Black Spots on Tomato Leaves

Peter,
Could you help me out please. The tomatoes in Jack’s garden have black spots on the leaves. How do I fix?
Thanks,
Teemu

Err, that’s awkward. Black spots on Tomato leaves is a tricky problem. We were plagued by this disease for many years. Actually there are a number of diseases that can produce black spots, but let’s assume that the spots are caused by bacteria.
At Scotsburn, we almost completely eradicated the disease through good nursery hygiene and a ‘balanced’ feeding program. In the bad old days we were continually spraying copper solutions (like Bordeaux mixture) to prevent the bacterium infecting our Tomatoes but we found moving Tomato pots up onto benches much more effective. Moving to benches reduced the amount of water that was splashed around the plants – splashed water can pick up and transmit disease.
We also worked on the theory that our plants needed to be growing vigorously to prevent the disease attacking. This is a good theory but it turns out that the execution was a ‘bit out’. We were feeding our Tomatoes so much that they became lush, soft and very prone to minor physical damage which gave the bacterium access to our plants.
The solution came from Peter Wood who used to run Woodlyn Nursery and he happens to be my mum’s cousin. Peter suggested we cut back the Phosphorus (P out of the NPK ratio) in our fertilizer blend. I have previously related Phosphorus to fatty food. Great if you need it but seriously addictive. Tomatoes love it and it doesn’t take much to get your plants jumping out of their skins. So what did we do? We found a ‘balanced’ liquid fertilizer with equal quantities of Nitrogen and Potassium and almost no Phosphorus. Problem solved.
Can this be fixed at home? I think so. If you are planting in pots, use a quality potting mix. I recommend Debco’s Terra Cotta and Tub mix. If you choose to add additional fertilizer I suggest Phostrogen – Tomato Food (phew their analysis agrees with mine, takes the Potassium levels even higher). We are in the process of trialing Debco’s Organic potting mix but I don’t have any suggestions for organic fertilizers in pots yet.
I haven’t mentioned growing in soil. Soil is great, use organic fertilizer like manure. Well prepared soil protects your Tomatoes from many disease problems.
Image from University of Minnesota. Michelle Grabowski. Click on the image to see the original.

Impatiens Downey Mildew.

3 seasons back we first heard of a Downey Midew disease specific to Impatiens walleriana (It does not affect New Guinea Impatiens). We are somewhat isolated here in Keysborough so we didn’t see any until very late that season. The following year was tough and Impatiens production was nearly wiped out. Last year it appeared that the disease had gone away again but… It’s Back!
The good news from our perspective is that so far we are clean, despite the weather conditions being ideal for the development of Downey Mildew.
The bad news is if you have had diseased plants in your garden you will have to take particular care to ensure clean plants you introduce are not immediately infected. HYGENE! You have to remove, dump, destroy all infected plants and clean pots and surrounds with household disinfectant. It’s best not to reuse garden beds for a number of years.
The only other tip I have is keep plants as dry as possible (HA, HA!), this includes watering early in the day to ensure maximum time for plants to dry out and keep them in a full/high light sun position. Full sun will not bother Impatiens until we get into January type conditions, just be careful of windy days.
By the way, I nicked the pic of the underside of an infected Impatiens leaf from a web site and have forgotten where. My appologies.

Tomato Categories, a summary

I have been asked quite regularly about the way I categorize the Tomatoes we grow. "What d'ya mean Hertitage?" Well this is a summary...
Heirloom. Technically refers to plants not bred for commercial production. These varieties were bred or selected by enthusiasts mostly for there own use or shared amongst friends. Because of their breeding they can be a bit variable in the way they grow and they definitely have a magnificent range of flavours. Heirloom Tomato varieties we grow at Scotsburn include Radiator Charlie's Mortgage Lifter; Cherokee Purple; Stupice (Czechoslovakia); Principe Borghese; Riesentraube (Germany); Black Russian; Tommy Toe and Green Zebra (Green Zebra doesn't quite fit any of the categories, follow the link to see why).
Heritage. Older commercial varieties with freely available genetics. When we couldn't buy Tomato KY1 any more we collected some seed. Many of these varieties were developed from simple crosses of existing favourites Grosse Lisse & Rouge de Marmande. These varieties look and taste like Tomatoes! Heritage varieties we grow include: College Challenger, Burnley Surecrop; Heinz's ES58; Roma and Colonial.
Hybrid. Many of the latest vegetable hybrids are far too expensive to grow in punnets or small pots, I have heard Kumato costs around $1.00/seed! Just the seed! It is grown under license only so you will not see it in back gardens for a long time yet. Modern breeding has produced much more prolific and disease resistant plants but some people believe this is at the cost of flavour. I believe the loss of flavour is more related to the cultural practice of picking the fruit very early. Our Hybrid varieties include Mighty Red (aka Carmelo); Apollo; Health Kick; Patio Roma; Mr Ugly and Tumblin' Tom.

