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Late Summer Tomato Care

Portland gardeners,

We are about halfway into August and that leaves us about one month left for our tomatoes to ripen before cooler weather and shorter day lengths begin setting in with autumn. How are your tomato plants doing? My observation is this summer's weather is considerably cooler and cloudier than our recent past summers. Is that also your feeling?

This year I grew two tomato plants in our raised bed: 'Lemon Boy' slicer and 'Sungold' cherry. This raised bed was moved from our old garden to our transitional home and filled with a new load of white lightening compost from Dean's innovations. The new raised garden bed is a south-facing location and shaded from the east in the morning hours by a tall laurel hedge and then receives full sun from about 11am until sunset.

I am pleasantly surprised this year I have the largest healthiest tomato plants loaded with more fruit than I've experienced in 20 years of gardening in Portland. Which is interesting given the cooler temperatures this summer and tomatoes thrive in HOT summer weather. Both tomato plants are huge. The cherries are ripening nicely and I'm enjoying picking them daily for fresh eating!

I counted 45 tomatoes on the 'Lemon Boy' plant!! That is way more than I ever harvest off one plant here in Portland. However, it is now mid-August and not one 'Lemon Boy' is ripe. Here's a photo of the first fruits starting to turn yellow.

As you know, I am a big advocate of pruning tomato plants. Indeterminate types of tomatoes, that includes most all slicing and cherry varieties, never stop growing. Here in Portland our summers are not long or hot enough to allow unregulated tomato plant growth.s

When we selectively prune off branches and suckers it promotes good circulation and encourages the plant to sink energy into fruit development rather than leafy green plant growth.

In this photo you can see the entire 'Lemon Boy' plant and how it looks after several prunings. Loads of fruit, some leaves, and no non-fruiting branches left.

See in this photo how I've pruned the tips, stems, flowers, and tiny fruit off? This is an important strategy in August for growing tomatoes successfully here in Portland.

To encourage plant health and production I have pruned my tomato plants throughout the growing season.

Now in August I get downright ruthless with my pruning and I encourage you to do the same!

We want you to have an excellent tomato harvest by the end of September. After September the weather is not favorable for ripening tomatoes.

In this photo you can see what could be pruned off to promote those green tomatoes to ripen.

Everywhere you see a red line prune there to eliminate those smaller stems with flowers. The red circle is a "sucker." Prune all of those suckers out!

At this point in August we do not want our slicing tomato varieties to produce anymore flowers. There is not enough time for those flowers to produce fruit that will actually ripen this season.

This is a really important practice to do right now in your garden. I assure you it will help a lot!

Now let's look at the 'Sungold' cherry tomato plant. Since cherry tomatoes are much smaller than slicing varieties they are quicker to ripen. I think it is ok to leave new flowers on cherry tomato plants until the end of August. They should develop and ripen by the end of September.

However, I do recommend pruning off all suckers and branches without flowers and fruit now in mid-August. Remember, it is time to be ruthless!

In this photo you can see where to prune. Pruning in this place will remove a large stem with several suckers and no fruit.

Now that we've mastered pruning tomato plants let's turn our attention to watering and fertilizing. Tomato plants continue to need watering throughout the month of August. Consistent watering frequency, duration, and quantity promotes healthy tomato plants with uniform fruit development. Inconsistent watering can result in stressed plants and cracked fruits.

During this peak heat of summer I am watering the raised bed every 2-3 days. When I dig down a few inches I see the soil is dry in between watering and this is how I determined how often to water.

How about fertilizing? We know tomatoes are heavy feeders and benefit from monthly applications of organic granular vegetable fertilizer.

Phosphorus promotes bloom and fruit. Remember when you look at a package of fertilizer it shows three numbers for example 10-5-5. That middle number is phosphorus. The first number is nitrogen. Nitrogen promotes leafy green plant growth and that is not what we want our tomato plants doing in August and September.

Organic granular sources of phosphorus are bone meal, fish bone meal, and rock phosphate. You can top dress the soil around your tomato plants with any of these organic sources. They slow release to the tomato plants.

For speedier results, use an organic liquid bloom fertilizer. Liquid fertilizers are water-soluble and make nutrients immediately available to your plants. I like to use concentrated Big Bloom by FoxFarm (0-0.5-0.7) made up of earthworm castings, bat & seabird guano, rock phosphate, sulfate of potash, magnesium, and kelp. I purchase it at Portland Nursery.

I hope you are enjoying your vegetable garden this summer and a bountiful tomato harvest.

Happy Gardening,


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