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Wednesday - February 19, 2014

From: Oak Park, IL
Region: Midwest
Topic: Pollinators, Shrubs
Title: Berries on cultivars of Ilex verticillata from Oak Park, IL
Answered by: Barbara Medford

QUESTION:

I have three ilex verticillata cultivars (2 Nana, 1 Jim Dandy) planted on the west side of my house in a very shady site (there's a mature over-spreading hackberry on the parkway just to the west and it is a very small front yard). They were planted in late October 2012 and last year produced hardly any berries at all. I am not sure if the problem has been light or perhaps moisture, or if I simply need to wait longer for them to establish. And debating moving them into a slightly sunnier area of the front garden, where they wouldn't get much sun but it would be strong midday sun, or I might be able to squeeze them into various places in the back where they would get more sun (still mostly partial or dappled shade; there is a large magnolia tree to the south, and four huge spruce trees to the east in back), but to find a space for them, they might have to go under the drip line of the Spruce where the soil is more dry, and I understand they like moist, even boggy, conditions, so might that be worse? Where would they best flourish to produce berries, and given the limited space, could I divide them between front and back, given that would put them over 50 feet apart, and might that affect pollination? (Alas, hordes of sparrows will devour the berries in the back.) Other new plantings in this front shady site (like an echinacea cultivar) also didn't do incredibly well (an amelanchier was happy though), and in general I am wondering if it is better to reposition/replace young plantings sooner rather than later into more suitable spots, or wait (how long?) to see if they establish better?

ANSWER:

Holly shrubs are dioecious and need a mate, so you can correctly reason that the lack of berry production must be attributed to one of two possible causes: You have a male holly shrub OR you have a female holly shrub, but its flowers haven't been pollinated. Ordinarily, this is pretty hard to determine, but in your case, the cultivars of Ilex verticillata (Common winterberry) that you have include 'Nana' which is female and 'Jim Dandy' which is male. In many cases, it is not known which sex of an Ilex is being purchased from a nursery - mostly clones are sold in nurseries. Both sexes have flowers, but only the females will produce berries. Since you know you have male and female plants, we might guess that the immaturity of the plants is a contributing factor to the small berry crop. But we don't know that is the only reason, as you pointed out. The best way to really know about a native plant is to go to our webpage on it; in this case, you can follow this link to our webpage on Ilex verticillata (Common winterberry). From that page:

"Growing Conditions

Water Use: High
Light Requirement: Sun , Part Shade , Shade
Soil Moisture: Dry , Moist , Wet
Soil pH: Acidic (pH<6.8)
CaCO3 Tolerance: Low
Soil Description: Moist, acidic soils. Sandy, Sandy Loam Medium Loam Clay Loam, Clay
Conditions Comments: Winterberry tolerates poor drainage and is quite winter-hardy. You must have both a male and female plant to have berries. The male must be the same species as the female and bloom at the same time. Because hollies are such popular landscape plants, it may be worth the risk to plant a female and hope there is a male nearby."

Note that this plant can tolerate "sun," which we consider to be 6 hours or more of sun a day, "part shade," 2 to 6 hours of sun a day and "shade, " which is 2 hours or less of sun. We don't know anything about Ilex needing moist, boggy conditions, it just has high water needs. You should also note that it can tolerate some ordinarily pretty inhospitable soils. It does prefer acidic soils, but it can grow in clays, which many plants cannot.

From the Missouri Botanical Garden, here are articles about the cultivar 'Nana," and the cultivar 'Jim Dandy'.

In answer to your original question, we always feel that more sun prouduces more flowers and hence more berries. However, we also feel that transplanting can be very traumatic to any plant. If you want help making your decision, start by timing how long there is sun on each part of your garden you are considering. The hackberry, beneath which you have the winterberries planted now, is deciduous, so the plants will have more sun in the winter and early Spring, which might help the blooming. And don't factor in the berry-eating sparrows in making your decision; the birds can fly and they will find the berries. Bees and some butterflies are the pollinators so don't go spraying insecticides on your plants.

We always check to make sure the plant is native not only to North America but to the area in which they are being grown. This USDA Plant Profile Map shows your winterberry grows natively in Cook County, so there is a pretty good chance that your soils are suitable. Once you have measured the amount of sunlight your hollies are getting in their present position, you are the one that can make the best decision on whether to move or leave the plants where they are.

From the Image Gallery

Common winterberry
Ilex verticillata