Tropical greenhouse design and build

Tropical greenhouse design and construction :

Wooden Tabletop on Cinder Blocks
With Drip Water System

PROJECT One :Building a Low-Cost Greenhouse

courtesy to : www.hiddenvalleyhibiscus.com/care/greenhouse.htm

Hidden Valley Hibiscus
Growers & Hybridizers of Exotic, Tropical Hibiscus

Hibiscus Plant Care

Eventually almost everyone who grows tropical plants comes to the conclusion that it would be very nice indeed to have a greenhouse to move their tropical plants into in winter. Not only is winter protection very desirable, but a greenhouse also extends the blooming season and helps the plants get an earlier start in spring. Yes, a greenhouse would be nice, but surely it would cost too much and take too much expertise to set up. Wouldn't it?

A Low-Cost PVC Greenhouse
Is Easy to Build

Not at all. Greenhouses come in every conceivable size and price range. In the end what they do is trap the energy of sunlight inside a room that quickly warms up in response. There are more ways than one to achieve this, and they aren't all expensive, nor do they require expert construction skills. This article will take a look at the subject of greenhouses, and make some suggestions for those of you who may be ready to take the plunge.

At the top end of the price range, there are very beautiful and functional greenhouse units that can be purchased fully equipped and installed on your property by a contractor. We're not going to talk about those. If you're interested in one of these, you can acquire catalogs from a number of suppliers and start your search. Some of the information below will still be of interest to you, because whether your greenhouse costs $50,000 or $500 it still needs to be able to accomplish many of the same tasks.

This article will focus on "do-it-yourself" or "my-spouse-will-do-it-for-me" type greenhouses. You can build a surprisingly functional greenhouse with materials that are not expensive and are easy to work with. Home Depot and other similar home supply stores have most, if not all, of the materials you need. Since there are so many variations and so many individual circumstances, we are not going to try to give a step-by-step manual like we did with the drip system a few months ago. Rather, we will take a look at the features that any greenhouse needs to include and a few nice-to-have options as well.

One other note: This article is not about greenhouses for places where snow loads are high. That is a special circumstance that requires good design and materials that can take heavy snow loads. You can still have a home greenhouse in snowy areas, but unless you are an expert at construction, you probably will need to have a contractor build your greenhouse according to the needs of your area. This article is for greenhouses in areas that have some winter freezes, perhaps an inch or so of snow from time to time, but not blizzards and several feet of snow each winter. If you need a greenhouse for heavy snow loads, contact a company that supplies these types of greenhouses to obtain one that fits your locale.

Where To Start?

First lets consider size. If you live in an area that is heavily regulated by zoning or subdivision rules, you should check those before you build the greenhouse only to have someone complain that it is too big or too high or not allowed at all. Assuming you are good to go, then how big a greenhouse do you need? It is a rare person who builds a greenhouse and then finds that it is too big for their needs. The opposite is almost always the case - your plant collection will rapidly grow to fill it, and you will be looking for more space. So, the best thing to do is to build as big a greenhouse as you can in the space you have available, or build it with the idea that you will add onto it as needed. Greenhouses are wonderful additions to a home property, and can provide many hours of pleasure while the weather outside is rotten and cold. Build it as big as you dare!

What to Build The Frame Out Of

There are three main types of materials used for building greenhouses at home. These are:

1-PVC Pipe:

Yes, common PVC pipe that is used in irrigation systems makes a fine frame for a small greenhouse. It is cheap, easy to work with, has all sorts of available connecting pieces to accommodate almost any design, and is lightweight. The light weight can be a problem in high wind areas, because the greenhouse can blow away. So in windy areas, the plastic covering may need to be removed during the stormy summer months to help prevent this.

2-Wood:

Stronger and more stable, but also more expensive unless you have access to cheap wood. A wood-framed greenhouse requires some basic carpentry, and it helps if you have some basic power tools and a little experience working with wood.

3-Metal:

The strongest and longest lasting material for the frame. This would seem to be outside the reach of most people, but in reality it's not. There are several suppliers that provide pre-drilled metal parts, including all connectors for constructing even small greenhouses at quite a reasonable price. This is a very good option for those who want to have a somewhat larger structure, say 24 feet wide by 48 feet long or bigger.

