Answer: Marguerites, Argyranthemum frutescens, do best in full sun. In part day sun, they may weaken and bloom less.
Since they bloom for a long period, when grown in a container they need regular fertilization with a water-soluble fertilizer formulated for blooming plants. (They like a neutral to slightly alkaline soil, so do not use a fertilizer for acid-loving plants.)
Read and follow the label instructions as to the dilution rate; in summer when watering is most frequent you may get better results using the fertilizer at the "every time you water" rate to compensate for leaching.
Make sure that you are keeping the soil evenly moist but not sopping wet. Although this plant will tolerate a somewhat dry soil, it is preferable with container plants to keep it evenly hydrated to help the plants overcome summer heat stress and bloom their best. You may want to dig down a bit into the soil a few hours after you water to see how much water is actually needed to moisten the soil.
Finally, trim off the flowers as they fade. This helps keep the plant looking its best but also helps stimulate additional blooms. Avoid leaving bare stem tips and shape the plant as needed by cutting just above a leaf when you remove the old flowers. To some extent, the more you cut, the more the plant will bloom so try to do this regularly.
I hope this helps you trouble shoot.
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