Frequently Asked Questions
HOW CAN A GREENHOUSE HELP ME PROVIDE FOR MY FAMILY?
A greenhouse, regardless of type, gives the gardener an advantage using the sun primarily, to help propagate and start summer/winter gardens. The savings, variety favored by gardener, ability to raise saved seed, control against pests, and the joy of watching the process of seed to hardening to garden to harvest is reward unto itself. If you find you and your family spending hundreds of dollars a year on starts, using new seed each season, regardless if it is all vegetables and herbs or flowers or both, a greenhouse will save you money. Even if you do not spend this much each season, the excess either sold or given as garden gifts make this a worthwhile purchase or project.
WHY SO MANY TYPES?
For some gardeners, an abandoned patio door used as a cold frame is enough of an edge to healthy frost protected starts. My grandfather who grew one of the most prolific truck gardens imaginable used two abandoned sash windows for his starts. He lived in a milder climate than we experience here in the Rogue Valley.
Had he been able to, he would have devoted a small part of his land to a greenhouse, much like he did with his compost bin.
The reasons for so many types vary from so many crops, to hiccups like what is easily shipped. What is essential to the first time buyer is to match gardening goals with the right product We hope to help you do that just that, even if it means showing the serious gardener a technique that puts a breathing greenhouse in reach of most everyone.
STEEL FRAME GREENHOUSES
Steel frame greenhouses evolved as wooden framed, glass glazed, poly glazed, models fell out of style. While there is still a market for Cedar framed kits, one only has to look to what the commercial grower has adapted to, to see why today, galvanized steel is the most cost efficient. The frames can be recovered in excess of 40 to 50 years. Depending on what you choose to cover it with, recovering can be limited to 4-5 times over the life of the frame. Little to no hail damage, easy to install, best value for the commercial grower.
Aluminum greenhouses come in two very different types. The majority are made in China, feature polycarbonate walls and roof, with a small door and skylights for climate control.
Some are available with jalousie windows as well. The other type is those available using the same style and strength of extruded aluminum used in storefronts. Here the glazing options run from single, dual, triple wall polycarbonate glazing to exotics like fritted glass that is tempered. The doors are often of a more comfortable size. They come available with interior shading systems. Many are considered contemporary conservatories. When added to the south facing portion of your home, many people find it convenient to remove their patio doors, and enjoy the solar gain.
Cedar greenhouses are now sold mainly as kits that can be shipped easily. Being that the Cedar is covered against the elements, the decay properties are superior to pine or fir. However, the humidity of the interior of many greenhouses makes wood less than first choice for longevity. Though designs exist for larger Cedar models, using a truss method of spanning the length, the trade off is a larger pattern of shadow, and sometimes the need to run a center beam to help bridge the load. Check the many How to You Tube videos, the plans available in Mother Earth News and publications like Fine home Building by Taunton Press.
For a season maybe two, PVC frames covered by big box 6 mil or 10 mil plastic can work. The downside is that both types of plastic are not designed to hold up to the degradation of sunlight. In short order they are destined for the landfill. Until we can see a market for this oil based product recycling, we think this short term view is hazardous. Of course, in a pinch, ¾” pvc schedule forty, bowed like a hoop house, covered with plastic that saves your crop will be its own blessing.
Whether a Lean To or stand alone, having a greenhouse lowers gardening costs. When a south or west facing wall can be used for the 4th wall and much of the structural support, a Lean To greenhouse can be ideal. Here’s why. Often the 4th wall is insulated, and can benefit from solar gain. With a pass through pair of doors at each end, flow through ventilation is available. Or a door on the cool end and an exhaust fan at the hot side. Cover with clear fabric, clear polycarbonate single wall, or double or triple wall that adds a bit of insulation. The opportunities are the same to propagate and nurse your starts. Good place to store that citrus or tow in a pot.
Ornamental Conservatories were the beginning of what could grow when the climate was a bit controllable. They were the rage amongst the wealthy, who initially used them to raise exotic flowers, and other botanicals. One of the best known examples of the master carpentry that went into the grandest conservatory on the West Coast, the San Francisco Conservatory of Flowers. It was recently saved from total decay with a structural makeover that can be read about in Fine Homebuilding.com. The compound curves struck to replace the existing wooden parts was a work of wonder. Today we can find Conservatory Designs and elegant Kits from firms found under conservatories in our search engines.
The oldest glass greenhouse we’re aware of is the wood and glass model the Hanley Sisters had put up for what is known as the Hanley Farm, Or Century Farm. We’re told they had it built before the War. It was the first in all of Jackson County. 1938 or 39 is the date most used. It is still in use today. The original roof was glass as well. Hail damage, rocks by hooligans were all part of the challenge. They persevered and paved the way for propagating starts early enough for our region. Glass greenhouses still exist today. Many are used to raise flowers in the Half Moon Bay, CA area.
WHAT IS THE DIFFERENCE BETWEEN A COLD FRAME AND A GREENHOUSE?
Generally a cold frame, small or large, is a structure with open ends. Often designed so that if the temperature plunges, the open ends can be closed. Often, with some crops, this is all that is needed. Most definitions of a greenhouse, would at minimum include all sides and roof covered against temperature extremes. Much like homes, greenhouses used in Nursery applications, or for commercial growers, uses climate controls to offset extremes in temperature, control humidity, and move the air inside, acting as artificial wind. Without fans to move the air robustly, tall spindly starts that fall over outside follow. Stagnant air leads to problems just like in your home. An unheated greenhouse however can be used for the fall and spring.
WHY SO MANY DIFFERENT KIND OF COVERINGS?
The easy answer is that there are so many different types of crops. In looking closer however, we see certain types prevailing, in the different temperate regions.
