In some cases, suckering indicates that the tree is stressed. Stress
could be caused by incorrect planting (too deep, too shallow), incorrect
watering (too much or too little), insect attack, etc.
Suckering can also be a characteristic of the technique used to graft
the scion onto the root stock. Finally, some trees (e.g., poplars,
crepe myrtle) just enjoy suckering.
Suckers should always be pulled away from the trunk or roots. If they
are merely cut, they will quickly grow back.
While plum and apricot are both in the genus Prunus, they are quite
different species and should not be expected to grow the same.
--
David E. Ross
Climate: California Mediterranean, see
<
http://www.rossde.com/garden/climate.html>
Gardening diary at <
http://www.rossde.com/garden/diary>