greenhouse – The Garden Professors™

Home Greenhouses III: Basic Structure Types

Over the last few months I’ve had the chance to talk about the popular topic of home greenhouses. We covered a few of the basics in my first article, then touched on some regulations that might effect the building and management of home greenhouses in some areas. In this installment we’ll talk a bit about common structures used for home greenhouse construction so you can consider which structure(s) might be right for your situation.

Types of Structures

Greenhouse structures can range from simple to the very complex. While home greenhouses tend to fall on the simple construction side, there are still varying degrees of complexity within structures. Greenhouse structures can be put into a few main categories that we’ll cover below. The key to home greenhouse success is picking the structure that works best for you, your situation, and your budget.

Lean-to structures

Lean-to structures get their name from the fact that they “lean” on something for support. Not in a literal sense, but in a sense that another structure, usually a house or maybe a storage building, provides at least one structural wall. A common lean-to setup would have a three-sided greenhouse structure attached to the side of a house or another building. This could range from a structure that is a few square feet for starting seedlings in the spring up to a full-size greenhouse attached to the side of a building. A sun-room, if equipped for starting plants, could be considered a lean-to greenhouse (at least it would at my house, since it would be primarily for plants). This type of structure can be cost effective. You reduce the amount of greenhouse surface you have to build and cover, unless you have special issues for connecting it to your home or other structures (like foundation issues, siding that is hard to attach to, etc). You do want to make sure it is done right especially if attached to your house so you reduce the chance of damage to your home.

A quick search finds many lean-to greenhouse kits available, from small to large and every size in-between.

One benefit to a lean-to is that it can use the wall it is attached to as a heat sink – the wall absorbs heat through the day and then slowly releases it at night when it is colder. If you have a large lean-to greenhouse that serves almost like a sun room you also add functional space to the house where you can enjoy the sun on warm winter days. The heat generated by an attached greenhouse can help provide warmth for your home in winter or at least provide some extra insulation. But it can also result in excessive heat gain in the summer. Lean-to greenhouses are also protected a little more structure wise – they use the building they are attached to for structural support and can often withstand weather, like high wind, a little better than free standing structures.

Free standing structures

Simply put, a free-standing structure is one that isn’t attached to another structure. It stands on its own structural framework. There are a few different options we’ll talk about here which will be further expanded in future article installments on different types of materials used.

Hoophouse greenhouse

A hoophouse greenhouse is built out of the same structure used for a high tunnel or hoophouse. It consists of framing made by bent metal pipes and is covered with polyethylene plastic sheeting. A high tunnel greenhouse would have heating, ventilation, and watering equipment added and would therefore require connection to electric, gas, and water utilities (see my previous article about what this means for a greenhouse being a taxable “permanent” structure). You may also pour a concrete slab for the floor of a hoophouse-to-greenhouse conversion, but gravel or any other floor covering is fine as long as it provides a stable surface and weed control. The “greenhouse” that I inherited from the previous homeowners was left with bare ground so they could plant it like a conservatory.

While these may not be the most attractive greenhouses, they are usually a more cost-effective option for a high-quality, efficient greenhouse. Initial construction costs will likely be lower for a comparable quality framed greenhouse though the polyethylene covering will need to be replaced every few years as it becomes more opaque and light transmission reduces.

Free-standing structures

When envisioning a greenhouse, many people envision this type of greenhouse – one with straight sides, built with a frame covered in solid material. These are definitely more attractive than hoophouse greenhouses and can add an attractive feature to your yard. The most common way for home gardeners to build a free-standing greenhouse is through purchasing a kit. There are a myriad of kits available online these days, of varying prices and qualities usually depending on the materials used in the construction. The kits can be complex but set-up is usually pretty easy to follow though you might want to factor in the cost of hiring a contractor to help with the construction on a bigger kit. Most often these kits need to be built on a concrete foundation or pad so you’ll want to consider the cost and logistics of pouring the needed support. And you’ll also want to think about the utility connections to the greenhouse.

A frame built greenhouse. You can buy kits to build structures like this yourself, or you may want to hire a contractor to help if you aren’t handy. I saw this one at a community urban farm in Trenton, NJ.

Ridge and furrow greenhouses are framed greenhouses that are built together in tandem. These structures are usually used only in large-scale commercial production, so I’ll skip those for home greenhouses.

