AusBonsai

Im a newbie at the bonsai thing and i need help with my two trees. The Trident Maple has black spots and the leaves are drying out and falling off. I have sprayed with them both with rose spray cause of the black dots and the Japanese Maple had powdery mildew. Now the Japanese Maple has one leaf with the black spots but otherwise looks ok and some advice on placement and watering would be greatly appreciated.

A photo would help with the diagnosis if you have one?

Here are some photos

Are those pots sitting in trays of water?
The black spots do look like a fungal problem but the scorched ends of the leaves might be caused by rotting roots. Damage looks very similar to scorch from being too dry. Is it possible they were dry, even for a few hours recently?

It looks like these are outside. Maples do need fresh air and sunshine.

Can I see white marks on the leaves. Not sure if it is really there or just a trick of the photo? Where does your water come from?

Do you think the trident may have out grown that pot? The roots do seem a bit much but i dont know how much to trim. I did spray them with the rose spray. To try and stop the black spot. The trident did get dry in the soil from an absolute scorcher. Im trying to find a place with some morning sun then filtered midday sun and shade in the afternoon. Im thinking of building a shade house for them and future trees. We only have tank water here which is only rain water. Oh and no they are just trays i have for them to sit in. When i water them i chuck out the excess water from the tray

Hi maybe you could try a bit of chopped up sphagnum moss over the soil to cover those exposed roots to get it through summer till it's ready to repot in spring. It helps to retain some moisture in the hot weather preventing the soil from drying out. My Trident seems to like full sun as long as it has its water. Japanese Maples not so much full sun with the leaves being so delicate they will burn.

Where would you get moss?

Should be able to find bags of sphagnum moss at most nurseries. I picked up a bag from bunnings where all their soils and other media is.

I find that a humidity tray is a far better way to extend pot moisture levels through the day. You could use the trays you already have under these bonsai.

Get a tray that will hold water. Mine are around 4 cm deep but the depth is not critical. For individual pots try a large black plastic pot saucer/ drip tray. I have some larger trays about 2m long and 60 cm wide 4 cm deep that cater for most of my smaller bonsai.
Fill the tray with coarse gravel - again does not really matter what size but larger chunks allow more water to fill the spaces. I have 6-10 mm gravel in some and 6mm maidenwell diatomite in others. When you water your bonsai the tray fills with water. The pot sits on the gravel so it is just above the full water level and it can't get waterlogged. As the day warms up the water in the gravel tray evaporates. The evaporating water cools the air around your bonsai and increases humidity so your bonsai uses less water from its soil so the water in the soil in the pot lasts longer.
Roots will often grow out the drain hole and into the tray below. That does not matter, in fact it allows the tree access to even more water and space and the trees grow better.

BikesandBonsai wrote:Hi maybe you could try a bit of chopped up sphagnum moss over the soil to cover those exposed roots to get it through summer till it's ready to repot in spring.

Outstanding advice! Cover fine roots, expose nebari. It's not just a newbie error either, plenty of seasoned bonsai folks make the same mistake.

Cheers,
Mojo

I use an old bucket lid for my banksia on hot days. The lip on it is around 1cm deep possibly less, and the lid is only slightly bigger than the pot by about an inch all the way around. I do it on a mid 30's day and over, the water has completely been soaked up half way through the day and by the time the sun goes down the soil is just damp. Granted this may not work well with Trident roots but being in water.

shibui wrote:.

As the day warms up the water in the gravel tray evaporates. The evaporating water cools the air around your bonsai and increases humidity so your bonsai uses less water from its soil so the water in the soil in the pot lasts longer.

Actually this has been found to be a bit of a myth. Orchid growers have taken RH readings around plants sitting in these types of trays and have found no measurable difference to the rest of the growing area.

I have a Japanese maple forest I struggled with leaf mould every summer. This year not a spot as I tried a new position out of full Sun under a massive lemon tree providing spotted light only... This is also a very breezy spot which I think helps. I also have rarely burnt tips and watering just once daily no tray required. They are a cool climate tree where as the trident will want full Sun and does not get the leaf mould problem that I have seen. Humidity will bring on leaf mould too. Hope this helps. [WINKING FACE]
Btw - this is in Sydney climate

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May well be a myth Mike but something is happening because my smaller pots definitely stay alive and grow better on the humidity trays.

Well i put some advice into practice and put some spaghnam moss down, i got some rocks and a tray to make that humidity tray, then bought a cheap green house from bunnings and covered it in shade cloth but the plastic can still be put on during winter as it does get pretty cold here. I would like some feedback on my next idea, i fitted the green house with sprayers that i have plumbed up to a 5L pressure sprayer for really hot days. Here's some photo's, let me know what you think. On the plus side i think the rose spray has started to rid the black spot now just got to deal with the heat problem. I really hope they pull through. It's all a learning curve.