Blossom-End Rot: Scourge of the Tomato Hordes

Composed July 15, posted July 25, Blogger used to let ya change the date when you had a draft saved up!

Just when you think that nothing stands between you and more tomatoes than you possibly know what to do with, disaster can strike, in the form of blossom-end rot. A brownish or blackish patch appears on the very bottom of a tomato, and spreads. If only a small patch, the tomato can be harvested and used-- just cut the patch away. It's not guaranteed to spread, but it can do so. A really bad case will spread up to the whole bottom half of the tomato, which will quickly become an oozy smelly mess. Heartbreaking!

Here is a small paste-type tomato with a minor case of blossom-end rot. Fortunately, the other tomatoes on the plant seem unaffected. Its brethren on the same cluster are also normal, so this particular tomato must have been having a bad day. I'm definitely going to be keeping an eye out, though.

If you'd like to minimize your chances of finding out about this first-hand, there are a lot of things you can and should be doing. Blossom-end rot often appears first when the weather gets very hot and dry, and the tomato is going into its heaviest bearing phase. For many Bay Area gardeners, especially in the South to mid-Bay, that time is about now.

First, let's look at the factors that go into blossom-end rot. It's fundamentally caused by an inability to get minerals, water, and nutrients in the right ratio to the right place. However, the situation leading to this could be any one, or combination, of the following:

• Simple lack of water. Lack of water can start blossom-end rot on a day to day basis, but once it starts, it will continue on affected fruits.
  
• Lack of available minerals, specifically calcium, and to a lesser extent, magnesium, due poor soil or competition from other plants.
  
• Dry, hot winds that evaporate water from the plant faster than the plant can replace it.
  
• Over-fertilization, leading to sudden growth spurt demanding more nutrients than readily available. Especially easy if foliar feeding with too rich a mix.
  
• Using blossom-set sprays which encourage the plant to start more fruits than it can currently support.
  
• Sudden change in watering, such as trying 'drought watering' during heavy fruiting, or having someone over-water plants while you are on vacation.
  

How to keep this situation from arising?

• Keep a regular watering schedule of deep waterings, and adjust them appropriately as the plant grows and bears. If you've been watering shallow and often, rather than deep and seldom, you are in for a long summer: your tomato plants probably have not bothered to root deeply, and you'll have to keep watering them frequently to get them through the summer.
  
• Get a simple, under $10, moisture meter from the local hardware store, the kind with prongs that you press into the soil. On days which are supposed to get hot, dry, and windy, check your plants before you go into work, or in mid-morning if you have the flexibility. If the soil does not read 'moist' at the 6 - 8 inch layer, and you are due to water within a day or two, do it now.
  
• If you see your plants drooping when you get home, and/or when there is not bright sun overhead, mist them heavily to help normalize the water in the plant. They can take it in through the leaves. Look at the top few inches of new growth to decide what's 'drooping'; most tomato varieties have straight tips. A water-starved plant will let the top couple of inches droop over, like someone slumping after a tough day.
  
• When you plant your tomatoes, in addition to compost you should add bone meal or a cal-mag supplement. If the supplement is 'prilled', that means it's pelleted: make sure the box says it's safe for veggies. Some iron supplements are prilled with material containing arsenic, for instance, and are unsafe to use on citrus or veggies. The manufacturers shrug and say "the product is labelled for lawns only". Anyway.
  
• Mulch your tomato plants with at least an inch of compost, cocoa hulls, straw, or other plant material. The feeder roots near the surface are responsible for accomodating changing conditions in moisture and nutrients to deal with day-to-day growth. The mulch will prevent the top layer of soil from drying out. I prefer compost, though if I had a bigger garden, I'd use straw over compost. The compost gives the plants nutrients directly, whereas cocoa hull or straw will take long enough to break down that it won't contribute significantly to this year's garden, only to next year's when you rake it into the beds after clearing them out. Note that if you are mulching for the first time, water first, then mulch, then give the mulch a soak-down. Otherwise you will interrupt your watering cycle, as the mulch will suck it up. If you are watering under the mulch via soaker or drip, ignore that last, and just spray down the mulch a bit to keep it in one place and avoid having it sponge up water from the soil, away from your plants.
  
• Full-grown plants bearing fruit will need an additional dose of nutrients and minerals as they begin to settle down to ripen the fruit. They need this at least a couple weeks, ideally longer, before they REALLY need it, as these things take time to break down to a useable form. Watering on top of compost mulch will take care of the nutrients, by and large, but minerals will need to be sprinkled around the plant (6 - 12 inches from the stem, where the feeder roots are greatest) and scuffled or raked into the compost/mulch. If you are using a drip or soaker that is under the mulch, you'll need to scrape back some mulch and work the mineral supplement lightly into the top half-inch or so of soil. Then re-cover it with the mulch you scraped back.
  
• Be cautious about using foliar feeding after your plant is about half-set with fruit. You could push it into overcommitting. If you are a very experienced gardener (much more so than myself), you probably know enough not to overdo it. I'm not sure about it myself, so I don't want to lead anyone astray. I first did foliar feeding this year, while trying to save some tomatoes which had to be moved as almost-mature plants (long story, involving neighbors' construction project). I tried it on some of the non-moved plants, too, but didn't want to go crazy with it. :-)
  
• Don't try calcium sprays and the like. From what I have read, those are not going to do you any good, unless possibly you spray them on the soil around the base of the plant. Nutrients fed into the leaves tends to stay in the leaves, giving them more 'excess' sugar production to send to fruits. Dissolved minerals, on the other hand, especially calcium and magnesium, form layers of mineral salts on the leaves if used heavily, and can interfere with normal photosynthesis. Think about the white stuff that gets all over your nice shiny plumbing in places with really 'hard' water-- same kind of thing. Not what you want on leaves.
  

