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Hobby Greenhousesfor the Southeast Texas Area

Introduction/Design and Construction/Operation and Maintenance

Our first 8x8' hobby greenhouse in El Lago, Texas

IntroductionAlthough the Gulf Coast and Central Texas area lie in an area known tobe relatively warm year round, tropical plants intolerant of freezing ornear freezing temperatures require winter protection from the variouscold fronts that sweep through and drop temperatures below or near

freezing for short periods of time. In order to ensure healthycontinuation of growth for such plants, a hobby greenhouse is virtuallya necessity for the serious plant collector. This page will offer usefuladvice on this subject in regard to design, construction, operation andmaintenance of a Hobby Greenhouse suited for the Central Texas orGulf Coast regions. Some practical tips based years of experience inHobby Greenhousing by the author will also be provided. The following

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assumptions will be used to discuss this topic. A hobby greenhouse willnot exceed 12x12' size, be used only for hobby/plant collectionpurposes, and be located on an average residential lot. The main usewill be for over wintering tender plants or for display of collection plantsthat are not used in the landscape during the outdoor growing season. I

will assume that the expense of building and operating a hobbygreenhouse is a luxury to a family's budget and therefore a concern.The hobby greenhouse described here was a backyard, utilitarian typestructure that lacked aesthetic appeal but was very effective ininexpensive to build and operate.

Design and ConstructionMaterials:A hobby greenhouse can be framed in aluminum/stainless steel, wood,or any other durable product. The most important element is the clearcovering which can be either glass, fiberglass, or polyvinyl. Unless thegreenhouse is being constructed as an attached add-on to your homefor use as a conservatory, glass is not a preferable alternative. It is themost aesthetically pleasant choice, but the easiest to damage.Aluminum/stainless steel framing also generally is associated with

attached greenhouses. Aluminum and glass are also the most expensivealternatives. On the other extreme, the least aesthetically pleasant andleast durable product is polyvinyl. Its advantage is easy up and easydown when needed and not needed. Polyvinyl is also considered atemporary or seasonal greenhouse solution, but it does work effectively.Polyvinyl is used by most commercial nurseries because is relativelycheap. It also damages easily in severe weather. My choice, bydeduction, is fiberglass - not any, but UV coated greenhouse gradefiberglass of fairly rigid thickness. The UV coated fiberglass blocksharmful Ultraviolet rays and produces a more useable, less damaging

form of light. Corrugated fiberglass is hard to seal and has more surfacearea for heat loss, therefore I recommend flat. Since aluminum is muchmore expensive than wood and not as versatile for construction, Irecommend cedar wood framing for a beginning greenhouse. Pleasenote that chemically treated lumber can be toxic to plants when waterdrips over it. Treated lumber can be used for side supports and exteriormolding, but never for roof beams or areas above plants. Any dripping

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from treated lumber will be toxic to plants below. An aluminum stormdoor works well with an wooden frame and is more durable over time.Location:Location is important from a heat conservation and light availabilityperspective. The most ideal location to the least ideal is: south,southeastern, southwestern, east, west, northeast, northwest, north. Thesouth side obviously shelters the greenhouse from the cold northernwinds and when the angle of light is lower on the horizon during winter,the south side captures more light during the shorter daylight period ofwinter. A greenhouse located in the middle of a yard without any barrierto the elements is the same as a fully northern exposed location.Although it would capture more light, it would be far less heat retentive.A location close to a circuit breaker box is best for accommodating

electrical service to your greenhouse. Choose your site carefully.Construction Tips:The following tips assume you have chosen wood framing withfiberglass and chosen a more favorable location.

A hobby greenhouse should be aesthetically pleasing since it is ayear round structure but used mostly in winter. Landscapingaround it helps make the structure blend with the garden and yard.

Location helps in this respect as well. Greenhouse grade UV fiberglass comes in standard 4' wide rolls.

Therefore, a framework that accommodates 4' wide panels reducesconstruction costs and complexity. This approach accommodates8x8'. 8x12' and 12x12' structures where 4x4" side beams arepositioned at 4' intervals. The same theory should be used in roofconstruction with 4' wide sheets overlapping at least 6" on thedown slope to prevent leakage and provide a tighter seal. A singleangled roof raised 18" to 2' toward the rear side is the leastexpensive and easiest to construct. Allow for a 12" overhang for

drip control during storms. Windows should be plenteous to allow good aeration and cross

ventilation during spring through fall. They can be eitherprefabricated aluminum sliding type or wood framed withfiberglass hanging on hinges. I chose the latter due to the costfactor and prop my windows open with 12" sticks. I also seal themtight in winter using exterior swivel braces. The door can be either

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wood framed fiberglass on hinges or prefabricated aluminumstorm door. I chose the latter because they were inexpensive andmore durable over time.

All exterior wooden surfaces to which fiberglass is attachedshould be covered with 1x4 framing to tightly seal the fiberglass.

