Ferns in himalayas:
I am planning a family trip to the himalayas (for 5-6 days in 2nd half of March). Please suggest a region where I may find a significant variety of ferns different from those found in the plains (in this season).

there, which part of the Himalaya do you want to visit and in which country?
In the Indian west Himalaya I could recommend going to Kedarnath Mandir in Uttarakhand.  I mean, there are masses of places!  But that is a good area. Or for more westerly species up in J. & K. somewhere.  Another good place is going up the Rohtang Pass above Manali, N. of Kulu, in H.P.
Further east in the central Himalaya there is a wonderful area near Pokhara in Nepal .(no visa needed for Indian nationals) and then heading up on the Annapurna trek (get a local porter where the bus drops you at Naya Pul), a route which has good lodges, great views and superb ferns!  Or, of course, in India in West Bengal, go to Darjeeling and up Tiger Hill and then on the Sandakphoo trek up to Tonglo – and if you are energetic go on up to Phalut, the triple point of Nepal, Sikkim and West Bengal – that’s a great area with fine views of Kanchenjunga Himal and lots and lots of lovely ferns!.
N.E. India is hard of access in the East Himalaya, but  itis very good to go to the non-Himalayan hills from Shillong, Meghalaya – visit Sohra (“Cherrapunji”) and Mawsmai cave and down the spectacular views and dense forest down towards Shella.
All those places have good places to stay and great ferns.  Suggest looking them up and seeing which might suit you best!