6 Best Propane Heaters For Temporary Greenhouse Heat to Prevent Seedling Loss
Prevent seedling loss from sudden cold snaps. Our review details the 6 best propane heaters for providing safe, reliable temporary heat for your greenhouse.
We’ve all been there. You check the forecast, and that gentle spring evening is about to turn into a late-season frost. Your greenhouse is packed with hundreds of tender seedlings, and the thought of losing them all overnight is sickening. This is when having a reliable, temporary heat source isn’t a luxury—it’s the difference between a successful season and starting over from scratch.
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Why Propane is Key for Emergency Greenhouse Heat
When a cold snap is driven by a storm, the power is often the first thing to go. An electric heater is useless without electricity, making it a fragile link in your seedling protection plan. Propane, however, is self-contained, portable, and powerful. You can store a 20-pound tank for months, ready to deploy at a moment’s notice.
This independence is propane’s greatest strength. It allows you to bring significant heating power exactly where you need it, without running long, potentially hazardous extension cords. Whether you have a small polycarbonate greenhouse or a larger hoop house, a propane heater provides the BTUs (British Thermal Units) needed to fight off a sudden, deep freeze. It’s the most resilient tool in your arsenal for that critical 8-hour window when temperatures plummet.
Mr. Heater Buddy: The Safest Portable Option
The Mr. Heater "Buddy" line is probably the most common choice for this exact scenario, and for good reason. Its main selling point is safety. These units come standard with a low-oxygen sensor that automatically shuts the heater off if oxygen levels dip, and a tip-over switch that kills the flame if it gets knocked over. For a crowded greenhouse full of flammable trays and plastic sheeting, these features are non-negotiable.
The standard Buddy heater (MH9BX) is perfect for smaller hobby houses, think 6×8 or 8×10 feet. It sips propane on its low setting, making a one-pound cylinder last through the night, but can be hooked up to a 20-pound tank for longer run times. It won’t turn your greenhouse into a sauna, but it will absolutely keep the air just above freezing, which is all your seedlings need to survive. Its radiant heat is gentle and won’t scorch plants placed too close.
The tradeoff for this safety and efficiency is raw power. It’s not designed to quickly heat a large, frigid space. If you open your greenhouse door and it’s already 35°F, the Buddy will struggle to catch up. It’s a maintainer, not a blaster.
Dyna-Glo Forced Air: For the Quickest Heat-Up
If you walk into a large hoop house and realize you’re already losing the battle against the cold, you need a cannon, not a rifle. That’s where a forced-air propane heater, often called a "salamander" or "torpedo" heater, comes in. These units are designed for one thing: dumping a massive amount of heat into a space as quickly as possible.
A model like the Dyna-Glo Pro 30,000 BTU heater can raise the temperature in a large structure by 10-15 degrees in minutes. It uses a powerful fan to push air over an intense flame, creating an instant wave of warmth. This is the emergency button you press when you’re behind schedule and the temperature is crashing.
However, this power comes with significant tradeoffs. They are loud, burn through propane at a startling rate, and produce a lot of moisture as a byproduct of combustion. The open flame and intense, directional heat also require much more care with placement to avoid melting plastic or damaging plants. This is a brute-force tool for urgent situations, not a subtle, all-night solution.
Camco Olympian Wave-3: Efficient Catalytic Heat
Catalytic heaters are the opposite of forced-air units. They produce heat without an open flame, using a chemical reaction with a platinum-coated ceramic mat. The result is silent, incredibly efficient, and gentle radiant heat, much like the warmth from the sun. The Camco Olympian Wave-3 is a popular wall-mounted or portable example.
The primary benefit here is fuel efficiency. A catalytic heater can run up to three times longer on the same amount of propane as a blue-flame heater of similar BTU output. Because there’s no fan, it uses no electricity and operates in complete silence. This makes it an outstanding choice for maintaining a stable temperature over a long, cold night without worrying about running out of fuel.