The Very Simplest Greenhouse Frame
One-Inch PVC Pipe Bend into a Hoop

A PVC Greenhouse Frame

A Metal-Frame is Best for Large Greenhouses

The Floor

The greenhouse floor does not have to be totally flat nor do you have to grade a perfectly horizontal surface for it. I have had greenhouses on the side of a hill and they still work just fine. It is easier to build the greenhouse "square" if the surface is level, but if you cannot make a level location, you can still build your greenhouse. A slight slope inside the greenhouse is actually beneficial because excess water will flow more quickly out of the greenhouse.

We should really call this the "floor" rather than the "foundation". It is not at all necessary to pour a concrete foundation for a greenhouse. Water run-off is always an aspect of having a greenhouse full of plants. If there is a concrete floor, the water cannot sink into the ground and must find some other way to exit the greenhouse. If you must have a concrete floor, then think through how the excess water is going to be removed from the greenhouse.

Prepping a Greenhouse Floor

The Covering :

Greenhouses are mainly frames covered with some sort of material that allows light to enter. The frame is the main structure, and determines the strength and shape the greenhouse will take. The covering is mostly for keeping the warm air inside and barring the cold air from entering. It is not load-bearing, and is usually cheap and flexible.

Greenhouse polypropylene is the least expensive material we recommend for your greenhouse. "Poly" is graded by how many years it is expected to last in the full sun, and by how thick the it is. Four-year, six mil (mm) thick poly is ideal for most greenhouses. This can be purchased in many widths and lengths from horticultural and agricultural supply companies, and of course just about anything can be ordered from online suppliers. There are also many types of rigid material that provide excellent insulation and yet still let light through. These are good for side walls and can be used to cover an entire greenhouse although they are much more expensive than flexible poly (also called greenhouse film by some suppliers).

Polypropylene or "Poly" Covering

One of the main considerations when designing the greenhouse and choosing a covering is rain. Rain water must be able to run off the top and sides of the greenhouse. For example, if a greenhouse is built with a flat roof and covered with flexible poly, that will be a disaster when it rains. Rain water is heavy! It weighs 2 pounds per quart. Once rainwater starts collecting in any hollow or depression in the poly, its weight will stretch the poly and create big sagging sections full of water that can't escape. The important thing to remember is that all surfaces covered with poly must be angled so that water will flow off the surface and not collect on it. This is one of the main reasons that "hoop" greenhouses are so popular - the round shape sheds water very well. A-frame type greenhouses also work well to shed water.

Doors and Windows :

Besides allowing entrance to the greenhouse, doors and other openings in the greenhouse are crucial for allowing heat to escape. Greenhouses are very efficient at retaining heat while the sun is shining. The temperature in a fully closed greenhouse on a warm sunny day can reach 125°F (52°C), a temperature that is dangerous to both plants and people. Ideally, the greenhouse temperature will be kept under 100°F (38°C) and most plants grow best below 90°F (32°C). Doors and windows are the cheapest way to keep the greenhouse reasonably cool.

Unattached Side Poly Rolled up in Summer

Another method for creating windows is to leave the side wall material unattached to the ground around the bottom of the greenhouse. Instead, cut the side wall material extra long and leave it lying loosely on the ground so that it can be rolled up and tied up during hot days. This allows air to enter and exit and helps remove excess heat. During the winter months, the excess side wall material can be held tightly to the ground with cinder blocks or other heavy material.

Heat rises, so a way to let it out of the top of the greenhouse is always a good idea. Cutting simple roof flaps is one way to let heat out. Another way is automatic window openers that are set to open windows at a specific temperature and close them when the temperature drops. These do not require electricity but work on the principle of expansion and contraction of certain materials as they heat and cool. As the material expands it pushes the window open, and as it contracts it allows the window to close. Of course you can manually open and close windows as well, but whenever it is possible to automate something in the greenhouse, you will find that it is helpful to do so.

Simple Roof Flaps to Fold up or Down

Water :

All greenhouses need water for the plants. It can be from a hose, or you can easily run some PVC pipe into the greenhouse. Working with irrigation parts may seem daunting, but it is actually very simple and straightforward. All the parts are available at home supply stores and all you do is glue them together.

Heat :

Greenhouses are heated by the sun any day it is shining and even when it is cloudy. However, a cold and cloudy day may not allow for enough heat to be generated to keep the greenhouse as warm as you would like. Nights are the bigger problem, since inside a greenhouse the temperature will drop to within a couple of degrees of the outside temperature a few hours after dark. That may be sufficient for areas where the nights never get below 30°F (-1°C), but for most people, some greenhouse heating is worth considering. Both electric and propane/natural gas greenhouse heaters are available to do the job. Due to the high humidity, sunshine, and temperature swings inside a greenhouse, we have found it best to use heaters intended for greenhouses because they hold up better.

