GREENHOUSES, LIKE REGULAR HOUSES, require some maintenance from time to time. If you don’t maintain your greenhouse, eventually paint will peel, glazing will be covered with dirt or algae, and glass glazing will crack or drop out of its frame. If all of this happens, your greenhouse could end up holding a lot of dead or dying plants and enough leaves to mulch a forest, and it may smell pretty bad, too.
The trick to keeping a greenhouse in top condition is to do a little maintenance whenever you enter it. Most maintenance chores are fairly simple: removing leaves that fall on the floor, cleaning up spills, cleaning the glazing, and making sure that everything is working properly. Along with more frequent maintenance, at least once a year you should conduct a maintenance blitz that brings back every part of the greenhouse to tip-top condition.
Greenhouse maintenance is ongoing. Neglecting it one year means that you’ll need to catch up with it the next. Performing a little maintenance every time you enter it reduces the onerous chore of spring or fall cleaning to a day or two rather than a week. If any greenhouse parts need replacing, try to perform this maintenance in the winter (for a cool greenhouse) or in summer (for an empty heated greenhouse), when the garden does not demand so much time (unless the repair involves the function of heating or lighting). For example, I planned on replacing acrylic-covered windows with double-pane glass ones, so I built the new windows in the basement over the winter and fitted them into the greenhouse in summer, during a regularly scheduled maintenance session.
Some chores and monitoring in the greenhouse must occur on a regular basis to keep your plants healthy and the greenhouse in fine working order.
Look for signs of systems/structural problems. Whenever you’re working in the greenhouse, check plants for signs of disease or damage and ascertain the cause. It may be that systems and conditions need maintenance attention or repair. For instance, the heater may be malfunctioning and poisoning plants with fumes. Learn the plant signs of greenhouse structural or systems problems. For example, open-flame propane burners may emit a small amount of sulfuric acid, which shows up as white spots on plant leaves. During the winter, check your heating system daily to avoid finding all your plants frozen. Simply make sure that it is running properly and that the greenhouse temperatures are where they should be.
Perform general cleanup. Remove dead leaves before they accumulate and start to rot. A dead leaf resting on a plant can invite a potentially fatal bacterial infection that might spread throughout the greenhouse. When you pot up plants, clean up spills and detritus right away. Wipe surfaces with a solution of 1 tablespoon of bleach mixed with 1 gallon of water to eliminate germs.
Keep mold and algae at bay. In the moist, warm atmosphere of a greenhouse, mold and algae grow readily. The only way to keep them at bay is to clean everything religiously whenever you finish a job. Pelargoniums that are moved into the greenhouse in fall seem especially susceptible to leaf mold as temperatures fall.
Clean glazing. Although the glazing on your greenhouse always needs to be monitored for cleanliness, it’s especially important to do so during winter, when light levels are low and you want the maximum amount of light to reach your plants. Use a commercial window cleaner on the inside windows, but test it first on plant leaves. Some window cleaners will adversely affect plants.
The best way to clean outside glazing is to start with a mop on the end of a long broomstick to wet the glass or polycarbonate or other material and swab away the worst of the dirt, and then to wash the exterior with a hose. Finally, squeegee the surface to get off the moisture before it dries. I use ordinary dishwashing soap and water for my cleaning, but a proprietary window cleaner does an equally good job; it just costs more. Of course, if you live in an area that experiences cold and icy conditions in winter, you’ll have to wait for warmer, fair weather to clean glazing on the outside.
You’ll find that most of the dirt builds up on the inside of the glazing, where the humid atmosphere of the greenhouse makes it easy for grime, green algae, and insects to colonize window spaces. For this inside dirt, household window cleaners may do a better job than soapy water alone. If your glazing is glass, take extra care when wiping cracked panes, which can easily cut both rags and fingers. If the green algae buildup is severe, the only way to remove it may be to pressure-wash the windows.
A number of maintenance checks and chores should occur on a monthly basis or at least every 3 months.
Check the condition of the glazing. You could also do this more frequently, when you clean the glazing. It’s especially important to monitor its condition if it’s been installed with putty or is the old-fashioned overlapping variety. Look for cracks, chips, and scratches. Cracks and chips especially could be indicative of fractures about to form or could point to a potentially more serious problem: The greenhouse is twisting, or racking, in the wind and the glazing is not moving with it. A small crack will eventually become a big one, so catching it when it’s small may prevent a more costly repair or help to diagnose a larger problem early on.
Check caulking throughout the greenhouse. Some types of caulking turn brittle as they age. The first sign of this is often loose or damaged caulking pulling away from the glazing. If you have to replace caulking, silicone sealants perform well, but they cannot be painted. If you want to paint it, use polysulfide caulking (see chapter 7, Caulking and Weather Stripping).
Check your greenhouse frame for signs of rot, decay, and rust. If you have a wood-framed greenhouse, examine the wood inside and outside the structure. Look for flaking paint, soft spots, and areas that stay wet after a rain. These could all be indicators of the onset of rot. If you find any areas that are soft, check to see what’s causing the softness. If the wood is rotting, it should be replaced as soon as possible. If paint is flaking from exposure to sunlight and the elements, scrape and sand away the flaking paint, let the area dry, and repaint it with an outdoor primer before top-coating it. As I’ve mentioned, I used a marine paint for one of my greenhouses and it’s held up very well. (See chapter 6 in general and specifically Painting Your Greenhouse, for more information on kinds of paint and painting procedures for this application.) If you have wooden benches, check them as well and repair and repaint them as needed.
If you have a metal greenhouse and find an area of rust, either sandblast or sand and scrape it until it’s shiny and new-looking again, then paint it with an outdoor enamel metal primer or other outdoor primer before covering it with a top coat. Do the same for any metal benches and shelving in the greenhouse.