Waterwise Colour!

Last Sunday I was out doing errands when I drove past this stunning display just around the corner from my place. Instantly I knew what I would be writing about this week, so I stopped and went back to take a photo. The gardener was busy in her garden so I said “excuse me, can I take a pic…” at this point Lyn stood up “oh hello, it’s you!” Now, anyone who has met me knows that I am hopeless with names and it took 5 minutes for me to remember and I have to admit to having completely forgotten her partner’s name.
Anyway, Lyn used to work at Burdett’s House and Garden in Langwarrin and I have bumped into her a number of times locally, but I didn’t know where she lived.
In the mean time the whole neighborhood has noticed the most striking garden in the street. About 2 years ago this garden had been dramatically transformed. The cream brick fence pulled down and recreated as a sculptural feature, tasteful timber decking, undulating sand and pebble mulch and striking Dracaenas and Cacti. I had thought of taking a photo and sharing it but I didn’t want to promote Desert landscape too heavily.
But on Sunday afternoon … WOW! The Livingstone Daisies (Mesembryanthemum crinifolium) were just luminous. Lyn tells me that they have been flowering since late July and are now past their best (I usually drive past early in the morning when the flowers are still closed for the night). And how about this, the whole front garden of Livingstone’s started with 5 of Scotsburn’s 8” bloomer pots that were being thrown out at Burdett’s. After 2 years of self seeding Lyn is in the process of thinning them out so be a little careful, in the right conditions they will self seed freely.
Here’s my point, seedlings are not necessarily thirsty plants! Remember that Petunias, Marigolds and Portulaca are all native to dry parts of South America. I am a great advocate of intelligent use of water and that doesn’t mean you can’t have a beautiful, colourful garden.

Moving Spring Vegetables Outside?

HI Peter,
I am growing a variety of vegetable seedlings indoors (tomatoes, capsicums, zucchini, pumpkins, corn etc) and am wondering when I can plant them outside?
Regards,
Miriam
Have you noticed the forecast for Saturday? 3deg in Scoresby and frost patches not to mention the hail we have had this week.
The question of when to take young plants out from under protective cover is always vexed and you have to take a bit of a risk. The slightest hint of frost will make a terrible mess of Tomatoes, especially if they have only recently been moved outside.
Having said that the rule of thumb is these plants should thrive in the garden from early October. As a gardener you will develop a sense of when the Spring weather really turns. My feeling is this is still a week away this year, much later that it has been for a number of Spring seasons.

Sunshine is essential

Peter . I was shocked when I read about denuding Tomato plants. I have always followed Peter Cundall`s advice that heat was the essence of riping not sun directly on the tomato but I can see the logic of the goodness going into the fruit and not the leaves. This year I will try cutting the leaves on the south side of the plant after it reaches 50cms. Have you any advice for Mt. Waverley climate. Laurie

I had previously directed Laurie to this web site with a rather radical suggestion for increasing Tomato yields and flavour.

Ohhh, there’s so much to discuss in this little note. Including disagreeing with the much loved Mr Cundall. Peter did a great job educating and encouraging gardeners of all ages to enjoy vegetable gardening, so I need to take care but I believe many gardeners misunderstand the importance of light as distinct from heat.

Light levels play a critical role in controlling the way a plant grows and stimulating the formation of buds. I received an unrelated but similar enquiry a few weeks back:

I have a young desert rose plant that isn't looking to well. The bottom of the trunk seems to be a little wrinkly and soft some of the leaves are turning yellow. I had been watering it every 2-3 weeks, but have stopped doing that as I thought I maybe over watering. It sits on my coffee table in the lounge but gets the sun. Any advice would be appreciated.

Unfortunately I haven’t seen this plant to comment with authority, but my first thought is It’s just too dark for the plant to grow properly in that environment.

One of the first things I learnt about growing Cyclamen is that once they have germinated (in the dark) it is essential to get the very young plants in to the brightest position available to ensure that flower bud development is stimulated. Of course the trick is to protect these young plants from drying out… without keeping them too wet.

Like everything, balance is needed. There is no doubt that extreme mid Summer sun can be very damaging but as a rule of thumb the more light you can give your flowering/fruiting plants the better.

While I’m thinking of Peter Cundall, don’t forget that The Gardening Australia Expo is on at the Caulfield Race Course over this weekend. Get along and ask John Patrick a few curly questions!

Enough for today, I’ll have to come back to planting tips we still have a few weeks until Cup Day.