Hi Ninja @lasttemplar,
Welcome to the forum. Fifteen years is a significant investment in these trees, and I completely understand your concern about their decline. Before I dive into my answers, though, could you upload those three photos you mentioned? I can see you intended to attach them, but they don't appear to have come through on my end. Images will make a huge difference in how accurately I can diagnose the leaf damage and assess the overall condition of the trees, so please add them when you get a chance, and I can give you a much more targeted second response once I've had a look.
In the meantime, based on everything you've described, I can already give you a thorough answer to all six of your questions.
Are the Trees Salvageable?
Almost certainly yes, and here's why I'm optimistic. The fact that your trees are still producing new growth and have flowered tells me they are very much alive and have not given up. Olive trees are extraordinarily resilient plants that have evolved to survive drought, poor soil, and serious neglect in their native Mediterranean habitat. Even a tree that has been left unpruned for years and has become congested or misshapen can usually be brought back into good shape over a season or two of careful corrective pruning. Sparse, bare branches and reduced foliage density after years in the same pot are symptoms of a tree under stress, not a tree that's dying, and that's an important distinction. With the right interventions, which I'll go through below, these trees have every chance of recovering well.
Root Binding After 15 Years
This is, without question, one of the primary contributors to their decline, and your instinct here is spot on. Fifteen years in the same pot is a very long time even for an olive, which is more tolerant of being pot-bound than many other trees. What happens over that period is that the roots gradually fill every centimetre of available compost, eventually circling the inside of the pot in a dense, tangled mass that leaves no room for new root growth. When roots can't expand, the tree can't absorb water or nutrients efficiently, regardless of how well you feed and water it, which leads to the gradual thinning and decline you're describing.
With the size of your olive trees, you don't want to be repotting them every few
can cope with it, and it will make them more stable in high winds and make them less reliant on you watering them as much. Repotting into substantially larger containers with fresh compost and good drainage should be one of your first priorities this Autumn.
Repotting Versus Planting in the Ground
Given that you're in Newcastle, this is genuinely the most important decision you'll make for these trees, and I want to be straight with you about the considerations involved. In containers, olives are spectacular, and the pot can be moved under cover during exceptionally harsh winters, largely eliminating hardiness concerns. For a northern location like Newcastle, that ability to move the trees under cover during the coldest spells is genuinely valuable protection that you'd lose if you planted them in the ground.
My recommendation would be to repot into significantly larger containers rather than planting out, for that precise reason. Choose pots that are at least 30-40% larger than the current ones, use a gritty, free-draining compost mix (a John Innes No. 3 with around 20-30% horticultural grit mixed in is ideal), and ensure every pot has excellent drainage holes that aren't blocked by compacted roots. When you repot, gently tease out the circling roots and remove as much of the old exhausted compost as you can from around the root ball before placing it in the new container.
When to Prune: Wait for Autumn and Better Conditions
This is where I'd urge a bit of patience, given what we're currently experiencing with the heatwave. Whilst olives can technically be pruned from late spring through to late summer, pruning a tree that is already under heat stress is adding insult to injury. When temperatures are high and the plant is struggling to move water efficiently through its system, every pruning cut is an additional demand on a plant that's already working flat out just to stay hydrated. Fresh pruning wounds need energy and moisture to seal over, and right now your trees simply don't have that to spare.
My strong advice would be to hold off on any significant pruning until early Autumn, ideally September or October, once temperatures have dropped and we've had some meaningful rainfall to thoroughly rehydrate both the trees and the compost. Pruning after a period of good Autumn rain rather than during a drought makes a profound difference to how well the wounds heal and how vigorously the tree responds. You'll also be able to see much more clearly which branches are genuinely dead and which are simply drought-stressed and temporarily bare once the trees have had a chance to recover with some cooler, wetter weather.
In the meantime, the only pruning I'd recommend right now is the removal of anything that is visibly dead and completely desiccated, as dead wood places no additional demand on the tree and its removal won't stress it further.
The Leaf Damage
Without seeing the photos, it's difficult to be definitive, but irregular damage around the leaf edges in northern UK olives is most commonly caused by one of three things: wind scorch (very common in exposed northern gardens), frost damage to leaf margins during cold winters, or occasionally olive moth larvae,e which nibble leaf edges in a characteristic pattern. Scale insects can also cause a general decline in vigour accompanied by leaf damage. Once your photos come through,gh I'll be able to give you a much more precise answer on this one.
Should You Remove the Strawberries and Ground Cover
Yes, remove them. This is not a minor factor in your trees' decline, and I'd prioritise addressing it promptly. Strawberries are surprisingly vigorous and competitive plants, and over the years of spreading they've described, they will have colonised a significant proportion of the available root space in each pot.
Olive trees in containers are already working with a restricted volume of compost and root space, and having strawberries compete for every available drop of water and nutrient within that same restricted volume places a serious additional burden on trees that are already struggling. Clear everything from the pots except the olive trees themselves, repot into fresh compost, and give the olives the full resources of their containers without competition.
Further Reading
My full guide to growing olives in UK conditions covers all of this in comprehensive detail, including winter protection advice that's particularly relevant for your Newcastle location:
Please upload those photos when you can. These trees sound absolutely worth saving, and I'd love to give you the most precise advice possible once I can see what's going on with the leaf damage.
Happy gardening!
Lee Garden Ninja
Lee Burkhill: Award Winning Designer & BBC 1's Garden Rescue Presenters Official Blog
