Tomato plants are a staple of a summer garden, and are easy to start off from seed. Tomatoes take months from seed to harvest, and must have the right conditions in order to produce juicy, flavoursome fruits. We'll go through the process from beginning to end, with a focus here on why it's so important to harden off your tomato plants.
What is Hardening off?
Hardening off tomatoes is a crucial step when growing tomatoes. Whilst you might start-off your plants inside, they'll eventually be planted out into the garden where they can enjoy the most of the summer sun, preferably in a sheltered spot. Taking new seedlings and putting them outside too early is generally a recipe for disaster - and a mistake that any new gardener will make at one point in their planting career.
To ensure that tomato plants will survive different temperate conditions, they should be gradually introduced to colder overnight temperatures. Exposing plants to the elements over a period of time will acclimate them to the outside, so that they are not adversely affected by a shock change in climate.
This is done by putting plants out into a sheltered spot or cold frame during a cloudy day, where the new plants will not get too warm or too cold, too quickly. Gardeners have debated for years about whether it's worth it to harden off plants, but the answer is undoubtedly, yes.
Tomato Seedlings are certainly frost sensitive plants, so it's important to harden off plants at the right time.
When is the Best Time to Harden off Tomato Plants?
The best time to harden plants off will vary depending on when you'd initially sown your seeds, and your local temperatures. We've sown Tomatoes as early as late-january in the past, with less than perfect results. Our Gardeners Delight tomatoes are best sown in late-March/April, but can be sown earlier if they can be provided with sufficient sunlight. In all cases, tomatoes should be started-off indoors, and not exposed to outdoor conditions until the danger of frost has passed.
By extension, the best time to begin hardening off your tomato plants around 6 weeks after they germinated, and around 3 weeks before you plan to plant them out into your garden.
Preparing Young Plants for Hardening Off
When it comes to hardening off tomatoes, timing is key. It may be tempting to treat tomatoes harshly, setting them out into the garden early so they can grow for longer - but it's essential to make it a gradual transition from indoors to outdoors. Exposing tomato seedlings to sunlight too quickly can lead to scorching, whilst if it's too cold or windy, young plants will wilt or bend.
Tips for Successful Hardening Off
Monitoring Weather Conditions for Optimal Timing
Keep a close eye on the weather predictions, and adjust your schedule based on temperature and rain forecasts.
Protecting Tomato Seedlings from Pests and Disease
To prevent your tomatoes being munched, you can use coverings to shield from slugs and moisture. We've had mixed success with copper tape to put-off slugs.
Common Mistakes to Avoid
Rushing the Hardening Off Process
Walk before you can run! Putting plants out into the colder temperature too early runs the risk of shock to tender plants like tomatoes.
Overexposure to Direct Sunlight or Harsh Weather
Gradual exposure to cooler, outdoor conditions is key to avoid sunburn or wind damage.
Neglecting to Harden Off Plants Before Transplanting
Don't just transplant your tomatoes straight outside - bother hardening them off, making sure that they're covered to avoid scorching when the sun is strong, and well in a well-sheltered position to help the stems stay strong.
