Broadleaf evergreens, like this holly plant, have green leaves that stay on the plant all winter.

Common Questions About Trees & Shrubs

Because of the cooler temperatures, fall is a great time to plant shrubs and trees. Jon Carlson, owner of J. Carlson Growers, in Rockford, answers questions commonly asked by customers.

Broadleaf evergreens, like this holly plant, have green leaves that stay on the plant all winter.
Broadleaf evergreens, like this holly, have green leaves that stay on the plant all winter.

Jon Carlson, owner of J. Carlson Growers, has forgotten more about trees and shrubs than most of us ever knew. Here, he answers some questions commonly asked by customers who visit his nursery at 8938 Newburg Road in Rockford. Fall is one of the best times to plant many kinds of shrubs and trees, after the weather starts to cool down.
Q: What’s the difference between shade trees, ornamental trees and shrubs?
A: Shade trees are generally more than 30 feet tall at maturity, whereas understory and ornamental trees are 10 to 25 feet tall. Shrubs are typically under 10 feet.
Q: Are rhododendrons and azaleas the same?
A: They’re related. There’s not a simple way to distinguish one from the other, but azaleas in our area are most often deciduous, meaning they drop their leaves in cold weather, and they tend to be smaller plants than rhododendrons. So, we list them in the “flowering shrub” category in our catalog.
Most rhododendrons are broadleaf evergreens. They don’t lose their leaves in winter, although there are exceptions.
There are two main categories of rhododendrons that we carry: smaller-leaf varieties, like P.J.M., that tolerate more sun, and larger-leaf varieties, like Haaga, that perform better in some dappled shade. They both love well-drained acidic soil and are not fond of heavy Illinois soil. The newer Haaga rhododendrons are a hybrid from Finland and are super hardy.
Q: There are so many kinds of hydrangeas these days. Which are best?
A: It depends on what you like the looks of. Some people like the big, round, white mop-head blooms from a reliable old standby like the Annabelle. Other people like the newer panicle varieties that have more of a cone shape.
I sell one panicle, an Oakleaf variety called Alice, that I really like. The blooms are a nice raspberry hue, it has red foliage in fall and it tolerates shade well, like the mop-heads do. Limelight and Little Lime have huge celadon green panicle blooms. There are also lacecap varieties – the blossoms are shaped more like flat caps with frilly edges. We carry one with a nice blue color. Called Blue Wave, it does well, given the right conditions – well-drained acidic soil and heavy acidic fertilization.
Once you know the general bloom shape you want, it’s a good idea to ask people which varieties are doing well in their yards. Some of the ‘latest and greatest’ varieties don’t always live up to the marketing hype, but some are fantastic. In general, hydrangeas do very well in our region and it’s nice to see more kinds of them these days. You can also buy them trained into a tree shape.
Q: What’s the difference between conifers and broadleaf evergreens?
A: Conifers make cones and have needles or small, scale-like leaves. Examples would be firs, pines, junipers, larches, spruces, cypresses, yews, hemlocks and arborvitae. There’s a huge variety of shapes and characteristics in the conifer category, and I honestly believe any property looks better with at least a few conifers providing some contrast and winter greenery.
Broadleaf evergreens are plants with more typical-looking green leaves that remain on the plant all winter. Examples would be boxwood, holly, mountain Andromeda and most rhododendrons. Boxwoods are great because deer don’t like them and they don’t require a lot of care. And holly has a very pretty, glossy leaf, with bright red berries on the female plants.
There are also evergreen vines and groundcovers like winter creeper, Thorndale ivy and vinca.
Q: What are some of your favorite conifers?
A: I find that people have good luck growing Serbian spruce, Canadian hemlock, white fir, globe dwarf blue spruce, dwarf white (mugo) pine and the small weeping Norway spruce, among others. It’s great that we have options for smaller, dwarf varieties these days, since conifers can get really large. I’m steering people away from Colorado Blue Spruce right now because they have some problems.
Q: What are some great flowering shrubs?
A: There are so many good ones. I like viburnums because they grow in a nice, neat vase shape, bloom with white flowers in spring, make dark-colored berries that wildlife enjoy and have colorful fall foliage.
There’s a viburnum called Arrowwood, with super-straight stems, that works well as a privacy shrub, especially if planted in two staggered rows.
I also like fothergillas, which give you a tapestry of yellow and red fall foliage color and have fuzzy-looking white blooms in early spring; hydrangeas and rhododendrons, which we already talked about; roses, which are a lot easier to grow these days; and so many others, like lilacs, quince, forsythia, sweetspire, burning bush, hardy hibiscus, ninebark, bayberry, sumac, weigela, weeping redbuds like Lavendar Twist …
There’s also a nice new white-flowering weeping redbud called Vanilla Twist. Also a new weeper called Ruby Falls that’s very compact and has clusters of lavender-red blooms in spring, with small, glossy heart-shaped leaves that turn yellow in fall.
Witch hazel is really interesting, too. It can be either a large shrub or a small tree. The common witch hazel blooms deep yellow in late fall and is more shade tolerant; the vernal witch hazel blooms a bright, happy yellow in very early spring, as early as February, and has a nice spicy scent. Nothing bothers it.
Q: What’s your most important advice to customers?
A: Think about the place you want to plant something and then come look through our nursery. If you can take a picture of the site on your phone and bring it with you, that’s great.
Also think about having something of interest outside your window in every season of the year. If we know something about your planting site – how much light it gets, whether it’s soggy or dry, how much room the plant will have to spread out – we can help you to make a good decision and be successful.