How to Grow Kale in the Portland Area

Kale is a delicious versatile green beloved by many. It is a vegetable that can really thrive in our climate and can be grown nearly year-round. It can also get destroyed by pests if measures aren’t taken to prevent damage. Perhaps one season your kale grew wonderfully and the next it was riddled with pests. Many folks give up on kale altogether because of this, but once you know a few strategies to address common issues, you will be able to grow beautiful kale with much more consistency.

Sunlight:

Kale thrives in full sun, but compared to many garden veggies it can tolerate more shade than some others. In the summer your kale can tolerate and even be happy with some afternoon shade (particularly during the hottest hours of the day). During winter, kale prefers as much sunlight as possible. Regardless of the spot you choose, make sure the kale will receive a minimum of 6 hours of sun per day.

Fertility and plant spacing:

As with all veggies, excellent fertility is of the utmost importance and kale is a relatively “heavy feeder”. This means that in most cases, in addition to the foundational spring soil amendment (see this blog post to learn more about that) kale will do well to have ¼ cup of all-purpose organic fertilizer mixed into each hole when you are transplanting the starts. Although the starts looks small at the outset – don't get fooled. Give the kale plants at least 18” between themselves or any other plants. If the kale is next to a plant which will grow taller than it (say a tomato) make sure to place the plants strategically so they get enough sun. Put the taller plant to the north of your kale or (only during the summer) to the west of your kale (which will only block sun in the heat of the day.)

Timing of Planting and management:

Spring kale:

March is an ideal time to plant your Spring kale (although you can plant as early as late February or through the month of April. Early in the season, we recommend covering the plants with a floating row cover, sometimes called frost blanket. This will make your kale grow more quickly AND protect it from insects and bird damage. You can grow beautiful kale without cover at this time of year, as it is quite frost tolerant, and pests are typically not as active. It will simply be more at risk to pest damage and grow more slowly.

Using a frost blanket or 'row cover' can help early spring plantings from being damaged by freezing temperatures

Fall and Winter Kale:

While it is possible for your spring kale to maintain health for the whole season and last through the winter, you cannot count on it happening every year. For that reason we generally plant our overwintered kale between mid-July and mid-August. Kale is a cool season crop but you will be planting it in the heat of summer, so you do need to take extra care growing it during this generally hot time of year. Make sure to avoid planting it directly before a hot spell, and provide the plant with plenty of water. Additionally, pests will be very active this time of year and your plants will be small, so pest management is very important for success. That being said, if you are able to establish healthy plants heading into the colder months, you will have lovely greens to eat all winter long!

Pests:

*Please note we are not paid by anyone to recommend any products we discuss below. We are simply sharing practices / products that have worked well for us.

There are four main kale pests that are important to know about: aphids, cabbage looper maggots, slugs and birds. If you consistently address anticipated pest issues from the start, you should be able to maintain relatively pest free plants with only 10 minutes of your time every other week.

First, to address aphids, you must get to know what an aphid looks like! Then, you will thoroughly search your plants for them bi-weekly and use insecticidal soap to kill off any aphids you find. Make sure the look under any curled leaves and all the itty bitty new growth – they are VERY good at hiding!

Second, for cabbage loopers, it is less important to know what they look like because the management is preventative. If there are no eggs or caterpillars on the leaves, covering the kale with frost blanket (in cold months) or insect netting (in warm months) is an effective method to prevent cabbage looper from reaching the plants. If your kale has no cover, thoroughly spraying the plants with Bt every other week should keep the caterpillars at bay.

Bt (‘Bacillus thuringiensis’) is a non-toxic bacterial spray that interferes with the digestive systems of the caterpillars that feed on kale and other brassicas. Make sure to find a dry window and/or spray the bottom of the leaves to prevent the rain from immediately washing it off the plant. Additionally, because Bt is a living organism, it can be killed by high temperatures, so avoid spraying Bt during the hottest part of the day for maximum efficacy.

Third, in the cooler, wet seasons of the year, we find it works well to preventatively apply Sluggo weekly or bi-weekly. You want to apply it BEFORE you see slugs because once the slugs are in your kale plant, the Sluggo won’t be as effective. That being said, at any time of year, if you see any evidence of slugs, immediately apply Sluggo and do a thorough search of the leaves removing any slugs you find.

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Finally, if you are taking all of these measures and you are STILL seeing a series of little holes that are generally near the flattest part of the leaf, it is likely from little birds that are perching on the leaves and pecking for a snack. Just start watching the plants and you will see them. If you don’t mind a few holes, this actually does not damage the quality of the greens from a culinary perspective. Perhaps the easiest option is to accept some leaf damage. Other options are to grow curly or frilly leafed kale that birds cannot perch on, or to keep your kale covered with insect netting, bird netting or frost blanket.