Geothermal greenhouses

Geothermal greenhouses are gaining in popularity, mainly because people are excited about reducing the need for using electricity or gas to control the temperature. And I say reducing, because in extremely cold weather there will likely still need to be supplemental heat. These structures are definitely different than your standard greenhouse. These structures are usually sunken into the ground to take advantage of insulation by the soil and also the constant geothermal temperatures. There is also usually a high solid wall on the north side of the structure, with a slanted roof made of light-passing material that faces to the south. This allows maximum light to enter the structure and allows that light to heat the solid wall to hold and release it during the night when it is colder. There is also usually an air intake in the ground a few hundred feet away that allows for the pulling of air through a tubing system to warm or cool the air with geothermal temperatures, depending on if it is cold or hot outside.

This geothermal greenhouse project is run by the North Platte Natural Resource District in Scottsbluff, NE. Note that there is a solid wall to the right (with trees growing against it) and that the ramp leads UP to the ground level. The floor I’m standing on in this picture is about 6-8 feet below the ground surface. In addition to standard fare, this greenhouse grows citrus, pomegranates, and figs in one of the coldest parts of Nebraska.

A walpini greenhouse is a specialized/rudimentary style geothermal greenhouse that is sometimes referred to as a pit greenhouse. Instead of building a structure, it is constructed of a pit dug into the ground and covered with a transparent roof. While they sound simple, there are several drawbacks to these structures. One – they don’t do well in wet areas or areas with high water tables, for obvious reasons. Secondly, they were initially designed for use in areas near the equator with the sun almost directly overhead. To function in latitudes far north or south you almost always have to build up a wall on one side to slant the roof cover toward the sun. And even then it is unlikely that light will reach the floor of the structure where plants are growing.

Summary

There’s a lot to consider when picking the type of greenhouse structure for your home greenhouse. There’s often a trade-off between cost, quality, and aesthetics. Options range from the simple to the complex in terms of size, structure, and function. So think about the goals you have for your greenhouse and consider the many different options available to you.

Sources

https://aggie-horticulture.tamu.edu/ornamental/greenhouse-management/greenhouse-structures/

https://extension.uga.edu/publications/detail.html?number=B910&title=hobby-greenhouses

Home Greenhouses Pt. 2: Regulations & Restrictions

Last month I dipped into some of the considerations of owning or building a home greenhouse, having just “inherited” a greenhouse with my new house. The questions and comments were numerous, so I decided to continue on discussing considerations for home greenhouse ownership and operation. There will likely be a few more articles down the line….so strap in.

This time around, I thought I’d talk about something that we hate to talk about, but is important to understand: rules and restrictions around what you can and can’t do, especially if you live in an urban area or municipality.

I know, I know. We all just wish we could do whatever we want, but when we live in close proximity to others there are usually some sort of rules we have to follow to keep the peace. I have a little better understanding of how it works, now that I helped write an urban ag ordinance with our city planning department (fingers crossed is passes city council next month!) that will “decriminalize” urban farming, including controlled environment ag structures like greenhouses. Of course, aside from what you can and can’t do there are tax implications that you should be aware of, no matter where you live (more on that in a bit).

Zoning, Ordinances, and Planning Commissions – oh my!

Most agricultural activity, which includes greenhouses, is likely regulated to some extent if you live within a municipality. Even if you don’t live in a town or city, there could be certain building codes or ordinances on county or state levels that you’ll want to check into.

You’ll want to look up your municipal code online, or call your municipal administration (like city hall, mayor’s office, planning office, etc.-whatever you have) to see if there are specific allowances or restriction for or against greenhouses. There are a few scenarios that could play out here, so you’ll want to be prepared on how to proceed. In general, you might find that greenhouses are:

Permitted, but only in certain zoning areas (more on that later)
Permitted, but requiring a permit of some sorts
Restricted altogether
Not mentioned at all

If you fall in that last category, then anything you do will exist in a gray area, where it isn’t strictly legal or illegal but the fate of your greenhouse (or any fines you might incur) would be up to interpretation by whoever is in charge of compliance (and what side of the bed they woke up on that day). And your greenhouse could be made legal or illegal at any time in the future if some sort of ordinance or decision is made. In the case of our new ordinance here in Omaha, greenhouses and structures like high tunnels will be allowed, but only in certain zoning areas. People who already have structures (and have for years) will now find that those structures are either allowed or banned (or will require a permit). Of course, enforcement of issues like this are often complaint-based, meaning that the municipality probably isn’t driving around looking for your greenhouse but if you and your neighbor aren’t on good terms they can call and turn you in.

