My bed of pachysandra is about 5 years old and is well established, but is now turning yellow and not as full as it was. Does it need fertilizer? Thank you.
Too much sun can cause yellowing of leaves.
Also too much water or too dry and the leaves will yellow.
If your soil is not acidic enough the plants cannot access the iron in it and can develop the condition Iron chlorosis.
Test the ph of the soil along with a soil test. Generally a lower ph is preferred but ideal is a ph between 5.5 and 6.0.
A spring application of fertilizer such as 15-30-15 can be used for a overall feed, but rely on the soil test results to pinpoint any other needs.
Your local Extension Office can help with a soil test.
Here is a link to find the closest office.
Check the leaves for small bumps. This could be Scale insects and the leaves can yellow from an infestation. Heavy infestations can kill the plants.
Neem Oil is a good treatment.