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10 Awesome Facts To Grow Lettuce You Didn’t Know

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Grow lettuce at home because it is easy and one of the most popular vegetables among home gardeners. Except for celery and chicory, most green salad plants are easy to cultivate and, except for celery, are among the few vegetables that tolerate moderate shade.

Salad crops, in general, fit into the healthy trend for low-calorie, high-vitamin diets.

Lettuce (Lactuca sativa) is part of the Composite (Asteraceae) family (artichokes, sunflowers, and chicory). Lettuce is a fairly hardy, cool-season vegetable that thrives when the average daily temperatures are between 55 and 65 °F.

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A hundred years ago, all lettuce crops were grown in home gardens. Since then, the popularity of lettuce has rapidly increased, and the latest production statistics show that, on average, each individual consumes about 25 pounds of lettuce per annum [Source].

So, let’s see what it takes to grow lettuce – here are ten facts you may not have known.

1. You Can Grow Lettuce in The Shade But They Like Light

You will note that some of your seed sellers advise you to grow your lettuce in full sun – as long as the temperatures allow. However, lettuce is one of the vegetables that can be grown in shady spaces where other crops won’t cope. It also depends on which cultivar you’re growing.

Studies show that if loose leaf cultivars (Lactuca sativa L.) like Grand Rapids Forcing, Waldmann’s Green, and RubyConn, get extended light (up to 24 hours), their yield can be increased by 30% to 50%.

The same does not apply to butterhead varieties, where extended photoperiodism makes little to no difference.

This is interesting because the heavy varieties tolerate shade better than the head lettuce, requiring at least 4 to 6 hours of direct sunlight to flourish.

My advice – experiment with your lettuce in different light environments and get to develop your own unique knowledge.

Keeping a journal of what you did when and where in your garden helps you better compare results. Log everything you see and do in your garden in your gardening journal.

2. Lettuce Have Shallow Roots

One of the reasons I prefer to grow lettuce from transplants is because of weeding challenges.

There are 27,000 lettuce seeds per pound – they’re tiny little balls of potential.

Seeds that small with very shallow roots make cultivating a challenge – so I only want to add them to a bed or container once they have some life in them.

Shallow-rooted plants have a couple of implications:

  • Water evaporation means your plants need regular irrigation rather than occasional soakings. Low moisture levels can cause lettuce leaves to taste bitter. Drip irrigation or soaker hoses are the best way to irrigate as late afternoon overhead irrigation causes wet leaves and increases the possibility of bacterial infections.
  • High levels of organic matter (compost) benefit water retention capacities, so use enough quality compost rich in microorganisms to boost the soil biota.
  • Leaf picking can stress plants, so cut harvested leaves off using a sharp knife or gardening shears.
  • Intercrop onions or broccoli with your lettuce. Studies show that onions help prevent pests, and broccoli has a similar soil nutrient requirement to lettuce.[Source] Deep-rooted plants help prevent the soil from becoming compacted.
  • Cultivate with care – in situ planting makes it harder to manage weeds early in the planting season. Transplanting grown lettuce makes it easier to eliminate smaller weeds.
Grow lettuce to accompany other salad
French Lettuce

3. Grow Lettuce in Containers For Great Results

When you grow lettuce in flats, tray and get the polystyrene flats that create a tapered wedge root system.

If you are using plastic cells, make sure that the soil doesn’t overlap the top – clean the surface between the cells from any soil.

This is important because it prevents the roots from one plant from intertangling with the roots of an adjacent plant – minimizing stress to the plant when you transplant it.

Wet the mix after filling the trays and leave to soak through. After a couple of minutes, tape the trays on a solid surface to allow the soil to settle, leaving about a quarter-inch gap at the top.

Spead about tree seeds in each cell and cover lightly with perlite – water again until the water soaks through.

Ensure the seedling trays remain damp for the two weeks it takes for the seeds to germinate. Seeds can germinate in two days if the soil is 70 °F and seven days at 50 °F – higher than 70 °F, and they will go dormant.

