Tomato Frequently Asked Questions

In this Newsletter: tomato frequently asked questions, tomato blight and blossom end rot, humidity in the greenhouse, pot sizes, Crimson Crush, tomato seedlings and plant hormones.

If you have recently joined the Newsletter and are new to growing tomatoes, you may like to click on the photo below for answers to some of the most common FAQ’s.

tomato frequently asked questions
Tomato frequently asked questions.

Two of the biggest problems for home growers have been overcome:


  • Tomato Blight
  • Blossom End Rot


Tomato Blight

EU regulations meant that we couldn’t use Dithane or Bordeaux mixture to help prevent blight. These were two traditional methods of protecting our plants. However, and thankfully, the blight free variety is now available.

So the answer to Tomato Blight is to grow blight resistant varieties such as Crimson Crush.


Blossom End Rot

This very common problem is caused by allowing soil to dry out when roots need both moisture and calcium.
The issue is – how to keep soil moist on a 24/7 basis.

The answer to Blossom End Rot is to use a self watering planter (SWP) or similar device for 24/7 watering.

The photo below shows the Oasesbox design.

Oasesbox - Self Watering Planter


If you have air pots and fabric type pots from previous seasons (see below), a watering valve in a tray is still a very good way to keep your plants watered and fed 24/7.

Options for a tray and valve system.


In The Greenhouse – Humidity

If you grow in a greenhouse or polytunnel, blight isn’t as much of an issue – if we keep the rain off our leaves, we should be OK.

However, Blossom End Rot (BER) can be a bigger issue in a greenhouse because higher temperatures will dry out our soil/compost more quickly.

Humidity also plays its part. High humidity reduces moisture loss from the leaves (see transpiration) which is important for the uptake of water and nutrient through the roots. High humidity = low moisture/nutrient uptake which can cause Blossom End Rot.

This is a good reason to keep plenty of air circulating in a greenhouse to prevent the humidity from becoming too high –
it will also help avoid fungal problems. Open the greenhouse windows or better still, use a fan heater.


Pot sizes

When growing tomatoes from seeds or buying small plug plants, we normally transplant them into a 3 inch pot to start with, then maybe a 4 inch then a 5 or 6 inch before we put them in their final position, such as a large pot/container or grow bag.



But why do tomato plants need to be potted on in stages, why can’t we just sow a seed into a big pot or grow bag to save all that time and messing about?

Here are a few reasons why…

  • It saves space – imagine having a large pot for each seedling sitting in the windowsill. Remember, that they can’t go into a greenhouse  until the end of April and they can’t stay outside overnight until the end of May. Or when the danger of frost has passed in your area.
  • More mobile – plants can be moved around more easily in small pots – in the greenhouse or outside during the day and indoors at night.
  • The most important reason – When the roots of tomato plants reach the sides and bottom of their pots, they “get a move on” or in other words, mature more quickly to the flowering and fruiting stage.

The over-riding goal of a tomato plant is to produce seeds for the creation of its next generation. If it thinks that it has limited resources or room to grow, it “gets on with it” and grows faster.

A plant grown from seed in a big pot will not mature as quickly. It will take longer for its roots to reach the sides and will sit around in the sun thinking it has all the time in the world and be lazy – fruiting will take longer!

Of course we don’t want plants to become pot-bound (when the root area becomes much too big for the pot and the plant’s growth becomes stunted), but we do want to pot them into bigger pots in stages, and let them “feel the sides” as it were.


Crimson Crush F1?

Update as to whether Crimson Crush is a hybrid or not …?

Let’s compare a packet of Crimson Crush with the F1 Lizzano – both from Suttons.

My packet of Crimson Crush seeds says it contains 10 seeds on the packet.

Actually, it contained 23 seeds – of varying shapes and sizes.

My packet of Lizzano F1 seeds says it contains 7 seeds on the packet,

It contained 7 seeds – all exactly the same shape and size.

The possibilities are:

  • Suttons are extremely generous with their Crimson Crush seeds,
  • There was an error when filling the packet or
  • Crimson Crush seeds are an inexpensive non hybrid variety.
Crimson Crush – blight resistant and tastes as good as it looks!


I know a couple of tomato growers who have grown saved seeds from CC and have had excellent results.

I also had an email from someone who had sown saved CC seeds and grew some very odd looking tomatoes indeed!

The question remains … if you have any thoughts on the subject, please leave them below.


Tomato seedlings and plant hormones

If you have ever wondered why seedlings lean towards the light source, this is the reason.

Hormones coordinate growth. They send a message from one part of a plant to another, to tell cells to do something.

For example, when a seedling leans towards the light.

This happens because the hormone auxin is sent from the light sensitive seed leaves, down the shade side of the stem which elongates the cells on that side.Hormone auxin and tomato seedlings
Because the cells are elongated on the shade side of the stem, and not the light side of the stem, the seedling leans or bends towards the light.

Auxin is also used to promote rooting activity so it’s the stuff gardeners use when taking cuttings by dipping the stem in the rooting powder or gel.


The Weather!

We’ve had a few sunny days in most parts of the UK this week – seedlings have been growing well in the sun. However, snow is on the way for many of us … again!

Let’s hope this is the last of it and spring will be well and truly sprung soon!



Please leave comments below or email me at [email protected]



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