By Kathy Widenhouse, award-winning author of 9 books, content writer, website publisher, and owner of Tomato Dirt, the web's leading online source of for growing tomatoes in the home garden.
If you’re new to gardening, you may not be aware of when to mulch tomatoes … indeed, whether you need to mulch tomato plants at all.
To answer the second question first.
Mulching tomato plants has many advantages. Mulch keeps moisture in. A layer spread over bare soil allows the area to soak up more water. The outer layer dries faster than the soil below it. That reduces the rate of evaporation from the soil, plus it lets the soil to retain moisture for your tomato plants.
Plus, mulch regulates soil temperature. In the heat, a layer helps keep the underlying soil cooler. But when temperatures are cooler in the spring and fall, a layer of mulch keeps tomato roots warm.
Mulch also cuts down on weeds and prevents disease and fruit rot. And if you use organic mulch – like straw, grass clippings, shredded bark – or even newspapers – the mulch can improve the soil by breaking down during the off season.
Should you mulch tomato plants? Yes. But the question is when.
You’ve worked the garden soil … added plenty of compost … measured the appropriate 24-36 inch distance between tomato plants … filled the prepared holes with a couple of inches of water … even topped off the surrounding planting area with a bit of fish emulsion, bone meal, and other yummy nutrients.
And now you’ve gently set the tomatoes in their new homes, filled the trenches, and tapped down the dirt to anchor the plants. You’ve even inserted tomato stakes or cages next to your young seedlings so you won’t disturb their root systems later on.
But don’t make a costly mistake: mulching tomatoes too early.
Wait until the soil has warmed to mulch tomato plants – about 2-5 weeks after setting plants in the garden. Tomatoes like heat. The soil needs to warm before adding layers.
If you mulch tomato plants too early in the season, the ground is still cool (especially in northern regions or where the temperatures dip at night). The mulch traps cold in the soil. That means delayed blossoms, which delays fruit development, which leads to a later harvest.
On the other hand, don’t wait for hot weather to take over before you add a layer of protection around your seedlings. Mulch keeps tomato plants and their roots warm during the spring, but mulch also keeps the soil cooler when temperatures soar. If you delay mulching tomato plants until the soil is overly warm, then the added layers will trap excess heat and stress to your crop.
Bottom line: wait 2-5 weeks after planting to set out mulch or you’ll be waiting extra-long to eat fresh tomatoes. Except for …
There’s one exception. If you’ve set out sheet plastic weed block or black plastic to warm the soil early in the spring, then you needn’t wait to mulch tomato plants. The soil temperatures have already warmed, thanks to the fabric or plastic covering the garden surface. Poke or cut holes in the material for your seedlings.
Black plastic mulch offers additional advantages for your tomato crop. It holds in moisture, reduces weeds, and prevents diseases from spreading.
But if you don’t use black plastic, recycled plastic weedblock or other fabric and sheet mulches, never fear. Tomatoes adore organic mulch like shredded leaves, straw, grass clippings, compost, newspaper, biodegradable weed mats, shredded hardwood, sawdust, and wood chips. Organic mulch is good for the soil. As it decomposes, it adds organic material to your garden. Most organic mulches are cheap or free. Take care to use grass clippings only when the yard has not been chemically treated.
The time to mulch tomato plants is after the garden soil has warmed. Unless you use sheets of black plastic, then that time will be 2-5 weeks after planting. You can use a soil thermometer to make sure your garden is ready. Once the soil temperature is over 70 degrees Fahrenheit, your plants are ready for their extra layer of protection.
But first, give them a dose of Tomato Tone or Miracle Gro Tomatoes. Pour water into holes. Then spread a 2-3 inch layer of mulch, making sure you leave a couple of inches of room around the stems to protect plants from disease.
And let the mulch do its work.
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