Mark Bennett – Page 53 – Gardener Report

Lavender will grow in mildly acidic soils from pH 6.5 but they much prefer to be in alkaline soils up to pH 8. This replicates the lavenders natural soil conditions in the Mediterranean where they grow in well draining, sandy, alkaline soils. Keep reading if you don't know how to detect the pH of your soil (there is an inexpensive way to find out) and what your options are for growing lavender if you have acidic soil... Lavender in Acidic Soil Lavenders are adapted to growing in calcareous soils in the Mediterranean region of southern Europe therefore Lavenders grow best in sandy or gravelly soils with an alkaline pH of around 7.5. However lavenders can live in soils with mild acidity (pH 6.5) particularly the English lavender species which tends to be more hardy and still produce oil, and display flowers. However lavenders will either be very short lived or not grow at all in soils that are acidic with a pH lower then 6.5 (the lower the pH the more acidic). Whilst some other commonly cultivated garden plants will thrive in more acidic soil, the lavenders will not be able to absorb nutrients and will die if the soil is more acidic then pH 6.5. If your soil is between pH 6.5 and 7 (slightly acidic to neutral) lavender can still grow very well, without problems. Lavender only really starts to show signs of stress (poor growth, fewer flowers) when the soil acidity is below pH 6.5. However if you do have acidic soil and want to grow lavenders then your three most practical options are: Plant or transfer lavender into a pot. You have complete control over the soil mix for lavender in a pot whereas in a garden soil will have to be heavily amended. (Read my article How to Transfer Lavender to learn how to do this without transplant shock). Plant lavender in a raised bed which has the same advantage as pots in that you can introduce new soil that is better suited for growing lavender. Amend you garden soil with lime or wood ash (both of which are alkaline) to raise the pH from acidic to the alkaline range preferred by lavenders. Lavenders in raised beds How to Determine Whether your Soil is Acidic, Neutral or Alkaline Most garden soil tends to be slightly acidic if not neutral due to the fact that fully decomposed organic matter tends to be between pH 6-7. However there can be significant differences in garden soil pH due to a variety of factors. Establishing the soil pH before buying plants is a sensible precaution that can save you a lot of money in the long run. The most cost effective way to determine the pH of your garden soil is with a soil gauge which you can buy on amazon. This device is very simple to use and requires no technical knowledge. Just push the probes all the way down into the soil and it will display a reading of your soil pH and best of all, it is available for a great price! I use this gauge around my garden to ensure that all my new plants are planted in the appropriate soil pH. Soil gauge for measuring soil pH before planting lavender. If your garden soil is chalky then this will be perfect for growing lavender as chalk soil drains fast which replicates lavenders preferred growing conditions and chalk soil is alkaline (usually around pH 7.5) otherwise it is difficult to tell the pH of the soil without using a gauge to accurately test. How to Amend Acidic Soil for Growing Lavender If the soil in your garden measures lower (more acidic) then pH 6.5 then it will need amending before growing lavender. The easiest solution is to grow lavender in a pot (the pot should measure at least 16 inches across, to hold enough soil for lavenders) add to your soil mix and mix 1 table spoon of agricultural lime into the soil (which has the effect of increasing soil pH to be more alkaline) This is all that is needed to provide the right pH range for growing lavenders in a pot with the volume of soil held in a 16 inches across (and the same proportional height) of a container. (Read my article choosing the best pot for lavenders for more information) After you have mixed in the lime there will be no need to keep amending the soil and the lavender should be perfectly happy in its new home. (Read my article to learn about the optimal soil mix for lavenders in pots). With raised beds and planting lavender into the garden soil you have to apply lime more diligently as you are dealing with a much greater volume of soil so it is important to follow the specific instructions from the manufacturer. If you plan to plant several lavenders in an area of acidic soil in open garden, then you need to make a long term change in the soils pH so it's suitable for lavenders. Prepare the soil (with added lime and sand or gravel for improved drainage) for three months before planting and test the soils pH periodically to ensure the soil is at least pH 6.5 if not closer to pH 7.5. It is important that you amend the soil to a depth of 18 inches for each plant as this will accommodate the lavender roots when it is at full maturity. Use a soil gauge to test the soils pH and add more lime if necessary, but I must emphasize always follow the manufacturers instructions and you should get the right result. Don't add too much lime in one go as the soil may then be too alkaline even for lavender and then you will need to balance the alkalinity with sulphur to stabilize the pH. Key Takeaways: Lavender can only grow in mildly acidic soil (pH 6.5) but prefers to grow in alkaline soils up to pH 8. English lavender varieties are hardier then French and Spanish varieties and can tolerate mild soil acidity better then other species. If you have acidic garden soil then you can plant lavender in pots or raised beds as an alternative or amend your garden soil with lime. Establish the pH of your garden soil with a soil gauge which will determine whether it is acidic, neutral or alkaline. These are easy to use and can take out the guess work so you can spend money on plants confident that they will thrive in the right kind of soil. You can amend soil with cultural lime which raises the soils pH from acidic to alkaline and therefore creates suitable growing conditions for growing lavender.