Why You Shouldn't Cut Things Back After a Freeze

The first hard freeze of the year will damage most summer vegetables, annuals, and perennials. Once freezing temperatures become a regular occurence, it’s time to pull out summer vegetables and annuals that won’t re-seed and put them in the compost pile. If tempted to cut back your frost-damaged perennials and re-seeding annuals, here are the reasons why you shouldn’t.

Reasons to leave frost-damaged plants standing

1) If you cut everything down to the ground in your perennial garden right now, it’s going to look barren and empty, and there is no benefit to doing so. Leave perennials standing through winter to provide visual interest in your garden.

Look at how beautiful an unpruned Piet Oudolf garden looks in winter:

Piet’s extensive use of ornamental grasses is intentional because it creates magic through winter months. Consider adding more ornamental grasses to your gardens next year.

2) Even when frost killed, perennials are an important source of food and shelter for wildlife, and the foliage can provide insulation for the root crown. (For perennials that can be iffy through winter like Salvia Mystic Spires, mulch the root crown heavily now for optimal insulation.)

3) Leave re-seeding annuals like gomphrena, zinnias, and cosmos in the garden as long as possible to encourage a repeat bloom next year. Once the dead plants get too unsightly for you to bear, however, you can crush up the seed heads and scatter around the garden before pulling out the plants.

4) Pruning a perennial or shrub back can actually make it less resilient through the winter months. Pruning stimulates new growth, and we don’t want new growth on our plants as we go into winter. New growth is even more damage-prone than older growth during freezing weather.

When to cut plants back

The best time to cut back perennials and shrubs is late winter and early spring.

I cut back my shrubs that need shaping or size control in late February. At the same time, I will cut back my woody perennials like salvia greggii, Texas rock rose, and caryopteris back by 50%.

Note that any spring-blooming shrubs or vines should only be cut back only after the spring bloom is complete. Otherwise, you risk cutting off the bloom buds.

For ornamental grasses, I hate the way they look when drastically chopped, so I prefer to clean them up by raking out the dead grass to make room for new growth. The practice of harshly cutting back ornamental grasses each year eventually leads to extensive and irreversible plant damage.

I wait to cut back tender perennials like salvia farinacea, echinacea, and nepeta until new growth emerges from the base of the plant.

A note about garden hygiene

When pulling out spent vegetables and annuals, it is important to remove the entire plant, roots and all. If you’ve been told to leave roots behind to break down and add organic material to the soil, you’ve been given bad advice.

For plants that have problems with pests and diseases, like vegetables, leaving any part of the plant behind can make these problems worse. This is because destructive organisms will stick around in the soil when you leave things behind for them to feed on.

Even if you only use organic pest and disease treatments, the use of these treatments can still disrupt your garden’s ecosystem. A truly sustainable garden requires little to no use of treatments whether organic or synthetic. To reduce our reliance on treatments, we must focus on preventing problems before they occur.

Prevention strategies

Some of the best ways to prevent pest and disease problems in your garden include practicing crop rotation and maintaining a clean, debris-free garden.

A simple crop rotation strategy for home gardens is to avoid planting anything from the same plant family in the same location the following season or year.

For example, if I plant tomatoes in “Plot A” this year, I should avoid planting tomatoes or any plant from the nightshade family like eggplant or potatoes in that location for at least two years.

To keep your garden debris-free, remove entire plant from the soil when it is done producing, and clean up all fallen fruit or foliage.