Days to germination: 14 to 21 days
Days to harvest: 100 days
Light requirements: Full sun
Water requirements: Frequent but light watering
Soil: Well-drained with organic matter
Container: Suitable but not ideal
Though flax may be better known as a crop grown for its fiber, the seeds are nutritious and eaten as an additive to many foods.
Linseed oil comes from flax seeds, and the seeds themselves are high in fiber and omega-3 fatty acids. Though seldom eaten on their own, they are an excellent supplement to many dishes. It has a slightly nutty flavor.
Flax may be grown for its seeds, but it is not your typical grain plant. It is more like an ornamental with a lovely blue flower. Some varieties of flax are annuals, and some are perennials. The type of flax usually grown for seed harvesting has the botanical name of Linum usitatissiumum and is not usually considered a floral garden plant. It may not be sold at your local garden center, but seeds can be purchased online or even at some agricularal co-ops. This kind of flax is an annual, so you don’t need to overwinter your plants.
Starting from Seed
Flax can be started indoors, and then transplanted out later or just sown directly into the garden. If you have a short growing season, you may want to start your seeds inside so your plants can mature and go to seed before the frost.
In small peat pots, plant seeds 5 weeks before your expected last frost date. Keep them in a sunny place and water often enough that the soil does not dry out. They take a while to germinate, so be patient.
Dig your soil well, and add in a good helping of aged manure or compost before you plant. Flax thrives on organic-rich soils. Your plants won’t get overly tall, seldom higher than 3 feet so shading shouldn’t be a huge problem.
Seeds can be sown out early in the spring, and covered in just a thin layer of soil. Keep your seeds about 12 inches apart, or at least thin down to that spacing once your plants start to come up. You can do this a week or two before your last spring frost.
Because it can take up to 3 weeks before you see any sprouts, you will have to keep the area well-weeded or you may find your flax seedlings are overwhelmed before they can get established. Mark where the seeds are so you don’t accidentally weed out something you shouldn’t.
If you are putting out started seedlings from indoors, its best to wait until the frost has passed.
Flax will needs a lot of nutrients, so you should give your plants a feeding with a standard formula fertilizer once a month through the growing season.
You will also have to water fairly frequently, though not overly heavily. Flax does best in moist but not soggy soils. Good drainage is important.
Though the flax plant is small enough to be grown in containers, the number of plants you will need may make it a difficult task. As with any seed crop, one plant usually produces a very small yield. In order to get a reasonable harvest, you need to plant a larger number of plants. Trying to do this with containers is usually inadequate.
Pests and Disease
Flax is quite prone to various fungus infections, so be prepared with the fungicide if you are going to grow flax. Many kinds of rust and wilt can infect a flax plant, so you need to be on the lookout for any strangely colored patches on the leaves, or wilting stems. Treatment with a regular fungicide is a good idea.
If that wasn’t enough to deal with, there are a few insects that are a problem with flax as well. The flax bollworm is one such pest. The adult moths lay eggs in the flowers, which hatch into hungry green striped caterpillars that eat the seeds out of the pods. Treating the plants with pesticides when the flowers are blooming can help to control the adults, and you should pick off any caterpillars you see later in the season.
Typical garden cutworms are also an issue with new flax plants. If cutworms are present in your area, use small cardboard collars to protect your seedlings or they may get sliced right through overnight. Once they are more mature, cutworms should not be an issue.
Harvest and Storage
Your seeds are ready to harvest when the large seed pods are yellow and starting to split open.
Cut the pods from the plants, and spread them out somewhere where they can dry further (not out in direct sunlight). Once the seeds are dead ripe and cannot be dented with a fingernail, you just have to separate them from their seed pods. For a small harvest, you can manually pop open each pod and take out the 4 to 6 small seeds inside.
If you have more flax to deal with, you can crush all the seed pods at once (also called threshing), by whatever means you wish. You can put them in a bag or pillowcase, and beat them against a railing or a chair, or even crush them underfoot.
Then you can use a fan or the wind to help sort the seeds from the debris. This step is called winnowing. Use a couple of containers, or even do it over a large sheet. Just pour handfuls of the debris from several feet up, and let the wind blow out the lighter pieces of leaves and seed pod. The heavier seeds will fall straight down.
As long as the seeds are completely dry, you can store them in any tight container for 8 to 10 months at room temperature. It can also be stored in the refrigerator, but it doesn’t usually prolong its life any longer. That might be a more suitable option though if your house is warm.
For an expected harvest yield, a quarter acre of flax will provide you with at least a bushel of seed.