Hi Sheila,

Thank you for contacting the UNH Extension Yard & Garden Infoline. This is Debi Green, the Master Gardener volunteer who spoke to you on the phone. Here are some links and information for you to have in writing regarding the soil for your raised beds. Good luck and happy growing!

"We usually recommend filling raised beds with a mix of 70% topsoil, 30% high-quality compost. Taller beds can be great if you have limited mobility, or if you simply like the idea of not having to bend over as much to tend to your garden. However, taller beds both take more materials to build (read: more expensive) as well as take more soil to fill. Not much can be done on the building material side for tall beds but on the soil side you can borrow a part of the German practice of “Hügelkultur” by first placing down some logs and/or sticks at the bottom of the bed to fill some space before you put your soil in. This has the added benefit of the wood at the bottom acting like a sponge — it holds onto water as it breaks down, leading to reduced water needs in your garden." Information taken from: https://extension.unh.edu/blog/2024/04/how-utilize-raised-beds-small-space-gardening

"Some mulch yards sell topsoil and compost blends, or you can use soil from your property and mix in compost yourself. Either way, you’ll want to aim for no more than 50% organic matter. Ideally, compost will make up 10-20% of the total soil volume. And just like gardening in the ground, it’s always a good idea to get the soil tested to make sure proper amendments are added."https://extension.unh.edu/blog/2019/03/what-are-benefits-raised-beds-how-can-i-construct-one-myself

You are correct, purchasing the soil in bulk will be a far more economical option. Many suppliers offer a 50/50 mix of compost and screened loam. I personally have used that proportion with very good results. As we discussed, you can order a 2:1 ratio of separate yards screened loam and compost to make it closer to 70/30 percent. The supplier will be able to tell you how much you will need.

I hope you find this information useful, and please do not hesitate to reach out with any further questions. We are always happy to help!