The optimal soil pH for growing roses is slightly acidic with a pH between 6-7 with a pH of 6.5 considered ideal. If the soil is too acidic (lower then pH 6) or too alkaline (higher then pH 8) the roots of the rose will have difficulty absorbing essential nutrients and the rose will likely die.
Garden soil that has regular applications of mulch will be in the range of 6-7 acidity due to the fact that most organic material when decomposed is either slightly acidic or pH neutral which is perfect for roses.
However soil can be particularly acidic or alkaline and therefore be unsuitable for growing roses for a number of reasons.
Before planting roses in a new area of your garden you should test the pH of the soil to make sure you have the correct conditions.
Keeping reading to learn..
- How to test soil pH for rose growing
- How to amend highly acidic soil for roses
- How to amend alkaline soil for roses
- How to maintain the soil at the optimal pH for growing roses
How to Test your Soil pH for Rose Growing
Buying roses can be expensive so it is a good idea to establish the pH of your garden soil before planting.
The best way to do this is with an inexpensive soil test kit from amazon. The one I am using here accurately reports the soil pH, soil moisture and the amount of light that particular spot in the garden receives per day.
All these factors are very important for growing healthy roses. (Roses need at least 6 hours of direct sun per day and a soil that holds moisture whilst allowing excess water to drain away).
Using a soil test kit is the most reliable and in expensive way to find out the pH of your soil so that you can confidently plant your roses in the ideal conditions.
A pH of 6-7 is perfect for rose planting, but if you have tested your garden soil and it is either too alkaline (pH 7.5 or above) or too acidic (pH 6 or lower) gardn soil you will need to amend your soil before planting roses.
How to Amend Alkaline Soil for Roses
If you garden soil is particularly alkaline (if the pH of the soil is over 7.5) then roses will not be able to grow as they will not be able to access the nutrients they need from the soil.
To balance soil that is highly alkaline (with a pH of over 8) I recommend:
- Amending your soil with ericaceous compost.
Ericaceous compost is available from garden centres (and amazon) and has an acidity of around pH 5, which will help rebalance the particularly alkaline soils.
However it is unusual to see soils with such high alkalinity and more common to see slightly alkaline soils in the pH range of 7.5-8.
If your soil is in this range then the most effective solution is:
- To heap lots of organic matter onto your rose bed and dig it into a depth of 15 inches.
You can incorporate the organic matter into the soil by either digging it in manually or by using a tiller which is less labour intensive.
Once garden compost has rotted down fully, it will be either pH neutral or slightly acidic, which is perfect for roses.
Even acidic pine needles, (which have a pH of 3-4) once fully decomposed will be at a neutral pH thanks to the ecology of the soil.
Again you need to bear in mind the depth of the rose’s root system so you will need to dig in your compost or ericaceous compost to a depth of 15 inches.
After you have applied your soil amendments you will need to consistently test the soil to see if it is in the appropriate range to grow roses (between pH 6-7).
Give the soil a chance to settle and perform a soil test one month after amending the soil. Retest the soil until for three months it is consistently in the correct range to grow roses.
Changing an alkaline soil to a slightly acidic soil is likely to require some trial and error as every garden has different conditions.
As long as you consistently test your soil after every amendment and adjust your strategy accordingly then you should eventually end up with balanced soil that is slightly acidic and perfect for growing roses.
How to Amend Overly Acidic Soil for Roses
If you have measured the pH of your garden soil and it is below pH 6 then you will have to make some adjustments to the soil so that the roots of the roses can successfully take up nitrogen, potash and phosphates which are required for healthy growth and a good flower display.
Changing the pH of your soil is a gradual, ongoing process that will require retesting periodically.
There are two ways to raise the pH of soil effectively.
- If your soil is particularly acidic with a pH of lower the 5 then I recommend using garden lime to re-balance the soils acidity.
You can buy garden lime from amazon and all well stocked garden centres. Garden lime is best applied to the rose planting area in the winter.
Always follow the manufacturers instructions as it is very easy to overdose an area subsequently raise the pH too high into the range of alkalinity (over pH 7).
If you have soil pH of 5 then the best option is to:
- Add compost and wood ash to the rose planting area and till or dig the compost into the soil to a depth of 15 inches.
Wood ash is naturally alkaline so it is a great natural remedy to overly acidic soils. Ash from bonfires and indoor fireplaces is great but avoid ash from coal or charcoal from barbecues as they may contain toxins and compromise soil structure.
Garden compost is also pH neutral (if not slightly acidic) so it will help to decrease the acidity of the soil and will add fertility, improve soil structure and stimulate the soil ecology, all of which will promote healthy rose growth.
Mix 2 cups of wood ash with compost and dig it into the soil at a depth of 15 inches.
You need to dig the amendments into the soil at this depth as this will accommodate the maximum depth of a rose’s root system when it is fully mature.
Leave the soil for a month before testing it and I would recommend retesting once per month for three months ensuring the readings are consistently in the range of 6-7 pH before planting your roses.
Amending overly acidic soil is never an exact science and requires trial and error, hence why consistent testing over three months and ongoing mulching is necessary.
If you are in doubt you cannot go wrong by adding ordinary garden compost as this will balance out your soil pH whether it is too acidic or alkaline.
Maintaining the Right Soil pH for Roses
Fortunately once you have your soil at the right pH for roses it becomes easily manageable to keep it in the optimal pH range if you have a good regime of mulching your rose bed regularly.
Adding mulch to your rose bed has many benefits such as increasing fertility, improving drainage whilst retaining water and cooling the root system in the height of the summer.
But most importantly well rotted compost once fully decomposed will be slightly acidic or neutral and therefore provide the perfect conditions for roses.
So to maintain the optimum soil pH for roses you should add mulch to your rose bed at least twice per year.
The first application of mulch should be at the start of spring as this has the added benefit of retaining soil moisture in the coming hot summer months and the second application should be in September to help insulate the roots of your rose from the worst of the cold so they can continue to establish over winter.
Apply the mulch in a 2 inch thick layer around the base of your roses, although you need to keep the mulch at least 6 inches away from your rose canes.
If the rose wood that is above ground is exposed to moist material for prolonged periods it can rot the wood so allow some bear ground between the layer of mulch and the rose canes.
There is no need to dig the mulch into the ground as digging could damage the roots of the rose and disturb the beneficial soil ecology unnecessarily.
Always spread mulch onto the surface and let microbes and earthworms do naturally incorporate the material into the soil for you.
For the purposes of maintaining soil pH I recommend a type of mulch that breaks down quickly such as garden compost, leaf mould or horse manure so it can decompose and become part of the soil over the course of the year and thereby keep the soil conditions just right.
I would advise against using organic material that takes a long time to decompose such as pine needles and wood bark.
These types of mulches decompose much slower and can take years to work into the soil and therefore they have less of an influence on maintaining optimal soil pH for your roses.
- Roses thrive in slightly acidic soils so they can absorb the nutrients they need to thrive and produce a beautiful display of flowers.
- You can amend over acidic soils with wood ash and compost to help cancel out the excessive acidity.
- If the soil is too alkaline then adding ericaceous compost and plenty of organic material will balance the soil and result in the desired more neutral or slightly acidic soil condition.
- Maintaining the pH of the soil so it is suitable for growing roses long term can be achieved with regular applications of mulch in the early spring and before winter although mulch can be applied at anytime of the year.