Some Optional Goodies for the Greenhouse :

Over time greenhouses tend to be improved upon as the people who use them figure out what is important to them. You can start growing hibiscus in the basic greenhouse described above. It provides for warmth and water and that is what it is all about! But below are some of the goodies you may want to add as you work with your greenhouse.

Tables for Plants:

Tables are great - they raise the plants to a warmer air zone, keep them out of water runoff with the potential for spreading disease, and make it much easier for the normal person to work on the plants without having to stoop or bend over all the time. Tables can be made yourself. Make table tops out of 2x4 wood frames with 1x6 wood slats, and use cinder blocks for the table legs. Plastic waterproof tables are available from many sources as well

The topic of greenhouses is a huge one. We are not able to cover more than the basics in a newsletter, but if you have questions or want to get into the details about any topic concerning greenhouses, please visit the HVH Forum and ask your questions in the Greenhouse Section. If you have some experience with your own greenhouse, please share it with the many people who read the HVH Forum. Photos are welcome!

Drip System with Timer:

Nothing frees up the plant lover like a drip system operated by a timer. This is by far the best way to water hibiscus, so that the watering is regular and uniform and does not flood the pots. Try it, you'll like it !

Wall Fans:

One of the best ways to maintain air flow through a greenhouse during warm weather is to install one or more big box fans into one of the walls of the greenhouse. These blow out, not in, and the pressure they create draws fresh air in from the windows and doors that are left open

Horizontal Air Fans:

These are installed high up in the greenhouse and are intended to keep a gentle current of air circulating inside the greenhouse. This helps prevent fungal diseases and also mixes the air so that the greenhouse does not end up with hot and cold layers of air during the night.

Horizontal Air Fans

Evaporative Cooler:

Often installed at the same time as the Wall Fan, the evaporative cooling system is built into the wall opposite the fan. It consists of water dripping down special material that is collected in a gutter and recirculated. When the fan is on and the water dripping fresh air is drawn through the wet material where it is cooled 15-20 degrees. The fan draws this humid cooler air through the greenhouse and out the opposite side. This "fan and pad" system will turn a 105°F (41°C) day into an 85°F (29°C) day inside the greenhouse - a great improvement in summertime heat

Roll up Side Walls:

Available in both powered and manual versions, these walls can be rolled up during hot days and lowered at night where they fit snuggly into a ground level track to prevent air leakage

Grow Lights:
Grow lights are not a real necessity for most parts of the world where hibiscus are grown. However, if you live in the far north or where clouds obscure the sun much of the time, adding HID or the new LED type grow lights to the greenhouse will give your hibiscus a boost when they need it most.

Insect Netting over Doors and Windows:

One of the easiest ways to control insects is to exclude them from the greenhouse with insect netting. There are now special net cloths that have holes small enough to keep out almost every known pest, including thrips which are very skinny.

Electronic Controls:

The irrigation timer is the simplest example of an electronic control. However, fancier ones can also control the heater, the fan, the pad cooling system, and any doors, windows or walls that are powered to raise and lower. In fact, electronic controls can control anything that runs on electricity, either by timers or by sensing conditions such as temperature.

PROJECT Two : GREENHOUSE MODIFICATIONS FOR HOT CLIMATES

courtesy to : www.instructables.com/id/Greenhouse-Modifications-for-Hot-Climates/

In the late summer of 2015 I was given a 10 x 12' (3 x 3.7 m) greenhouse as an early holiday present. It was on sale so my family decided it was a good time to purchase one.

Currently, I am living in Bullhead City, Arizona. The summer temperatures compete with Death Valley and in the winter it can get below freezing. The temperature extremes along with the strong winds in Bullhead City each create their own set of challenges that required modification to the greenhouse.

With the right modifications the greenhouse became the perfect climate for growing rare tropical plants, starting seedlings, and keep my plants alive all year. This instructable is not a step-by-step of each sub project, but rather an overview to give you guidance if you are unsure where to start.

Step 1: Build Greenhouse +/- Foundation

A greenhouse in Arizona can create a very special climate and allows you to grow plants in a greenhouse that growers in other states cannot. Be creative!

I hope that someone finds this helpful.

Good luck!

Obviously, there are many creative people that can build their own greenhouse from scratch. I am not one of those people.

