How To Protect Your Precious Tomatoes From The Frost

There has been a lot of conversation since my last article, where I boldly stated, its Tomato planting time. If your soil temp is 15C or above, it still is. This year Spring is very early by about 4 weeks and the indicators are clear. Last October I wrote about the mid Spring snow, while my soil temp was 20C. It can be wild at this time of year.

Listen to the Soil

In August we followed the Subtle arrival of Spring as soil temps started to rise and the garden indicators started to speak. Your soil temp is the only true guide to planting out, even if there is risk of frost. It’s never safe to plant out in our Unpredictable Highland Climate, but we must, sometime. So why not use the soil temp as our guide?

In recent weeks, the garden has received several light frosts, some hail and wannabe snow, and the winds have been blowing up to 100km/h. It’s harsh on our hill but we grow tomatoes every year to eat by Christmas. Last year we ate in the first week of December. This year we are on target to eat Tomatoes 2 weeks after Tomato Cup Day.

How do they survive?

So how do our tiny Tomato seedlings handle all that unfavourable weather? You may be very surprised to know the solution is very low tech, and we’ve been doing it for ever. Cold sensitive Tomato seedlings are available everywhere, grown in greenhouses and shipped from sea level to 600m up here to our gardens. That’s an extreme journey for any little seedling and that’s why I started growing my own.

Even the most acclimatised tomato seedlings will struggle in air temps under 5C, their preferred air temps being between 10C and 25C depending on variety, climate of origin and your unique garden microclimate.

How We Do It?

I strike our seeds in a box, then our slow grown seedlings spend their time growing as close to our garden temps and environment as possible. Only receiving protection over night when the temps are unfavourable. It’s that simple.

Good Coverings

I continue this protection regime once the seedlings have been planted in the ground, by simply covering the tiny Tomato seedling with a humble cardboard box. I have tried other coverings with mixed success. The foam box that the seedling was raised in, is also a good covering in extremes, although the air inside may become very wet overnight as the plant transpires. This may create a bit of shock when the box is removed, and the high humidity is stripped away.

Not So Good Covers

We have tried using plastic pots laying around the garden, but the plastic offers no insulation resulting in the plant freezing inside as the pot gets covered in frost. A super large pot works better than a pot of similar size to the seedling but it’s not as good as a box.

Glass cloches were used initially but offered troubling results. The glass transfers the frost directly to the plant, effectively melting it. In the early morning, the glass cloche needs to be removed or the greenhouse effect inside the tiny space will melt the seedling from heat build up. If left in the sun all day, the cloche can act as a magnifying glass, and burn the seedling or set fire to the mulch. I don’t recommend glass cloches for our climate, save them for indoor terrariums.

Really Good Covers

My favourite place to plant my tiny Tomato seedlings is under frost hardy plants. Because I don’t have to check with the weatherbots, as they are protected every night. If you had a go at winter growing, you will have plenty of living cloches to take advantage of. Right now, I have plenty of broccoli that has provided tucker and is now going to seed, so I planted under that. 

I also like to plant under the Snowpeas I planted in Autumn. They are significant enough that I can plant under them, and the environment is favourable to tiny seedlings. It’s warmer, receives filtered sun and has warm feet. The perfect combo to grow Tomatoes in early Spring.

The companion planting offers protection while the frost is around and when the plant grows out of its cloche, the frost is not as much of a problem. This is my number one solution for early spring plantings, but this year it didn’t work.

Failures and Losses

Not because my system failed, but because our resident possum has been slowly munching its way through the Broccoli patch at night. This morning the last of the protection was eaten. No more Snow peas either, they were eaten in the frost a few nights earlier and their wards were frozen. I lost 2 of the 3 seedlings in that area. But the one that has survived is looking good. Of 16 Tomatoes only 3 have been lost. It was worth the risk, and they are looking staunch.

This Week

The frost was significant and Monday mornings low temps across the region were surprising and caught a lot of us out. It was colder than our coldest winter night. Its something I would expect from mid winter, but this year a low of -4C is all the garden has experienced. If the seedlings were left out in the big cold, they certainly died. If they were offered light protection, they likely died. Only those with the genetics to handle the cold survived…

Oh No! Melted Stock

On arrival to restock Bellchambers Produce, staff were anxious and apologetic about the state of our Tomato seedlings. They had survived the frosts on Friday and Saturday morning without protection. So, our Tomatoes seedlings were left out on the rack over the weekend. No one expected a -6 on Monday morning…

Monday morning, staff arrived to find the seedlings melted. But not all of them were melted. We were very excited, to the surprise of all the staff. This was the first real frost to test the seedlings. A purging process we do every year.

We only sell the survivors. We took the survivors home to plant them, so the seed can be collected, and the genetics saved for next year. The more cycles the better the genetics. Who knows what may come. 

Now the frost has passed again, what are you waiting for? See you at the Haig Park Village Markets on Sundays and lets get our grow on together.

Stay Awesome

The Gordon Gnohm