As for zoning, there are several different categories and sub categories. The ones you’re most likely to encounter are residential, commercial, industrial, and agricultural (there are others as well). And then there are usually numeric (or named) sub-zones within those zones denoting the density or intensity of use on those zones.

For example R-1 (Residential 1), might be for a single-family dwelling whereas R-3 would be for a small apartment building. C-1 (Commercial-1) might be for a single-use building like a stand-alone fast-food restaurant and C-8 might be for a skyscraper office headquarters. Municipalities use these codes to denote what is and what is not allowed in certain places. For example, the code we worked on for Omaha allows certain types of farming on all residential zones with a conditional use permit and on commercial zones without a permit. (Home gardens and even community gardens are not considered farms and are allowed on all residential zones without a permit.) Many municipalities may also have agricultural zoning on properties around the periphery but still within the city/town limits. On lots like this, most agricultural practices are allowed.

Three things you can do with NYC's new zoning and land use map - Curbed NY — Your municipality may or may not have a map available showing lot zoning, like this small area of NYC.

Since a greenhouse is a structure, there may or may not be a requirement for a permit for the structure, even if it is allowed. This could be dependent on a number of factors, including whether it is considered a permanent or temporary structure, whether there are utilities going to it (which is usually the case for a greenhouse), or even how the structure is constructed. In some areas, it comes down to how pretty or ugly the city and your neighbors think the structure might be. In discussions for our ordinance, there was talk of not requiring a permit for a greenhouse but requiring permits for structures like high tunnels/hoophouses because there’s an (incorrect) assumption that greenhouses are prettier than high tunnels. But many people make greenhouses out of those structures (the greenhouse I inherited is just a high tunnel with a space heater). There was also an assumption that a greenhouse wouldn’t have loud, flapping plastic but a greenhouse would (I kid you not).

The tax man cometh….for your permanent agricultural structure.

One other thing you’ll want to consider about a greenhouse has to do with the tax bill. Since greenhouses are considered permanent structures, many places consider them a permanent improvement to your property and will add them to the tax bill like they might do an out building or garage. The municipality will definitely know about it if you have to apply for a permit or if you get a visit from the assessor. But this could also be dependent on how your structure is built. If you build a solid sided greenhouse (one of the nice looking ones) with a concrete slab floor, permanent utilities, etc then it will definitely considered permanent. But if your structure is more like a high tunnel/hoophouse like mine (a high tunnel in a trench coat pretending to be a greenhouse) then it could be considered a temporary structure and not taxable.

My high tunnel parading around like a greenhouse

High tunnels are considered temporary since you could really take them down at a moment’s notice (and some planning department officials think this means that you take them down and put them up each season, despite how much an extension educator tries to convince them otherwise….but I digress). So your mileage may vary depending on your local rules and how your structure is constructed.

So what home greenhouse topic should we cover next? I’m sure there’s plenty of questions out there – be sure to leave them in the comments. Also – would you like to have your greenhouse featured in a future article (this means I don’t have enough home greenhouse pictures)- feel free to send them to me at john dot porter at unl.edu.

Buying locally-grown plants

Of course we want to buy locally-grown plants! There are a gazillion sound reasons to do so. In a paper that may be from near here, or not, I perused the gardening column over Sunday coffee, written by (a human) (name withheld to protect the very, very nice and usually accurate author). But in this particular article, the writer ventured deep into huh? territory.

And that territory is my area of expertise: nursery and greenhouse production and marketing. My favorite talk to give to gardening groups is “From Grower to Garden Center.” As the Garden Professor Least Likely To Get Riled Up, it pains me a bit to even bring this up when someone’s willing to crank out a column week after week. Heck, I haven’t been able to write anything lately, accurate or otherwise. The bulk of the article was correct and positive, plus promoted a great local grower (of which we have very, very few), BUT there were a few statements made that I thought might make good points for clarification (teaching moments) and maybe generate some discussion.

