Question
I successfully grow lovely large zinnias from seed every year. However, on the other side of the walk (4feet away)they do very poorly although all the conditions and soil are the same..  I'd be very grateful for your advice.  Thank you, Maryanne

Answer
Maryanne,
Are you sure that the sun is as strong on the other side of the walk? Have you looked, once the leaves are fully out in early June, to see if the same amount of sunshine falls on that side of the walk?  Zinnias like at least 6 hours of dead-on sun including the noon hour, and since these plants are from Mexico, the hotter the better.  My first suspicion would be that the other side isn't as hot, probably because there is less sun.

Drainage might also be a factor - is that side of the walk more poorly drained? Is there more organic matter there, or are there nearby shrubs or trees that might have root systems that effect the soil quality on that side?  Have you had the pH tested for each side? If it's wildly acidic or alkaline that could effect growth. Leaching from cement can effect pH, as can the liming of gardens or lawns.

Is the soil more compact on one side or the other due to traffic or age of the bed? Are both sides loosened the same way in the spring?  Is there more gravel or rocks under one side or the other, or does the irrigation hit one area but not the other side?

Something about that area is different - you just need to keep asking what the situation might be.

I hope this helps,
C.L.