The downside is a slower heat-up time and a higher initial purchase price. It warms objects, not the air, so it takes longer to feel the effect in a cold space. It’s the perfect choice if you anticipate the cold and get it running early, but it’s not the best tool for a last-minute temperature emergency.
DeWalt DXH12B: A Rugged, Cordless Choice
For those with a greenhouse far from a power source, even starting a typical propane heater can be a problem. The DeWalt DXH12B solves this by integrating with their 20V MAX battery system. The battery powers the fan and electronic ignition, making it a truly cordless and self-contained heating solution.
This heater is built for job sites, so it’s rugged and can handle being knocked around. It combines radiant heat with a fan for quiet, effective circulation. It’s an excellent hybrid that gives you both the gentle heat of a radiant unit and the air movement of a forced-air system, all without needing an outlet.
This is a specialized tool. If your greenhouse is right next to your house, the cordless feature might be overkill. But if your hoop house is at the back of your property, this heater’s ability to run anywhere, anytime, makes it an invaluable piece of equipment for off-grid peace of mind.
Mr. Heater Big Buddy for Larger Hoop Houses
Sometimes the standard Buddy just isn’t quite enough. For a larger hoop house, say a 12×20 or bigger, the Mr. Heater Big Buddy (MH18B) is the logical next step. It offers up to 18,000 BTUs, double the output of its smaller sibling, and can effectively heat a much larger volume of air.
It retains all the critical safety features: the low-oxygen sensor and the tip-over switch. It also adds a small, battery-powered fan to help circulate the warm air, addressing one of the main limitations of purely radiant heaters in a larger space. It can run on two one-pound cylinders or be hooked directly to a larger tank.
Think of the Big Buddy as the perfect middle ground. It provides significantly more heating power than the standard model without jumping to the noise, fuel consumption, and open-flame risks of a forced-air torpedo heater. It’s the right-sized tool for the serious hobbyist with a structure that’s outgrown the smallest heaters.
ProCom Ventless: A Permanent Wall-Mount Fix
If fighting late frosts is an annual battle, you might consider a more permanent solution. A ventless wall-mounted heater, like those from ProCom, can be plumbed directly to a large propane tank outside. This gives you a reliable, thermostat-controlled heat source that’s always ready to go.
These heaters use either blue flame or infrared technology to heat the space efficiently. Because they are "ventless," they are designed to be safe for indoor operation, but that claim rests heavily on having a non-airtight space—something every greenhouse is. They provide a clean, stable, and set-it-and-forget-it solution.
This is not an emergency, portable option. It’s an infrastructure upgrade. The installation is more involved, and the cost is higher, but it replaces last-minute panic with automated protection. For a grower who has invested heavily in their greenhouse and seedlings, a permanent fixture can be a very wise investment.
Critical Safety: Ventilation and CO Monitors
Let’s be perfectly clear: any unvented combustion heater consumes oxygen and produces carbon monoxide (CO), carbon dioxide (CO2), and water vapor. Running a propane heater in a sealed greenhouse is a recipe for disaster, not just for you, but for your plants. High concentrations of CO2 can harm plants, and the added moisture can promote mold and mildew.
Proper ventilation is not optional. You must provide a source of fresh air. This can be as simple as cracking the greenhouse door an inch or opening a roof vent slightly. The goal is to allow oxygen in and exhaust gases out without creating a draft that negates the heater’s effect. It’s a balance, but one you must find.
The single most important accessory for your heater is a battery-operated carbon monoxide detector. They are inexpensive and provide an essential early warning if CO levels become dangerous. Place one inside the greenhouse near your seedlings. Do not run a propane heater without one. It is the cheapest, most effective insurance you can buy.
Choosing the right heater comes down to your specific situation—the size of your space, your access to power, and how quickly you need to raise the temperature. The key is to have your chosen heater and a full propane tank on hand before the cold weather arrives. A little preparation turns a potential catastrophe into a minor inconvenience, ensuring your seedlings live to see another sunny day.
