How to grow lettuce right through summer (without it bolting!)

I love having lettuce on hand right through the summer so each meal can be completed with a refreshing garden salad, and of course we like to use them in our summer sandwiches too. But unfortunately, leafy crops such as lettuces don’t cope well in harsh summer heat, and it is not uncommon on a hot day for a crisp round head of lettuce to morph into a mound of bitter bolting leaves, right before your eyes. And of course this tends to happen just as the weather warms up and we want them the most!

This was something that used to happen to me a lot when I was beginning my growing journey. Although I found I had quite the knack for getting my lettuce seeds to sprout, when it came to growing them on in the garden, it felt like I was doing everything wrong, and instead of lettuce each night of the week, I ended up with entire beds of bolting greens which were good for nothing other than to feed our chickens. Don't get me wrong - I like growing food for my chickens, but I like having lettuces for our summer meals much more!

I realise now that back then there were a few simple mistakes I was making, and now I have learnt exactly how to manage my lettuces so that I can grow them right through the hot months - at the time of the year we actually want to eat them.

1.       Grow the right variety for the season

The first thing to consider if you want summer lettuces is the type of lettuce you are planting. Some varieties of lettuce can handle the heat surprisingly well, so these are the ones you should aim to grow. Iceburg lettuces like Great Lakes and some loose headed lettuces, especially Oak Green Leaf are brilliant to grow right through the heat of summer, but if you enjoy a bit more flavour, butterhead lettuces such as Tom Thumb and Buttercrunch are nice and compact and will handle the heat well. However perhaps my favourite lettuce to grow over summer is Merveille des Quatre Saisons, a lovely maroon tinged butterhead variety which, as the name suggests, does well through every season of the year. However it doesn't handle extreme heat quite as well as the other varieties mentioned, so I always plant this one on the fringes of summer and ensure it gets lots of water and a bit of shade.

"Merveille De Quatre Saisons" lettuce is my favourite

2.       Plant them in your shadiest spots

Most of us have areas of our garden that don’t get as much sun as we would like; this could be a garden on the southern side of the house, or an area that it is shaded by buildings or large trees. For me it is a garden that has a cluster of nikau palms to the north. When we put the garden bed in the palms were only thigh high; now they tower up above everything, and although the garden behind them gets early morning sun and late afternoon light, during the hottest part of the day the palms create a pocket of shadow over the entire bed. This may seem like an unfortunate mistake but in fact it was intentional – our hillside gets very hot and we were hoping those nikaus would create a cool shady zone. This is the perfect spot for our summer lettuces, which I pair with other plants that thrive in warm shade, like calendula, parsley and spring onions. If you don't have a specifically shaded garden that's fine because lettuces are very shallow rooted and easily popped into the shady gaps between other plants, especially in bare pockets under and around trees, or next to larger fruiting plants like tomatoes.

This Great Lakes lettuce is enjoying the shade created from the cherry tomato above it

3.       Grow them fast with good soil and plenty of water

A huge mistake I see people making when growing lettuces is that they don’t put enough care into the soil before planting or give them enough water - hence the plants don’t grow as fast as they should, resulting in bitter leaves and bolting plants. Lettuces like the ground around them to be kept consistently moist and need light but rich friable soil that is loose and well-draining; this is the type of soil that you can dip your hand into and scoop up with ease. After planting, it pays to give them a top dressing of compost to act as a nutritious mulch.

4.       Grow them from seed in successions

Chances are you have bought one of those 6-cell packs of lettuce from the garden centre before and planted them only to find flower heads forming in what seems like a matter of days. This is often because the plants have been on the shelf for a long time, and they are stunted. It could also be because the environment they have been growing in is so far removed from their planting environment, that they become shocked – remember what I said earlier about lettuces liking consistency? This includes environmental consistency – they don’t like to be shocked and will react badly if they are.

This is exactly why with something as fast growing as lettuce I really do recommend growing them from seed. Just sprinkle a small amount into good quality seed raising mix and prick them out into punnets once they are large enough to handle. If you grow them in successions - planting a small amount of new seeds each time you pot the previous ones up – you will have a continuous supply right through summer.

Something I teach in my gardening program - The Nourishing Kitchen Garden Mentorship – is to grow lettuces in successions like this and plant them close together for thinning later, by removing every second plant once they are a decent size for eating as tender baby lettuces. This is a great way to extend the crop to always have lettuces on hand.

5.       Water with intention

As already mentioned, lettuces like to grow fast with lots of water, but water them in the wrong way or at the wrong time and you’re asking for trouble. The best time to water your lettuces is early morning before the sun hits. This will help them cope with that day’s heat, and ensure the leaves are nice and crisp for that afternoons picking. In the early days while your seedlings are still getting established, try not to water them at night; night-time watering can send an invitation to the slug population to come over and feast - not ideal!

Being so shallow rooted lettuces like the ground around them to be kept moist, and consequently they do better with regular light watering rather than periods of on and off watering. Also, if they get too much rain (like a few days of heavy downpours) the leaves can rip or even start to rot. This is why I like to have hoops and plastic (or something similar) ready to put over them while they are young in case there is a summer storm forecast. This isn’t so imperative once they have bulked up, but in the tender early stages of life you want to keep damaging heavy rain off them as much as possible. 

Finally there is one last thing I would like to mention. I often visit people who have gardens with amazing large heads of lettuce growing, only to discover that they are still buying their lettuce from the supermarket. This is an anomaly to me, and I'm never entirely sure why this even happens, but I wonder if its because either not enough lettuces were planted to begin with - so there is an element of scarcity around the few that are growing - or if the person growing thinks the ones that are growing aren't ready for eating yet.

A lettuce left in the ground too long will become bitter and just as they should grow fast, they should be eaten fast, which is why I am so passionate about encouraging people to grow their own from seed. This way there won't be an air of scarcity over the one of two lettuces you have growing in your garden, and there will always be enough to go around without having to hold on to the plants you have for longer than you should.

Happy lettuce growing!