What Tomato Plants Need in August – 5 Essential Tasks to Enjoy Bumper Harvests of Plump, Flavorful Fruit

The right plant care in August has a huge impact on the flavor and appearance of tomatoes, as well as how long your harvest lasts for. We’re approaching peak tomato harvesting period this month, so how you look after your plants directly affects the quality as well as quantity of fruit. Start redirecting the plant’s energy on fruit formation and ripening, rather than needlessly growing more foliage, and you will be rewarded with tons more tastier tomatoes.

Without appropriate, targeted care in August, your tomatoes may split, develop unsightly black spots on their bases, and plants might fall prey to fungal disease and red spider mites that put an abrupt end to your harvest. With the right care, however, plants will stay happy, healthy and continue to produce plump, flavorful tomatoes for many weeks to come.

None of these 5 steps are a difficult part of growing tomatoes so get this essential August tomato care right and you can look forward to your best harvest yet. Understanding why you’re doing each task is a key part of keeping tomato plants producing all summer. Why? Because then you’ll be able to tweak each care task to perfectly suit your growing conditions and tomato varieties, whether you’re raising cherry toms or beefsteak tomatoes, outdoors or in a greenhouse, in any zone. Here’s everything you need to know for tip-top August tomato plant care so you can enjoy your best crop yet.

1. Strip Off Lower Leaves to Reduce Disease

First on the list of what to do with tomato plants in August is to strip off some of the lower leaves of indeterminate tomatoes. These plants will be dense with foliage by now, and removing some at stem bases allows better airflow, which in turn reduces the risk of disease. It also allows sunlight in to ripen fruit, and allows you to spot any developing issues faster.

This seems like a fairly drastic task but, as long as you don’t strip off leaves any higher than the halfway point of the plant, you’re doing more good than harm. I start by stripping lower leaves at soil height at the start of August, then take off another layer every week, gradually raising the leafless height to halfway as peak harvesting time is reached. This gradual strip doesn’t shock the plant, and reveals tomatoes just as they need the ripening sun.

Why bother? Well, late tomato blight, when fungus-like organism Phytophthora infestans infects plants and causes both leaves and fruit to rot, is a big risk at this time of year, particularly for outdoor toms. Indoors, leaf mold – which brings similar symptoms to the leaves, often with a grey-brown mold on the undersides – is the harvest slayer to avoid. For both, good airflow around the plants is the very best prevention, and stripping off lower leaves is the number one way to achieve it.

Removing lower leaves from the plants also makes it much easier to irrigate without wetting the leaves, further reducing the risk of disease.

There’s no need to strip leaves from determinate tomatoes, though do remove any leaves touching the soil to reduce disease risk.

2. Prune for a Full, Flavorful Harvest

Channelling plants’ energy into growing fruit rather than foliage now is the difference between a basic crop and a bumper harvest so, if you're wondering how to get a good tomato harvest, get your hand pruners at the ready! Remember, indeterminate tomatoes are vines, and they’ll keep growing – and growing – until the frost kills them, so if you want lots of fruit you need to curtail that growth, and redirect that energy into fruit production.

Keep cutting or pinching off any shoots that grow in the junctions between the main stem and leaf stalks. This stops plants wasting energy on growing fresh stems and foliage.

In mid-August, or when a plant has around four or five trusses of tomatoes, pinch out the main growing tip of indeterminate tomatoes. All you have to do is use hand pruners to snip off the uppermost few inches of the main stem, or simply snap it off with your hands. This halts the vine’s upward growth, redirecting its energy into ensuring existing tomatoes grow.

Depending on your zone, the variety you’re growing, and whether or not you can be bothered to ripen green tomatoes off the plant, you can also snip off newly-formed flower trusses at the end of August as there’s unlikely to be enough time for them to develop fully before the season ends.

