How to Harvest Lettuce Seed

Saving lettuce seeds is a fun and sustainable way to garden that also saves you money and helps you grow plants adapted to your specific growing conditions.

If you continue to save seeds each year, you’ll eventually end up with lettuce that is better suited to your garden than seeds from off the rack. Knowing how to save your own lettuce seed also protects you from seed shortages, shipping delays, and ever-changing seed catalogue offerings.

Lettuce is a fairly easy crop to grow and a beginner-friendly plant to save seeds from. Saving your own lettuce seeds is a rewarding activity for both beginner and long-time gardeners.

Here’s a full guide on how to harvest lettuce seeds and save them for next year’s garden.

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Selecting the Right Lettuce Plants for Seed Saving

One of the first steps of seed saving is actually choosing the right plants to save seeds from.

To start with, you only want to save seeds from heirloom or open pollinated lettuce varieties. Hybrid varieties have been carefully bred for desirable characteristics and most often will not come true from seed.

This means you need to choose the right kind of lettuce before you even plant it.

Most heirloom varieties are clearly labeled, but you can do an internet search or ask the company you are buying from if there’s any confusion over what type of plants or seeds you’re getting.

If you’ve already planted your lettuce, there’s no harm in saving seeds, even if you’ve planted a hybrid variety. Just be aware that you’ll probably end up with a “surprise” lettuce when you plant seeds next year.

Once your lettuce plants are full size and happily growing in your garden, the next step is to select your favorites for seed harvesting.

Choose the ones that have the best flavor, color, texture, etc. and that look the healthiest and the strongest. You can get quite a few seeds from a single plant, so you only need to set aside one plant from each variety for harvesting seeds.

If you want to know more about the art and science of saving seeds, get a dedicated book like The Complete Guide to Saving Seeds. It doesn’t just tell you how to save seeds – it also includes information on how to germinate seeds and pollinate plants. Germination requirements vary widely for different plants. It doesn’t do you any good to have seeds if you can’t get them to grow!

Growing Lettuce for Seeds

Growing lettuce solely for the leaves is a little bit different than learning how to harvest lettuce seeds from your plants.

Normally, you harvest lettuce leaves frequently and try to prevent plants from bolting. Bolting is what happens when plants send up a flower stalk and the leaves turn bitter. To learn more about this process, see this complete post on bitter lettuce.

However, in order to collect seeds, you need your plants to bolt and flower. (If you have no idea where lettuce seeds come from, it’s probably because you pull lettuce out before it flowers.)

Once you’ve picked out your favorite/healthiest plant (or plants), you may want to stop harvesting leaves from them.

Your lettuce needs its leaves so that it has energy to put into flowering and producing seeds. This is especially true if you’re saving seeds from a fall planting of lettuce that may winter kill before the seeds are mature if you delay flowering. This is less of a concern for spring lettuces since most vanities bolt quickly when warmer temperatures arrive.

That having been said, as long as your plant has enough leaves to create a flower stalk, it will eventually bolt. I never grow true head lettuces, only leaf lettuces that I pick frequently. When I’ve saved seeds in the spring, summer, or indoors, I’ve harvested the plants regularly before they successfully produced seed.

Then, simply let these designated plants go through their normal cycle of sending up a stalk, flowering, and going to seed.

Preventing Cross Pollination of Lettuces

If you’ve never seen lettuce flower before, it’s quite an interesting sight. Plants typically grow to 2-3 times their normal height. They can shoot up over night.

I let lettuce go to seed in my dining room (yes, you read that right) to take photos for this post. The photo below was taken on January 4. You can see the central stalk starting to form:

Just five days later, the lettuce shot up to more than twice its original height:

The flowers lettuce produces are fairly small. I think they’re pretty cute! You need to notice when your lettuce flowers because this is when cross pollination becomes a factor.

Cross pollination is when pollen from one type of lettuce (a red butter lettuce, for example) is carried by the wind or insects and pollinates a different type of lettuce (a green leaf lettuce, for example).

The result is that if you collect seeds from the plant that was pollinated, those seeds will end up being a cross of the two different types of lettuce, instead of being true to the type you want. This new variety might be amazing and delicious, or it might be undesirable to you. You won’t know until you grow it next year!

