Calcium distribution is key in preventing tomato blossom end rot: Ask an expert

Gardening season is full steam ahead and you may have questions. For answers, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website, type it in and include the county where you live. Here are some questions asked by other gardeners. What’s yours?

Q: What is this? It’s on all my ripe cherry tomatoes, but only on one variety (Jaune Flamme). All the Sungold right next to it are fine. Should I pull out the one with this blight. Is it contagious? You don’t see it until they get ripe – the green ones look fine. The inside is brown all the way through. They are pretty crowded in an aluminum raised bed. – Benton County

A: This looks like tomato blossom end rot, a deficiency of calcium. One of our experts Chip Bubl recently responded to a similar question with this advice:

Blossom end rot (BER) is one of the most difficult problems to manage in tomatoes. It is essentially the inability of the plant to provide enough calcium to the developing fruit. The calcium deficient cells at the bottom of the tomato are weak and basically die. This leads to the browning at the bottom that we see.

Part of the problem is that calcium is rather complicated in its distribution in tomato plants. First, once it gets in a place, it stays there and can’t be later moved to somewhere else the plant needs it. Second, fruits, roots and shoots compete for calcium. Generally, the shoots win. If the plant is lush with shoots, a lot of the calcium is banked there. If it is dry, roots may get more to go deeper into the soil where there might be more water. Third, if it is dry, when water returns, the last mineral taken up is calcium. Finally, the genetics of some tomatoes make them more prone to BER.

So, what can you do to counter this? First, plan ahead on where you are going to put tomatoes next year and work lime into the soil this fall at the rate of 10-15 pounds per 100 square feet. By spring, the calcium in the lime should be available to your plants. You only need to lime an area once every four years.

Second, water evenly and deeply during the growing season.

Third, on cool days, remove some of the excess foliage to reduce calcium competition in the plant. That may be helped by reducing the nitrogen available to them.

Some people spray leaves with a dilute calcium chloride solution or even leaves and fruit with milk! I am not convinced either works consistently. Finally, keep records on which varieties are doing well re: BER and which aren’t. Weather plays a role so don’t give up on a variety for one bad year. But if the pattern is consistent, maybe stop growing that variety.”

Here is a useful Extension publication to help with further troubleshooting for this issue. – Elizabeth Records, OSU Extension education program assistant

Q: One often reads that for “normal trees” the root zone is out to the drip edge. When watering an espaliered tree, should we envision an analogous root zone mirroring the tree’s branch structure?

A: Espaliered trees’ root system extends far beyond the plant structure itself. Depending upon the tree species, the roots of an espaliered tree may grow out 5- 2 feet from the trunk, depending upon soil texture, impediments and watering pattern. The above-ground “manicured” structure does not reflect nor limit roots; it just limits the amount of photosynthesis that occurs due to less foliage. So, envision the tree’s rootstock variety as it would be growing naturally and water further out. Here is an article about roots. –

Kris LaMar, OSU Extension Master Gardener

Q: My English boxwoods have been declining in health rapidly over the past few weeks. We’ve been noticing leaf discoloration on one plant that is now spreading to the others. We were told it might be a blight, but I’m not sure. How should we treat this issue?

A: This article from Michigan looks at if there is truly a blight or some environmental damage.  Because of the intense and prolonged heat this article looks at heat as an issue.

Here is an article about blight from the PNW Disease Handbook with more photos and management options. This issue may require involved treatment options so please read and digest these materials and make the appropriate choice accordingly. – Jack Shorr, OSU Extension Master Gardener

Q: This cedar has a browning crown. I’m not sure if this would be considered flagging and the tree will recover, or if it’s actually the beginning of crown death, followed by the entire tree. Please let me know what you think and if there is anything I can do to help this tree. – Clackamas County

A: It is very difficult to know what caused the dead tops. The tree looks reasonably healthy overall. Cedar can have dead tops for several reasons: squirrel damage, drought effects, heat scorch or some fungal canker diseases.

Because the tree looks so healthy and the tops are so distinct, it may be squirrels debarked and girdled the stems at the top of the tree. In which case the tree is not unhealthy. However, it looks like you can’t really see what is going on. I would just monitor the tree and I think it will grow new leaders if it is healthy.

So far, the color of the tree looks good. If you think it is possible the roots are drying out a lot, you may want to consider watering the tree once or twice a month during summer. – David Shaw, OSU Extension forester

Q: Is there an online reference where I can look up a bee we saw in our yard in Portland? (If anyone can identify it for us, that would be nice too.)

We were cleaning under some trees and it appeared to be nesting in the ground. We have a bee box for mason bees on the other side of the house, but haven’t seen those black mason bees in a couple of months. This bee was near our “tiny pond” of standing water/wet planter in the yard. – Multnomah County

A: Here is a link to a guide to bees in the Portland area from the Xerces Society for Invertebrate Conservation. The bees you are seeing are black-tailed bumblebees (Bombus melanopygus). They are one of the common species of bumblebees we see in the Willamette Valley. Here is a bit more info from Wikipedia

“This bumblebee can utilize a number of habitat types, including agricultural and urban areas. It feeds on many types of plants, including manzanitas, Ceanothus, goldenbushes, wild buckwheats, lupines, penstemons, rhododendrons, willows, sages and clovers. It nests underground or above-ground in structures. – William Gerth, OSU Extension Master Gardener