The flooring should be 6" deep gravel stone, about 1/2 to 1"diameter, or pea gravel (1/4-1/2 in diameter) filling a sand bedcavity. Using an inorganic substance like stone allows forexcellent drainage and aeration, which in turn prevents diseaseorganisms from inhabiting your greenhouse, plus is effective weedcontrol. The outer foundation can be concrete block, brick,landscape timbers, or poured concrete. The 4x4" side supportbeams should be dug and concreted 18" into the ground.

Electrical appliances and accessories should include one or twogrounded receptacles (4 plugs) , each receptacle controlled by aseparate circuit breaker. Make sure electrical service meets allelectrical codes. Also, a 12"-18" louvered exhaust fan should beinstalled to prevent overheating conditions. An 8x8' house can besufficiently heated with one thermostatically controlled 1500 wattspace heater. If a really hard freeze occurs, a hanging 100 wattfrosted light bulb helps generate additional heat. An 8x12 or 12x12'size will need at least two space heaters. To install propane or gasheaters can add significantly to the expense . Since our really coldnights are few along the Gulf Coast, electric space heaters don't

significantly run up huge electrical bills but are very convenient touse. The only risk is a power outage. I have found that placing athick polyvinyl sheet or tarp over the top and trying it down alongthe sides can substantially reduce heating needs and keep agreenhouse warmer during severely hard freezes. This would bean emergency backup measure to consider. You should alwayshave a contingency plan for emergencies and severe weatherconditions.

Use of space can be maximized by designing and buildingbenches with 2x4's and using thick honeycomb shaped wire or 1x4

wood slats to cover the top. This allows for good air circulationand more light to get to the plants stored at floor level. Benchesshould not take more than 1/2 to 2/3rds of your greenhouse spacedepending on the size plants you will be over wintering. Someplants need floor space due to their height. Hanging baskets fromthe roof beams also allows you to use more space efficiently, butbe careful that they don't block too much light to the plants below.

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Whether you personally construct it or hire someone else to buildit, take plenty of time up front to design your greenhouse to meetyour personal growing needs and minimize potential problems andoperating costs. An ounce of prevention beats a pound of cure.The size of the greenhouse ultimately limits or self disciplines theplant collector. You can't have more plants than you can overwinter. It works for us.

Operation and MaintenanceThe following tips are offered for operating and maintaining a hobbygreenhouse along the Gulf Coast Area

The smaller the greenhouse relative to your needs, the better andcheaper it will be to operate and maintain. Space can be maximizedby cutting back all plants before putting in the greenhouse.Hanging baskets can be regenerated next growing season bytaking and rooting cuttings in 6" pots rather than storing largehanging basket plants or by pruning back significantly, any largerhanging basket plant.

Always do periodic inspections of plants during warmer days ofwinter to check for disease, insect pests, improper environmentalconditions that may harm plants, etc. This may mean pulling themoutside, removing dead growth and dropped litter, and visuallychecking each plant. Treat problems immediately. Insect pests anddiseases can spread very rapidly in this confined environment.

Remember that winter greenhouses can build up heat (greenhouseeffect) therefore plants may dry out quicker than you might expect.Hand water all plants based on need. Plants at lower light, coolerfloor levels could easily get over watered and rot in their coolermicro environment. All greenhouses have micro environments - besensitive to that. Plants should be positioned according to these

micro environmental conditions, Water plants in early to midmorning during winter months to avoid cold damp soil during thecooler evenings. During warmer days of summer, watering anytimeis ok.

Overcrowding can cause carbon dioxide deficiency and stuntgrowth. On warmer winter days, open windows to allow fresh air tocirculate (windows of opportunity - pun intended!)

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Scrub greenhouse transparent surfaces at least twice a year(spring and fall) to eliminate algae buildup and dust (which clingseasily to fiberglass especially). These buildups can reduce lightsignificantly. Visually inspect the structure for any problemsperiodically. (e.g warping, rotting, etc.)

Remove as many plants as possible during active growing monthsand leave the greenhouse open for good air circulation. I only usemy greenhouse benches for potted orchids during the warmerseasons. Most tropicals prefer to be out in our great Houston heatand humidity from spring to fall. The big guessing game is "Whenis it safe to take your plants outdoors'? The rule of thumb we usefor the Gulf Coast area is to have all our tender plants ready to putinto the greenhouse by Thanksgiving and we feel relatively safetaking them out after the first official day of Spring unless theextended weather forecast calls for temperatures below 50 degreeson a subsequent night.

We graduated to a pre-manufactured, stainless steel 8x12' glass lean-togreenhouse that is much more aesthetically appealing and energyefficient, however, was four times the cost of the self designedgreenhouse described above. We had this greenhouse for 4 yearsbefore moving to Austin.

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Above: Summer GH shaded with 80% shade clothRight: Winter GH filled with plants requiring winter

protection from mid November - mid March.

Above: New Austin GH immediately afterconstruction

Right: Austin GH filled with benches andtender plants

If you would like to become part of a nationwide association of hobbygreenhouse owners, visit theHobby Greenhouse Association. BETTERYET, BECOME A MEMBER

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Please return to SOUTHEAST TEXAS GARDENING for morehorticultural information.

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