We just arrived home after a week away to find our first perfectly ruby-red ripe tomatoes of the year... blighted by blossom end rot - blerg.
This is the second time in five years that we have had blossom end rot, which is an entirely preventable problem. The first time we had it we were complete rookies in the vege garden and I thought I had learned from my mistakes and that we wouldn't get it ever again... Ha! But as it has been a funny season with different rain patterns to the past few years, I figured we may not be the only ones who have discovered our tomatoes blighted by this problem. So perhaps I can lend some advice from our experience with it.
So, what is blossom end rot (BER)? It's not a disease or fungus or virus... it's more of a "problem" which affects your plants due to their prevailing conditions. This is good because it means that you don't have some pest running rampant through your garden. This is bad because it means there aren't any quick fixes. It can affect tomatoes, melons, capsicum and eggplant.
What causes it? BER is caused by a calcium deficiency in soil. The most common way to get it is by inconsistently watering your plants, especially at the crucial time when it has very early fruit. Even if there is absolutely no problem with the calcium levels in your soil, if the watering during that critical early stage of fruiting is insufficient or inconsistent it can lead to insufficient calcium uptake by the plant and then: blossom end rot.
Another common cause is over-fertilising. Too much nitrogen and potassium leads to acidic soils - which means a calcium deficiency leading to blossom end rot.
I am almost certain that both this occurrence of end rot and the one five years ago can be put down to watering issues. In our first year here, we were both working long days. In the summer months we would get up early to water before we left and then in the late evening when we got home we would do the same. Quite simply, this was too much watering... since then we have learnt that once a day is absolutely perfect. This year we went away for a couple of stretches, right when everything was in late flower/starting to develop fruit. We didn't have a watering system in place and so we suddenly went from daily watering to no watering (except when it rained... i.e. rarely). It is also possible I didn't adequately fork through the chook fertiliser that I added to our garden beds in early spring, which may have led to high nitrogen/low calcium in the soil - certainly I think this has at least played a part in this year's BER because so far (finger's crossed!!) it seems to be isolated to three or four plants at the far end of one garden bed.
So, what to do about it? Really, of all the problems you can get, this one isn't too bad. Kinda gross, yes, but not too hard to prevent. Firstly, if you already have end rot on your tomatoes, you will certainly know it and it is probably too late to completely resolve the problem. Here in the Southern Tablelands we still have lots of flowers on our plants yet to set fruit. So, if the pH of the soil is immediately amended by adding lime (calcium), there may be some fruit which survive unaffected. I have heard there are also calcium sprays that you can get to directly spray on to the plants which would obviously work more quickly, but I'm not sure whether or not they are okay for bees - I'll have to look into them further. You should remove any blighted fruit as soon as possible so that it doesn't encourage fungal growth (which is a lot more of a problem to control than BER, and is likely to spread to other healthy plants).
You can eat the tomatoes affected by end rot, just chop off the gross parts and use as per usual (although they won't be dinner party-presentable, they will be perfectly fine in cooking). If you really don't want to eat them, they are fine to go to the chooks or into the compost as they are not diseased.
For future years, to prevent a BER problem, make sure you test your soil pH before planting (you can get little tests at hardware stores and nurseries) and amend it as needs be. Don't over-fertilise and do make sure that it is really well forked through. Make sure that you water plants often and consistently but don't overdo it, and mulch each garden bed well to prevent moisture loss in the dry times.
Basically, keep it simple and consistent and exercise moderation in all things... probably a good plan for life in general as well as in the garden I suppose!