Phormium Feeding ?

I have a lovely Jester Phormium in a large container . I give it a good general purpose feed about twice a year ( spring and mid summer ) . Now the colours in the leaves are looking a little drab . What boost feed would you recommend ?
Sulphate of Ammonia ?
Sulphate of Iron 10%? ( worked great on a Fatsia )
or what ?

TIA

 

Hi H,

I used to use a rose fertiliser but only in the spring , as feeding mid summer can create too much new soft growth and if a harsh winter the late produced leaves would get easily frosted .

 

Thanks Spruce , I'll try a light feed with sulphate of iron followed by a general feed at the end of the month .

 

I always worry with the individual feeds if I overdo it, sulphate of iron etc I know I have various boxes in the garage I must get them out and see if I can use them up

 

Can I jump in with a question?

I have a purpley Phormium (can't remember the exact one without looking) and though it looks reasonably healthy is does look a bit washed out.
I don't have roses so no rose fertilizer, would a general all purpose granular fertilizer be appropriate? It is fairly big about 5ft high, and a solid clump, how much should I give it?

Thanks
GG

 

I suggested Rose fertiliser as the nitrogen content is normally long lasting rather than a quick hit , at that size 5ft high @Gay Gardener should be fine plus the one you grow is more robust than Jester as that variety is much smaller and is recommended for a container , but the best product to use and works quickly in making leaves look a lot less tired is seaweed feed which I use as a foliage spray on the trunks and the leaves of most of my plants once they have come into growth, but Phormium have a waxy coating on the leaves so best to treat the soil.

 

Thanks Spruce that's useful.