Jennifer Schultz Nelson
Extension Educator, Horticulture
Fall is a great time of year to evaluate the space needs of plants in your garden. If you are at all like me, each spring I think I have a lot more space than I actually have. I end up overcrowding my beds and sooner or later something has to be removed or relocated.
Take some pictures of your garden this fall. You will be glad you did in January when the first spring garden catalogs fill your mailbox. It will be easy to decide if you really have the room you think you do for new plants. I am notorious for having eyes bigger than my garden, and having pictures on hand does provide a reality check.
You may find in evaluating your garden this fall that some plants need to be moved. This may be a nearly impossible job this year considering the lack of rain this summer. Use a soaker hose or sprinkler to saturate the ground around the plant you are trying to move, and also water the location where you plan to relocate the plant.
When relocating perennials in the garden, dig the plant out with a large root ball trying not to damage adjacent plants. Keeping as many roots intact as possible will help the plant re-establish itself in its new location faster. If you are dividing plants, try to keep as much roots with each division as possible. Again, more roots will help the divisions establish themselves quicker in their new homes in the garden.
The key in getting fall planted perennials to survive the winter is timing and mulch. The plant's roots need to grow and establish sufficiently before winter sets in. Though the ground doesn't typically freeze in this area until December or January, the cold temperatures slow plant growth, including roots. A little extra mulch for the winter, applied in late October or November will help protect brand new or relocated plants. Just be sure to remove any mulch covering new shoots in the spring.
The safest advice to follow is to plant your perennials no later than September. That way, temperatures are still warm enough to promote good root growth before cold weather hits. I've violated my own advice here and there, planting perennials well into October some years. Some plants planted that late survived the winter at my house, some did not.
Plants that are particularly delicate or difficult to transplant are better left for transplanting in the spring before new growth is fully expanded. One example is false indigo, Baptisia australis. It has a deep tap root and so is difficult to transplant. I moved mine in early Spring of 2010 with great success. It was just starting to show signs of life when I moved it, and that first year it was a little small, but this year it doubled in size.
One way to lessen the shock when moving established plants in the garden is to root prune a season or two before moving the plant. To root prune, insert a sharp spade into the ground forming a circle around the plant, outlining as large a root ball as you can reasonably handle. Doing this in the fall severs a lot of the longer roots. The plant has several months to recover and adjust to a smaller rootball before being transplanted in the spring.
It's really not necessary to fertilize fall planted perennials. That said, many people will still feel like they must fertilize fall planted perennials. If adding fertilizer will make you feel better, stick to fertilizers containing only phosphorus and potassium, to encourage good root growth. Nitrogen fertilizers will encourage leaf growth, and what is more important in the fall is good root growth to sustain the plant through the winter. Frosts will come all too soon and nip those leaves anyway.
A gardener's work is never done, but try and find a moment or two to sit back and enjoy your hard work this fall before the snow flies. Far too often we are so absorbed in what we need to do that we fail to see what we have done.