March Growing Guide

Premier team

The weather in March is changeable. This is the month where there are the biting winds of winter as well as days of glorious spring sunshine.

While things remain mixed outdoors, for growers and gardeners it’s best to head indoors. Your polytunnel is the ideal enclosed space as it protects from adverse weather conditions and extends the growing season.

Now is the time to make the most of the extra time you’ve bought by using a polytunnel for your plants. This guide will show you how to focus on the things you’ve been growing and help you decide what to plant in March in the UK.

What’s inside your polytunnel in March

This is a particularly busy month as you look forward to a great growing season and some delicious summer crops. Before you concentrate on what vegetables to plant and what seeds to grow in March in the UK, however, it’s important you focus on your overwintering plants first.

Look out for plants that might be about to run to seed too early due to the cold snap in January and February. Some that may bolt at this time include lettuce and celeriac, so stop the process by trimming back all the leaves, leaving a handful on each plant. This should prolong them into April.

Celery - which can be overwintered in milder areas - will be doing well this month. If you planted some towards the end of autumn, it should be producing edible stems. There’s a short window for this though. Harvest while you can.  

Other overwintering plants to look out for are tomatoes, which will be flowering around now if planted in January. You have roughly 60 days from their first flowering to seeing the fruit appear.

Some of the plants that will be flowering now will be peas and broad beans, especially if you planted them in January. If these were planted towards the end of last autumn, they’ll be developing pods.   

Once you’ve checked on your overwintering plants, you can then shift your focus to the planting to do in March.

Top growing tips for March

The polytunnel may resemble a plant nursery at this time of year, with young plants and seedlings needing a lot of care and attention. To help you manage your polytunnel, work out what to plant in March and prepare for the year ahead, check out our handy hints and tips.

Prep your polytunnel

You might be spring cleaning other areas of your home right now. Why not add your polytunnel to the list? Clear out any trays and beds ready for summer crops, tidy away the areas used for overwintering plants and clean the plastic inside your polytunnel. By doing this, you’ll be ready for planting in March and well placed to prevent pests.

Once you’ve cleared your polytunnel, you can focus on adding staging that you might need to provide a home for your young plants and seedlings.  

Order tender plants

Take the time to work out what you want to grow. In a polytunnel in March, you’ll be ordering tender plants if you are not growing them from seed. Contact seed companies that supply tender crops or visit your local garden centre.

Care for seedlings

To keep them growing steadily, prick out or pot on seedlings as soon as they are ready. Be careful not to let them become root bound, overcrowded, or starved of nutrients. Taking these steps will ensure they don’t lose the precious advantage gained by early sowing.

Watering your polytunnel plants

As the weather begins to improve and feel spring-like, any planting you do in March will require a focus on watering and ventilation. Plants that may have been robust in the colder weather are being exchanged for those that need a little more attention, so having an efficient watering plan in place will ensure they grow well.

Begin the feeding process

As the weather warms up, start feeding tender herbs and fruit in pots. Give them a regular liquid feed or use nutrient-rich compost or slow-release fertiliser.

Get rotating!

Keep your soil healthy inside the polytunnel by rotating crops. Alternatively, use green manures to avoid the soil becoming dry and lifeless between crops.

Consider the weather

When you’re planning what veg to plant in March, factor in the colder nights that are still lingering from winter. Cover and protect vulnerable crops on frosty nights with a blanket, bubble wrap or even sheets of newspaper.

Another option is a polythene cloche for inside the polytunnel. This acts as ‘double glazing’, providing extra frost protection for vulnerable first shoots and young crops, and saving on heating costs.

What to plant in a polytunnel in March

So, what to sow and grow in March? To help you plan out the coming weeks, here’s an overview of key activity in your polytunnel.

What to sow

As mentioned, this is the time to focus on tender plants. Some of the best seeds to sow in March are aubergine, carrot, beetroot and cauliflower. This is also the ideal sowing time for lettuce, strawberries, radishes, spring onions, tomatoes and rocket.

What to grow

Potatoes and broad beans grow well now, so they’ll be in the growing phase if you planted these earlier in the year. The plants on the ‘what to sow’ and ‘what to harvest’ lists are also in the growing phase now.

What to harvest

We’ve already mentioned celery for harvesting now. Other plants that should be ready for harvest include turnip, sprouting broccoli and celeriac. If planted earlier, cauliflower, cabbage, rocket, carrot, spring onion, radishes and spinach will be ready around now. You’ll be harvesting what’s ready and might want to sow in their place.

You can also harvest chard, coriander and pak choi now. Any salad leaves such as lettuce are also looking ready to harvest in March.

Why choose Premier Polytunnels?

At Premier Polytunnels, we want you to get the most out of your planting in March and throughout the year. That’s why we offer a range of polytunnels in different sizes designed to suit a variety of growing needs. In addition, we provide gardeners and growers with the staging, raised beds, irrigation tools and other accessories designed to help you grow delicious vegetables and other plants.

You can join our mailing list for more information. But if you have any questions, please contact us on 01282 811250 or email and we’ll be happy to help you.