Fabric or film
Fabric or film are terms used to describe the same thing. A roll product, sold in running feet by width, it is used commercially in all but the coldest growing regions. Even in the Northeast, the Midwest, robust UV stabilized, often woven coverings offer 10 to 15 years before replacement. When recovering a 96’ long greenhouse, the upset to operations needs to be minimized. Fabric or two ply film with inflation bladder is by far the most cost efficient to purchase and when needed, recover.
Poly-carbonate has been available for some years now. The improvements have been impressive. The ability to stabilize against UV degradation has improved, the ability to meet some tough engineering criteria, has allowed the use of light weight poly-carbonate in places that benefit from the transparency. Nurseries can show off starts, propagation, flowers, through single wall poly carbonate with the clearest transparency with out the cost of tempered glass like in a patio door. Double wall poly carbonate kits, some with pvc frames, some with aluminum frames, some with cedar frames can be found at most big box retailers. They have a place in helping gardeners too. The 12 mil and 20 mil triple wall poly carbonate coverings are best suited for the colder growing regions and specialty exotics, like orchids. The cost and complexity of installation is something to be considered before any grower takes this type of model on. Often it is best to have a builder with experience in poly-carbonate construction assist.
Construction Plastic/6 mil/10 mil
For years the use of 6 0r 10 mil roll plastic has been used by the frugal gardener. Often covering a wooden structure, stapled and lath strapped into place. While in the short run the upfront costs are less, long term it costs more, takes up space in the landfill, and takes this side of forever to breakdown. Until we can see some market for the used plastic, a non-subsidized one, 6 mil or 10 mil will do in a pinch. We don’t recommend it because long term it costs more.
WHAT ARE ROW COVERS?
Row covers are now available that are light weight, easy to store when not used, easy to use, gives the gardener worried about unseasonable freezes an edge, and reduces the need for overwatering, they reduce evaporation from wasted irrigation. Like all additions to the gardeners tool kit, row covers do need to be set out before you need them, and you will need some room to store them when the summer growing season is on. Certain crops subject to sunburn can benefit with row covers that provide a bit of shade as well. While not as lightweight and easy to use, gardeners for years have used schedule 40 PVC pipe and 1 mil plastic to make hoop style row cover. PVC and 3 mil plastic need a method of keeping them in place, and our reservations are the same as those with 6 mil or 10 mil plastic. The sun eats their elasticity rapidly, the get brittle and the wind finishes matters after as little as one, two at most, intense summers like we experience in our growing region.
HOW DO I GET STARTED?
Getting started is as easy as talking to a friend or neighbor who has a greenhouse. Asking an experienced group of folkssuch as the Master Gardeners, who give advice and provide direction. For those wanting to join the ranks of folks who want to add to the joy of growing and propagating their starts for their gardens or Community Supported Agriculture groups these are great sources of experience. One of the most often listed sources of information, “The Greenhouse Growers Companion” by Shane Smith is full of useful information and while Author Smith realizes the limits to writing one book for so many types of seasons, his aim overall is good. We don’t see eye to eye on every item, we believe in using the same type of materials and methods the big greenhouse user follows. In this case value follows form.
One item that concerns us is when people are advised to attach their greenhouse or cold frame to their home, problems with moisture and humidity are not addressed fully enough. When advising people who want to add a LeanTo style of greenhouse to a south facing wall and then removing a large patio door into their homes, we advise a bit of caution. While solar gain can help heat a house, the conditions for forcing starts and keeping a home warm and free of humidity caused problems can be at cross purposes.
LOCATION AND UTILITIES
Location is often the most crucial decision in the difference between robust results and frustration. While some plots prevent less than ideal location, whenever possible locate your greenhouse to take advantage of the sun primarily.
If your using a small poly carbonate model with a small door and sky vents, taking advantage of the prevailing breezes will help ventilate. We find that a trellis system is needed to shade small poly carbonate greenhouses, to allow the sky vents to operate.
With all greenhouses having a source of water close by is needed. Using a garden hose to fill the greenhouse water barrel works very well, doesn’t freeze in winter, makes adding fertilizer or compost tea a snap. Larger models make it worthwhile to bring a insulated hose faucet into the greenhouse.
Commercial models require a dedicated source of clean, filtered, water available year round regardless of outside temperatures.
We recommend having a close source of safe AC power for all greenhouses, and here’s why. Even the smallest models with no climate controls benefit by having fans inside to move the air around. Moving air promotes sturdy starts, helps with dead zones of stagnant air, and helps with cooling.
In all three of the small models offered, AC power (15-20 amps) is needed to power the exhaust fan, box fan, pedestal fan, heat mats, and florescent full spectrum lighting. Often customers will hang a work light (cold start) in the ridge to allow work after dark when things are cooler.
Heating in the winter for this region is a balance of propane or natural gas greenhouse heaters, oil filled AC heaters, and solar. Solar exhaust and interior fans are now available. What is new is 4’x10’x5” black heavy neoprene water filled, steel supported, solar beds, that attach to the side walls of your greenhouse on the north side interior. The sun heats the water during all but the darkest of days, and releases the heat at night. As fuel prices escalate the speed in which these will pay for themselves will make them attractive to many more greenhouse growers.
Commercial growers often have a crop(s) in mind and design the heating and cooling to fit their needs. Climate controls for the commercial greenhouse can (short list) consist of temperature and humidity controlled exhaust fans, intake shutters, timer controlled misters, hydroponic pumps, large interior fans, Gas heat, quite large propagation areas using heat to force starts etc) Mortality rates to the commercial grower are the driver between profit and loss.
What kind of crops can I grow in my greenhouse
You can grow virtually anything that you want. However, you must consider “pollinators” for certain foods. Let’s talk more about this! Call us!