Troubleshooting
Penstemon 'Sour Grapes' problems — and how to fix them
Penstemon 'Sour Grapes' (Penstemon 'Sour Grapes') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Death from cold, wet winters
More penstemons are lost to waterlogged winter soil than to cold itself. Plant in sharply drained ground and leave old growth on for crown protection until spring.
Reduced flowering without deadheading
Spent spikes slow new bloom. Deadhead regularly and grow in full sun to extend flowering well into autumn.
Powdery mildew
Develops in humid, overcrowded plantings. Improve airflow, water at the base and space plants for good ventilation.
Short lifespan / woodiness
Clumps grow woody and decline after a few years. Propagate fresh plants regularly from cuttings to keep the planting vigorous.
Prevent penstemon 'sour grapes' problems before they start
Most penstemon 'sour grapes' issues are care-mismatch, not bad luck. Dial in the basics:
Looking for penstemon 'sour grapes' in general rather than its problems? Read the full penstemon 'sour grapes' care guide — light, water, soil and feeding.
Penstemon 'Sour Grapes' problems — FAQ
Why is my penstemon 'sour grapes' death from cold, wet winters?
More penstemons are lost to waterlogged winter soil than to cold itself. Plant in sharply drained ground and leave old growth on for crown protection until spring.
Why is my penstemon 'sour grapes' reduced flowering without deadheading?
Spent spikes slow new bloom. Deadhead regularly and grow in full sun to extend flowering well into autumn.
Why is my penstemon 'sour grapes' powdery mildew?
Develops in humid, overcrowded plantings. Improve airflow, water at the base and space plants for good ventilation.
Why is my penstemon 'sour grapes' short lifespan / woodiness?
Clumps grow woody and decline after a few years. Propagate fresh plants regularly from cuttings to keep the planting vigorous.