Don’s Expert Answers: Full sun plants that are wilting in the sun and failing to thrive

Question From:
Amye Wibberley in Maddington, Perth Western Australia

Nature of problem:
Full sun plants that are wilting in the sun and failing to thrive

Type of Plant (if known):
Cosmos, Cornflowers, Marigolds

Symptoms of Plant Illness (please try NOT to diagnose your problems yourself):
Plants are not growing very much at all- discovered that they weren’t getting enough sun and too much water so I water less and move into the sun but they just wilt in the sun and are not growing any faster!

Soil Type (e.g. sandy, clay or loam) OR Potting Mix Type:
General purpose potting mix with slow release fertiliser

How often do you water the plant:
every three or four days depending on moisture level of the soil

How many hours of sunlight does the plant get each day:
2-4 in the afternoon only

How long since you planted it:
3 months

Have you fertilised? If so, with what and when:
Seasol- diluted about once a fortnight

Is the plant indoors or outdoors:

Is the plant in a pot or in the ground:
Pot – have repotted one lot of cornflowers due to being too crowded

What other treatments have you given the plant:
Tried moving inside during a very dull wet week and they perked up and seemed to quite like being inside!!

Upload photo if available:

Other Comments:
Could this be possibly due to the fact that I have sown and grown them in mostly shade so as seedlings they are accustomed to more shady protected conditions and are smaller as a result? I have planted cosmos at home and totally ignored them and they are three times the height and are blooming prolifically! (They did get a lot more sun through- right from the start.)

Yours is a very important question Amye. Plants that need full sun (ie 90+% of all plants), will not grow well in the shade. Plants eat sugar that they make from sunshine – so, reduced sun = reduced health. Too little sun leads to tall, straggly growth (look up etiolation). That is, in the shade, plants grow taller, but spindly – the very opposite of what you said that you wanted.

You may well also have a problem with your (cheap & nasty?) potting mix being water-repelling. Maybe get some wetting agent such as Saturaid, and In future get only the best potting mix: Osmocote. Good luck, Don.