Leptospermum suddenly shedding leaves

clematisdorset · March 2023

I hope I can be pointed in the best direction: I have this leptospermum (since last autumn) and I noticed today that several stems seem to be bare. I am sure they were not last week. The leaves have fallen onto the top of the pot it is in. Would it be best to leave it and wait and see? I am worried because I always manage to kill lavender and I don't want the same thing happening to this woody shrub. Any help gratefully received!

GardenerSuze · March 2023

@clematisdorset Not a plant that I have ever seen or grown. My first thought for any plant suddenly loosing leaves would be stress or shock.

Perki · March 2023

I haven't grown it either but would like to, I am sure its on the tender ish side hence why I haven't tried to grow it . All you can do is cross your fingers and hope it leaves up later on in the year . The sharp freeze in December has done a real number on plants this winter .

Is it inside this plant under cover and where you grow lavender ? And are you watering it over winter . It probably best to barely water at all over winter

Dovefromabove · March 2023

Not a plant I’ve grown, but this may be of interest

https://www.jeremybartlett.co.uk/2018/01/15/manuka-leptospermum-scoparium/#:~:text=Leptospermum is hardy to about -5 degrees Celsius,equivalent to RHS Hardiness Rating H2 –%20H3%29.

clematisdorset · March 2023

Thank you everyone! I will have a chance to look at it and check the pot etc in more detail later today. I wrapped it in fleece in December during the minus 0 nights and it was looking fine until at least last week. I did see a bright almost lime green caterpillar on it and not moving for about 1 week 2 weeks ago. I will check again and let you know! Thank you!

clematisdorset · March 2023

Hello again! Thank you for your helpful comments and questions. I have been able to check the plant and pot in more detail. For info, it is sheltered from the east by the house wall 2feet away, and it is in a 15 litre pot raised up on bricks on slightly sloping pavers, 7.5 feet from both perimeter walls, in a sunny area, facing west-southwest. I intend to plant it and other potted plants when I have removed some inherited landscaping fabric from the ground and amended the soil but the removal project is very labour-intensive and taking me ages to do even small bits.

The weather has been up and down like elsewhere, possibly some fierce cold winds have rattled through more than usual and there have been quite a few freeze and rain cycles, but most of those were in December when I think temperatures got down to -4 degrees c overnight during those times, but no snow.

I tried to identify the caterpillar, the best I could come up with was an Angle Shades Phlogophora meticulosa which apparently feasts on hazel amongst other plants.

The leptospermum is in ericaceous compost with added grit, gravel and sharp sand and mulched with Strulch.

Today I removed it from the pot and checked the soil and roots. Things looked fairly normal to my untrained eye, but the compost was a bit damper than I expected so I mixed in more shar sand and grit and returned it to the pot. The Strulch mulch was doing a good job, but I noticed it was encroaching on the trunk and collar so moved it away. The lower collar looks damp from being close to the mulch.

The bud area is tiny and I thought I could see a few buds but was unable to detect if these are from last year or new, developing ones.

I have not watered it since late autumn when I mulched it. I don't even attempt to grow lavender anymore but when I did they were also in pots and I seemed to get the watering wrong, for instance I would give them minimal watering in the summer, trying to keep consistency, but the lavender gently died off as the summer ended.....
....anyway! I understand it should flower between April and June. Thank you @Dovefromabove for the Jeremy Bartlett link - I had not come across that, very informative.

Incidentally, I left a potted dahlia out nearby all winter with no protection and that is already growing, so I am surprised about the Leptospermum.

My best guesses now are causes related to:

Cold winds, caterpillar, mulch encroaching around the collar/trunk.

I feel I should not prune/cut anything, but keep it as sheltered and dry as possible but not too sure.

I would say the defoliated stems account for about 1/4 or less of the plant.

I do like the airy qualities of this plant, so intend to persevere with it, and would be glad of any comments.

Photos from today:

JennyJ · March 2023

I wouldn't expect caterpillars to cause leaves to dry up and drop off. If anything they would eat the leaves.

Is there any kind of consistency/pattern to the bare branches? eg just older branches affected, or all on one side of the plant?, or all coming from the same main branch at the base of the plant?

clematisdorset · March 2023

Thanks, @JennyJ for your suggestion. I will have a look at the branches and see if I can detect a pattern. I have been turning the pot very periodically, but I think the bare stems were more to the north-east facing area, when I detected the problem, but I cannot be sure.

JennyJ · March 2023

I'm thinking it could have been more exposed to a cold wind from one side, or sometimes plants lose leaves on a side that's up against a wall, or the bark on one branch could have got damaged.

clematisdorset · March 2023

Yes, that is a good suggestion @JennyJ, maybe the way the wind funnelled through affected 1/4 area. The wind from the south west can be quite harsh and I understand this is what leptospermum do not do well with. The wind would come over walls, hedging and plants but it would come. The warmest, sunniest area is also the area the wind travels through to exit via the north-east corner (the south-west facing corner by the house wall). Maybe it would have been better not to have turned the pot, then at least I could be sure there were not more variables involved! I only saw the caterpillar for 1 week - I found a curled up and vacated rose leaf nearby, so maybe it had been sheltering there. After 1 week of sitting vertically on one of the main vertical stems of the leptospermum, the caterpillar seemingly vanished and then a week after that, I became aware of the 1/4 bare stems. Maybe the pot was too damp. I thought rain would not get through the Strulch mulch that I laid on thickly in the autumn - maybe I underestimated how much rain can get in. I have never grown or kept this plant before, but when I saw the bare stems, it reminded me of that helpless feeling I got with the lavender in years gone by.

JennyJ · March 2023

I had one once, thinking it would like the well-drained sandy soil, but it only survived one winter. It's not really hardy enough for my conditions.

Leptospermum suddenly shedding leaves

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