Why Aren’t My Tomatoes Ripening? And How Can I Fix It?

A selection of September tomatoes from the author’s garden.

As summer starts to wane, gardeners everywhere become anxious for tomatoes to begin ripening. Those big green globes hanging on the the vine seem to take forever to turn vibrant colors. How can we get those tomatoes to mature before the garden season ends?

Brandywine, a classic beefsteak heirloom

Why Those Tomatoes Aren’t Ripening Up

First, let’s examine the reasons those green tomatoes aren’t turning beautiful shades of crimson, scarlet, orange, golden, chocolate, and purple. If we know the root cause, we can address it, and help our tomatoes ripen up.

The main reasons those green tomatoes aren’t maturing:

1. It’s too hot. Tomatoes stop producing lycopene and and carotene when temperatures exceed 85F for prolonged periods. If you’re experiencing a heat wave, it may slow the ripening process for your tomatoes.

2. It’s simply too early. Once tomatoes reach full size, they need 20-30 days to change color. (The time from “mature green” to fully ripe be slowed due to extreme heat. See #1 above.)

3. Larger varieties take longer. Small cherry tomatoes can begin to yield ripe fruit within 50-60 days. Larger beefsteaks can take 75. The classic huge Brandywine variety can take 80-100 days to turn color. Look carefully at your seed packet for “days to maturity”, and plan accordingly.

Large heirloom beefsteaks mature later

Let’s Get Those Toms Ripe!

While some physiological processes cannot be rushed, there are a few techniques that can push the plant into ripening its fruit earlier. We can communicate to our tomato plants that the season is winding down, and it’s time for them to get in gear and ripen the “mature green” plants that are hanging about on the vine.

YouTube player

How to encourage tomatoes to ripen:

1. Stop watering. Stress encourages plants to ripen up the fruit they have set. Plants rush to mature their offspring (seeds) in anticipation of their imminent death. Hence, thirsty tomatoes will stop producing new leaves and flowers, and put their remaining energy into maturing any fruit that has been set.

2. Pick off flowers and immature fruit. Remove all flowers, and continue to remove any new ones that set between now and when you pull the plant.

Check your last frost date. If it’s less than 40 days away, remove all immature green fruits that have no chance of ripening before cold weather hits.

Sungold, the most prolific tomato in the garden – sweet and abundant

Looking to Next Year’s Tomato Crop

I hope these tips help you understand why your tomatoes aren’t ripening, and how to assist them in maturing their fruit.

We all want to be successful gardeners. Those tomatoes we have lovingly tended all season need to give us a yield of beautiful fruits. When planning your garden for next year, triple check that selected varieties do well in your climate. Check “days to maturity”, and select options that are adapted to your temperature and growing season.

If you live in a cooler climate, or an area with short seasons, consider focusing on those “early” tomato varieties like Early Girl and Siletz.

Consider going with cherry tomatoes, which produce consistently and abundantly. Even in “rough tomato years”, cherries such as Sungold and Sweet Million never fail to produce bumper crops.

Enjoy your tomato harvest this year, and plan ahead for success in next year’s, as well!