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Ive spent a day working in the garden today, and I noticed that alot of the plants which I have seen elsewhere standing tall and proud (eg verbena bonariensis, ammi amongst others) are, in my garden, rather too floppy.  And then tonight, watching Gardeners World on the internet, Monty's cosmos were pert and upright whilst mine droop  Am I lacking Pottasium in the soil as I have read somewhere?  Or something else?  And if there is a lack in the soil, when should I be treating it - can I do it now in the autumn?  I usually mulch every spring with home made compost, but dont add much beyond the odd bit of liquid feed during the summer.  Also we've been overseas for a few years and this is my first season back, so it might be that our tenants simply didnt manage the soil the way I would have done.  Any ideas would be welcome, thanks 

I always support cosmos and bonariensis.  It's a lomg growing season here, early too, so most things do get tall.  I do 2 things.  Firstly, in mid spring to late spring I cut back to make bushier plants.  Then in early summer I support the main stems of bonariensis .  My plants are (6' plus tall and stand up,to anything). Cosmos grown in the richer parts of my garden are also supported.  

Come the autumn most plants tend to want to flop a little ..more moisture in the stems,  still extending, etc.

No, I wouldn't add any potassium.  

One point though......I,found that plants grown for the first time in a certain area will grow bigger but in subsequent years grow less vigorously.  In a new border made last winter everything planted there has been enormous.  I'm not expecting the same vigour next year


Also, Monty's show was filmed about 3 weeks ago I think, so maybe your flowers have just come to an end, for this season at least, the cosmos wont grow again but you will be inundated with little verbena bons next year!.

Thank you.  I did support the verbena and it still went lazy on me!  But I do take your points about it being late in the year, and as the plants went in new this year after I returned it might be that they didnt properly 'bed in'.  I'll see how they go next year. 

I do appreciate the advice!



All the advice sounds good adam - just another thought- are they a bit dry? Those plants are usually in sunny spots so if the soil's sharp and free draining they may just need some extrs watering. Some of my taller plants have been a bit droopy as it's been very dry here recently.

Good point fairy.  Not just a pretty face   Many people seem to regard bonariensis as dry soil plants but actually they...and most verbenas......need reasonable moisture supplies

star gaze lily

Think they do like to be kept watered,  I have some, - mine aren't floppy

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