Place the tray indoors under lights – lights are about 6-inches above the trays. I have an area of wood lined with reflective material that I place my trays into. Springle the seed tray with cinnamon to prevent fungal growth.

Once the seedlings are about three weeks old, start hardening them off by bringing them outside for several hours a day.

This allows them to acclimatize to weather conditions. Keep the trays moist, with short periods of drying out – this too helps harden the plants for life in the garden (containers).

Because lettuce has shallow roots, you don’t need a deep container – I use a 5-quart container with four half-inch holes drilled in the bottom.

If there isn’t a gap between the holes and the bottom surface of the container, use some adhesive to stick 3 to 4 bottle tops on the bottom to allow the container to drain better.

When you grow lettuce it is prone to root rot, so make sure the container drains well. I add a handful of blood meal to the 5-quarts container filled with an equal-ration mixture of coconut coir, compost, and perlite.

The blood meal is a good nitrogen source for the lettuce to produce a leafy harvest—water the mix in well before and after planting. You can fit two seedlings into each container.

4. Lettuce Varieties Are Unique Plants

According to the recently updated USDA Variety Name List, there are 4,427 lettuce varieties. [Source]

Does that make gardeners spoilt for choice or option-dazed? If you think that’s a lot, tomatoes have 6,489 varieties. So let’s shorten the list by grouping types and matching combinations.

Loose Leaf Lettuce (var. crispa)

An easy-to-grow lettuce variety that matures quickly, allowing you to start harvesting leaves as early as four weeks after planting.

It will mature 45 to 60 days after planting, which can be done early in the season – there’s a wide variety of leaf shapes and colors. Popular varieties include:

  • Green Leaf – Green Ice, Grand Rapids, Simpson Elite, Slobolt, Salad Bowl
  • Red Leaf – Lolla Rosa, New Red Fire, Red Head, Red Sails, Navara

Crisphead Lettuce (iceberg, var. capitata)

Crispheads, the most common variety in stores) are the most challenging type to grow, requiring a long cool season and 75 days to mature.

Your best chance of success is by setting out transplants in early spring. Please beware that crispheads will bolt quickly in response to stress.

Keep 18-inches apart in rows and space rows approximately 12-inches. Popular varieties include:

  • Great Lakes
  • Ithaca
  • Summertime
  • Tom Thumb
  • Raider
  • Nevada
  • Hollywood
  • Sioux
  • Webbs Wonderful

Butterhead lettuce – Also called bib, loosehead, and Boston lettuce

A type of lettuce known for its delicious flavor and quality and forms loose heads with oily leaves. Butterheads take between 55 and 75 days to maturity.

Compared to crisphead lettuce, butterhead types are softer and more fragile in texture and have thicker leaves and a smooth, buttery substance.

Butterhead types are more perishable than the crisphead varieties. Popular varieties include:

  • Buttercrunch
  • Esmerelda
  • Four Seasons
  • Diana
  • Tom Thumb

Romaine Lettuce – Also called Cos lettuce (var. longfolia)

Cos lettuce [Romaine] or celery lettuce has an elongated framework, smooth outer leaves, and a blanched inner head.

The leaves are more brittle than the other heading types, the midrib is heavier, and the flavor is uniquely sweet and mild.

Cos types usually take 65 to 70 days to mature and have the same essential planting and cultural requirements as the other heading types. The most popular varieties are:

  • Cosmo Savoy
  • Green Towers
  • Little Gem
  • Parris Island
  • King Henry
  • Sunbelt
  • Green Forrest
  • Darkland
  • Rosedale is a red variety

Grow Lettuce Called French Lettuce (also called summer crisp)

A type midway between a butterhead and crisphead lettuce.  You can harvest early, similar to leaf lettuce, or wait until heads form fully in 50 to 75 days.

  • Sierra
  • Cut and Come Again Mixes

5. Lettuce Grow Well in Vertical Gardens

In commercial hydro- or aeroponic systems, the debate is generally between the choice of Vertical Farming Systems (VFS) and Horizontal Hydroponic Systems (HHS). The study extract below settles the discussion.

