cover just a few plants from frost while they are in the ground. Many cold-weather gardeners actually use cut-up soda bottles and even old milk jugs to give their early spring and late fall plants the extra warmth they need. Cloches will not keep your plants as warm and cozy as a small greenhouse will though. You can count on an extra 1 to 3 weeks of cold protection with cloches.       

How do you make a small greenhouse?

Some of the cheapest and easiest small greenhouses are made from PVC pipe and sheets of greenhouse plastic. There are plans you can make in an afternoon for less than $50. Do make sure your small greenhouse design includes some ventilation to help your plants breathe properly and avoid disease. 

Many people even attach their greenhouse tents right to the frame of their raised beds making for a very simple solution. When the greenhouse is attached to the raised bed, you won’t need to take the time to move and transplant your vegetables. Some plants do not do well when transplanted, so tenting over your garden area is the ideal solution.

Anyone can build a simple PVC pipe and plastic small greenhouse with some good plans. But if you want to DIY a bigger better greenhouse, they are excellent plans for that too. We’ll break down the best greenhouse plans on the internet that you’d actually want to use. 

Raised Bed Greenhouse Cover Plans

This innovative raised bed cover attaches with hinges to the raised bed frame and is covered with garden quilt fabric. The gardener lives in an area with windy, foggy summers and built this beautiful cover to protect her plants. She details the process with excellent Q & A and breaks down the pros and cons for you. 

Apartment Therapy | plans—free | material cost $250

This simple PVC and plastic solution for a raised bed was created by a backyard gardener who needed more height in his small greenhouse so his broccoli could grow taller. His design also allowed for a stronger frame that could hold up to heavy rain and snow. This design is simply attached to the raised bed frame and covered with plastic. 

Grit | plans—free | material cost $50

Portable Greenhouse Plans

Affectionately referred to as the tomato fort, this plan was inspired by a home gardener to keep their tomatoes dry and free from diseases that can plague overly wet tomato leaves. But it works perfectly as a portable greenhouse you can place over any plants in your garden. It’s made of hose, PVC, plastic, and wood and costs around $50 and one afternoon to make. 

Sow & Dipity | plans—free | material cost $50

These very simple PVC plans use only PVC and plastic so it’s easy and lightweight to move. You will want to stake it down though so it doesn’t blow away in the wind and damage your plants in the process. Plans are very detailed and give you diagrams and measurements to easily create an arched greenhouse. If you like the plans, you can also use his row cover and cold frame plans for your garden. 

PVC Plans | plans—free | material cost $150 

Build a simple cold frame using an old window. This plan is functional, charming, and cost-saving using upcycled materials. If you can’t find an old window, you could also use clear plastic for the lid. The slanted lid helps capture as much solar energy and warmth as possible. Root crops would do great in this cold frame, and you can adjust the sizing as needed. 

Savvy Gardening | plans—free | material cost $75

Repurposed Greenhouse Plans

There are some wonderful repurposed greenhouse designs out there! My friend Lana used reclaimed windows and french doors she found at a reclaimed construction store, and a sunny side of her house to create this stunning and large lean-to-style greenhouse on a budget. Using the side of her house to create one of the walls, and using recycled materials, she created a large greenhouse on the cheap. 

Lana Stenner | plans—free | material cost $100

This creative grandma wanted a greenhouse, had an old tattered trampoline, and thought, I can do that! When it comes to DIY greenhouses, having a can-do attitude is the most important tool you can bring. Because this gardener use the curved pipes from her trampoline for the base of her hoop house, she saved a bunch and built this greenhouse for around $100.

How Does She | plans—free | material cost $100

These artists and gardeners created the most beautiful greenhouses out of reclaimed windows and doors. The peeling paint and mismatched sizes only add to its charm. Though every one of these will be completely unique in build, appearance, and cost, you can find lots of inspiration and instructions on the owner builder network.

The Owner Builder Network | plans—free | material cost $300

Permanent Hoop House Plans

Making your own hoop house is a great option because they are fairly cheap and easy to construct. The downside of hoop houses is they may not hold up well in high-wind areas, and the plastic will need to be replaced after a few years. Keep this in mind as you’re choosing your small greenhouse plans. 

This hoop house builder made his plans to be windproof by adding extra reinforcement in the center of the structure. This is a large 12×14 hoop house with almost 7-foot ceilings and was built in about two days. The builder shares a very complete tutorial with extra tips on choosing the right spot and preparing your soil. 

Natural Living Ideas | plans—free | material cost $500+

These are plans for an extra-long hoop house created by a Florida gardener. This hoop house is 10 feet wide, 10 feet tall, and an amazing 32 feet long. This is a great DIY option if you need tons of room in your greenhouse.

Florida Gardener | plans—free | material cost $800

Permanent Wood Greenhouses Plans

You can’t go wrong with plans from Ana White. We have used her plans on our homestead to make desks, tables, benches, and chairs. The popularity of her barn-style chicken coop plans is no exception. These plans are for a 10×12 greenhouse that is a good size for your standard family. DIY’ers have modified her plans for a 12×12 or even a 10×16 greenhouse. Most builders say this is about a week-long project or something you could complete over several weekends.   

Ana White | plans—free | material cost $1200-$1500

Here is an excellent step-by-step tutorial using Ana White’s plans to build a 10×16 all corrugated polycarbonate greenhouse

This is an innovative design for a permanent greenhouse, and the plans are only $5. This greenhouse will be an 8×10 size with 8.5-foot tall ceiling in the middle. This design includes a set of windows along the top that can be opened and closed for ventilation, which is a very important feature for a greenhouse to allow plants to breathe all year old. Ventilation is also especially important if you’re using it in the summer and don’t want to cook your veggies. 

Build Eazy | plans—$5 | material cost $500+

These plans make an extra-long 10×14 wooden greenhouse with plastic siding and venting at the top. These step-by-step plans are very detailed and give you everything you need to build yourself a beautiful greenhouse. 

How To Specialist | plans—free | material cost $1000

How about trying this 1980’s inspired geodesic dome greenhouse? It looks so cool, plus its dome design is said to be one of the strongest structure designs in the world. So if you live in an area with high wind or heavy snow, it won’t be a problem. We have a child’s climbing structure that looks just like this and could make a strong greenhouse in a pinch with just some clamps and plastic sheeting. It would be much smaller than this perfect size dome greenhouse with an adult-sized front door. 

Northern Homestead | plans—free | material cost $500

Stunning DIY Greenhouse Inspiration

When this couple priced out the greenhouse of their dreams, they found it would cost them around $24,000. Instead of buying one, they designed and built their own stunning greenhouse for around $3000! They used polycarbonate sheeting instead of glass to keep it strong and sturdy in inclement weather for years to come. These gardeners say it took them most of an entire summer to build, and they didn’t have any building expertise or fancy tools, but simply a love for tinkering. 

Instructables | plans—free | material cost $3000

This plant-loving couple suffered a miscarriage and decided to use their grief to create something new. Possibly the most stunning greenhouse you’ve seen, which they now use as a micro wedding venue. They used recycled windows, polycarbonate roofing, and created the massive structure themselves. Though this project is more for looks and less practical for gardeners, you could use their design as inspiration! It took this couple 7 months to build.

The Vaughan House | inspiration—free | material cost $ (a lot) 

Ready to start your garden the right way without extra headaches and missteps? Check out our Complete Guide to Gardening at Home + 5 Beginner Mistakes to Avoid.

What about you, have you ever built a greenhouse before? Which one of these plans are you thinking of using? Let us know your experience in the comments.