Hydrogen peroxide is considered a chemical, but it decomposes easily in water or oxygen.
Have no fear as this is safe to use even in organic gardening in varying conditions.
Learn how to properly use hydrogen peroxide in your garden with these 10 incredible tips byGARDEN TIPSon Youtube.

Image by: GARDEN TIPS
you gotta cut all of the dead branches and stem until the green zone.
Then take out the plant by its roots and inspect if there are any rots.
Prepare a diluted hydrogen peroxide solution using 3% or 6%.

Use 2 tablespoons of 3% peroxide per gallon of water.
Use half for the 6%.
Soak the roots into this solution for 6 hours.

Water it with the same solution and leave for a few days.
This help in better root development of the seedlings.
Disinfecting garden tools
Disinfect your garden tools, especially the cutting and pruning tools.
Deep the tool in a 6% h2o2 solution.
Wipe them with 6% solution without any dilution but verify to use gloves!
Water with 2 tablespoons of 3% hydrogen peroxide per gallon.
Weed killer
At 10% or higher concentration of hydrogen peroxide, it completely kills types of vegetation.
Fertilizer
Water your plants with a very dilute solution of hydrogen peroxide once a month.
Hydroponics and aquaponics
Adding this to the water can keep the plants healthy.
Effective pesticide and anti-fungal
It can control common pests and insects in the garden with its strong oxidizing effect.