They grow lettuce vertically in upright cylindrical columns comprised of individual modular units stacked on top of each other to reduce the system footprint. Each modular unit consisted of two stackable elements: a growing container (5-inches high and 3-inches radius) and a spacing collar (8-inches tall and 3-inches radius).

Five growing containers and six spacing collars were sterilized before filling each container with 130 g ± 0.5 g medium-grade.

Highly porous perlite was the substrate of choice to minimize the risk of root‐zone hypoxia and the resultant accumulation of ethylene within the airspace of the vertical column.

The perlite was held in place by horticultural frost fleece at the bottom of each growing container. The perlite in each container was leveled, and seedlings were placed on the perlite at 90° to the horizontal.

Each VFS contained 20 lettuce plants in total. The distance between the top of the VFSs and the light was 32-inches.

The results show that crop productivity, defined as yield ratio to occupied growing floor area, is 13.8 times higher in VFS than in the HHS.

This is likely because the VFS can grow 20‐fold more plants per unit area than the HHS by incorporating the vertical dimension into the growth environment.

However, these calculations are based on independent vertical columns and do not consider the effect of column spacing on yield per occupied growing floor area. 

Salad can get a bad rap. People think of bland and watery iceberg lettuce, but in fact, salads are an art form, from the simplest rendition to a colorful kitchen-sink approach.

Marcus Samuelsson

6. Cut Nitrogen for Personal and Lettuce Health

Contrary to popular belief, when you grow lettuce you should not bombard it with nitrogen.

Studies show that lettuce plants can only utilize a certain amount of nitrogen and consequently store the rest as nitrate in their leaves.

The effect of excessive nitrate intake is highly detrimental to personal health – so much so that the levels of nitrogen applications for lettuce crops are legislated in many countries.

The US Agency for Toxic Substances and Disease Registry (ATSDR) has references that would be inappropriate on this site [Source].

The site offers essential reading, especially for pregnant mothers. The point is – please don’t add synthetic nitrogen to your lettuce crop; use bloodmeal instead.

The application of nitrogen fertilizers influences the nitrate concentration in the edible parts of lettuce. Studies show that providing lettuce with a combination of organic fertilizers and liquid fertilizers is superior in terms of soil quality, appearance, and nitrate accumulation.

The inorganic fertilizers and the application of liquid fertilizers frequently increased the electrical conductivity of the soil and thus negatively affected the yield of the growing lettuce. [Source]

7. Grow Lettuce All Year In The Greenhouse

Polytunnels initially arose in the 1960s, when the plastics industry finally figured out how to make reliable wide-width polythene sheeting.

They are becoming increasingly popular with each passing gardening season.

The enormous plastic-covered walk-in frame tunnels are used to grow a wide range of crops, from lettuce to tomatoes and raspberries.

In theory, the size can be whatever you want, but most garden plots are six to nine feet wide and six to thirty feet long.

A minimum working height of 6 to 9 feet is required at the tunnel’s center.

Semicircular arc and high tent shape are the two main shapes available for purchase, and they can persist for years if they are well planned, built, and maintained.

Advantages When You Grow Lettuce In Polytunnels

  • Crops develop faster and maybe larger as the season progresses. Small is sensitive, while gigantic could be a silver cup, depending on your harvesting approach.
  • They are less expensive per square foot than glass or polycarbonate greenhouses.
  • There are several different sizes to choose from.
  • They absorb the sun and produce the most fruitful germination and seedlings. Spring-growing temps arrive two to six weeks before the open garden depending on your area.
  • They shield growing plants from rain, frost, snow, hail, and gales, allowing for the production of autumn, winter, and early spring crops.
  • Close planting in rows can be done by using irrigation tubing with drip holes. If you divide the growing area into zones, a multizone irrigation system will allow you to give blocks of tiny and large vegetables, soft fruits, and fragile fruit trees.
  • There are kits available that allow liquid fertilizers to be metered into the irrigation water system.