If you’re only growing one kind of lettuce in your garden, you don’t need to worry about cross pollination.

If you’re growing two or more varieties, you should either separate them from one another (Seed Savers recommends an isolation distance of 10-20 feet), or cover each flower stalk with a mesh bag to prevent any other pollen from being carried in.

Lettuce is self-pollinated, so there’s no need to let pollinators get to the flowers.

How to Harvest Lettuce Seeds

When to Harvest

Lettuce plants will typically bolt and flower shortly after the weather turns hot. This could be anytime from sometime in spring to mid or late even summer, depending on where you live, when you planted your lettuce, and what variety you planted. Lettuce will also bolt as it becomes older, even if the temperature is within normally acceptable ranges for the variety. My winter-grown indoor hydroponic lettuces all eventually turn bitter and bolt, even though the temperature inside isn’t too warm for them.

Lettuce seeds form within the flower heads and will continue to develop as the flowers fade and turn a dried up yellow or brown. This typically happens in mid to late summer or early fall, but once again depends on your climate.

These are red oak lettuce flowers maturing on the plant:

Lettuce seed takes a surprisingly long time to mature. Depending on your weather, it may feel like your lettuce is producing seed for longer than it produced tasty leaves for you to eat!

When you see white puffs coming out of the flower heads, you’ll know it’s time to harvest. The seeds are attached to the other end of the white fluff and will come out easily when ready.

Here are a whole lot of dry lettuce flower heads. Unless you have a seed selling business, you don’t need to pick this many!

Lettuce Seed Harvesting Methods

There are a few different methods for how to harvest lettuce seeds.

One method is to go out to your plants everyday or every other day to check for mature seeds. Bring a paper bag or a basket with you to put the ripe seeds in.

Then, either bend a flower head over your bag or basket and shake it to dislodge the seeds, or pull out the white puffs one at a time to get the seeds that come with it. (If the puffs don’t pull out easily, the seeds probably aren’t quite ready yet.)

This may sound tedious, but it’s pretty easy and you don’t actually need to collect a ton of flowers. One plant will produce way more seeds than you’ll actually need for next year.

Another option is to simply clip off whole flower stalks when most of the seeds are mature. You can then take them inside and shake or pull out the puffs and seeds.

This method is quicker, but you will end up with a collection of fully ripe and not fully ripe seeds.

Storing Lettuce Seeds

After you’ve harvested your seeds, the next step is to separate them from the chaff and fluff that come along with them.

Before trying to separate the seeds from the rest of the debris, first make sure they have been removed from the “puff balls.” They should come loose with a gentle tug or by rubbing them between your fingers.

After this, some people have found it useful to turn on a fan (a gentle one) to blow away the pieces of fluff. You can also simply pick out the larger pieces of debris by hand.

A little leftover chaff won’t affect the seeds at all, so don’t feel like you have to get them perfectly clean.

Once they are cleaned, lay the seeds out on a dry surface out of direct sunlight to continue drying for about a week.

Eventually you’ll have nice, dry, hard little seeds that you’ll be able to plant with pride next season. It is so exciting the first time you grow something from your own seed!

Per advice from Carol Deppe’s The Resilient Gardener, I now dry my seeds in my food dehydrator on low. I rip a paper towel into several pieces, weigh down the corners with something like a large binder clip or a clean, small rock, and place the seeds on top. Lettuce seeds fall through the cracks unless you have a very small mesh screen in your dehydrator. If you don’t weight the paper towel, it will flutter around and dislodge your seeds.

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You can then store them in airtight containers or packets and place them in a cool, dry, and dark spot until next year. Stashing them with a silica gel packet can help ensure they stay dry.

Lettuce seeds typically remain viable for 4-6 years, if properly dried and stored.

Remember to Label your Seeds!

As you enjoy learning how to harvest lettuce seeds, remember to label throughout the process! Mark down different varieties, the date you harvested, and any other details you want to remember. Lettuce seed appearances do vary (for example, Black Seeded Simpson has black seeds, but many other lettuces have lighter seeds), but they can be incredibly difficult (or downright impossible) to tell apart if you forget to label.