“Just like locally grown food, a locally grown plant is going to be much easier on the environment. Transportation and fuel costs are lower, and carbon footprint emissions are decreased. Plus, without a need for the special packaging to ensure a safe journey across the country, less packaging ends up in a landfill.”

I’ve unloaded plenty of trucks – the only things that use any “special packaging” are poinsettias and sometimes florist mums – sleeves and or boxes. “Cross-country” is rarely the case, even for big box stores – they work with regional growers (albeit large ones) for annuals and perennials. However, the writer’s point is well taken in that even here in the “far east,” some independent garden centers and big box stores get shrubs and trees from the west coast (Monrovia must give them a heck of deal). One of our two local garden centers carries Japanese maples from Monrovia; this retailer is located less than 10 minutes from a nursery that specializes in Japanese Maples. Go figure.

“Beyond the environmental impact, when you buy a locally grown plant you usually are buying a healthier plant. It will already be accustomed to our native soils and growing conditions.”

“Usually” is a good qualifier here. Regarding health, I’ve seen amazing quality from far, far away, and real crap from a couple local growers. Local does not automatically equate to pest and pathogen free, well-rooted, non-stretched, or any other criteria for quality. The second sentence, however, has haunted me for a week. Nursery and greenhouse plants are grown in soilless media – peat or peat alternatives; pine bark; fir bark; etc. How can that particular plant be accustomed to “our native soil”? To put a finer point on it, what, exactly, IS our “native soil”? Our own 19 acres has yellow clay, red clay, forest duff, sandy loam, loamy sand (I made that one up), and everything in-between.

Regarding growing conditions, your spring-purchased plant has most likely been in a controlled environment of some degree, whether a greenhouse or coldframe. If I went shopping at any retail greenhouse or garden center (which I probably will do this weekend), I would probably purchase some plants right out of the greenhouse. Of which they are accustomed.

“And, with less travel time, the plant is less likely to be stressed by excessive handling and is less likely to be over watered or over fertilized.”

On the truck, off the truck. Place on retail bench. This is how a plant would be handled whether it was grown by a local wholesale nursery 10 miles away or 1000. How excessive is that? And why would travel time cause over-watering or over-fertilizing? If anything, the inverse is true.

“New gardeners can be assured that they are buying a variety that grows well in our climate, as local growers supply what grows here. The plant will be put out for sale when it’s actually time to plant, not when a buyer across the country wants to sell it to you.”

Grows well? What grows here? I’m not even sure where to begin with that bit of information. Isn’t that part up to the gardener, new or otherwise?

And wherever you may live, I guarantee there were plenty of tender annuals, tomato transplants, and other jump-the-gun goodies available for sale from your local grower or garden center 45 days before your last frost date. What IS true – a good grower/retailer or garden center staffer won’t let you leave without a gentle (or not-so-gentle) reminder to keep ’em in until after last frost. To which I always nod, agree, and then commence with trying to produce the earliest tomato in the tri-county area. Because I’m an expert.
*snort*

A Real, Live, Learning Experience

What a crazy spring! But it finally, finally came here to the Blue Ridge Mountains (Linda Chalker-Scott refers to them “speed bumps”).

My Ornamental Plants Production & Marketing class has been at work since early February, growing plants and marketing them at the Hort Club Plant Sale as part of their lab experience. Of course, they are completely at my mercy as to what they get to grow (bwuhh ha ha *evil hand wringing*). And due to their professor being a complete plant dork, they wouldn’t know a potted mum if it hit them upside the head. Not that there’s anything wrong with mums. But with so much fabulous stuff to choose from – they can just look that mum crop protocol up in a book if the need arises. They do get to experience a few zonal geraniums, but that’s only because the University’s past-President buys 50 red ones from us every year.

So what do they grow? Fabulous goodies you could never, ever find at a garden center in SW Virginia. Variegated Manihot esculenta. Dr. Cho’s newest Colocasia ‘Black Coral’ (gloss black with deep blue veins). Awesome landscape begonias such as ‘Gryphon’ and ‘Santa Cruz Sunset’. Fun annuals like Torenia and Osteospermum. Fifty-two different things – fairly ambitious, considering there are only 11 students. We fill a 40′ x 80′ house plus two “research” greenhouse sections that I commandeer the moment they come available.

