Lettuce Plant Growth Stages | Lifecycle

With a myriad of different colors, sizes, and textures – there is a lettuce variety to compliment any dinner table this summer.

Lettuce (Lactuca sativa) plants require moist fertile soil and sunlight for the best results. They need little maintenance and are easy to grow from seed making lettuce the perfect leafy crop for beginner growers. The plants take up little room, are low growing, and are quick to mature which makes lettuce ideal for those who are short on space.

Conditions for Growing Lettuce Plants

This annual salad crop will benefit from 6-8 hours of sun each day in slightly acidic soil with a pH of 6.0 – 6.5. Lettuce plants are ideal for raised beds and containers and successful growth can be achieved in most regions. 

Although lettuces are typically enjoyed in summer, the cooler growing conditions of spring and fall produce the best results. In hotter climates consider growing in a shadier spot or in containers that can be moved somewhere cooler when necessary. 

Lettuce plants are extremely versatile and will happily grow in many climate zones. However, if conditions are consistently below 25°F or above 80°F, you may want to consider growing this leafy salad crop indoors on a south-facing windowsill. 

There are many different types of lettuce to consider when choosing seeds. Some of the most common types are:

  • Loose leaf – where the plant does not form a compact head. Young leaves are perfect for picking as and when required. Loose leaves are ideal for container growing. Reaching maturity in approximately 30 days. 
  • Romaine or Cos plants are distinguishable due to their compact, tall, and crisp oval heads and are considered to be more heat tolerant. Reaching maturity in approximately 60 days.
  • Butterhead plants form more open heads with loose slightly sweet-tasting leaves. Reaching maturity in approximately 60 days.
  • Crisphead plants have very crisp leaves and are typically rounded and compact. Reaching maturity in approximately 70 days.
Lettuce Plant

Growth Stages of Lettuce Plants

The lifecycle of lettuces is regarded differently from many other fruits and vegetables because we intervene before the lettuce can enter its final stages of this cycle.

1. Lettuce Plant Seeds

Lettuce plant seeds are very small with most seed suppliers providing hundreds of seeds in each packet. It is a good idea to sow lettuce seeds sparingly and practice successional sowing; sowing little and often to avoid an excess of plants maturing at once. 

When temperatures in your climate zone are consistently above 60°F, seeds can be sown directly into garden beds, containers, or seed trays – sprinkling thinly and finishing with a light covering of compost.

If started in seed trays, plants can be transplanted to their final growing position when seedlings are large enough to handle. This method will enable you to space plants adequately which will avoid the need to thin plants. 

2. Seed Germination

Lettuce seed germination should take place in 7-10 days provided the temperature is 60°F or above. If sowing in cooler conditions considers using a cloche or horticultural fleece on the soil to raise the temperature or a heat mat if sowing in a container indoors.

Sow in a sunny position and keep the soil moist to encourage seed germination.  

3. Lettuce Seedlings

Lettuce seedlings will begin life with their first set of leaves called cotyledons which will look different from those the mature lettuce plant will have. Cotyledons help the supply of nutrition to the seedling to assist in healthy growth.

The plant’s second set of leaves are called true leaves and will emulate the leaves of mature lettuce. The true leaves are a good indication the seedlings are happy and healthy. True leaves will emerge roughly 7 days after the cotyledons.

Keep a distance of around 6 to 12 inches between each plant (depending on the variety) – thin/remove plants to make space if necessary.

Pre-grown plants can be purchased from garden centers or plant nurseries at this stage of a lettuce plant’s lifecycle.

Always hold the seedling by the leaves and not the stem when handling it to ensure your seedling is not damaged.  

Lettuce Seedlings Lettuce Plant Growth Stages
Lettuce seedlings

4. Foliage Growth

Foliage growth will happen quickly if lettuce plants are grown in fertile soil and watered regularly. It is at this stage in the lifecycle when the lettuce plant is harvested and eaten.

Loose Leaf varieties can be harvested as soon as foliage begins to form. Once leaves are large enough, remove the whole plant by cutting through the stem or remove just a few outer leaves as required.

Foliage growth of Crisp Head, Cos, and Butterhead varieties will take longer due to the density of the lettuce heart. After 70 days have passed the foliage growth on these lettuce types should be sufficient and the whole plant will be ready to be harvested.

5. Flowering 

Flowering lettuces are not a typical sight due to plants being harvested at the Foliage Growth’ stage.

Lettuce plants will produce a flower stalk from the center of the plant when stressed which can be caused by a lack of watering or high temperatures. This is referred to as bolting.

Once this has occurred the leaves become bitter. To prevent this from happening water regularly and provide shade when temperatures are high.

6. Setting Seed

Setting seed is not a common practice for most lettuce growers, but it is possible to save seed from lettuce plants to be sown the following year – provided the original plants are not a hybrid variety.

Fluffy seed heads will form once lettuce plants have finished flowering.

These seed heads can be removed once the lettuce plant has dried completely.

Once all seed heads have been removed place them in a paper bag and shake vigorously – the dried seeds with fall and are collected in the bag.

The lettuce seeds can be removed from the paper bag and placed in a sealed envelope. The saved seed can be reused the following year if stored in a cool, dark, dry place.

Setting Seed
Lettuce flower head with dry seeds

FAQ Lettuce Plant Growth Stages

Citations 

You might also like to read Lettuce Companion Plants | Good and The Bad

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.