Growing Lettuce on a Windowsill

Growing lettuce is a simple, quick, and enjoyable way to provide your household with fresh, tasty, nutritious leaves year-round. Even if you have no outdoor space, relax in the knowledge there are methods available to enjoy homegrown lettuce, such as growing lettuce on a windowsill.

Why Grow Lettuce

There are many great reasons to grow your own lettuce. Not only is it easy to grow, but lettuce offers a range of health benefits. It contains vitamins A and K, which help eye and bone health respectively, as well as vitamin C and iron. The high water content of lettuce plants also helps the body stay hydrated.

Also, there are more ways to eat lettuce than most people think. On top of the normal methods in sandwiches and salads, lettuce can be grilled or braised, used as a wrap and filled with other ingredients, or used in soups and smoothies.

Types of lettuce

There’s a wide range of lettuces to choose from, offering different growing and harvesting methods, as well as a range of tastes and textures. Commonly, they divide into four main differing groups, with many varieties within each group.

Growing Romaine lettuce

Romaine (also known as Cos) lettuce is a very popular type, characterised by its tall upright leaves with prominent ribs down their centre, which combine to form quite a tight head of lettuce.

Romaine is a cool-weather crop suited to early spring or late summer and can take around 75 days to mature. It is a popular type green leaves for sandwiches or Caesar salads.

Growing green and red leaf lettuce

Loose-leaf lettuce comes in a plethora of shapes, colours, textures, and tastes. They don’t create a head and instead consist of leaves arranged in rows around a centre. The leaves, medium or large at full size, are narrow at the base and widen at the top.

Loose-leaf types allow for leaves to be harvested over a period of time, as they tend to be grown year-round just remove the outer leaves as required, and they will re-grow.

Growing Head Lettuce

Head lettuce has a densely-packed head of leaves that resemble a ball, with iceberg lettuce being the most famous of the types. It is a highly popular type of lettuce around the world and is best to grow in the spring as it has a tendency to bolt in hot weather.

Growing Butterhead Lettuce

Butterhead lettuce boasts a looser, softer form of head than others, with soft, velvet sweet-tasting leaves. These types are more temperature-tolerant than other lettuces, being slightly more tolerant of heat and not bolting as fast, while also being able to withstand colder temperatures. That means they can be grown for most of the year. In addition, butterheads mature faster than romaine or head lettuce.

Consider looking further afield

Away from the main lettuce types, there are many other options for leafy greens to grow indoors on a windowsill. Try oriental leaves, such as mizuna or mustards, to provide a peppery kick to a salad, or go for the likes of spinach or rocket. All of these are well suited to growing on a windowsill.

So buy seed packets with oriental mixes or leaf mixes, which can provide a pick-and-mix of tastes and textures.

Choose the right lettuce for you

The right lettuce will depend on the size of the container, what you want to use the leaves for, and how long you want to wait to harvest it.

If you have just a small pot, go for cut-and-come-again loose leaves, as you could get several harvests off of each plant. However, if you want bigger leaves, then opt for head lettuce.

There is such a range of options for growing lettuce that it allows for mixing and matching to ensure a salad bowl contains a range of leaves and flavors.

Growing lettuce from seeds

Lettuce can be sown at any time of the year indoors, provided it has enough heat and light to germinate. Check the seed packet to make sure you are sowing at the right time and also to ensure you are sowing the seeds at the right density. If you over-sow then you will need to thin out seedlings to give the lettuce plant the space it needs to grow strong.

How to sow lettuce seeds?

• Fill a container with compost and brush off any excess to give a level surface
• Gently push the compost down to leave a one-inch gap at the top of the container
• Sow a few lettuce seeds evenly over the top of the seedbed
• Scatter a thin sprinkling of sieved compost or vermiculite over the seeds
• Gently water the soil with a watering can that has a fine rose attached, or place the container in a bowl of water to soak up the water.

Buy lettuce plants

Rather than grow from seed, you can save time by buying lettuce plants from the garden centre and pot them up into your windowsill container. The lettuce plant will often come with information on the spacing required, and a ready-bought plug plant could be ready to harvest within 30 days.

How long does lettuce take to grow?

Leaf varieties of lettuce grow the quickest and can go from sowing to maturity in around 30 days, while if you are wanting to harvest baby-leaf lettuce then it can be as little as three weeks from sowing.

