Feeding and watering tomatoes go hand in hand because nutrients are usually delivered by way of watering plants at their roots.

For those who like to “keep it simple” just follow the directions on the container of your chosen tomato feed and ignore this newsletter – look away now!

Fertilising + Irrigating = Fertigation

That’s a strange word but stands for one (or two) of the great challenges in tomato growing … “how much food and water should I give my plants?”

The only person who knows is you!

There are so many variables when growing tomatoes including: temperatures, light intensity, humidity, the size and the amount of leaves on a plant to name but a few!

Leaves Top and Bottom
The important thing is to observe old leaves and new top growth.

Old leaves will often show signs of nutrient deficiency and this is not a problem – they can be removed if necessary.

However, because plants focus their energy on new growth and send their nutrients to the top leaves, nutrient deficiency at the growing tip is a problem and should be acted upon – especially at this time of the season (June/July).

Iron DeficiencyA common problem with tomato plants grown in containers is iron deficiency and shows itself on new growth.

This happens not because there isn’t enough iron in the soil, but because there isn’t enough air in the soil.

Plants need oxygen in the soil in order to absorb iron through their roots. So plants grown directly in the ground, and can spread their roots out at surface level, have much better access to oxygen and don’t usually suffer from iron deficiency.

There are a number of products on the market containing iron such as SP Plant Invigorator.

If you are growing in containers, plants will probably need watering everyday in sunny weather.

When the nutrients in a container’s compost are used-up, plants will rely on the food that we give them.

It’s Similar To Hydroponics
Growing in soil that lacks nutrients is practically the same as growing hydroponically and plants will need every nutrient by roots or leaves* to produce a good crop.

Perhaps a good question to ask is “do plants produce a better crop if they are fed once a week, twice a week or at every watering”.

The point here is that if there are no nutrients in the soil to dissolve when water is poured in, plants will go hungry when water only is given. Therefore, if you include feed every time you water, plants will always have access to food.

So the old saying “feed a little and often” is good advice.

Also, if a plant receives nutrients on a regular basis it won’t grow a large root system because it doesn’t need one.

Red Alert in Rockwool Cube

The Red Alert above has been grown in a 4 inch rockwool cube and kept in a tray containing 1 or 2 cm’s of water and nutrients.

Once soil nutrients have been used-up, feeding at every watering or at every other watering is about right.

When feeding tomatoes, some varieties will need a higher strength of feed than others. For example, larger tomato varieties usually need more food than the smaller varieties … they’ll definitely need access to more water to help avoid Blossom End Rot.

Legend Milk SprayThe legend above has been sprayed with 50/50 milk/water to help avoid calcium deficiency and Blossom End Rot. Spray medium and large varieties when fruit begins to form.

What has water got to do with Blossom End Rot?

This question inspired me to learn as much as possible about tomato growing and create this website because I found it so irritating to be told: “frequent watering helps avoid BER” and not told why!!!

A root area with dry patches of soil reduces the amount of nutrients (calcium in this case) available because roots can’t absorb nutrients from dry soil.

Also, you will probably notice that plants in smaller pots have lighter coloured leaves than plants in bigger pots. Why is that? The plants in the smaller pots have used up the soil nutrients sooner and will need feeding sooner.

*Foliar feeding is mainly for giving supplements when plants show signs of deficiency of one or two minerals such as iron or magnesium. Also calcium to prevent Blossom End Rot.

Adding modest amounts of organic nutrients to the soil as a supplement is fine – such as seaweed extract. However, if you add synthetic nutrients to your soil along with the a tomato food, the soil balance may be upset and some nutrients blocked altogether. Much better to add supplements as a foliar spray!

The season so far has been reasonable and we haven’t had any long periods of rain or dull weather, unlike the past few Summers!

I’m off to the polytunnel (spelt it correctly this time) to fertigate my toms!