It’s almost July, and that means it’s hot.  In a greenhouse, it’s even hotter.  We’ve been flying through shade cloth as if there were some kind of national shortage.  But chances are pretty good that, this time of year, a simple shade cloth may not cut it.  With some shade and no other form of ventilation or cooling, temps in your building can still soar above 100°F; more than enough to torch your precious plants.  Exhaust fans and shutters can help a ton, but even with fans, shutters, and shade your greenhouse can only reasonably attain the outside temperature +/- a few degrees.

For heavy duty cooling, you need to call in heavy artillery.  By that I mean evaporative cooling, called variously a water wall, cool cell, wet wall, or swamp cooler.  With these systems you can actually lower the temperature inside your greenhouse 10-20 degrees below outside temperture, possibly more, depending on your specific environmental variables.

Evaporative cooling can make a big difference in your greenhouse environment.

Evaporative cooling works kind of like a filter.  All of the air coming into your building passes through the pads of the cooler.  The cooler must be sealed properly so this is the case.  These pads have water running down them driven by a pump.  As the air passes through, water evaporates into it.  The evaporation process pulls heat out of the air, thus cooling it.  This air then flows into your building and is usually circulated with the help of circulation fans.  Something to keep in mind with evaporative cooling is that since it relies on water evaporation, efficiency is greatly increased in dry climates.  This is because humid air is already chock full of water, and cannot easily take on much more.

There are two main types of evaporative cooling systems, along with simple portable coolers.  The portable ones simply cool and recirculate the air inside your building and require only a water source and standard wall plug.  These are great for small hobby greenhouses, and can be coupled with a plug-thermostat to give you by-the-degree control.

The first kind of evaporative cooler is a negative pressure system.  Known as a cool cell, water wall, or wet wall, these are wall-sized systems that work in conjunction with your fans and shutters.  They are typically installed inside your building along one wall and sealed to the building.  Inlet shutters are located on the outside of the same wall, and exhaust fans stand opposite both.  When the exhaust fans kick on they pull air out of the building, and in through the shutters and cooler.

Cool cell, water wall, or wet wall.

Two kinds of cool cell systems are available from us: an aluminum system and a PVC system.  Both are excellent options for your cooling needs.

A swamp cooler.

The second kind of evaporative cooler is a positive pressure cooler, commonly called a swamp cooler.  These are used often in lieu of true air conditioning in hot, dry locations such as the American Southwest.  They are small, box-shaped units that sit external to your building.  Inside is a round fan, often called a “squirrel cage.”  As the fan rotates, it pulls air into the unit through the cooling pads.  This air is then pushed into your building, and shutters located opposite the cooler allow for the hot air already inside your building to escape.  Again, circulation fans help move this air around a more consistent temperature.

Any of these options can help make the summer months bearable and productive in the greenhouse, and as always the efficiency of any cooling system can be increased by a simple shade cloth.  So analyze your situation, and if it calls for more ammo to fight the heat, consider an evaporative cooling solution.

Great article here in the Wall Street Journal that discusses all the new products and gadgets aimed at recruiting younger, first time gardeners.  These include a multitude of products from growing boxes and bags, pre-fertilized soil, water conservation granules, and so on.  With the ranks of those growing at least some of their own food swelling this year, the gardening and gardening products market is having an influx of innovation.  Most of these products are geared toward making the likelihood of success much greater for a first time gardener since it can be incredibly frustrating to purchase 20 or 30 seed packets and end up with little to show for it.

These products are also good for the urban gardener who may not have the space for a garden of the in-ground variety.  Most of them can be set up on a patio or deck to yield plenty of  fresh vegetables for use throughout the growing season.

Even though standard container gardens can accomplish much of the same, at a lower cost, and the article portrays in-ground gardening as a much more tedious and difficult task than it really is, it’s still nice to see this kind of innovation in our industry.

Contributed from Garden and Greenhouse Magazine
by Gini Coover

Choosing the Right Size, Location, and Type of Greenhouse

June is a good time to start planning your new greenhouse, so it can be completed and ready for use by the fall or winter. Whether it is your first greenhouse or an additional one, you will want to choose the right size, location, and type to reduce costs, create an efficient work environment, and make sure you don’t run out of space.