Many other types of lettuce take between six and eight weeks to reach maturity. The season will affect how quickly the lettuce grows, reaching peak speed in the summer and taking longer in spring and autumn.

Lettuce seeds are very fine, be careful when sowing not to over-fill the container. Seeds germinate prolifically, so the more you sow the more important it will be to thin the seedlings.

Growing lettuce indoors in containers

Growing lettuce is possible in small spaces, so anyone without a garden or outside space is not deprived of the chance to grow their own tasty leaves.

Lettuces work fantastically in containers and, due to the range of sizes of lettuce plants, it means there are options for any space. If you live in a flat or busy city, then grow lettuce in a small container on the windowsill.

It is possible to grow lettuce indoors all year round, including during the winter in the right conditions, but spring and summer represent the ideal times to start your indoor salad container and ensure you can enjoy homegrown hand-picked leaves throughout the season.

What to grow indoors?

There is a range of pot types available to grow lettuce in, including options to recycle old cartons or containers. The container should be fairly flat and not too deep, anything up to 15 cm will suffice to give lettuces space to root and grow successfully.

Use the likes of seed trays, small pots, or transplant trays that can be bought from the garden centre, or research options of recycling old takeaway cartons or milk cartons into growing containers.

Make sure to wash the old container well and cut some drainage holes in the bottom. Remember to set the container on a plate or bowl to collect the excess water and prevent it flooding over the windowsill.

Multi-purpose compost works perfectly as a medium to fill the container with and that can be supplemented with a slow-release fertilizer to boost the soil, as it will need to work hard if you want to grow successions of lettuce throughout the year.

Choose the right spot

Like all plants, lettuces require sunlight and water in order to grow. They will grow great in a spot on a sunny windowsill, ideally one that gets around 12 hours of sunlight each day. Also make sure that the windowsill doesn’t suffer from cold drafts that will hamper your crops, and be careful to keep the plants safe from household pets.

Growing under lights

If you don’t have a spot that gets a good amount of natural light, then consider artificial LED grow lights to give plants the sustenance required for photosynthesis. You can buy specifically designed systems for growing crops indoors or rig up a homemade set-up with LED lights that are readily available online.

How far apart to plant lettuce?

When you plant lettuce, they should be spaced between four and seven inches apart (10-20cm) to allow them space to fully grow. There is the option of growing them closer together if your plan is to continuously harvest leaves as they grow rather than let the plant get to full size.

Watering and aftercare

The key is keeping the soil moist. Water regularly and do not allow the soil to dry out, as lettuces have shallow roots and require constant moisture near the surface. In hot conditions, there is a risk that plants will bolt if the soil is dry, which can cause the leaves to become tough and bitter.

Take care when watering to avoid splashing the leaves, as this can result in downy mildew. Identified by yellow patches and fuzzy mould/mold on leaves, it can strike indoor plants due to high humidity.

However, if identified and affected leaves removed, the hearts can still be harvested.

See here for further information about lettuce downy mildew.

Check leaves regularly for signs of infection or pests such as aphids or flea beetle. These can be treated with organic sprays, or look online for recipes to make homemade horticultural soap sprays.

How to harvest lettuce?

The harvesting lettuce method will depend on the type of lettuce grown, but all are simple procedures.

For whole lettuce, wait till a firm central head has formed and cut the entire stem at the base. Loose-leaf varieties allow for a continuous harvest and repeat picking of leaves over an extended period.

To harvest leaf lettuce, pick the leaves as soon as they are large enough to eat.

You might want to read about how to sow seeds if you are starting, or need to refresh your knowledge.

Good luck and let us know below your thoughts and recent experiences in growing your own lettuces.

See some Frequently asked questions below.

FAQ’s

Why is lettuce healthy and good for you?

• Because when eating lettuces, you get vitamin K content according to webmd.com, which is also measured in nutritional content on each leave.

What type of lettuce is easy to grow indoors?

• There are various but the easiest, low maintenance lettuce to grow in-house is the leaf lettuce (crispa), which you can start eating after 3 weeks upon germinating – it becomes fully grown in 40-42 days.

How lettuce is harvested?

• You can cut the lettuce at the base or just pick the leafs you need. But you can jump to “How to harvest” section above.

When & how to eat lettuce?

• Lettuce can be used in mix salads, smoothies, but it can also be eaten in wraps, tacos, stir-fries and sandwiches.

Credit Image: by John Lee from Pixabay