Cherry tomatoes typically take around 45-60 days to grow from flower to full-sized ripe fruit; beefsteak toms can take up to 90 days. As well as cold weather slowing growth, temperatures above 86°F can slow development, too. So, keep your eye on the thermometer and gauge whether or not it's worth remove any new flower trusses to concentrate the plant's energy into existing fruit.

3. Water Consistently for High-Quality Fruit

How consistently you water your plants now will directly impact the quality of your crop. Erratic watering can cause tomato skins to split, and lead to dark, flat patches at the base of fruit, called blossom end rot. While blossom end rot is caused by a lack of calcium, it’s very rare that soil or compost lacks this element – the problem almost always lies in a lack of consistent water which the plant needs to transport calcium to where it’s needed.

Aim for consistent, steady watering to keep a fairly even level of moisture in the soil. Shading your tomato plants from the harsh midday sun will dramatically reduce evaporation, so this is another way you can help even out soil moisture levels. If it’s easier to rig up more general shade, then using a shade cloth that blocks 30-40% of rays will still allow enough sunlight through to ripen fruit.

Once most fruits have set and are ripening, if the weather isn't too hot, slightly reducing watering will concentrate sugars and flavor. Never reduce irrigation so much that leaves wilt, and it's also important to lessen the volume of water given rather than reduce frequency, so moisture levels remain consistent.

4. Feed Weekly, But Know When to Stop

If you're wondering when you should stop feeding tomato plants, you're not alone as this is a common query. And knowing when to stop fertilizing plants is just as important as knowing when to start, and one of the most critical pro growing tips for a long-lasting tomato harvest.

Until the uppermost clusters of fruit are full-sized, you should continue feeding your tomato plants once a week with a high-potassium tomato fertilizer such as Espoma Organic Tomato! Food, available from Amazon. However, as soon as you start redirecting the plants’ energy to ripening fruit that’s already set, especially if you halt the upwards growth of indeterminate plants by pinching out the tip of the main stem, it's vital not to over-fuel. Too much food can cause fertilizer burn, excess foliage and actually slow fruit production

So, from mid-August, gradually reduce the strength of the feed, tapering off so you don’t abruptly stop this supply of nutrients.

5. Watch Out For Spider Mites

All the hot, dry air of this El Niño summer has created ideal conditions for red spider mites. These sap-sucking critters can ruin a harvest, but are easily controlled if you spot them in time and act quickly.

Don’t rely on being able to see the mites themselves as they're tiny. Instead look out for:

• Moving dots. While the mites are minute, you may spot what looks like moving specks of dust. And don't expect them to be red! At this time of year red spider mites are often a yellowish green, only turning red – and becoming more visible on leaves – in fall.
• Damaged leaves. If there’s an infestation, leaves will first become stippled, where individual cells have been sucked dry, then turn mottled, pale and eventually die and drop.
• Fine silky webs around stems or leaves.
• A build-up of white cast skins and egg shells on the undersides of leaves.

The quicker you act, the better, as high summer heat speeds egg hatching from around 55 days to 7, and a female spider mite can lay 10-20 eggs a day. Remove infected leaves and wash the plant with a jet of water. Coat all surfaces, but particularly the undersides of leaves with a neem oil spray.

Do double-check if the neem oil is already diluted: if you have raw neem oil, mix 1-2 teaspoons into a quart of warm water, before using. To help the oil and water combine, add half a teaspoon of mild liquid dish soap to the water first.

Spray plants once a week for three weeks to catch any newly-hatching mites and break the lifecycle. Sprayed leaves are more easily scorched by the sun, so consider shading if necessary.

Tomato plant care in August is all about directing energy towards producing a plentiful harvest, and keeping plants disease-free so that process can continue for as long as possible into fall. Stripping lower leaves, tactical pruning, consistent irrigation, well-timed feeding and controlling pests will all help your plants happy and healthy, so they can keep providing you with a flavorful harvest week after week. And that's more than enough reward for the time it takes to complete these simple late-summer tomato care tasks.