Shrubs, Perennials and Ornamental Grasses
It’s spring. I’ve been digging in the garden—at least between snow storms. My back muscles (and knees and shoulders) ache, there’s dirt under my broken fingernails, and a huge smile on my face. In fact, there’s dirt in my teeth—I’ve been pulling weeds and shaking the soil off their roots before piling them into the compost bucket, and I keep forgetting to close my lips.
One of the joys of spring is adding new plants to our garden. What gardener can resist the dazzling displays at the garden center? Forgetting about budgets and the size of our yards, we load up the cart. Then we get home and the work begins. It’s time to start digging holes.
Unfortunately, most of our purchases don’t come with planting directions. Yet, there are plenty of ways to do it wrong. In fact, many of the problems that show up at our Master Gardener help desk originated when the tree or shrub was placed into the ground. Proper planting pays off in healthier plants that live out their natural lifespan.
Pick a mild day
The best weather for transplanting is overcast, and not too hot or too cold. Trying to find a day with no drying winds can be difficult this time of year, but your plants will thank you. You don’t want to stress your plants more than necessary.
Get your plants ready
Check the pots to make sure the soil is damp enough. Gently hold the plant in place to keep anything from falling out. Then turn the plastic pot over and tap it to loosen the soil. Ideally, the contents will form a single unit of potting mix and undisturbed roots. If not, water a few hours ahead of planting.
Dig the hole
It’s tempting to dig a hole just large enough to accommodate the root ball, especially if our soil is hard and compacted. But just think—if we can’t get a shovel into the soil, how will the roots manage? Instead, dig a hole at least two, and preferably three times the diameter of the pot your plant arrived in. If the soil is too hard, water it a day or two ahead of time to soften it.
The good news is that you don’t need to go very deep. Most roots are in the top two feet of soil. In some cases, they’re even shallower than that. So just dig a hole as deep as the pot. You want a firm foundation under the shrub or tree so that it doesn’t sink as the soil under it settles.
The soil that you use to backfill the hole can be amended according to the results of your soil test (you did get it tested, right?) Feather the amended soil into the native dirt so that there is no sharp discontinuity. You don’t want to create a barrier to those roots. This is when to add any granular fertilizers needed, too. Organic or time-release fertilizers are best, as they’re less concentrated and won’t burn the roots.
Potassium (K) is often touted as the “root growth” fertilizer. It’s true that K is needed for root growth, and a deficiency will cause problems. However, here in Colorado at least, there is plenty of K in our native soils. More than the plant needs is not helpful, and can actually hurt. Only add K if a soil test indicates your soil is lacking.
Place the plant
Sliding your plant out of its pot, place it in the center of your hole, disturbing the roots as little as possible.
If necessary, adjust your hold so that the plant is at the same depth it was in the container. Remember, roots grow only where there’s oxygen. Placing them too deep will suffocate them. (One exception is grafted roses. Since the graft union can be killed by very cold temperatures, plant roses so that the union is buried by two inches of soil. This will help insulate the roots. You want your roses to be from the cultivar you chose, not the rootstock!)
Cover it up
Don’t leave the roots exposed longer than necessary. Air drying will kill the delicate root hairs that feed the plant.
Tamp the soil around the plant to ensure contact with the roots, but don’t squeeze all the air out. Healthy soil should consist of 45% mineral matter, 5% organic matter, 15% water, and 15% air. Roots take in oxygen and give off carbon dioxide, just the same as we do. We don’t want them to suffocate!
Water to settle the soil
If you live in an arid area, create a watering basin or add new drip emitters to make sure the soil stays slightly moist. Plants need to be established (which takes one to two years) before they can withstand drought, no matter how xeric they are. Don’t forget to add emitters as your plant grows.
Another common practice is to add vitamin B12 to “stimulate root growth” and “prevent transplant shock.” Actually, plants do not use vitamins. While adding B12 won’t hurt anything but your pocketbook, it won’t help at all either.
Mulch over the root area will help keep the soil from compacting. It will discourage weeds. Mulch keeps moisture in the soil. And, it makes earthworms happy.
So there you have it. Now go put your tools away, wash your hands, pour a glass of lemonade, sit down, relax, and enjoy your garden. You’ve earned a rest!
Planting a tree? That’s the topic for next time.