Most warm-season vegetables (heat-lovers like tomatoes, peppers, eggplant, squash, and beans) can be grown here in the Pacific Northwest..... If you can give them the right conditions. But with our cool, wet springs and short summers, sometimes it can seem like an uphill battle. Luckily, there are ways to ensure success for the PNW gardener, from season-extending tools to growing tips for happy plants and great harvests.
How to Choose the Right Plants
Swansons' growers provide us with varieties of plants and seeds that generally grow well in our PNW conditions. When choosing varieties, here are some other tips to help you succeed.
Tomatoes - For reliably large harvests, cherry tomatoes are the way to go in the Pacific Northwest. Even during a colder or rainy summer, they will have time to ripen. If you desperately want large tomatoes, try an early variety (look for days to maturity signs and try to find varieties with less than 75 days).
Peppers - Look for smaller peppers and those that taste great green as well as fully ripened to orange or red. Hot peppers may not be as spicy if growing conditions aren't ideal.
Eggplant - try smaller Asian varieties, which will ripen more quickly.
Curcubits - The plants of the Curcubit family include summer and winter squash, cucumbers, melons, and pumpkins. Summer squash and cucumbers usually do well in our area if they have enough light. Try smaller varieties of winter squash, mini pumpkins, and melons bred for a short season.
Beans - Beans grow quite well in the PNW. Choose pole or runner beans for harvest over a long season and provide them with a trellis for support. Bush beans generally ripen over a shorter period and do not need supports.
When to Plant
Warm-season vegetables are tender annuals in our climate and cannot handle cold, wet weather or frost. These vegetables are best planted outside when the weather begins to warm up in May and June.
Season-extending tools can help you plant warm-season vegetables earlier and encourage them to grow in cooler weather. Harvest Guard® (also called row cover) is a lightweight fabric that can be draped over garden beds or even wrapped around tomato cages to help warm the air and soil. You can also try Season Starter™ plant protectors around small tomato, squash, eggplant or pepper plants. This is a ring of flexible plastic tubes that can be filled with water to form a sort of warming tee-pee around the plants, which can be removed once the weather warms up and the plants outgrow it. Remember to open any covering during the day when plants are in bloom, to allow for pollination!
Sun & Warmth
Most warm-season vegetables need full sun, meaning at least 6-8 hours of sun each day. More sun is even better! Try a west- or south-facing area of the garden or use pots that you can move around to follow the sun. Planting warm-season veggies against a west- or south-facing wall can also help radiate even more heat for them to enjoy.
Warm-season veggies need a lot of space to thrive. If you've ever seen a pumpkin patch, you'll understand what I mean. Space is important for root and foliage growth but also for adequate air flow. Give your plants room to breathe! Read the individual plant tags to determine the recommended spacing for your specific vegetable varieties. If you lack garden space, try trellising plants such as beans, cucumbers, squash, and pumpkins vertically to save room.
When growing warm-season vegetables in pots, always choose a bigger pot than you think you need (trust me). Large pots give your plants room to grow strong root systems and also need to be watered less often than smaller containers. As a rule of thumb, pots should be at least this deep for the following plants:
Tomatoes & summer squash - 12-14"
Eggplant - 10-12"
Cucumbers - 9-12"
Bush beans - 8-12"
Peppers - 8"
Melons, winter squash, and pole beans are not recommended for containers.
All vegetables need consistent water to thrive. Create a schedule to help you water regularly but allow yourself the flexibility to adapt to changing weather conditions (hotter weather = water more often) and to your own observations. If you notice, for example, that the surface of the soil is still damp when you plan to water, you might wait a day or two before watering, making sure, however, that the plants do not dry out entirely or begin to wilt.
A drip irrigation system or soaker hose is the best option for watering in my opinion, but if you decide to water by sprinkler or by hand be sure to water in the morning so the leaves have a chance to dry before evening. Morning watering is best no matter what type of watering system you use because it is cooler so there will be less evaporation.
Mulching can help conserve moisture. Try adding a 1-2" layer of compost around the plants, which has the added benefit of offering extra nutrients to the plants. I like E.B. Stone™ Organics Planting Compost for my vegetable garden.
Speaking of nutrients, warm-season veggies have a short period of time in which to do a lot. They have to form strong root systems, lots of leaves, grow big and strong, produce flowers, then fruit, and then ripen the fruit all in our short PNW summers! The more essential nutrients they have the better.
The first step is adding compost to your garden soil before or when planting and mixing it well with the existing soil. This step isn't necessary for containers, but be sure to use a high-quality potting soil to fill your pots.
Next, add some natural fertilizer at planting time, following the directions on the package; I really like Dr. Earth® and Espoma® tomato and vegetable fertilizers. Most warm-season veggies need to be fertilized at planting and then again 3-6 weeks later. The exception is beans, which don't need any additional fertilizer after planting. Potted vegetables often need even more frequent feeding because nutrients are washed away more quickly.
