Hydrogen peroxide (H2O2) has an extra oxygen atom than Water (H2O), this extra oxygen atom breaks down and the molecule of water releases from this separately. It is this extra oxygen atom that makes the hydrogen peroxide so useful. The Hydrogen peroxide is used in cleaning, bleaching, sterilizing, as a disinfectant etc. but it can also be used in horticulture. In simple words, Hydrogen Peroxide acts as an oxygen supplement for plants (beneficial if used in low strength). It works by releasing oxygen and also aerates the soil.
1. Disinfect pots, tools, and greenhouses
Hydrogen peroxide is widely used in medical and laboratory establishments for sterilizing surgical tools and work surfaces because of its broad-spectrum antimicrobial activity. Use 6%-9% solution to disinfect seed trays, pots, and other containers before they are reused. Dip pruning tools in the solution before use, and between plants, to reduce the risk of introducing pathogens into the wounds. Use it in a sprayer to disinfect the air as well as all the surfaces in greenhouses.
Hydrogen peroxide is effective against most types of bacteria, viruses, and fungi. It can even destroy spores when applied at concentrations above 10%, but such concentrated solutions should be handled with extreme care since it can burn skin and plant tissue. However, it can be used to prevent mold and mildew from clouding glass panes of greenhouses.
2. Disinfect growing medium
It is important to use a sterile growing medium for seed starting and in propagation trays. You can use washed river sand instead of perlite and vermiculite if you disinfect it with hydrogen peroxide. When you make your potting mix with compost, sand and other additives added to garden soil, use this chemical solution to destroy soil pathogens, including nematode worms that can harm your plants.
Thoroughly soak the sand or soil mix with 3% to 6% solution and cover it loosely with a plastic sheet. Exposure to the highly oxidizing chemical will kill even the eggs of worms. Allow time for the complete decomposition of the chemical, preferably overnight, turning the mixture well once or twice.
3. Sanitize seeds
Seed-borne pathogens can kill off young seedlings even before they get a chance to take hold. Avoid this by disinfecting seeds before you sow them. Soaking in 3% hydrogen peroxide heated to 1400F for 5 minutes is recommended for all types of seeds.
When you make sprouts for personal or commercial use, disinfecting the seeds and the sprouting trays is a must to avoid foodborne illnesses caused by Salmonella, E. coli, Listeria, etc. After the 5-minute soak, wash off the chemical by placing the seeds in plain running water at room temperature for a minute.
4. Accelerate germination
Seeds soaked in diluted hydrogen peroxide germinate faster and display healthy growth. This is because of the oxygen released when hydrogen peroxide breaks down. Since oxygen requirement of sprouting seeds is very high, this extra oxygen supply is obviously beneficial.
It is a good idea to mix in this chemical in the soil when you sow seeds in the garden beds or use a weak solution to water the bed for the first week or two after sowing. Gardeners who have used it vouch for its efficacy in supporting faster seed germination and strong growth of seedlings.
5. Boost root development
Hydrogen peroxide can help root development at any stage of growth, thanks to the oxygen generated as it decomposes. The root zone is often starved of oxygen because of soil compaction; especially in the case of clayey soil that has very fine particles.
Mix one pint of 3% hydrogen peroxide into a gallon of water and use this solution to water the plants once a week, soaking the root zone thoroughly. Use a weak solution of hydrogen peroxide for rooting cuttings and when bare root plants are planted in the garden.
6. Fight fungal infections
You can use hydrogen peroxide to combat almost all kinds of common fungal infections affecting your garden plants. Mix 4 tablespoons of 3% hydrogen peroxide in a pint of water taken in a spray bottle and use it for spraying potted plants that show signs of powdery mildew, rust or other fungal infections.
Since this chemical can burn plant tissues, correct dilution is important. One pint of 3% H2O2 in a gallon of water is the standard dose for spraying plants, but some gardeners insist that it is safe to use 6% – 9% H2O2. Always experiment on a small area before large-scale spraying.
7. Prevent and control bacterial rot
Bacterial infections often cause fruits, flower buds, bulbs and tubers to rot into a liquid mush. Cuts and bruises on plant tissues are the major causes of bacterial infections, but sometimes insects spread the disease. Protect the crops by spraying hydrogen peroxide solution. It is a good idea to apply it on fresh cuts of tree branches or spray it after pruning. Bulbs and tubers can be dipped in the chemical solution when you prepare them for storage.
8. Use as insect repellant
Hydrogen peroxide acts as an excellent insect repellant, drastically reducing the pest population in the garden. Sap-sucking insects are the most affected, but the chemical solution can kill the eggs and larvae of moths and other harmful pests with its strong oxidizing effect. It is easy to use, cheap, and environment-friendly too.
9. In hydroponics and aquaponics
If you have a hydroponic or aquaponics system, the addition of hydrogen peroxide to the water will keep them healthy. The roots of plants, as well as the aquatic life, appreciate the extra supply of oxygen.
Hydrogen peroxide can also prevent root rot, which is a common problem in hydroponics. Since it completely decomposes to oxygen and water without leaving behind any toxic residues, it is much safer than other chemical antiseptics used to combat rot.
10. Weed killer
Hydrogen peroxide at 10% concentration can be used as a weed killer instead of commercially available herbicides that contain toxic chemicals. Pour the solution on weeds growing between concrete or flagstone pavers and on moss on brick sidewalks. Leave it on to scorch the leaves as well as the plant parts below. Sunlight quickly breaks down hydrogen peroxide, so early mornings and late evenings are the best times to apply it for prolonged action.
Since hydrogen peroxide, at 10% concentration and above indiscriminately destroys all types of vegetation it comes in contact with, use with caution near your plants. If it accidentally splashes on your hands or gets into your eyes, flush immediately with lots of cold water.