Digging a hole is neither as hard nor as easy as it's made out to be.
Here's what we've boiled it down to after 30 years of planting shrubs.
How to Plant a Shrub
These are at-a-glance instructions. Keep reading past these first 10 steps if you want to become an expert.
- Dig the hole as twice as wide as the rootball you'e about to plant;
- Dig the hole only as deep as the rootball;
- If there is a mass of roots, score the root mass with your pruners to encourage further branching of new roots;
- Cut off any roots that have hit the side of the container and started to circle around the inside of the pot;
- Uncover and expose root flare.
- Plant your shrub so that the top of the root ball is even with the land around it (planting up to a half an inch high is okay, but be sure to slope the backfill up to cover the high roots);
- Then backfill with the native soil that you dug up from the hole;
- Plan for irrigation - if drip tubes, lay them now;
- Mulch thoroughly;
- Water daily for the first several weeks, especially if planting in spring or summer. Gradually back off to every-other-day, then just a couple times a week. Next summer, water according to the particular shrub's requirements.
Things Not to Do
Just as important as what to do are the steps not to take.
- Don't dig the hole deeper that the size of the pot you're about to plant;
- Don't plant the plant too deep (don't bury the root flare);
- Don't backfill with potting mix or compost;
- Don't forget to mulch;
- Don't forget to water.
The Details of Planting a Shrub
Now we'll roll up our sleeves and explain the finer points of how to plant a shrub.
- Dig twice as wide: If you have a true 1-gallon container (approx. 7 3/4" diameter), then dig a 15" diameter hole. Digging the hole twice as wide breaks up enough soil to make it easy for the roots to penetrate the surrounding soil and become established. If you're digging in wet/moist clay and create smooth sides with your shovel, score and rough up those smooth slick sides - those smooth areas can sometimes create a barrier to roots further penetrating into the surrounding soil.
Dig only as deep: Here you are spared a whole lot of extra work. If you have a true 1-gallon container (approx. 7" tall), then dig your hole only 7". If you dig too deep, toss some dirt back in. Or set the plant in, back fill and water in, then grip the rootball to tease it back up - this process will allow dirt to fill in underneath the plant.
- Score the root mass if it's thick, dense, and tight: It's just like pruning - each cut of a branch usually results in two more branches filling in that area. Same with roots, they will branch out to become a greater root system.
Cut off pot-bound roots: Look for roots that behave badly and cut them off.
A) Roots that hit the side of the pot and circle horizontally;
B) Roots that hit the side of the pot and go straight down;
C) Roots that hit the side of the pot and wrap back over the root ball (this would cause a girdling root). These are also called "J" roots because of their shape. They are typically obvious.
Uncover and expose root flare. This step is not talked about as much as it should be. Look around in the forest or any place shrubs or trees have planted themselves. You'll see how the base of the woody plant gets fatter and flares out - there may be big woody roots visible before they dive into the earth. This area of the plant is called the root flare. It's important not to keep it exposed to air by not burying it underground. Sometime as cuttings are stepped up into larger pots, this root flare gets too far under the soil. Now is an ideal time to check on root flare and uncover it if necessary. That will set things right going forward. Here's a video about uncovering root flare when you plant a containerized shrub.
- Plant your shrub: Besides making sure I plant even with the native soil line (or a little higher), I take a little time to think about the plant structure - which side do I like the best and will see most often? Sometimes I have to dig it up and re-situate it, though re-situating is easy because the hole is already dug.
- Backfill with the native soil that you dug up from the hole. Don't backfill individual holes with nicer soil or compost (however, when I plant a flower or shrub bed, then I amend the whole area with a whole lot of compost - to the tune of 1 cubic yard over 500 square feet). The roots will enjoy that too much and won't grow into the surround soil. When the soil is too good in this nice little area you created and they don't grow far and wide, it is called the "bathtub effect." You don't want that.
- Plan for irrigation: If using drip tubes or soaker hoses, lay them now so they end up under the mulch. We also install Tree Diapers now, so they are under the mulch.
- Mulch: Spread mulch to a depth 2-4 inches, but keep it 2" away from the trunk(s). Mulch is a cover for insects - if you leave the 2" mulch gap, insects are less likely to damage your tree.
- Water daily for the first several weeks, especially if planting in spring or summer. Gradually back off to every-other-day, then just a couple times a week. Do that until dormancy in the autumn or until you're sure the tree's roots have recovered from transplanting and have established. Next spring/summer, water according to the particular shrub's requirements. General rule of thumb is to provide at least 1" of water per week. If it rains 1/2" inch, then water a few days later to provide the rest. This is why we love rain gauges - clear feedback!
Have we missed an important step or could have explained something better? General questions? Let us know. If you have a question, that means other do too. They may be too shy to ask. Be the bold one.
Happy Digging Twice-as-Wide-but-Only-as-Deep,
Hillary & Mike