My production students always start out the semester rather tentative, and then get more engaged as time goes on. We do a 2.5 day field trip across the state to visit top greenhouses, nurseries, and garden centers in early April. My gang comes home with a real appreciation of the hard work and long hours required to be successful; more important, perhaps, is their exposure to the tremendous passion and enthusiasm of the people in the business, many of who are alumni of our department.

SO…thirteen weeks later, we have greenhouses crammed full of really great plants,a bunch more ordered in from top area nurseries, an enthusiastic mob of customers with pent-up plant lust, and some very proud students.

And that’s the best part – the students get to/have to work with (gasp) the PUBLIC. Very disconcerting for some of them. The Plant Sale Chair for the club, who is also in my class, is a terrific student but a bit shy. Of course, he got the loudest customer of the day. She hollered “Hey, boo boo! Tell me about this plant! Sez here you grew it!” Ten shades of red later… I thought he was going to faint. But he did regain his composure and helped her with some other things. He also made me promise to never, ever tell his classmates what she called him.

But you’re not in my class 😉

Here comes “boo boo” with his very nice Cissus discolor (Rex Begonia Vine).
Names withheld to protect the totally embarrassed.

Closing the loop

Just a short post today as I am participating in an Extension planning meeting for most of the day. One up-side to the meeting is we are meeting and having lunch at Brody Dining hall here at MSU. If you’re around my age and attended college in the 80’s, the thought of eating at a dormitory dining hall might elicit memories of a hair-netted cafeteria lady glopping amorphous slop on your tray next to the mystery meat of the day. Boy, how times have changed. Today, the quality of dining hall food is point of competition for universities angling for students. The Brody dining center is set up like a food court, daily choices for students include a fresh salad bar, southwest food, sushi, made to order pizza, home-style comfort food, even kosher food.

The dining halls are also part of MSU’s sustainability initiative. Food wastes from the dining halls are collected and sent to an anaerobic digester and composted at the MSU Student Organic Farm. The compost is used at the recently completed Bailey hoop-houses on campus to produce salad green and herbs for use in the dining halls, providing a closed-loop system. Is the food produced in the hoop-houses going to make the dining halls completely self-sufficient? Probably not in the foreseeable future. But they do provide a good opportunity to promote horticulture. The project has generated numerous press articles and there are posters around the dining hall highlighting the project. In an age when many bemoan the public’s disconnect between farm and fork, the Bailey GREENhouses remind students, especially those that might not think about it otherwise, where their food comes from.

Bounce – it’s not just a fabric softening sheet…

…it’s an Integrated Pest Management tool!

[Note added after-the-fact: this was a tongue-in-cheek bit of hyperbole – kind of like “it’s not just a Job, it’s an Adventure.” Did not mean to imply that it actually IS an IPM tool. Very badly worded. Hence the beating I took in the comments. Live and learn.]

Fungus gnats (Bradysia spp.) are a pain in the bottom for commercial greenhouse growers. The adults are more of a nuisance than anything else –it just looks bad when a customer picks up your 6” pot of pansies and a bunch of little black gnats take flight. It’s the larvae that are problematic. Adult females lay the eggs in especially damp growing media, and the newly-hatched larvae feed on the roots. There’s both direct damage and also speculation of easier infection of root-borne pathogens, of which there are plenty.

Fungus gnat larvae, just making a living…

Standard control measures include insecticide drenches, biological controls including a specific strain of Bt (Bacillus thuringiensis – sold as GnatrolTM), nematodes, etc. One of the easiest control measures is the one I teach my students: to not over-water, i.e. “grow dry”. But that can be difficult in a big greenhouse range with many different-sized containers, all which drain/dry out at different rates. Propagation houses also have high humidity levels and have to stay moist for rooting/germination purposes and are thus favored by fungus gnats.

Entomologist Dr. Raymond Cloyd of Kansas State University and his group were intrigued by Master Gardener anecdotes of dryer sheets repelling mosquitoes, though no research had been done. Could your common Bounce sheet also repel other pests? And, to take it a step further, what, exactly, repels them? The answers are “yes” and “lots of volatile compounds.”