Choosing the Correct Size

Size is determined primarily by the quantity of plants you plan to grow during the period of cold weather when additional heat and protection from frost is required. Plants that prefer warmer climates can continue to grow inside the greenhouse to produce flowers, fruits, or vegetables through cold and warm seasons. Plants, requiring shade during both cold and warm weather, can be protected from direct sun with a shade cloth. Size also will be influenced by the amount of space and money you have available.

The square footage required can be determined by laying out a floor plan that includes growing areas, walkways, and work and storage spaces not provided for in other structures. Enough space should be provided to prevent plants from touching greenhouse walls during freezing weather and to allow adequate air circulation. Plants should be reachable from walkways or from between benches and beds to allow for regular watering, fertilizing, and insect and disease control.

Walkways must accommodate the movement of workers, customers, equipment, plants, and vegetables in and out of the greenhouse. However, you want to minimize your walk, work, and storage areas as much as possible, because only the growing areas provide income or plants and vegetables for your own use.

Will trucks need to back into the greenhouse to load and unload? If so, its doors will need to be large enough to accommodate them.

If money is tight, you can make the permanent greenhouse smaller by using less expensive temporary structures to raise early and late vegetables. Bedding plants can also be moved outside early to harden off, using temporary covers to protect them when frost is predicted.

Double and triple uses of greenhouse space allow for increased production per square foot. A simple wooden or metal frame can be built over a supply-storage area, creating more room for flats of plants. Temporary benches, filled with plants, can be set between rows of transplanted vegetables and moved as space needs change. Lettuce, spinach, radishes and other quick maturing crops can be planted early between tomato and pepper plants and harvested before later crops grow large enough to block the light.

Greenhouse rafters should be high enough to hang baskets above the heads of workers and customers, especially in walkways, yet low enough to water and fertilize regularly. They will need to be spaced far enough apart to grow without crowding and to allow light penetration to plants below.

Choosing the Best Location

Ask yourself a number of questions about possible locations. Is there room for delivery of supplies and removal of plants and vegetables? Can excess snow slide off the roof and be removed? Is the ground sloped adequately for drainage, but not too hilly or bumpy to work and move equipment safely?

Is the greenhouse far enough away from property lines, streets, tree limbs, and potential hazards? Never place your greenhouse within fifty feet of the drip line of black walnut trees if you plan to grow vegetables in the ground. The black walnut and some other nut trees produce juglone, a toxin that prevents tomato and pepper plants from growing.

Will sunlight reach all areas of the greenhouse for most of the day? All or portions of the greenhouse can be shaded if you plan to grow plants that require shade. If both sun and shade plants will be grown, the greenhouse can be located in the sun. Shade cloth can be used wherever shade is needed to allow flexibility in plant varieties from year to year.

Locate the greenhouse to maximize use of prevailing winds, but never locate plastic-covered greenhouses in a natural wind tunnel where high winds are likely to destroy the greenhouse film and blow flats off plants off their benches. Calculate its height before building begins to make sure it will not interfere with utility lines or block a priceless view. Make sure doors are conveniently located and accessible to other buildings.

Do you plan to open the greenhouse to the public? If so, can you provide adequate parking, space for customers to shop, and room for their children to wander around safely?

Consider long-term possibilities before placing your first greenhouse. If expansion is possible, consider where additional greenhouses will go. When you have concluded your first successful year, you will be tempted to expand. Then you will be glad you placed your first greenhouse in a location where it can stay and continue to be a useful part of a bigger operation.

Should You Buy a Manufactured Greenhouse or Build Your Own? This topic will be discussed in the Garden & Greenhouse July/August issue. If you are eager to begin building sooner there are two books that will provide you plenty of information. To build using wood and greenhouse film, read chapter 2 in The Natural Greenhouse, Growing Plants and Food for Profit, http://www.sunandshadepublications.com/. To use metal frames, glass or polycarbonate panels, read Greenhouses for Homeowners and Gardeners by John W. Bartok, Jr., http://www.nraes.org/.

Gini Coover is the author of The Natural Greenhouse, Growing Plants and Food for Profit. She has grown greenhouse plants and vegetables for twenty-six years, selling retail and wholesale from her greenhouse and at the Athens (Ohio) Farmers’ Market. She promotes natural greenhouse production through presentations and workshops. She can be contacted at gini@sunandshadepublications.com and the book can be ordered at http://www.sunandshadepublications.com/ or 740-594-4147.This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

It’s certainly shade cloth time of year, and orders for the stuff are absolutely pouring in! I figured this to be an excellent time to post the chart we use as a rough guideline to use when selecting the density of cloth to use with your particular plants. Hope this is helpful, and be aware that shade cloth may take a few weeks to arrive to you this time of year.

