MAGNOLIA GRANDIFLORA

The leaves on my magnolia have become yellowish brown, so 2 weeks ago I used Sequestrene to feed it (two sachets in 4.5 litres of water as directed). Pack directions say one application lasts all season but can I feed again, indeed should I feed regularly until I see some improvement?  What more can I do to help things?  Not sure how old the magnolia is but it's now about 12 feet high.

Thank you!

Pinkpeony, Magnolia leaves are prone to frost damage and we had some heavy frosts over the last few weeks.
My way would be to forget the spray feed and use a good mulch of hummus rich soil around the base of the plant then wait, it should repair itself.
Depending on which type you have their needs vary Neutral or acid soil and some will grow in alkaline soils but all should be well drained.
Shelter from prevailing winds and some shade are needed, Mine gets early morning sun and shaded from the winds it has done well.
hope this helps.

Frank.

Palaisglide - thank you for your reponse.  I didn't use a spray just applied the liquid feed direct to the soil; I will use a mulch as you recommend and wait and see...... I'm a relatively 'new' gardener and have learned I'm also a very impatient one! 

Thanks again.

My one is 20 years old and it always loses it's oldest leaves at this time of year. I've got some with brown and yellow patches on but the plant does not seem to be suffering. Could be due to the wet and warm spells, but I'm not worried too much as there's lots of new leaves and flower buds forming.

The result of taking your advice - thank you!  More flowers this year than ever and the leaves are regaining their colour.