Bark chippings will stop seeds growing through so always mulch once seeds have grown 2-3 inches. Bark chipping layers will stop weeds seeds and seeds that you have planted from growing. Leave the ground bare after planting flower or vegetable seeds so they can get the light and will sprout through.
Cover bare soil that you don’t intend to plant in with bark chippings to prevent weed seeds from growing through.
Top reasons why you should not put bark chippings over seeds
There are 3 main reasons you should not put bark chippings over seeds. Let’s explore each reason and why mulching over seeds is a bad idea.
1. Bark chippings block light
Bark chippings are generally in large pieces or will knit together tightly stopping sunlight from reaching the soil. The seed will not get enough light to continue to sprout and grow through the bark chip layer so most seeds will fail if they are covered with mulch.
2. Bark chips are heavy and will stop soft seed stems
Bark chips will stop seeds from growing as the heavy bark chip will weigh down the soft stem. Most seeds including flower seeds such as violas, vegetable seeds such as carrots, onions and tomatoes will all struggle to grow through bark chippings.
Any stems that might manage to poke through would have used up a lot of energy to make it through the bark layer and may be softer and less hardy. They may also be lighter in color as the bark chips can limit photosynthesis as it will take longer for leaves to reach the light.
3. Bark chippings are great at stopping weed seed
One of the main benefits of adding bark chippings over the top of soil is to prevent weed growth. This is achieved through the same process of blocking light and stopping the stems from growing through the mulch.
A 2-3 inch layer of bark chips will stop almost all weeds and therefore will stop the growth of any other seed you plant.
How to mulch with bark chips for seed success
Here are the easy steps to use bark chippings around seeds without stopping their growth.
1. Remove any old mulch from the soil
The best way to use bark chips to successfully grow seeds is by starting with removing all mulch from the soil first. Use a rake to move any old mulch back from the soil and pile it on the side of the bed. This can be used on the bed later or removed altogether for a neater look.
2. Rake the soil flat and improve the soil
Add extra aged cow manure and compost to the soil and rake it flat, removing any large pieces of compost so the seeds have nice, soft soil to grow through.
3. Sprinkle the seeds on top and water them
Plant you seeds on top of the raked soil, cover them with a light layer of seed raising mix or more garden soil. Water them in using a sprayer nozzle on the hose. Seeds should be watered gently to prevent them from washing away.
4. Keep bark chippings away until the seeds grow 2-3 inches
Allow the seeds to sprout and grow through the soil. Thin them down to your desired spacing and wait for them to grow their second set of leaves. By then, most seedlings will be 2-3 inches high and will be well established.
Once this has happened you can move the old bark chippings back around the plants. Keep them back from the stems at least 2 inches to make sure you don’t smother the seeds.
Bark chippings work great for flowers and vegetables. In my vegetable garden I like to use a lighter mulch like sugar cane or straw as it breaks down quickly, near the end of the season it will be broken down and can be dug straight into the soil.
Can plants grow through bark chippings?
Most plants will not grow successfully through bark chippings. The best way to use bark chippings on garden beds is to keep them 2-3 inches back from the stems of the plant and just layer them on the surrounding soil.
The one exception is when you plant bulbs. Bulbs like irises are large, contain a lot of energy so will be strong enough to push through a thin bark mulch layer.
For more on this, check out my previous article on how to mulch irises.
Can I mulch over sunflower seeds?
While sunflower seeds are large, strong and grow easily it is best not to mulch over them. Even these large seeds will struggle to grow through bark chips or straw and even if they make it through they may be weaker in the long run.
For sunflower seeds to grow successfully leave the soil free of mulch. Instead mulch any surrounding paths to prevent weeds and then mulch can be moved around the plant once it has established.
Will seeds grow through bark chippings? | Summary
Seeds will not grow through bark chippings as the mulch will block the light, making it more difficult for the seed to sprout through. Bark chips are great for stopping weeds for the same reason. Keep them off of the seeds you plant until they have grow large enough to hold themselves up and have at least 4 leaves.
I like to use bark chips around my wildflower seedlings once they have established in clumps. I will plant the seeds out into a pot and then transfer the whole pot into my garden and move the bark chips around the edges.
For more seeds I like to start them in seed raising mix and plant them out. The exceptions include large seeds like pea or beans as these seeds don’t like to be moved and it can slow their growth.
All seeds like a good amount of light to sprout so keep the bark chips away until they are bigger.