What to Do With Tomato Plants in September: 4 Key Tasks
Your tomato plants may be starting to look a little tatty by September, but don’t be tempted to forget about them entirely. In all likelihood, they’re still fruiting and ripening, and a few easy jobs could keep them healthy and productive to the end of the month, or even beyond.
If you’re growing tomatoes in the US, there’s a huge range of stages you might be at with your crops: in southern states, you’re likely in full harvest mode with fruits looking good for weeks to come, or further north productivity will be tapering sharply off this month with frosts very much on the horizon. Either way, there are jobs to do in September to get the most from your tomato plants.
One of the most important things to know about growing tomatoes is when to harvest, and we’ll cover that here, as well as how to make the most of the early-fall sunshine for ripening, and how best to support those last harvests on the plant. What I always enjoy at this time of year is a pretty harvest basket like this wooden one from Amazon. It brings so much joy to the season.
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1. Adjust Your Watering Regime
After a hot summer, and likely a week or two of neglect when you may not have been able to care for your tomatoes while on vacation, your tomato plants will be in need of a good drink, with added water-soluble fertilizer. Miracle-Gro from Home Depot is ideal. Feeding tomatoes is one of the essentials when learning to grow these crops.
I give them this boost to provide the energy for a final harvest, and then begin to reduce watering. This tip is for outdoor tomatoes especially. And regions where you’re starting to get the first September showers. Wherever you are, the days will be starting to shorten and that fierce sunlight is beginning to mellow. Naturally, your tomato plants will need less water. I then cut back gradually to help concentrate the sugars in those last harvests, making for sweeter tomatoes.
Exactly how much water do tomato plants need? Before I reach for the watering can (I love this Bloem EZ Pour from Ace Hardware), it’ll get water direct to the roots where it’s needed), I always check the top inch or two of soil (you can use this soil moisture meter from Amazon). It’s best to wait until the top of the soil has dried out before watering or you risk causing root rot, a fungal infection caused by over-saturated soil and that can quickly set in and kill the entire plant.
Consistency is important too, as too much (as well as too little) water can cause your ripening tomatoes to split.
2. Tidy Up Your Tomato Plants
(Image credit: Getty/nikkytok)
As the heat of summer fades, tomato plants will need all the energy they can muster to ripen those remaining fruits. If you haven’t done this already, it’s time to give your tomato plants a little trim, which will help to redirect the plant’s energy into ripening rather than maintaining stems and foliage.
First of all, I cut out the main growing tip of each plant (also known as topping tomato plants) to leave 2-3 leaves above the top truss of tomatoes. This stops the plants growing upwards, which is pointless at this time of year. These micro-tip Vivosun pruners from Amazon are a great no-nonsense tool here.
Next, I take out the old lower leaves of my tomato plants and thin out any foliage that is shading trusses of green tomatoes. It’s one of the key ways to get tomatoes to ripen on the vine as it speeds up the ripening process by letting in more sunlight.
You’ll have been doing this all summer, but don’t forget to keep pinching out those side shoots too – the ones that develop between the main stem and each side stem. They’ll only cause bushy growth at the expense of fruits.
Then, and this one is for the majority of gardeners (if you’re in the southern US states you might get away with ignoring this one for another few weeks), I snip out any new flower clusters as these won’t have time to mature, and will just waste the plants’ precious energy.
Finally, if your plants are flopping all over the place, like mine, I tie wayward growth back into its supports where fruits will ripen more quickly and healthily. I use a system of easy to adapt supports like these from Home Depot. A decent gap of around 12in (30cm) between the lowest leaves and the soil helps to keep plants healthy.
3. Remove Spent Plants
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Early September is the time to take a tour of your tomato plants and assess. There may be some that are looking healthy, with ripening trusses of fruits. Others will be beaten up an weather worn – it’s the end of the season after all and all good things come to an end.
It’s wise to be realistic at this stage in the year, so I earmark anything that’s diseased or overly shabby for the compost heap. Then you can concentrate on your best, most productive plants.
Removing old, underproductive plants will also slow down the spread of common tomato diseases, which can be particularly rife among tomato plants at this time of year. A quick note here: if you’re taking out heavily diseased plants, it’s best to keep these out of your home compost bin or heap. I find a rolling garden cart like this one from Amazon a great fuss-free help with jobs like these.
4. Harvest Your Tomatoes
Most tomato plants ripen from midsummer onwards, almost until the first frosts. Smaller fruits ripen more quickly while large beefsteak types can take a lot longer to color and sweeten up.
Knowing when to harvest your tomatoes is an art, and will depend on the type of tomatoes you’re growing and the predicted weather for your area. In general, of course, USDA Zones 1-3 will have a lot longer for ripening, while those further north will need to think about cut-off times in a matter of weeks.
For the best flavor, you’re looking for fruits that are evenly colored and ripened with a good amount of sun. After a few weeks of dull weather and rain, your tomatoes will begin to taste insipid.
Once I get to the point that tomato ripening is stalling, I bring them indoors to ripen off the vine. Full sized tomatoes are best here, and even better if they have a hint of colour. I take them off the stems, wash them carefully, dry them then keep them in a single layer in paper bags on a warm windowsill (popping a ripe banana in with them to speed up the process) and they soon take on more color and flavor. A tiered organizer like this one from Amazon can be helpful here.
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Your tomato plants don’t need a great deal of care in September, but those little tweaks you do get round to will make all the difference, giving you better harvests for longer, into mid-fall if you’re lucky and you’re growing in one of the warmer regions.
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