You may be familiar with borage as a beautiful garden herb that produces delicate little blue flowers, blossoms that are perfect for freezing in ice cubes for a refreshing summer twist in your favorite chilled drinks.
But did you know that this herb, known to us in botany as Borago officinalis, can also be used as a ground cover to improve the soil?
It can even be used as a green manure when mixed into your soil or compost as a source of organic matter and nutrients.
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I will discuss how to use this herb as a green manure, and the garden benefits of using it as a ground cover. I will also provide some solutions on how to buy borage seeds.
Here’s an overview of what’s ahead:
Borage garden benefits
When you think of ground covers, borage is probably not the first thing that comes to mind. Perhaps you imagine a field sown with buckwheat, field peas or clover – or perhaps with grains such as rye or oats.
Crimson clover used as a ground cover between rows of vines.
Two other ground covers that are also quite widely used – comfrey and phacelia – are closely related to borage, and all three are members of the borage family, Boraginaceae.
Both comfrey (Symphytum officinale) and phacelia (Phacelia tanacetifolia) play a prominent role in agricultural research into the benefits of cover crops and green manures.
Phacelia used as a cover crop.
But while borage has proven itself useful in removing heavy metals from soil, it hasn’t been extensively studied for other types of soil improvement.
However, as we gardeners embrace more organic gardening methods, we expand our repertoire of soil-improving plants, and many gardeners are experimenting with using this herb for this purpose.
More hard research needs to be done to assess borage’s usefulness in this area, but in the meantime, let’s look at the known benefits this herb can provide as a ground cover.
Much like daikon radish used to “work” the soil, this herb can enhance it with its roots – it has a long taproot that dives deep underground.
When plants are lifted or plowed under and allowed to break down, the effect of these taproots results in improved soil drainage and aeration.
To get the best out of your plants this way, you need to let them mature so that their taproots grow large.
Borage grows quickly in early spring and has broad leaves so it can act as a living mulch.
These broad leaves cover the bare soil, protecting it from runoff and erosion where regular spring rains might otherwise wash away the soil.
To take advantage of this herb as a living mulch, it can be sown on fallow land, planted among other crops, or grown in garden beds as a cool-season cover crop, then removed before planting warm-season vegetables.
Suppression of weeds
Another benefit of this herb’s broad leaves? They spread and suppress weeds that might otherwise benefit from sunlight, water and space in bare soil.
In an article published in 2012 in the International Journal of Agricultural and Biosystems Engineering, F. Zaefarian and colleagues concluded that interplanting borage with sweet basil and maize resulted in greater suppression of weeds compared to monocultures—that is, crops of one type not interspersed with other types.
To reap the weed-suppressing benefits, plant your main edible crops with this annual herb.
When your main crops are spreading out and need more space, borage can be removed before maturity and added to your compost, providing organic matter and nutrients.
Another benefit of its status as a living mulch is that borage can help keep the soil from drying out and help retain water.
Bare soil loses water easily through evaporation, while areas planted with borage instead retain moisture longer.
In addition to the mulchy leaves, the roots can also aid in groundwater retention.
The roots of these and other plants allow the water to filter into the soil, allowing rainwater or irrigation water to sink in instead of draining away.
Ground covers are sometimes used as insect plants, plants that attract beneficial insects such as pollinators and predatory insects.
Borage works fantastic as an insect, the bees and butterflies in my own garden can confirm that!
It provides beneficial insects with both food and shelter, and blooms from about June to September, providing nectar for much of the summer to bees, butterflies, and many other pollinators.
In addition to home garden use, this herb can be sown in orchards to provide an early source of food for pollinating honeybees in the spring.
Lacewings lay their eggs on the leaves, and painted female butterflies use it as an anchor for their pupae to go through their transformations from simple caterpillars into beautiful butterflies.
To take advantage of this herb as an insect plant, allow it to bloom and remain in your garden for the entire growing season, or at least until you can provide the insects with other sources of food and shelter.
And if you want to learn more about the art of cover cropping, dive into our article on the subject!
Borage as green manure
Plants are used as green manure when tilled or worked into the soil – just as you would with animal manure.
And while the research on using borage in this way is not yet final, at the time of writing, that doesn’t mean farmers and gardeners aren’t doing it.
Borage grown as green manure. Photo by Simon Mortimer, via CC BY-SA.
Remember when I mentioned that this herb can be used to remove heavy metals from contaminated soil?
The plants absorb heavy metals through their roots and store them. The plants are then discarded, leaving a safer, less contaminated soil.
Well, heavy metals are not the only thing this plant can extract from the soil.
Because this herb has a long taproot, it pulls up nutrients from deep in the soil and stores them in the leaves, just like comfrey.
Like other plants used for this purpose, the nutrients once in the leaves and stems of the plant can be worked on and returned to the upper levels of your soil to help feed other crops – or added to your compost to enrich it.
Working this plant into the soil or placing it on the compost pile will transfer those nutrients to wherever you want them.
Keep in mind that if ground covers are grown in areas contaminated with heavy metals, all plant material should be discarded, not composted, or the contaminants put back into the soil.
Cabbage left on the ground as green manure.
However, it is important to remember that there is a difference between green manure and animal manure.
Animals such as chickens or sheep have already broken down the original plant material for you by eating it and converting it in their digestive system.
Animal manure is also usually “aged” or composted before spreading on garden beds, as it can be quite acidic and can burn plants.
Green manures, on the other hand, have not yet broken down. If you add it to your soil as is, it will gradually break down, slowly releasing nutrients.
Plants that are plowed with a shovel.
Once you have this herb in your garden, you can decide if you want to use it for this purpose.
If you choose to do this, dig the plants back into the garden before flowering, as they self-sow easily.
Also, an article in Mother Earth News by Barbara Pleasant recommends waiting 2-3 weeks after mixing plants into soil before sowing new crops.
This is because, like the addition of compost or worm manure, it can temporarily warm the soil and inhibit seed germination.
When you’re ready to grow this plant, learn everything you need to know in our “How to Grow and Care for Borage Plants” and the “When and How to Plant Borage Seeds” supplement.
At Eden Brothers you will find seeds in different package sizes.
Borage, you are bottom good to me!
Even if the full scientific report is not available on this garden herb, it can still provide garden benefits as a ground cover and perhaps even a green manure!
Just be ready for borage volunteers to pounce if any of those plants were allowed to go to seed. As for volunteers, you could do a lot worse.
Have you tried growing borage as a ground cover? Share your experiences in the comments. And have you tried working this herb in your soil? Tell us, we would all love to hear how it went for you.
If the idea of improving your soil to grow bushels of delicious produce is your thing, here are a few more articles that might interest you:
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