[Hitwoman]

Hello. I am growing San Marzano outdoor tomatoes and Gardeners Delight tomatoes for the greenhouse.  Both plants however are showing signs of pale leaf discolouration on their older leaves.  Does anyone have any ideas as to what might be causing it?,  They are in a greenhouse with only enough heat to keep the frost off at night.

Thanks

[JoshP]

What compost have they been grown in? Have they had a feed yet?

[mumofstig]

Yellowing leaves with green veins is likely to be magnesium deficiency, but assuming they've recently been potted up - it seems unlikely.

Have they been in strong sunshine before they had a chance to harden off?

[Hitwoman]

Hello both.  They are in verve potting compost in the greenhouse, so not hardened off yet and not yet fed as I thought the potting compost would have enough food for you plants - is that ring to assume.  They are on the shelf in the sun.

[Trikidiki]

I am growing five varieties of tomatoes and all have received the same treatment, same compost etc. My San Marzano are showing a slight yellowing of the older leaves as well, the other varieties are uniform colour. I felt it wasn't significant enough to be worried about it but did notice it just this morning and in my mind put it down to them being in a corner of the greenhouse where it is slightly shaded by a New Zealand Flax in the garden.

I'll take a closer look tomorrow.

[3759allen]

is the greenhouse heated?

maybe cold nights and strong sun during the day not helping.

[oldgrunge]

Have got a similar problem with some of my tomato plants. I have been putting them in th greenhouse during the day, bringing them into the kitchen at night. I think I've let them get scorched, the greenhouse soon heats up, even at this time of year. They've got the sulks now, just hoping they'll pick up.

[Hitwoman]

Ok thank you, I will try moving the out of the direct sunlight then.