Rain and Tomatoes
Yesterday evening, in my part of the world, we had thunder and lightning and heavy rain. This morning, many of the trays and saucers in which my pots are standing are filled to the brim with rainwater and the potting soil is saturated.

The problem is that saturated soil contains no air and root health deteriorates very quickly without air.

So it’s best to empty your trays and saucers when they become filled with rain.

Split Skins
Another issue is that ripe tomatoes often split after a heavy downpour as skins contract and the liquid content of the fruit increases.

Tomato Split

Rainwater and pH
However, rainwater is good for tomato plants because it doesn’t contain added chemicals and also because of its pH of around 6.2.

pH is the acid/alkaline balance that is measured in both water and soil. under 7.0 is acid and over 7.0 is alkaline.

Tomato plants growing in soil like a pH that is slightly acidic – around 6.8.

My tap water is pH 7.2 which is slightly alkaline, so when my plants receive rainwater, the pH drops – albeit for a short time until the rain water loses its effect.

Potting Soil – Grow Bag Soil and pH
Potting soil is composed of both acid and alkaline elements and is therefore said to be “buffered” because it adjusts its pH as both acid and alkaline elements or minerals in the soil dissolve.

So even if rain water is around pH 6.2, the buffered soil will pull the pH value back up as alkaline substances are dissolved. The soil gets its way in the end, but the tomato plants benefit temporarily from the rain water.

The reason why pH is important, is because certain nutrients are only available to plants within a certain pH range – see  chart below.

nutrient availability chart
If the pH is too high the intake of phosphorus, manganese and boron will be reduced. The pH would have to be very low for any of the above nutrients to be in short supply.

The chances are your tap water is around pH 7.0 but you can find the pH and water quality of the tap water in your area from your water provider’s website.

Usually, pH is not a problem especially if you are growing in good quality compost, but understanding pH means that you can make a few adjustments from time to time and get the very best results.

A few drops of lemon juice in the watering can is a good way to reduce the pH of your tap water if it is over pH 7.0. One drop per litre is enough … it’s powerful stuff!

Hot Weather and Blossom End Rot
It’s great to see those trusses of tomatoes developing on the plants but one of the big disappointments in tomato growing is when we look underneath the fruit and find Blossom End Rot!

Blossom End Rot

One of the problems with hot weather is that soil dries out so quickly, especially in small containers.

As water becomes in short supply around the roots, however temporary, dissolved nutrients are also in short supply and the growing fruit don’t have access to calcium when they need it.

The advantage of larger containers is that they don’t dry out so quickly and the supply of water and nutrients is less likely to be interrupted – less chance of BER.

The way around this problem is a constant water/nutrients supply by using aqua or smart valves, or even capillary matting.

Just make sure that soil doesn’t become saturated by standing a container in a tray/saucer of water 24/7 and that there is air for the roots – it’s a difficult balance when growing tomatoes in containers.

Seed Inconsistencies
I’m sure that many of us have experienced a disappointing result from seeds that we know didn’t perform as expected. Also from seedlings and mature plants that didn’t have the vigorous growth of previous seasons.

Of course, growing conditions have a great effect on plant growth, but there are times when we know that seeds just didn’t perform as well as they should have done and the quality was poor.

If you have experienced poor quality seeds or even genetic abnormalities then please let us know (in the comments below) the variety and the seed company on the packet.

Also, if you have had great results over a number of seasons from a seed company, then we would like to know that too!

It will help us when choosing tomato seed for next season.

I hope that your cherry tomatoes are ripening and the larger varieties are not far behind!