What are these red marks on the leaves of my pelargoniums?

Question

There are separate questions about mistakes that I made in the repotting process:

• What to do (immediately) with a waterlogged pot plant?
• What to do (after two weeks) with a waterlogged pot plant?

TL;DR

What are these red marks on the leaves of my pelargoniums?

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I recently repotted a bunch of house plants into larger pots, with new compost.

I mixed into the compost some water-retention crystals - the kind that absorb loads of water and can then release that water gradually. I did this because I struggle with under-watering the plants and was hoping that this would result in the dampness of the soil being more stable over time.

A) If this was a terrible idea from the get-go let me know :)

Perhaps I mis-judged the amount of crystals, or perhaps it was an error to soak the crystal-enhanced pots like I do for the rest of my plants, but the upshot was that the pots became extremely wet for a long period - I would say waterlogged.

There was water seeping out of the pot into the saucer for 2-3 days (which I would regularly empty), and the surface of the soil was definitely wet to the touch. I then didn't water the pot for a week and a half, and left the plant outside on a South-East facing balcony for a very hot(23-27 degrees) and sunny week. and by the end of that week and a half, the soil is still not particularly dry (although it is at least not actively WET now).

I perceive that the plants definitely suffered from this - several (though not all) of the leaves very suddenly went extremely pale and then died, other leaves have gained a pale halo around their edge, and for the 3-4 days after I did this, the plants appeared to wilt (as though I'd UNDER-watered them) though it has now recovered.

I have multiple questions, so the above set up has been duplicated on multiple posts, but my question here is ...

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On one of the plants (a red pelargonium) a few of the leaves died, but almost ALL the leaves now have red leaf-shaped marks on them.

What are they? Are they related to the over-watering or is that just a coincidence?

Answer 1

Nothing to worry about, if you're referring to the semi circular red area on the leaves - these are zonally marked Pelargoniums, and that's what they should look like.

Answer 2

You are telling us that you repotted your geranium in compost and water holding gel crystals?

I'd go get a bag of plain sterilized potting soil. Don't mess with those crystals unless you go on vacation. You've seen that those crystals actually cause saturation of the soil and that means the roots aren't getting oxygen.

Compost is not a planting medium. Compost is excellent for the outdoor garden soil but not for pots. Not sterilized for one thing and there is no soil. Repot into just soil from the bag. Dump the old soil out into your garden. Put just soil in the pot with no gravel or rock at the bottom and transplant again. Gentle with the roots. It is okay to leave the compost on your roots. Don't try to wash it off as those roots have already been stressed from the first transplanting. A little stress is a good thing but adding more stress of saturation and then a second transplanting so soon could set your plant back.

Raise the bottom of your pot off the surface of the saucer or top of wall or the patio using pieces of tile, or rock. Just a little to allow air between the bottom of the pot and surface and that really helps drainage. Water the soil as you put the soil in the pot, firming to remove large air pockets, then plant your geranium and firm the soil around your plant. Leave 1" space between the top of the soil and the rim. Pick up the pot and plant to feel the heft of your plant watered. Wait until the entire pot and plant are lighter before watering again. For outdoor plants in the summer watering every day is normal. But do not water unless the soil has dried out enough that you can tell there is a huge difference in the weight. The soil will be dry on top. If you lift it tomorrow and it is still heavy do not water until the next day if it feels light.

Cut off flowers as soon as you can bear it. This plant will go nuts if you keep taking the flowers and dead or dying leaves off. A lot of energy goes into the flower and seed making and by removing the flowers and dying leaves all that energy goes back into the entire plant that will get bigger and set even more flowers. Pretty soon you won't be able to keep up with all the flowers.

I'd go once a week to clean up the 'color install' of a development for instance. I'd cut every flower off. To the horror of passersby. I'd give them all a little lesson and told them to check back in a few days. They'd actually make a point to meet me the next week and they'd help cut flowers off to learn where to cut them off. They were simply amazed. The development was suddenly full of huge hanging baskets and potted flowers and people out cutting off flowers. You don't have to be so brutal cutting off flowers but at the beginning it really helps get your plant to grow vigorously. Otherwise, it will kinda look the same all season with one or two flowers gone to seed.

You have to use a bit of fertilizer which is just the chemicals the plant has to have to do photosynthesis and make its own food for energy to make all that groth and flowers. If you have already fertilized let me know how long ago and with what product and formulation. You've dumped out the majority but to add too much fertilizer will kill your plant.

My favorite easiest and safest fertilizer for people to use is Osmocote 14-14-14. Even numbers to ensure flowers and vegetative growth. If the formula has the first number, percentage of Nitrogen, larger than the other two you won't get many flowers. Osmocote is extended release and will last 3 months or more.

These flowering plants have one job to do and that is to produce seed. Annuals in particular. The more you cut those 'babies' off before setting seed the more that plant will try to make more flowers and more seed. Once a few flowers are allowed to set seed that signals to the plant that its job in this life is done and it can go ahead and start dying. For perennials, the plants just stop flowering and setting seed for the season.

And Bamboo has already told you that red ring is totally normal for zonal geraniums.