Eco-Answers from the Pros: Reining in Raspberries for Wildlife

We have raspberries growing in our field and would like to promote their growth to feed the wild birds and mammals. Can you tell me “best practices” for mowing the field, including the raspberry bushes, to make it healthy for diverse species. Should we mow annually, or every other year, more frequently? I’m in mid-coast Maine and cannot find references that address this topic.

Rasbak from nl.220

Rubus idaeus ‘Schönemann’

The simple answer to this question is to mow in late March or early April every other year. This will accommodate the life cycles of most bramble fruits. It may not lead to maximum productivity, but the plants will continue to be part of the meadow flora.

However, meadows are often more complex than my simple answer addresses. If the field is too wet to mow in early spring, then mowing after a hard freeze in the fall would be the second best time. For the ideal management of the raspberries it would be best to know what type of bramble they are (black raspberry, summer bearing raspberry, fall bearing raspberry, blackberry or other Rubus species) in which case you may want to change the management to a regimen that suits the pruning need of your particular type depending on the size of the patch and the time you want to spend thinning and pruning. Are there other plants  in the field whose growth you might want to favor? For the most part a late fall or early spring rough mowing will promote a diversity of grasses and forbs but if there are other grasses or plants that favor a different mowing schedule it might be good to spot mow parts of the meadow in accordance with their needs. If an invasive species like oriental bittersweet (or an aggressive native like poison ivy) starts to take over the field it may become necessary to mow more often for a time or have a plan to remove or kill the invasive plants before they destroy the diversity of the field.

Tricia Diggins, Senior Gardens Horticulturist, Wellesley College

Leave the field unmowed for a year until you can determine when the fruit set is for the berries. If they double fruit, then you can mow easily in the fall. If the plants only fruit once then you will have to mow every other year  – and there will be an alternate gap space in fruit production as well. You might consider adding a whole lot of cheap Heritage raspberries (double fruiting), allow them to grow for a couple of years, and then work into a late fall (mid-October or later) mowing.

M.L. Altobelli, Owner of M.L.’s Greenery in Motion in Westminster, MA

Raspberries certainly provide some support for wildlife in terms of browsing and shelter, but relative to other plants, their value doesn’t rank particularly high. The fruit is relatively low in nutrients and protein. I’ve noticed that birds never seem to show much interest in my little patch. Totally different story with the viburnum and dogwood fruits which attract hoards. Some animals browse leaves and canes, but thorns limit their use for many animals.

Rhubus odoratus, native to MA, in bloom.

Rhubus odoratus, native to MA, in bloom.

Raspberries are biennial. A cane grows for two years, then dies, with new canes continually emerging. There are summer or ever-bearing types, and types which bear fruit mostly in the fall. Without knowing what type you have, it’s hard to give specific advice. Effective management of raspberries to maximize fruit production can become a fairly involved affair, with selective pruning of canes—removing old floricanes, pruning back primocanes every year, and tip pruning during the growing season. (Refer to Pruning Raspberries and Blackberries, Cornell Cooperative Extension.) I think that most people would conclude that hand pruning a large field of raspberries isn’t really practical, especially given the relatively marginal wildlife value.

This leaves mowing as the only efficient way to manage a field situation, but mowing represents a blunt instrument here, and isn’t the best way to maximize fruit. I’d think that mowing every other year might be the best compromise between managing fruit production and limiting the growth of vegetation that might compete with the raspberries.

My general impression is that if one is going to exert much effort toward supporting wildlife, it would be better spent on other types of plants.

Nick Novick, Small Planet Landscaping, Ashland, MA

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