In the pictures you can see that I have laid the base of the greenhouse over gravel. Later, I realized that this was a bad idea. If you can, the better option is to place about 1.5 feet (~ 46 cm) deep foundation with about 4'' (~10 cm) sitting above ground level. Why is this? To keep it from blowing away? No! The problem with keeping your foundation at ground level is when you water your plants the water will flow out rather than down. I can't tell you enough how much I deeply regret not making an underground foundation. Alternatively, if you are dead set against this or you have no idea how to make a cement foundation you can make a small garden around the perimeter of your greenhouse. This way when the water flows outwards it also waters the plants outside the greenhouse. Also, if you are going to have a tree next to you greenhouse (preferably on the north side so that it doesn't block light) allowing the water to flow outward would allow you to water the tree and the greenhouse simultaneously.

The point is, you want to decide whether or not you want a foundation based on how best to use your water. If you decide to simultaneously water your tree or a surrounding garden then the water isn't wasted.

Step 2: Cooling System

If you have a greenhouse without a cooling system, it's just going to get hotter inside the greenhouse. Evaporation coolers are pretty much the way to go in terms of energy usage and maintenance. Also remember that your plants are not going to necessarily be comfortable at temperatures you're happy in. Really, most of you plants are probably going to be happiest at about 90 F (~ 32 C).

In the picture you can see I've constructed a wooden structure to hold up my evaporative cooler. I also wanted a small table or bench, so made it chair shaped on the inside of the greenhouse.

The evaporative cooler I purchased can be used as both an evaporation cooler or just a fan. This is good for the fall season when you don't want excessive moisture in the greenhouse, but it gets a little too warm during the days.

One thing to note is that if you have very hard water you will likely end up buying a new pump every year ($14-35 ea). You can find an assay of your ground water online or from your water company. A 2009 assay showed that we have 51-204 ppm calcium (very hard), sodium 98-180 ppm (hard), and sulfate 101.6-430.6 ppm (very hard). These are all naturally occurring the from erosion of volcanic rocks around our basin (fun facts!).

Lastly, during the first summer I believed that I should leave the roof panels open to let the hot air escape. After sealing the windows, I can tell you that there is still enough holes to let hot air escape. A sealed greenhouse is better.

Step 3: Sealing Cracks

With my greenhouse I was never able to keep the panels from blowing off in wind storms no matter how many clips I placed on them (and I bought extra!). Every time a panel blew off it might get bent and scratched up (bad!). Retrospectively, I also realize that a lot of air was escaping prior to sealing the greenhouse. To solve this problem I sealed each panel with silicone. Sure, this will be more of a pain to deal with if I need to replaced a panel, but so far it has worked out great! This also keeps the entire structure from shifting in strong winds.

Step 4: Shade Cloth

During the first summer when the plants were just getting started I needed shade cloth. There was no ecosystem or microclimate. Just a big plastic house full of dirt and tiny tiny plants under a blazing hot sun. So, I put a large shade cloth over the entire greenhouse. Given the very high temperatures I decided to go with Aluminum shade cloth. This way most of the light/heat is reflected rather than absorbed. If you would like one that is more easy to acquire and readily available I would recommend tan or green shade cloth. A black shade cloth should absorb more heat/light and that is what you are trying to avoid. Why does it matter if it's only covering the top of the greenhouse? If the shade cloth is sitting on top of the greenhouse some heat will be transferred to the greenhouse. In 120 F (~ 49 C) would you rather wear a black shirt or white shirt? If you don't know the answer to this you might not live in the desert (hint: white shirt).

Now that I have a canopy layer in the summer I am less concerned with shade cloth. This is because (1) the canopy provides dappled sunlight to the lower level plants and (2) the increased vegetation in an established ecosystem will be shedding more moisture and helping to keep the greenhouse cool (my theory).

Step 5: Planning Walkway and Laying Dirt

You can have no walkway, but eventually you'll end up stomping on plants. Also, if you let your pets in the greenhouse they will also end up trampling plants. I separated the growing area from the walkway with hollow bricks so that I could grow herbs in the bricks. Mix your native soil with good quality soil followed by a layer of composted mulch. Fill your walkway with gravel to just below the top of the brick to hold the bricks in place and to allow good drainage from the walkway. If you spill dirt the gravel filled walkway will allow the dirt to seep downward when you hose off the path

Also, if you see mushrooms growing in your garden - don't be alarmed! Mushrooms can break down wood and are breaking down the wood in your mulch. This means they are giving you more soil! You can add more mulch from time to time when the soil level has sunk to continuously create a supply of good organic material.

.Lastly, add worms! The easiest way to get them is to buy them from a fishing store. I like red worms because they are so prolific and compost quickly, but you can get normal earthworms too!