You may have noticed the lack of a post last week…well, that’s because I’m a new father for the second time.  My wife gave birth Monday night, and here I am back at work (at least in the office) a week later.  The vacation from kids, housework, and weary wife is welcome.

I just wanted to post an update on my garden.  I used seeds from the Greenhouse Megastore, and they have been in the ground for just over two weeks.  I can happily report that everything has sprouted.  Even some tomato seeds I had serious questions about ended up germinating.

These are some of my mixed lettuce popping up!

Lettuce, tomato, onion, leeks, kohl rabi, beets…even cayanne and chili peppers have sprouted.  And it’s been pretty wet and faily cool since planting, so I feel especially confident in the quality of seed we offer.  The spinach sprouts even have their first real leaves already.

Needless to say the family is very eager to harvest some of our very own, garden fresh food.

As this article is written, a gentle soaking rain falls outside.  This gets me thinking about the fact that my freshly planted garden really perked up after our most recent rainfall.  After not even a week of being in the ground, I was seeing some sprouts.  Small and sparse though, even with diligent watering twice daily to keep the ground moist.

Mother Nature can really get your garden poppin'!

One gentle soak by Mother Nature, a little sunshine, and in one day the amount of visible sprouts doubled.  This, to me, just really drives home the necessity of being patient and trusting that nature will be able to do, in a fraction of the time, what you may devote weeks to accomplising.

Whether you are large scale commercial greenhouse grower with a multi-acre production facility, or a homeowner with a backyard greenhouse; increasing the efficiency of your greenhouse equipment is a must.

Many growers, large and small, set the fate of their crops in the hands of little grey boxes set to control all of those sophisticated environmental systems. I’m talking of course about thermostats. Thermostats are an excellent and inexpensive way to control the environmental systems you choose to populate your greenhouse with. There is, however, a significant downside to using them, particularly in a commercial setting.

“It is hard to think of that innocent looking device hanging on your greenhouse wall as the culprit that may be robbing you of hundreds, even thousands, of dollars in wasted greenhouse energy. But yes, that in fact is most likely what is happening.”

Those words were written by Tom Piini, president of Micro Grow Systems. Micro Grow is our supplier for electronic, microprocessor controlled greenhouse environmental controls.

Sophisticated controls such as these can help save thousands of dollars in energy costs.

Basic single and two-stage thermostats, while initially cost effective, are limited to single temperature set points. Sure, they will kick on and off at a certain temperature; but, there is no way to set them for different temperatures during the day and night, or for different periods of the day. Meanwhile, many plants do not require their night-time temperatures to be the same as during the day. Many times, setting a 75-80 degree daytime temperature and a 60-65 degree nighttime temperature is sufficient. That is a 15-20 degree temperature differential that over the course of several years can result in substantial energy savings - if, of course, your controller allows you such ability. Sophisticated control systems are akin to a souped up version of the programmable thermostats many of us use in our homes to run furnaces and air conditioners.

For instance, say that using a microprocessor system allows you to cut down on just one hour of cooling during the summer. In actuality you would probably gain more, but for the sake of argument one hour is easy. Let’s say that between fans, shutters, and evaporative cooling your electrical and water costs are around $1 per hour (this figure does not necessarily represent your estimated actual costs, it is merely for illustration). Cost savings from that one hour can easily reach to a few hundred dollars. Now factor in winter heating, where the cost savings will be even more, and you approach a cost savings that is nearly equivalent to the price of the control system. All this in just one year.  A sophisticated, microprocessor operated control system can save you thousands over the life of the system.

All to say, before you decide to “save a few bucks” and purchase a non-programmable thermostat to control your greenhouse equipment; considering a microprocessor control system for your greenhouse can help take the edge off of opening your monthly power bills! Not to mention that with a microprocessor controlled system, most other environmental systems, including irrigation, shade, and circulation, can be integrated into the operation of the controller. These sophisticated controllers also have digital readouts that give up-to-date information on the environment in the greenhouse, making it a one-stop location.

These controls certainly aren’t for everyone, but when you are contemplating the operation of your greenhouse, be sure to factor in the true costs of all of your equipment. You may find that the pricier initial investment is well worth it in the long term.