With this article, Horticulture Review unveils its new online Forum. Each month we will post a question via e-mail and print the responses. We are looking forward to member’s participation and hope to spark some lively interaction as well as share timely information between peers. Shortly you will receive an e-mail inviting you to the LO Forum. I will be moderating the forum, if you have questions to pose to your colleagues, please submit them to sarahw@landscapeontario.com.

This month the topic is winterizing the garden centre. How do you take care of your inventory at the end of the year? Do you try and sell everything off, or carefully overwinter your investment until next spring?

Here’s what several growers and retailers said about protecting their plants.

John Moons, Connon Nurseries, NVH Holdings, Waterdown: for a retailer, the best thing to do is to overwinter as little inventory as possible. However, some retailers take advantage of deals in the fall and stock their poly houses over winter. I think growers have experience and specific knowledge about how to best overwinter each variety and so may have a better-looking plant come out of the poly houses in spring.

For example, poly houses containing broadleaf evergreens at Connon’s are protected with a layer of styrofoam placed around the outside of the base of each hoop house. In early spring it is critical to monitor and possibly vent the poly houses to ensure the temperatures don’t rise too high inside.

Containerized trees are overwintered at Connons by laying them down and covering them with plastic. If we have old tarps available, we layer them on top of the plastic.

Kevin Joyce, Cudmore’s Garden Centre, Oakville: well-watered container trees are overwintered pot-to-pot in a corner of the garden centre. We put them on an old piece of 4 mil poly so they don’t freeze to the ground.

Shrubs and evergreens all go in one hoop house we cover with 4 mil poly. The plants are watered well before the house is closed up. The poly house has a low profile which seems to hold moisture in well. We clean the plants up in the fall before putting them away; they look nice and fresh in spring and we sell them right from the poly house.

We try not to carry any small perennial pots over the winter. We have good success putting our one and two gallon perennials pot-to-pot on the ground on porous black fabric and covering them with a frost blanket.

Tom Intven, Canadale Nurseries, St. Thomas: fragile material, such as rhodos, are overwintered in a minimum heat inflated polyhouse. Our minimum heat polyhouses have a temperature-activated furnace that keeps the interior temperature at freezing to avoid fungal growth. We have found that a double inflated layer of poly provides an extra 10 degrees of protection. And, covering plants inside a polyhouse with a microfoam blanket provides an additional 10 degrees of protection on top of that.

Once dormant, perennials are cut back, weeded and a quarter of an inch of sawdust is layered on top of the pots. This provides insulation for the roots, and the mulch helps to reduce weed pressure in the spring when we are busy.

Our container trees are heeled in the ground with the help of a trencher, and soil is thrown on top of the root balls.

Andre Langendoen, Langendoen Nurseries, Niagara-on-the-Lake: once plants are dormant we put them in the hoop house frames and spray everything with a fixed copper spray. We put on a fairly heavy coating which has anti-fungal properties. The copper spray must be completely dry before the poly is put on the frame. Retailers putting plants into covered hoop houses could spray copper inside on a windy day if they opened the doors to help the spray dry quickly. Once dry the copper coating lasts a long time, and can withstand several waterings if necessary.

Once the pots have frozen inside the poly houses we give them one good heavy watering in mid- to late-November before we close everything up. A dry root zone freezes quickly, whereas a well watered pot freezes solid and insulates the roots.

We use a single layer 50 per cent shade poly on our houses. Sensitive crops like cotoneasters and hydrangeas are covered with a thin frost blanket once the pots have frozen. The frost blanket is reasonably priced and easy to handle.

Plants should be packed pot to pot, but not crushed too tightly together. Evergreens especially shouldn’t be jammed together as they can start to rot and the needles turn brown. Spending a bit more money providing extra space for the plants will pay off in the long run.

Finally, we put down mouse poison in the poly houses. We are starting to put plants in the frames now and will bait the houses to get whatever is around at the moment and then rebait in November once the plastic is on. We also check the poly houses every two weeks throughout the winter to check for rabbit damage as well.

Joan Johnston, Peter Knippel Nursery, Gloucester: we are trying to manage our inventory more carefully so we are not overwintering much material. We have a sale of plants we don’t want to over winter, and put them on for 50 per cent off with no guarantee at the beginning of October. We are trying to clear our inventory that’s been in the store for a year or two, recognizing its better to have fresh, new vibrant plants in spring. What a privilege it would be if you could sell out each year and start fresh next spring!

That said, we have bought our shade trees for next winter and they have already been heeled in. Our perennials have been on sale since the beginning of September. We start with the 4-inch pots and then move on to the one gallons. One of our perennial suppliers takes back any larger plants that don’t sell – innovative ideas like this are great.

We’re not selling customers old tired plants and are still bringing in fresh stock – we had two loads in last week, but we’re buying more carefully. Now we’re resisting the temptation to stock up when wholesalers have overstock of plants we don’t need.

One way we are proactively managing our inventory is that we have created a database of local landscapers and sending them e-mail notices and inventories each week to let them know what we have available. This may not work in the Toronto area where landscape contractors have easy access to growers, but in Ottawa it is working well for us.

Susan Richards, New North Greenhouses, Sault Ste Marie: we put together all left-over trees and shrubs into groupings with the pots pushed tightly together. P.V.C. tubes joined into a 'T' shape are stuffed with plastic bags of mouse bait. Bait tubes are placed throughout the group of pots. Once the weather is consistently cold, we shovel shredded mulch up along the sides and the tops of the pots. The groupings of trees or shrubs then freeze solid as winter arrives and stay frozen until we start up again in the spring. We have few losses.

Left over perennials are grouped together in a similar way, bait tubes are spread around, heavy white frost blanket is spread over the pots and mulch is put around the edges of each grouping. We have learned that no matter how much bait is used, the mice get into pots of lilies, toadliles and some grasses. We try not to have any of those varieties left. In past years, we have sprayed the frost blanket with Ropel That did work, but the chemical stays embedded in the frost blanket, and is a real hazard for staff. We don't use Ropel anymore.

We have a fall sale to clear out left-over plants, rather than trying to over winter too many. Saving plants is a lot of work in both fall and spring! I would rather get some money for the plants in the fall. We do reuse the mulch the next spring to top up the pathways in our large display garden.