Get It Growing: Growing a greenhouse Greek salad

This is the year! This is the year I will make Greek salad with produce grown in my own garden, or more correctly, grown in my new greenhouse (see recipe in trailer).

In past years I have at times — but not consistently — grown a few tomatoes, cucumbers and peppers successfully in my particular micro-climate along the Strait of Juan de Fuca. Sure, it’s supposedly a Mediterranean climate, but with a lot of wind and not much heat. The average temperature can be 3-6 degrees cooler in summer than downtown Sequim, only 6 miles away.

Tomatoes, peppers and cucumbers are warm weather crops and enjoy a long, warm growing period. The cool growing season can be a challenge, but one that can be solved in a greenhouse.

Problem solved? Not entirely. While a greenhouse is an excellent way to modify the growing climate by increasing the temperature at both ends of the growing season, it will require some extra time and attention. Greenhouse-grown crops can suffer from several problems, including temperature extremes, excessive humidity and lack of pollination.

Get venting

Even on a cool sunny day, greenhouses can get very hot. Good ventilation is the first step in temperature control. Automatic roof vents in combination with lower side vents are a good start. The warm air will rise pulling cooler air in through the lower vents.

If vents are not sufficient, an exhaust fan is a tool to keep the air moving. This expels the hot air as it effectively pulls in fresh air to increase air flow and cooling. It will also help moderate excess humidity.

Ironically, a greenhouse can get too much sun. A shade cloth to filter out the intensity of the mid-day sun and protect the plants from scorching is usually required, especially in a glass greenhouse.

Other considerations

While the climate controls touched on above are critical, other best practices such as seed selection, pollination and good hygiene are important.

Favorite garden varieties of tomatoes, peppers and cucumbers can be grown in a greenhouse, but consider selecting a variety specifically bred for greenhouse conditions for better success. These varieties have good heat tolerance, disease and disorder resistance and can be found listed in popular seed catalogs.

Pepper plants will stay compact, but train indeterminate varieties of tomatoes to a main stem or leader. Cucumbers can also be grown up a trellis or net which keeps them off the ground and saves space. Plants that are too closely spaced or that grow too dense can greatly reduce air movement.

Just like in an outdoor garden, too little or too much water can both cause problems. A timed and closely monitored drip system is highly recommended for greenhouse plants.

Pollination power

Most tomatoes, peppers and cucumbers are self-pollinating, meaning they have both the stamen (male) and pistil (female) parts on each plant. They do, however, need the pollen they produce to move from the stamen to pistil.

Outside the greenhouse, pollination is usually satisfied by insects and air flow. Inside a greenhouse, you may need to alter conditions and manually aid pollination. Some cucumbers are parthenocarpic, meaning they don’t even need to be pollinated (read the catalog descriptions).

There are several ways to help with pollination. Once the flowers are in bloom, rattle the supports or gently flick the flower clusters every day to spread the pollen. To mimic the action of insects (especially for cucumbers), hand-pollinate using a very soft paint or make-up brush (natural fiber is best).

Gently twirl the brush into the open male flower(s) to collect and transfer pollen. If self-pollinating more than one variety, use a separate clean brush for each.

Photo courtesy of Image courtesy of Utah State University Extension

Excessive humidity can make the pollen too heavy to move around, so choose a time of day with the lowest humidity to self-pollinate. Midday is when pollen is normally distributed.

Keep it clean

Keeping the greenhouse clean can stop problems before they start. Avoid bringing regular garden soil into the greenhouse. It’s best to start with a growing medium that is clean and free of pests and disease. If reusing pots, give them a 1/2-hour soak in a 10% bleach solution (rinse well) to sterilize.

When bringing potted plants or starts into the greenhouse, check them carefully for bugs, including little fungus gnats, in the soil. It’s always a good idea to keep new plants quarantined until you know they are pest free.

For more detailed information on growing vegetables in general, including pest management, disease identification and plant management, the WSU Fact Sheet, Home Vegetable Gardening in Washington, is a good resource. It can be downloaded free at pubs.extension.wsu.edu and search for “WSU publication EM057E.”

Susan Kalmar is a Clallam County Master Gardener volunteer.

Greek salad

1 cucumber, sliced

2 large tomatoes, chopped (or equivalent cherry tomatoes cut in half)

1 (6 ounce) can pitted black olives

1 green bell pepper and 1 red bell pepper, chopped

1 red onion, thinly sliced

1 cup crumbled feta cheese

6 tablespoons olive oil

1 lemon, juiced

1 teaspoon dried oregano

Ground black pepper to taste