Things To Consider in Purchasing a Hoophouse

  • Plastic sheeting cover strength and wearability
  • The sheeting’s UV resistance and expected longevity.
  • The galvanized or protective painted metal framework’s quality.
  • Construction simplicity
  • Entrance sealability.
  • The possibility of installing a temperature-controlled fan for summer usage
  • If you don’t want to pay for a fan, you can partially roll the sides up in the heat.
  • Is it possible to easily install shade and windbreak material?

Check out this article on which is best, A greenhouse or a Polytunnel

8. Grow Lettuce In a Sterile Medium Then Plant On To A Good Potting Soil

Lettuce is a fast-maturing cool-season plant. It may grow in various soil types but prefer a rich sandy loam with a high compost content. Make sure there is sufficient moisture from the onset.

Add compost to the bed you plan on using at the same time as plant your seeds in trays for transplanting – more than six weeks before transplanting.

Lettuce is a cool-season crop that thrives in temperatures between 55 and 65 degrees Fahrenheit, and this crop does well in a loamy, high-organic-matter soil.

Because lettuce seedlings are quickly dried out, they should be protected from the wind. To safeguard vulnerable seedlings from wind damage and to give support, scatter a handful of pine needles around them.

The ideal soil temperature for seed germination is 60 to 80 degrees Fahrenheit. At a soil temperature of 95 degrees Fahrenheit, lettuce seeds will not germinate.

If at all possible, use primed seed. Priming is a water-based procedure that improves seed germination, reduces germination time, and aids in the establishment of a better crop stand.

9. You Can Root Out Root Aphids in Lettuce

According to a recent study by Agricultural Research Service horticulture Eric Brennan, organic lettuce growers in California are adopting Alyssum (Lobularia maritime) as a companion plant to help naturally defend their crops from harmful insects.

Hoverflies are attracted to the small, graceful flowers of Alyssum, an easy-to-grow annual.

Hoverflies feed on the nectar of Alyssum and eventually lay eggs.

The larvae feed on aphids found in lettuce crops once the eggs hatch. Aphids are especially difficult to control on lettuce plants because they like to reside in the plant’s inner leaves.

According to the study, Alyssum is so successful at defending lettuce crops from aphids that California farmers are employing it on up to 10% of their acreage.

Brennan demonstrates that the optimum approach for companion planting is to scatter Alyssum throughout the lettuce rows at random intervals, encouraging hoverflies to feed and lay eggs more equally throughout the crop.

Brennan also concluded that randomly interspersing alyssum plants throughout all lettuce rows would be better than intercropping lettuce with strips of Alyssum in specific rows.

Some lettuce growers have already implemented this method.

The Alyssum might be dispersed across the field to reduce lettuce-alyssum competition. Adult hoverflies may be more likely to feed for pollen and nectar more uniformly across the field due to this.

This option would also minimize alyssum strips that are difficult to manually weed—an essential factor in organic agriculture because hand weeding is expensive, and weeds that survive can develop seeds that infest subsequent crops.

Because alyssum shoot residue can be challenging to assimilate into the soil, mainly when concentrated in strips, scattering Alyssum throughout a field could reduce postharvest tillage requirements.

10. When You Grow Lettuce Humidity Can Be An Issue

Lettuce germination and early growth rates are primarily determined by temperature. The apical meristem of young lettuce plants is near the soil surface, so plant growth is often more closely matched to soil temperature than the air temperature.

Warm temperatures and high humidity can result in tip burn, and this disorder is due to rapid growth rates and is associated with localized calcium deficiency.

A few days of high temperatures (90 °F) can cause enough visual damage to cause total crop loss. Improving soil calcium availability does not alleviate the problem if there is insufficient root hydration.

Balancing water availability and humidity levels requires an intelligent solution – preferably managing temperatures and avoiding misting. As you want to maximize CO2 levels for lettuce, airing your crop is not always the best route.

Conclusion On How to Grow Lettuce

Lettuce growing allows gardeners to try varieties that generally aren’t commercially available. As a container crop combined with onions and broccoli, lettuce is easy to grow.

I hope that you’re finding the ten-facts-of series interesting.

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