At this point I’ve dug my share of holes in this good ole clay we have around Weaverville. One thing I’ve noticed is that people are quick to throw in the towel with their native soil, even the professionals. They go to a lot of trouble and expense to build raised beds with trucked in top soil. I suggest you try to make the best use of what you have. This will save you time, money, and most likely give you better results in the long run as your own soil is built up for future additions.
Like you, when I started out I did a bunch of research on best way to grow things when you have heavy clay soil. You know the internet never lies. I tried doing all sorts of complicated stuff; from soaking cow poop in a bucket to laying out logs underneath my garden rows.
Whatever you decide to do–please, please don’t put logs in your garden.
Things like compost tea don’t really help much because the issue is drainage. Roots need oxygen, which they have a hard time getting in our heavy soil, especially during winter rains. After much trial and error I decided that it was best to keep things as simple as possible. That boils down to a little technique, some good mulch, and patience.
Step 1: Get a nice big pile of double ground BARK mulch.
The first rule of buying mulch is that you never have enough. Skip the bags and get a nice big pile delivered from one of the many fine mulch yards around Asheville. Hardwood or pine doesn’t matter so much as long as its all bark and not the whole tree. Some places only sell bark and others sell some of everything, so make sure you ask for bark. It’ll be more expensive. Around $30 per yard is great but the price seems to be going up.
Keep in mind that the finer the grind the quicker it will break down. I found all the options confusing at first, but unless you want it to look a certain way I’d suggest just getting the cheapest all-bark mulch and then choosing the grind depending on the area you are mulching:
Soil amendment, gardens, or plants you like to baby: pine fines or triple grind
General purpose, perennial beds, landscaping: double grind
Slopes, neglected areas for weed control: single grind or anything cheap (no need for an all bark product). I get some single grind up the road from me for $200/dump truck load.
Step 2: Plant that sucker.
- Amend your native soil as little as possible. You don’t want to end up with the majority of the soil you plant in to be different than what the plant is going to grow into. My rule of thumb is this: If you can dig the hole with a shovel, it really doesn’t need to be amended. If you need to use a mattock or digging fork to dig the hole, amend at a ratio of about 25% bark to 75% broken up native soil. More if it’s really hard and compact.
- If you amend, your only goal is to help with drainage so your plants don’t suffocate with our winter rains. What do I use? A shovelful of that good good bark mulch you happen to have a pile of nearby. Mix it right in and break that clay up as much as possible. It helps to do it when the soil is moist but not soggy. I like to wait until its been dry at least 2 days, planting on the 2nd and 3rd day. Break that clay up as much as possible. I break up the clods by hand until I have enough to pack in the soil around the plant.
- Go very light or not at all with the fertilizer, especially with fall planting. You don’t want to flood young plants with nitrogen, leaving them weak and spindly. Our clay hangs onto a lot of nutrients.
- Plant level with the soil or just slightly above. Do not plant below the soil line, especially in heavy clay soil. That will cause water to pool on top of the root system.
- Break up the soil as much as possible, but pack it back down around the roots once its planted to eliminate air spaces. This will seem counter intuitive but you don’t want the roots exposed to air pockets below the soil.
- Give it a good drink. This is a good habit to get in and helps settle it into its home, but I admit to sometimes slacking on this step. If you water the plant before you plant that is often fine, especially with woody plants.
- Mulch mulch mulch like crazy on the surface around the plant. I’d mulch around my bum if it would stick. Just go wild with it. Nice and thick and wide, but of course leave some space from the base of the plant. I like to go extra wide around trees so I can plant flowers around it the following season.
- If you want to really baby them, give them a few scoops of compost or manure on the top of the planted root ball, right before mulching. The mulch and compost combo will slowly break down and give the plant all the nutrients it needs for the season.
What about fertilizer?
I go back and forth on the necessity of using fertilizer on perennials. I’ve planted in areas where the soil was almost pure clay with no topsoil and the plants did pretty well with just a good top dressing of mulch, without soil amendment or fertilizer. There have also been times when that didn’t feel like enough and I wish I’d fertilized. At this point I think that with heavy clay soil the most important thing is improving the texture and drainage. If you do that, you don’t need to worry much about adding nutrients, especially once the plant is established for a season.
I believe fertilizer has its place, especially when it comes to food production. I fertilize the pots I sell, the tomatoes I grow, and flowers and shrubs if I get around to it.
It’s a big topic, and one for another post, but my rule of thumb is this:
1. For fall planting I give no fertilizer if it’s an established bed, or a small amount of low nitrogen formula for plants in new areas.
2. I top dress the first year in spring with a slow release, high nitrogen formula.
The trick is always to keep mulching (yearly). For perennial beds, that mulch will continue to break down and build up your soil, providing all the nutrients your plants need.
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