Check the frame and surfaces for mildew. Even if the paint coating on your greenhouse is in good shape, it may be discolored with mildew. You can remove mildew with soapy water or with a proprietary mildew cleaner. If you plan to paint the greenhouse, remove all mildew before applying paint. In this case, it’s best to wipe the woodwork with a solvent to keep mildew from ruining your paint job.
On a monthly basis, check the heating elements or pipes. Wipe them down to remove dust. Vacuum fin tubing, if it’s part of your heating system, to keep it at its maximum efficiency. If you have a burner in your heater, check to see that it’s not clogged with soot or other debris.
On a monthly basis, check the temperature-alarm system and greenhouse insulation. I once discovered that a mouse had tunneled into the insulation and set up housekeeping behind the drywall! Needless to say, I had to catch it before it made a snack of my newly planted seeds.
It’s best to make biannual checks on your greenhouse in spring and fall. If you have a cold greenhouse, you can check its condition any time during the winter to ready it for the coming growing season. A warm greenhouse should be checked in late summer or early fall, before plants that have summered outdoors go back inside for the winter. All greenhouses should be cleaned thoroughly at least once a year to keep ahead of mold and algae. I have settled into a routine of cleaning the warm greenhouse every summer and the cold greenhouse every winter, when both are empty. This entails washing all the woodwork with a solution of bleach and water to get rid of mold and mildew before it has the opportunity to grow. A shiny paint on the surface of wood or metal is easier to wipe clean than is a flat paint.
Certain chores in a cool greenhouse should be tended to in the spring to ready the greenhouse for the growing season.
If you don’t do so more frequently, completely clean all the glazing inside and outside. This ensures that plenty of light can get to newly started plants. For this kind of thorough cleaning, a sponge soaked in a solution of water and bleach to kill plant disease pathogens works well.
Check all lights. If you have supplementary grow lights to increase the spring day length, you should check them and make sure that all the bulbs are working properly. (See chapter 5 for more on light choices for the greenhouse.)
Prepare growing beds. I find that I need to water the growing beds copiously for about a week if they’ve been left empty during the winter. Before doing this, make sure to thoroughly incorporate all soil amendments, fertilizers, and manure.
Check fans, window openers, screens, and vents, doors, and windows. Make sure everything is clean, oiled, and ready to go. If you have a cooling system, clean the filters and check it for leaks.
Certain chores must be accomplished in a heated greenhouse to prepare for the shorter, colder days of winter.
Remove shading material. Before storing it where mice and other rodents can’t burrow into it, check that the material has not caused any damage to the roof or to the roof glazing and caulking and check for damage to the material itself. Usually, removing the shading material goes hand in hand with cleaning the glazing beneath it.
Check your lighting system. Make sure that it’s ready to face the winter. Remember that fluorescent bulbs gradually weaken and may need to be replaced long before they actually fail. The ends of the tubes of older fluorescent bulbs will turn black. When you see this telltale blackening, change them. Clean all reflectors, and the tops and bottoms of lights, and check terminals for corrosion. A quick spray with CRC or a similar anticorrosion and lubricant material can prolong terminal life indefinitely.
Check the heating system. I find it’s best to do this check in August so that I have time to order parts to correct any problems. If you wait until late September or October, when the greenhouse is full of plants, it could be difficult to get parts and repairs done in time to heat the structure before the first frosty nights.
Start by cleaning the thermostat with compressed air to get rid of spiderwebs and insect debris. You may also have to wipe the contacts if they are exposed to ensure that they make and break properly. A quick swipe with an emery board cleans any exposed contacts. Look over all the wire connections to make sure that none is loose or about to break. Check the cable from the thermostat to the burner to make sure no portions are frayed.
Check the on/off valves of propane or natural gas burners. Make sure that they move freely. Look over the wiring and the burners. Clean all the debris and soot from heating units. Light the pilot light and confirm that the burner goes on when the pilot is lit.
If you have a hot water baseboard heating system and haven’t been doing so on a monthly basis, vacuum all the fins on the heating pipes and make sure that air can flow freely to the burner or furnace.
Check furnace filters, burners, flue pipes, motors, and igniters. Make sure that the burner chamber is free of soot, which can increase energy usage by up to 10 percent. Check that the furnace runs smoothly and operates within a few degrees of the thermostat reading. Make sure that the flue has no leaks or holes created by rust, and repair all problems.
Note: A wood-burning stove and chimney should be cleaned and checked for damage and leaks in spring, after the winter’s heavy use. At the same time, cover the log pile (you may want to purchase wood early on, when prices should be lower, and allow it to dry for a few months) so that it’s ready for winter. Sprinkle stove ashes on your garden or add them to the compost heap to be mixed with composting materials.
Perform a greenhouse heat-retention check. Look to see if you need to apply additional glazing or an inner liner to the greenhouse to increase heat-retention capacity. You may want to install weather stripping or other materials to increase the R-value of the glazing. Check doors and windows to make sure that weather stripping and seals are in place and functioning properly.
There are a number of chores to be taken care of if you plan on shutting down your greenhouse for the cold winter months.
Choose and install a rodent-deterrent method. A greenhouse is a great place for these small animals to set up house in the winter.
Store items safely. Wheelbarrows, lawn chairs, outdoor furniture, and garden carts should be stored in the greenhouse away from where any leaks might occur. Take your lawn or deck chair cushions into the house, where they will remain clean and dry.
A greenhouse should be protected and maintained just as you maintain your other assets. It adds value to your property and provides you with the means to unwind and enjoy your hobby. Keeping it in tip-top shape preserves and perhaps increases your enjoyment of it as well as its overall value.