I hope this helps you with your tomatoes. If somebody from your local Master Gardener extension program says something different, listen to them and not to me! Otherwise, I think I've got the basics here. Good luck, and good gardening.

Enormungus Scary Garden Update of Doom

Did a ton of gardening this morning, in both the front of the house, above, and the back. Still more to do, but I got way too much sun. You'd think that splashing cold water out of the hose onto my upper arms and face (while filling up the self-watering planters) would clue me in that I was getting sunburned. When I felt like doing it again, and again, and again, and kept doing it? Well, let's just say sometimes I get a bit too focused!

I redid the front area so that I could add perennials, like the dahlias, and the clumps of lilac, sage, and geranium on the edges. The frontmost bed will be for annuals. The one advantage of our clay soil is that once you get raised beds with some good light mix over the dirt, everything roots down into the clay layer and needs much less frequent watering. I've still been taking garden pix, but no time to post them on the net lately. Watered everything, mulched some more things with compost, tied up the big sunflower that wants to fall over-- and discovered that the ants are aiding and abetting its colonization by cottony scale, where the side flower stems join the main stem. Had to blast them out of each joint, what fun. At least I was in shade at that point.

I had already had to clean scale off the little Meyer lemon potted tree a few days beforehand, blasting each and every leaf, top and underside, with water. Boy, that was fun-- not! It seems to be recovering. Gave it a new top-dressing with compost, and a deep watering, and the leaves are definitely greening up again, but with considerable scarring from the little nasties. When processing the photo for uploading, though, I see there are still a few scale on it. Time to do it again, argh!


I'm starting to get tomatoes here and there, and finding that a bunch aren't what I thought they were. Some are easy to verify. This is definitely my Green Zebra, and next to it, a Hawaiian Pineapple. I have an Aunt Ruby's German Green about which I'm pretty confident, too.

On the other hand, this is so not my much anticipated Black Cherry. I thought maybe if I let the tomatoes ripen more, they'd darken, but no. Saw a Black Cherry in the Master Gardener tomato trials plot of the Sunnyvale Community Garden a couple of days ago. They go right from dark green to a chocolate-red color. Bzzt!

As for its buddy here, into which I put so much toil and worry while rescuing when I had to move all my raised beds? Well, it's definitely not my even more eagerly-awaited Noir de Crimee. Well aich ee double hockey sticks, as my Grandmere used to say.

No problem, I'm sure they're good, but I don't know if I got the seedlings mixed up (easy to do with a zillion tiny pots) or if some of the seed from eBay was from folks who don't know how to really breed tomatoes. There are basics like putting a bag over the flowers and pollinating with a paintbrush so that you are sure you are breeding true. Definitely a 'learning experience' with regard to labelling while starting seedlings, and while transplanting them!

I've been seeing a tremendous variety of pollinators lately, including large black carpenter bees and various types of tiny bees. I feel that my strategy of letting various things go to seed, and planting a mix of flowers and veggies, is really paying off in diversity. Here's some volunteer lemon balm and savory; note the tiny buzzy dude at twelve o'clock, in the top third, on a lemon balm leaf. I accidentally sprayed a new bug out of the air while filling the watering can. It was quite striking, gleaming a metallic dark blue, almost navy blue, and with dark wings. It hung out on the patio table, flicking its wings to dry them, for a few moments before flying off. Of course, I had already put the camera in the house on one of my trips to fetch something. I think it was a Blue Mud Wasp, though the picture on this website does not do it justice-- seen from above, it was really pretty, not scarily-waspy at all.

Keeping a saucer of water available on a stand in the garden also helps. It's supposed to be for birds, but I think a lot of insects drop by to avail themselves. This photo is from back in April. The stand is now across the path from its previous location, and there's barely room to get back there between the tomatoes!

The ones along the fence are all supposed to be paste tomatoes, except for the one cherry, a Principe Borghese. The one that's supposed to be Amish Paste is making fruits that start out with the oblong classical 'paste' shape, but several have rounded out and reached almost beefsteak tomato size. I have no clue what the heck is going on. Boy howdy, am I going to be a better labeller going forward!

There's so much more to tell, but I need a better workflow than Blogger and FlickR, and all of us probably have stuff to do! But please do follow the links on any of these photos (except the bird bath) to the full set of my July garden pix. More tomatoes, more flowers, including the daylilies I need to do a separate post about, insanely out of control lettuce going to seed (yes, that is a 3-foot tall tomato cage!) and more. Have a great summer, hope to post more soon!

Garden Desktop: Mexican Sunflowers 2006

Last year I started my Garden Desktop series with the wonderful Mexican Giant sunflowers that I grew from Parks Seeds. They're back!


They self-seeded a number of offspring, not all of whom survived the combination of snails and of my garden-bed relocations. I was delighted to see, however, that a couple of them came through with flying colors. I need to take them down at some point to move the greenhouse back about 3 feet, to clear a maintainance/inspection cover in the ground. However they're so pretty that I just can't quite bring myself to do it!

Easily 10 - 12 feet tall, with stems a few inches thick. We have some very strong winds here occasionally, so I took the precaution of staking the smaller pair, winding some tomato tape around the stems and back to the stake between them. The little finches who live nearby are already very excited about the ripening flower heads. :-) Here's the 1024 x 768 version. If you have a higher-res desktop, drop me a comment and I'll upload the 2592 x 1944 version for ya!