Their study was published last month in the journal HortScience. Honestly, I’ve never seen descriptors like “controls static cling” and “gives clothes a fresh scent” in a Horticulture journal. Hee! Plus the researchers made it clear this experiment specifically used Bounce Original Outdoor FreshTM. Still kind of humorous, but really good science and the part that’s usually overlooked in the translation to a News Story. Do NOT extrapolate results to include Bounce Spring Fresh, Fresh Linen, and certainly not Downy or Snuggle brands.

The study had a simple design, releasing lab gnats (ha!) into a many-chambered container and observing to which chamber the gnats gravitated to (or away from). There were five different variations on this theme, including an alluringly soggy media sample; when the sample of fabric softener sheet was introduced, they stayed away in droves. All five experiments showed a fairly drastic aversion to the sheet. To determine what was fending off the gnats, they did a steam extraction on sheet samples and ran the condensate through a gas chromatograph – mass spectrometer to measure the volatiles.

Figure from Bounce® Fabric Softener Dryer Sheets Repel Fungus Gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), Adults. Raymond A. Cloyd, Karen A. Marley, Richard A. Larson, and Bari Arieli, HortScience Dec 1 2010: 1830–1833

Well, there you have it. Linalool is a monoterpene alcohol found in lavender, basil, and coriander, and is known to be toxic to mites and insects. Citronello is another monoterpene and lends lemony-freshness to lemon balm, pennyroyal, and rose geranium and has short-term “repellent activity against mosquitoes.” Benzyl acetate, though not specifically mentioned in the results, is another natural fragrance compound, found in jasmine – and is also an industrial-strength solvent. One man’s solvent is another man’s perfume. Or fabric softener. I bet their lab smelled GREAT, by the way.

<
6

The Glories of The Winter Greenhouse

I’m a Southerner. With a capital “S”. Which is why I am Suffering, with another capital “S”. Here in the Blue Ridge mountains of western Virginia, we have officially surpassed Anchorage and Denver in total snowfall for the season. Today’s batch adds up to 24″ on the ground at our farm.

Blueberries in the snow. If one more person says “Probably good for all the insect problems,” I’m going to get violent.

The chickens are not happy. They’ve been cooped up (ha! I didn’t really mean to do that!) for 10 days straight. I myself suffer from cabin fever, limp hair, seasonal depression, and a persistent cough.

Hell no, we won’t go!

What keeps me from going totally nuts? Only the best $12,000 ever spent – no,no, not granite counter tops…it’s our very own greenhouse. This modest 24′ x 48′ polycarbonate sheet hoop house may not resemble a Victorian conservatory (you can get one of those beauties here), but it works like a champ. Yes, we have greenhouses on campus for research and teaching, but that’s work; and pet plants are frowned upon.

Nothing beats your own private winter hideaway. My plant-diva-friend Elissa uses her crowded greenhouse for not only her immense plant collection, but also a festive (if cramped) happy hour.

As sleet pelts the roof, I’m surrounded by green: tropical plants dug up from the garden before frost and those “pets in pots” accumulated from hither and yon. The humidity is wonderful – I can hear my skin go “aaahhhh” after a couple of hours.

Herd o’ Agaves and succulents. They’re perfectly happy with the cool temperatures – several are blooming.

I’ve dreamed of one for years; then finally took the jump 16 months ago. Again, it’s nothing a homeowner’s association would ever approve of; just a commercial-grade, heavy duty, Quonset-type production house. Stylistic concerns were sacrificed for square footage. The most common complaint from home greenhouse owners is “I wish I had built a bigger one.”

The other concern is heating costs. It has a propane heater, and propane’s not cheap, nor environmentally friendly. But we run it pretty darn cold – around 48 F night temperatures, which certainly helps. Are the tropicals thrilled? Not really, but they’re alive and hanging in there (however, the begonias are really grumpy right now).

Some PVC pipe + overhead misting + heating mat = broccoli spinach, and basil seedlings, happily germinating at a 75 F soil temperature, despite an air temperature below 50 F. Basil?! Yes, I realize I’m totally jumping the gun timing-wise here, made worse by the fact that I teach both greenhouse management and ornamental plant production (do as I say, not as I do!).

Yep, more fun than you can shake a shovel at!
I’ll take your questions, comments, and snowballs now…