The outdoor growing season for vegetables In Ocean Shores is relatively long for the Pacific Northwest because of the mild coastal climate. But summers are cool and mild, not hot, and at times windy.

Typical Ocean Shores growing season estimates are:

• You can often garden outdoors from March through November
• Frost-free growing season: about 200 days
• Average last frost: early April (April 6–20)
• Average first frost: late October to mid-December
• USDA zone: generally, 9a near the coast

Warm-season crops like tomatoes often struggle here but chances for success increase by growing short-season tomatoes. Popular short-season tomato varieties include Early Girl, Stupice, Glacier, Sub Arctic Plenty, Fourth of July and Siberian with expected maturities between 45-60 days after transplanting. In comparison, long-season tomatoes such as Brandywine, Cherokee Purple, Mortgage Lifter, San Marzano, Beefsteak, and Pineapple have maturities of 75-100 days.

TECHNIQUES FOR COUNTERING OUR COOL CLIMATE WHEN GROWING TOMATOES

The following ideas are based on first-hand experimenting while growing tomatoes in the PNW.

Warm Roots Matter More Than Warm Air

Tomato roots love heat, so an objective is to keep them as warm as possible. Even if the air temperature is cool, keeping the roots warm can significantly increase the odds of a good crop. Here are some tips to help accomplish that.

Covering your garden area — for example, a 4 x 8 bed — with black plastic helps retain a surprising amount of heat. In a bed that size, you can simply cover the entire area, then cut openings where each tomato plant will go. For example, cut an X in the plastic enough to expose a 12”x 12” area when the excess plastic is removed or just folded underneath.

Plant the tomatoes so that they are at least one to two inches lower than the surrounding ground level. This creates a trough which helps a LOT where watering is concerned. Also build up a wall of dirt around the trough area to further contain the water. If this is not done, the water can run all over the garden bed rather than staying at the tomato plant. Just put water in the trough. Other benefits of this include efficient water use and reduction in weeds since they will not be watered.

If you’re using drip irrigation under the plastic, lay the drip line first, with the emitters positioned where the plants will be. Then lay the plastic over the top, noting where the emitters are located before cutting away the plastic.

Two other advantages of using plastic sheeting are moisture retention and weed control. The plastic helps keep the soil from drying out and greatly reduces weeds. A few rocks can help keep the plastic in place when the wind kicks up. You can also throw a little soil on top to hold it down, but weeds can easily grow in as little as ¼ to ½ inch of soil, taking root right on top of the plastic.

With drip irrigation to automate watering, and plastic to contain the weeds, the time and effort to maintain the garden through the summer is minimal.

One additional tip: lay the plastic down a week or two before planting if possible. This gives the soil time to warm up before the tomatoes go in, which can make a noticeable difference in our cool coastal climate.

Plant The Tomato At An Angle

Another good way to keep tomato roots warm is to position more of the root system closer to the surface, where the soil is warmest under black plastic. To do this, dig the planting hole more like a shallow trench, roughly a foot long. Remove a few of the lower leaves from the stem, then lay the plant into the trench at an angle so the stripped portion of the stem will be buried underground.

I’ve buried as much as a foot of green stem before. Tomato plants can grow roots directly from the buried stem, so instead of having one compact root ball deeper in the ground, the plant develops roots along the entire buried section. Because the plant is laid at an angle, many of those roots end up closer to the warmer surface soil.

Combined with black plastic, this can make a big difference. A larger root area stays warmer and provides more nutrients for the plant, helping it becomes stronger and better able to handle our cool coastal climate.

This method does have a couple of drawbacks. Since the plant starts out leaning sideways, the top will naturally bend upward toward the sun over time. Stake the plant early to support it as it straightens out.

Another thing to keep in mind is that the roots extend sideways underground much farther than normal. In some cases, you could have roots running nearly a foot away from the visible stem. If you forget that later in the season and dig or plant too close nearby, it’s easy to accidentally damage part of the root system.

Still, the main advantage of this approach is that it creates a much larger, warmer root zone, giving tomatoes a better chance to thrive despite Ocean Shores’ cool weather.

The Wind

One of the biggest challenges in Ocean Shores is protecting more delicate plants from the steady coastal wind. Tomatoes, especially the larger indeterminate kind, fall into that delicate category.

Even with all the tricks above to keep the roots warm, and even using cages or other support methods, the wind can make growing tomatoes outside impossible since they are just not sturdy enough to withstand it. 

The prevailing wind direction in the warmer months in Ocean Shores is typically from the northwest to west/northwest. This is important to note when considering the wind mitigation technique discussed below.

For gardening purposes, the important seasonal wind pattern is roughly:

• March–April: often still rough, with strong coastal storms and frequent gusty days
• May: conditions usually begin improving, though windy periods still happen
• Late May into June: winds often settle down noticeably
• July–August: generally, the calmest and safest period for tender plants

Even when average winds decrease, Ocean Shores occasionally get strong gusts anytime because of coastal weather patterns.

The sooner you get your starts in the ground, the longer their growing season will be, leading to more mature plants and greater harvests.

A simple and effective wind mitigation technique is to put in place a plastic wall as you see in the pictures. To do this you’ll need:

• Poles
• Binder Clips
• Clear durable (4 mil) plastic sheeting

Only two of the 4 sides of the bed have the plastic wall which is oriented to block the northwest winds. This also helps with a little more heat retention inside the growing area.

The top picture is my bed not too long after the transplants are put in. The picture below it, is the bed mid-summer.

The binder clips make it very easy to open the entire bed for access to all sides for maintenance and harvesting. Circles cut into plastic walls at strategic locations allow air flow into the bed area, keeping the air fresh and moving which helps with pollination by moving and shaking the plants.

I used bamboo poles, but any pole that fit large size binder clips should be fine.

As an experiment last year, I grew one beefsteak tomato plant. The harvest was low but there were 5 full sized ripe and delicious beefsteak tomatoes! With a more watchful eye for when to add the proper nutrients to enhance flowering and fruit growth, and proactive pollination management, there is a good chance that harvest can be even better.

And that’s it! Warm roots and wind control can significantly increase the chances for a high-yield tomato harvest even when growing them outdoors in Ocean Shores.

For more information on this article or Garden by the Sea, contact us at info@gardenbytheseaoceanshores.org.