I recently built a raised garden bed that's 8 feet long, 4 feet wide and 1.5 feet tall. I am getting ready to fill it, so my question is in regards to fill. Should I use only garden soil/compost? Would it be ok/ideal to add a few inches of gravel at the bottom of the bed for drainage?
No - I would say that gravel is not necessary unless you have caliche right at the surface. There have been a few other discussions about raised beds and I'm not sure if you've had a chance to look at them. Try the search feature at the top right corner of the website. Here are a couple good ones:
I put in raised beds 18 months ago and I was told you do not want a barrier between the native soil and your new soil. You want to encourage the "bugs" from the old soil to migrate into the new soil and help amend the soil in your raised beds. (Although gravel is a permeable barrier, so it might not make any difference)
Just my 2 cents - Liz and Charles are correct - no gravel needed you want the contact with native soil. Also a mix of soil to make it not only nutrient rich but also "fluffy" is what you are looking for to counteract 'compaction'. Your height is good. The only other note would be if you have ground squirrels or gophers, putting down hog/horse wire first before adding soil, keeps them from coming up into the garden. Good luck and have fun.
Thanks Catherine. I was going to do a mix with soil bought from Singh's farm and compost. I'm assuming that's all I need. What's the optimum mixture? 60/40?
actually the guy at Singh farms told us that their planting compost mixture is intended to be mixed with native soil about 50/50. Here is his explanation verbatim: "Mix our stuff with native soil about 50/50 so that when you squeeze it in your hand it forms a turd, and when you tap the turd it crumbles." Both descriptive and memorable. That explanation definately stuck with our elementary school students who are working on this garden at the school.
So, if you have some native fill dirt on your property, that would work and you wouldn't need as much of Singh's stuff or you can always find free fill dirt on craigslist.
Joseph, follow Karis suggestion 50/50 is fine or 60/40.
Karis' description of the form of the healthy soil mix is right on. :-)
An FYI on Mr Singh's compost - it is still "hot" from reports of issues with new plantings, so you will need to wait a month or so for it to compost down a bit more before planting.
Ohhhhhh. I forgot to mention composting. We have been composting since we put in our raised beds. We mix in the compost into our beds. Our soil is beautiful, we grow amazing vegetables. The soil feels and smells good.
I would encourage you to begin composting ASAP. In spring Costco sells a very nice "tumbler" composter for less then $100.00. During the winter and summer the composter can be bought through Costco online.
Have fun with your garden. Don't forget to use shade cloth as we approach summer and watch for those February frosts!
BTW - We had great luck with melons, onions and peppers during the summer.
Do you recommend using the tumbler or just having a compost pile? What are the positives and negatives for each?
Both will make compost. Even if your pile is very large and you are willing to water your pile everyday, it will take much longer to create compost. The tumblers retain heat and moisture and are easy to turn so they should produce compost much faster.
Positives for piles are that size isn't an issue, so if you produce large volumes it's a great way to do compost. Negatives are that it can attract more rodents and such, looks messy, can dry out faster. The tumbler style composters are neat and clean looking, keep it moist and is easy to turn - all factors leading to faster compost production. The tumblers obviously cost more, work better when everything that goes in them has been chopped small (no big sticks or such) and work for people who don't produce lots of 'green' wastes. We use the recycled City of Phoenix old Garbage bins, which are cheap and easy to use. Here is a picture of our composting system. I don't turn the compost in them, just wait until they are pretty full then I lock the lid down with a bungee cord and kick the whole thing over. Dig out until I hit unfinished compost and tip it back up. I keep adding more on top and don't really care how long it takes to get a finished product. This is a 'cold' composting method that works for me...
Thanks for the technique tip.