Step 6: Creating an Ecosystem

Thinks of your greenhouse like a forest. A ground cover will keep moisture in, a canopy will shade more light-sensitive plants. Will you use pesticides and kill beneficial bugs? What about predatory nematodes? What about other pest predators?

Ground Cover: This is a very important step because water loss in the desert is a big issue, but in the winter plants will still have issue with fungus such as powdery mildew. My philosophy is to plant several vigorous ground cover herbs and let them fight it out - survival of the fittest and most productive! Alternatively, if you are okay with waiting a little longer you can cultivate less aggressive, but worthwhile plants. For example, I planted sweet mint, spearmint, spicy oregano, banana mint, apple mint, pineapple mint, and several other varieties of mint. The sweet mint and oregano out compete everything, but now I'm realizing that I really like the banana and pineapple mint. I'm constantly having to fight the oregano and sweet mint for space for the banana and pineapple mint to grow. Think it over carefully. Also, one thing to note is that all the mints appear to have a much more pleasant taste in the cooler seasons and a slightly, uh, tarry (?) smell in the summer. Not everyone notices this, but it really bothers me. This might also have to do with water quality.

Low Height Plants: This is any plant that doesn't get very tall, but still holds itself above the ground cover. If you grow these make sure they aren't being completely shaded by a taller plant. These are usually small herbs (sage, electric daisy, summer savory, etc.). Strawberries also might fall into this category.

Moderate Height Plants (Light Blockers): This is anything below the canopy that still towers above the rest of the plants. Although basil doesn't get more than 2-3 feet tall I would consider this a "moderate height" plant because it also grows densely and will create a lot of shade. This is especially true for a varieties of basil such as box basil and spicy globe - they are even shorter, but very dense and block out most of the light. A vigorous pepper plant might fall into this category. Staked Geraniums can be grown upwards towards the canopy and trimming the lower leaves might make it easier for the low height plants beneath to flourish. Only place lemongrass on the north side of your greenhouse because it will grow VERY dense and tall and block out most of the light.

Canopy: These plants will provide dappled sunlight throughout the hottest part of the year. The two plants I've used successfully are vining/indeterminate tomatoes (variety: "Sweet 100") and a wild north american passionfruit (Passiflora foetida). Next year I might try a larger variety of passionfruit along with my tomatoes. In the future, when my banana trees and plumeria tree are large enough, they should create a sufficient canopy and I might not grow the tomatoes or passion fruit anymore.

Step 7: Pests

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Pesticides: I don't use them. I had a lot of problems with white flies at one point in the winter, but I took out my cucumbers and grew them outside - now I have few white flies! I used to have problems with fungus gnats and since placing predatory nematodes in the greenhouse I haven't seen a single gnat. This doesn't solve all my problems though. Admittedly, I will have to spend 30 min in the summer every 1-2 days removing inchworms and caterpillars from my plants. Without pesticides I simply cannot grow (in the greenhouse) lettuce, bok choy, squash, or spinach. Despite this, there was only one day I decided to use pesticides. Earlier in the week I had become very excited about finding a praying mantis in my garden because they are ravenous predators. A plant adjacent to where the praying mantis was huddled was covered in white flies. I decided to spray the white fly infested plant very carefully to avoid any beneficial insect deaths. Unfortunately, I found my praying mantis dead the next day :( never sprayed pesticides in there again. As the greenhouse has progressed I have removed common plants with common insect problems and added rare fruit producing plants without many pest issues (ie: bananas!). This keeps my garden interesting and helps in maintaining a low pest population. And hey, if you're going to have a greenhouse why fill it with mundane stuff like lettuce when you could grow lemongrass and vanilla orchids? Also, do you want to expose your pets to that stuff?

Bees: Also note, if you spray pesticides they will likely kill bees. These little critters regularly visit my greenhouse and I love to watch them buzzing around my basil flowers. On a particularly quiet day I can hear a pleasant hum. My family, including my loving husband, used to be terrified of bees until they watched them buzzing around my greenhouse without attacking me for months (none of us have bee allergies). Sometimes they will be within inches of my face. I actually trim my different basil plants at different times so that there will hopefully always be some flowers available to them. You might say 'but what about the Africanized bees'? I have no idea how to answer that question. The University of Arizona has reported that most bees in Arizona have been Africanized already (based on genetics testing). Don't go up to a hive of bees and stick your face in it. If you have bees in your garden though, just be respectful of them and appreciate them for the valuable service they perform.