When planting tomatoes, remove the bottom third of leaves and plant the stem deeply into the soil. The plant will put out roots from each node where the leaves were removed for a more vigorous, layered root system and stronger plant!
Members of the Curcubit family dislike being transplanted. You can avoid this by sowing seeds directly into the ground in May or June (using season-extending tools to help them germinate and grow). However, starting with small plants from the nursery offers a head start on the growing season. When transplanting, just try not to disturb the roots too much. If there are several plants in one pot, plant them all together without separating them and snip off all but the strongest looking plant. It might be hard to do but it's definitely worth it to have a happy, strong plant!
Beans are similar to Curcubits in that they don't like their roots disturbed. Luckily, they are easy to start from seed directly outdoors. The plants are also often sold in packs that contain 4-6 "cells". Plant each cell together unless they break apart naturally and snip off extra plants to thin according to the directions on the tag. Bush beans generally like to be 4-6" apart while pole and runner beans should be spaced 6-10" apart.
Harvesting, like voting in Chicago, should be done early and often. It's surprising how quickly baby vegetables can grow and many taste better when smaller (especially green beans, squash, and cucumbers)! If you leave vegetables to over-ripen, the plant thinks it has done it its biological duty (producing seeds to procreate) and will slow down on production. Plus, no one wants a 4-foot zucchini.
If cold weather is on its way and your tomatoes and peppers haven't fully ripened, you can pick them and bring them in to ripen inside. Try placing them near an apple, which produces a gas that causes fruit and vegetables to ripen more quickly. Another, albeit more dramatic, tactic is to uproot the entire plant and hang it upside down inside a garage or basement to ripen. Some people swear by it. I find it creates a big mess.
Pests are a common problem in the vegetable garden, but most often are not serious enough to ruin an entire crop. A combination of preventative measures and vigilance is the best strategy to tackle pests.
To prevent certain pests from getting to the vegetables in the first place, try covering your crops with Harvest Guard® row cover. This lightweight fabric will let light, water, and air in but keep pests out. You can either drape it loosely over the bed to allow the plants to push it up as they grow or use small hoops to keep it above the tops of the plants, then pin the edges with rocks, boards, or garden staples so no pests can fly or crawl inside. Row cover has the added bonus of keeping the air and soil temperature warmer under the cover - great for warm-season veggies as they are starting out!
Slugs and snails can be an issue in the PNW and there are several options to keep them at bay. Row cover can help, but if the slugs find a way under the cover they will just be delightfully warm while they snack. I like to use two methods in combination. I crumble rinsed and dried eggshells and spread them on the soil around the plants. Snails and slugs do not like to cross over the shards because it cuts their soft flesh. Another very efficacious solution is to use a product called Sluggo®. These iron phosphate pellets are ingested by the slugs who then stop feeding and eventually die. Sluggo is labeled safe to use around people and pets.
Two diseases to watch for are powdery mildew and late blight. The strongest defense against disease is strong, healthy plants, so let's start there. Plants that aren't getting adequate light, nutrients, and especially water, are weaker and more susceptible to disease. That said, there are some things that can help.
Powdery mildew is ubiquitous around the PNW and can almost never be completely eliminated. The good news is that if you can keep it contained it will not kill your plants before the cold does. Give your plants enough space so they have good air flow and remove severely affected leaves as you find them. Some people swear by spraying leaves with a mix of baking soda and water or even wetting them down with water once in a while in the morning to wash spores off. I can't personally comment on the effectiveness of these tactics, but feel free to experiment (and let me know the results)!
Late blight is the more serious of the diseases and once a plant is affected, it needs to be removed and destroyed. Trellis and prune your tomatoes to encourage air flow, keep leaves dry, and try to keep water from splashing up from the soil onto plant leaves. Some people mulch with straw or plastic sheeting to help keep splashing of soil to a minimum.
Blossom-end rot occurs when the plant can't take up enough calcium from the soil. Water your plants regularly and if you notice blossom-end rot, add lime to your soil to help make existing calcium available.
Sometimes a plant is thriving and in bloom but the flowers drop off without producing fruit. This can be for many reasons, but one may be a lack of pollination. Try growing pollinator-attracting flowers near or amongst your vegetable plants to bring the bees. You can also pollinate by hand by taking a small paintbrush and transferring pollen from one flower to another (on squash plants transfer from the male flower to the female flower, recognizable by the small, swollen embryonic fruit at the base of the flower stem).
Hopefully, you are now armed with the information you need to successfully grow a multitude of warm-season vegetables. If you still have questions or would like to discuss any veggies not mentioned in this blog post, feel free to comment!
You can also always reach out to Swansons through social media for advice. Just use hashtag #heyswansons!
Our veggie courtyard is still filled with lots of warm-season vegetables and they are 30% off through June 17th, 2018!