if you can post a picture that would help with and assessment. I couple of ideas that come to mind would be this the tree will naturally try and grow upright so you could leave it be and see if a new branch tries to become the new leader. You could train the branch you have left to be the new leader by using the techniques that bonsai growers use. I had an off balance meyer that I tied one branch off to the pot to pull it the direction I wanted it to grow. After a couple of months it kept that direction on its own You could "pug" it meaning cutting the whole tree off, ABOVE THE GRAFT and let the new branches that will grow form the new canopy. the main trunk will most likely flush new growth at or just below the cut and will grow vertically again if it doesnt die off. Give it some good fertilizer and wait it out. Mike

You know you might be on to something here ... The most aromatic Makrut have really bumpy fruit and thick spines/thorns; prevalent with fruit/seeds brought in from Thailand. The fruit is nearly all seeds and oil; with very little juice. There is another variety with smoother fruit and smaller thorns that are not as aromatic (but still nice); and tend to bear juicier fruit with less oil. This seems more prevalent in the West. I wonder if the latter are somehow crossed with other highly similar smooth skin papedas, specifically either Khasi from India or Westeri from the Philippines. Since the aromatic compounds are in the oil; maybe the juiceless, thorny variety might actually be better! In any case, you might be able to remedy this somewhat by only using the very freshest leaves (should be full size for your tree but still have a waxy sheen) as those are the most aromatic. The dull older leaves are the ones with only the vague citrus/lime aroma (since the highly volatile scent would have been long gone). This post was edited by farm96744 on Mon, Mar 3, 14 at 17:19

Kaffir limes are one of the least cold hardy citruses. Unless you have protection from freezing and below freezing temperature to keep them warm above freezing temperature, they will not survive. It's leaves get damaged already when air temp are at 3 deg C if not gradually hardened off. It easily gets defoliated entirely in our zone every winter, and these are protected under the eaves of the roof overhangs with a west wall that serve as heat supply at night. Key limes are more cold hardy than Kaffir limes based on my own growing conditions here.

Something makes me think you may be in the UK. So I'll convert Patty's excellent advice to English English. First wash off that old soil. Swish it around in a bucket of not too cold water. Several times in fresh water if necessary. Re-pot in a much smaller pot than the one in your photos. Use something really free-draining. For a gritty mix, I use a mixture of equal parts Tesco low-dust cat litter, horticultural grit, and mini bark chips. (Not any cat litter - this one is special. And the best bark chips are sold for orchids, or as reptile bedding!) Add a teaspoonful of slow-release fertiliser to the mix. Don't plant too deep - those top roots should be at the surface. Use sharp secateurs to prune off the lowest green shoot. It is below the graft line, and therefore from the rootstock variety and not your lime. Cut off all the brown shoots at the point they turn brown or just above a green node. And cut back those little stubs closer to the main trunk. Water with a weak soluble balanced feed. The new gritty mix needs to be thoroughly watered, allowed to drain, and no water in the saucer. Keep warm. Now - if you think praying helps - pray! If the plant recovers, it will need more frequent watering than before but allow the surface to become dry.