FIMBY: Tips for planting bare-root trees, shrubs and vegetables

This is another installment in our Food in My Back Yard series, dedicated to edible gardening.

This is bare-root season when fruit trees, cane berries, deciduous shrubs (such as blueberries and roses), artichokes, asparagus, rhubarb and other plants are the most available – often at the most affordable prices of the year.

What is a “bare-root” plant? It’s exactly what it sounds like – a plant sold without soil. They can be sold bare-root because they’re dormant – naturally “asleep” during winter. It’s like they’re hibernating, waiting to wake up once they feel soil around their roots again (and get a long drink of water).

These trees, shrubs and perennials were grown in the ground outdoors, often for years. They’re dug up in late fall; their roots are carefully washed and cleaned, then packed in sawdust (which holds just enough moisture to keep the roots from drying out). Before shipping, they’re kept in cold storage (just above freezing).

When those bare-root trees and shrubs arrive in January to nurseries or your home, they’ve already been in storage for several weeks if not months. Those roots are thirsty!

The first thing to do when you get a bare-root plant: Give it a drink. Carefully unpack the roots and wash off the sawdust. Trim off any broken root pieces or stems. Fill a large bucket, basin or even wheelbarrow with water – enough to cover the plant’s healthy roots – and put the plant in the water. Let it stay in the water, roots submerged, for several hours or overnight. (And if need be, it can stay there for several days.)

Next comes transplanting. That bare-root plant can go directly into the ground or into a container. Even though its eventual home may be in garden soil, pre-planting a bare-root plant in a container first can get it off to a stronger start in spring.

This container-first method allows that plant to develop new feeder roots before plunging into its permanent in-ground home. This method is particularly helpful for deciduous shrubs and perennials as well as small trees.

Use a large black plastic pot, big enough to spread the roots inside without crowding. (A 5-gallon pot works for most shrubs.) Black plastic absorbs heat and will speed bud break (the first growth of spring). It’s like making spring come early for this transplant.

In the black pot, use a 50-50 mix of potting soil (which contains nutrients to stimulate root growth) and native soil (dirt from your garden). Add some root stimulating fertilizer (such as Sure Start, Quick Start, etc.); this adds microbes to help get those feeder roots started. Water just enough to keep the soil evenly moist, but not wet.

Note: Many nurseries now pot up some or all of their bare-root plants in 2-gallon-size or larger biodegradable pulp pots. Consequently,  you can skip this intermediate potting stage but be sure to remove or at least slit (in several places) that pulp pot when moving the plant to the next stage in spring. The molded pulp is supposed to "break down over time" but experience shows it won't do so fast enough for early root development.

If you've purchased a bare-root tree, berry or grapevine in a tall, narrow plastic "tree pot," treat it like the sawdust-packed bare-roots. Wash off the little bit of soil that's in the tree pot and soak those roots before potting into a larger container.

Next, in all cases, comes planting in the chosen spot. In April after the outdoor soil has started to warm, remove the plant from its pot, transplant the whole rootball with its new soil and healthy, growing roots into the ground. The plant will respond with faster, stronger growth and quickly become established (a.k.a. “put down deep roots”).

This method also comes in handy if it’s too wet to plant outdoors. Soggy soil needs a chance to drain. Never transplant a plant into over-saturated soil; its roots will rot.

Bare-root plants can stay containerized indefinitely. (That’s what most nurseries sell – plants in pots.) Container-grown plants tend to stay more compact because their roots are constricted; that’s an asset for small-space gardeners.

For trees and shrubs, growth above ground reflects growth below ground. So transplanting into the garden will produce a bigger tree or shrub – its roots have room to expand. (And that will lead to a bigger harvest.)

Deep (and wide) roots help drought-proof that plant; it can draw water and nutrients from a wider area and more soil.

How do you encourage those roots to grow deep and wide? It comes down to the hole.

The most common mistake gardeners make when transplanting is putting a plant in a deep, narrow hole filled with soft, fluffy potting mix and nothing else. Cut by the shovel, the soil around this fluffy mix becomes a hard, solid wall – sort of like the walls of a clay pot. Water can seep through but it tends to collect in that hole – and stay there. It can rot the roots of the new transplant. Also, the plant likely won’t push out its roots into the surrounding soil, stunting its own development. (Why push against a hard wall when growing in this soft medium is so much easier?) The plant can become rootbound in its hole much as if it stayed in a pot.

When digging a transplant hole (particularly in clay-rich soils common in the Sacramento area), make the interior sides ragged, not smooth. Even better, dig the hole twice as wide as necessary to accommodate the rootball or spread out the bare roots. The hole should not be deeper than the root ball.

With a spade or fork, work that soil down at least one foot; more is better. Break up the clumps well. Amending the native soil with compost or fertilizer is no longer recommended.

After creating this planting “zone,” dig your hole. Roughen the sides of the hole as well as the sides of the rootball of the plant to be transplanted. Then, drop the whole rootball in the hole. Pack the soil around the roots and water deeply.

If planting a bare-root plant, create a hill at the bottom of the hole and sit the plant on top of it, lining up the plant’s root crown just above the soil line. Spread the roots around the hill. (Think of them as fingers of an outstretched hand, holding a ball.) Fill in with the loosened native soil around the roots.

Don’t fill the hole completely; just halfway. Tamp down the fill soil and water deeply, filling the remaining hole. The water should soak in quickly. (If not, drainage could be an issue.) After the water has soaked in, fill in the remainder of the hole and water again.

Hold off on adding any fertilizer until the plant shows signs of growth in spring. Make sure to water deeply before fertilizing.