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I have a new lemon tree which has not set any fruit. The flowers appeared, the bees buzzed, the petals fell and that was it.
Any hints?
I have a new blackberry with spots of yellow powder on the underside of the leaves.
Any more hints?

The white spots under the leaves of your blackberry may be eggs from some sort of butterfly. Though, I'll have to check on that.

I don't know about the blackberry, but it sounds to me like you may have a nutrition deficiency. Have you tested your soil recently? Also, what area are you in, as this can change some of my answer.

Citrus trees'roots are fairly shallow and extend quite a bit beyond the spread of its branches. If you are in a dry climate, you will need to give the roots a good soaking on a regular basis, not just a steady trickle.

Citrus trees also thrive with a good nitrogen supply. Compost; well-rotted manure, blood meal or cottonseed meal works well. If your lemon tree is in a sandy soil, you will need to provide a heavier feeding because in the sand the nutrients leach out easily. Avoid using an inorganic fertilizer whose residues may accumulate and may make the soil too alkaline.

It is important to keep the area around your lemon tree free from weeds that may compete with the roots. Even mowed grass bordering too close to the tree may steal nutrients away from your lemon tree's roots. Consider using a ring of mulch around the base of your lemon tree to hold in the moisture.

I'd often seen citrus trees painted white at the base as a kid - it turns out that they often have delicate bark that can be succeptible to sunscald. I believe it's just a latex paint (water based).

We are in an area famed for its citrus fruit, the soil is volcanic, has had no chance to dry out, my horses provide a never ending supply of manure, and there are no weeds within cooee.


Surely you don't mean I have a nutrition deficiency?

Well, it is kind of a shot in the dark. I would still get the soil tested. If you are using horse manure, is it well-composted?

Apparently a better way to assess your tree's nutrition is to get the leaves tested: https://www.hortnet.co.nz/publications/science/kk0292.htm

How old is the tree?
Seems to me the tree has to be at least three years old before fruit will actually develop.

Yes, the age seems the more likely explanation. I'll just exercise patience.

Actually, I read on some more and found that if you started your lemon tree from seed, it can take 10 years before it starts to produce fruit! Yikes!

Fortunately I won't have to wait that long, as it came from a nursery looking pretty much like a lemon tree.

Oh good!
Hopefully you get fruit next year.

Citrus cuttings should fruit within about 3 years, grown from seed can take 10 years or more to bear fruit. That said, I planted some seeds from a supermarket pink grapefruit in January and a couple of them are showing buds which look as if they could be ready to flower. So, in short I don't know

Blackberries don't like it too wet and some of the best crops of wild berries I have tasted have been on beach sand dunes within a peble throw of high tide. They are a coloniser of bare ground and as such will tollerate and thrive in poor soil and full sun so you may be killing them with kindness if you are mulching with over-rich manure.

Yellow powder sounds like either egg masses (could be butterflies; we've a few that dine on that species...) or fungus. Look carefully as we wouldn't want to kill good guys, but we would like to get rid of the latter...

HG

As far as getting rid of the latter, my guess is that the only way to do this is to defoliate the blackberries (or just hack them down) and then burn the infected foliage.

If it is a fungus, after burning the foliage, bury the ashes somewhere where they won't bother anyone or anything. Some fungal spores can resist temperatures up to a thousand degrees Centegrate.

You can use Copper sulphate but, I would DEFINATELY NOT recommend it.

What do you think Scott?

The old Cupric of Sulphate is not such a bad guy in my book, although you will alter soil chemistry some (towards the acid). But I'm not convinced they are in need. All I've heard is about yellow powder, not leaf damage or necrosis. I'm still betting on egg masses...

HG

I concur, just putting the options out there.