Hi Matt,
There are a couple of reasons for this and the cause will affect what you should do with it.
If all the flowers were open then it is quite possible the phal was just at the end of flowering and it is quite normal behaviour. In which case just cut the spike down close to the leaves (as close as you can without damaging the leaves). It is then worth considering repotting because Phals from Home Depot are usually best repotted soon after you get them.
If there were still buds and they are falling unopened then you may have bud blast which happens with a change in enviroment, if that's the case the advise is still the same as above.
BUT early dropping of buds/flowers may indicate problems. If the buds have dropped early then it is really important to repot and check the roots carefull to ensure they are healty.
|