There is little more frustrating that discovering that mice have attacked your greenhouse. All those seedlings, which you have been lovingly tending, can be gone in a single night. I’m all too familiar with mice nibbling their way through my sweetcorn seedlings, or even digging up the seeds entirely, but fortunately there are some ways to fight back…
Build a Moat
While mice are surprisingly adept swimmers, the promise of a cold bath can sometimes be enough to keep them at bay. One trick to control mice in your greenhouse is therefore to carefully place your pots of seedlings within water-filled trays.
A side benefit of this technique is that it can also protect your seedlings from other potential pests, such as slugs and snails, who also will think twice before trying to cross your carefully-constructed moat.
Raise Up Seedlings
A second trick is to raise your seedlings up off the ground, where they are far more difficult for mice to get to.
For this I simply use old, unwanted shelving units. Mine are made from pine slats, meaning that a mouse will not only have to scale the height of the shelves to reach my seedlings, but they’ll also have to precariously shimmy themselves along the narrow pieces of wood before actually reaching my seed trays.
I have certainly found that those on the higher shelves are far less affected by the nibbling of mice than those on lower shelves.
Many seed trays can be bought with a close-fitting clear plastic lid. This acts rather like a mini greenhouse, helping to keep the seeds that little bit warmer and preventing them from drying out. However these same plastic covers can also provide a physical barrier for mice; quite simply when firmly fixed mice simply can’t get underneath them.
Even in your greenhouse, when you’re starting seeds consider covering your trays with these covers, which will keep your seedlings in perfect condition (at least until they grow too tall and the cover needs to be removed).
Mice don’t of course just magically appear in your greenhouse to dig up your seeds and eat your seedlings; they’re getting in from outside. Another method to deal with mice attacking your plants is therefore to carry out a thorough inspection of how they may be getting in. Look for any gaps in walls or panels, and plug these to prevent entry. In addition, be sure to keep the door to your greenhouse shut at all times.
Lastly take a look around the bottom of your greenhouse for any holes, as I have found on numerous occasions that a mouse has managed to burrow under the walls of my greenhouse, and pop up inside. Once against, plug these holes to prevent any further entry.
Try Ultrasonic Deterrents
If you’re really starting to tear your hair out, and mice are still attacking your seedlings, one addition trick is to try one of the many ultrasonic rodent deterrents.
These give out a shrill sound – which you are I are unable to hear – but which is very uncomfortable for mice. It’s like waking up with a hangover to find your neighbour doing their drum practise at 100 decibels! Just as uncomfortable it would be for you, so mice tend to avoid areas where these deterrents are in place.
As a low-cost and chemical-free option, these can be an ideal hands-off solution for the busy gardener.
While not everyone will agree, if you’ve tried all the other options here and your sweetcorn and squash are still getting mutilated at every turn then you may want to consider the use of rodent poison.
Place this carefully in the dedicated holders, and site them inside your greenhouse along the walls. Mice love to run along the side of walls, and are far less prone to scampering across open ground. As a result, such a positioning maximises the chances of success.
That said, rodent poison should only be used after careful thought. Firstly, placing those chemicals into your greenhouse, where you’re growing food crops, is not necessarily the wisest idea.
Secondly, you must be sure that children or domestic pets won’t come into contact with it and make themselves ill.
Thirdly, of course, rodent poison isn’t instantaneous, so it may still take some weeks before your rodent problem comes under control.
Finally there is of course the ethical element, of just how kind it is to slowly poison a mouse. Only you can make a decision about whether or not baited poison traps may be right for your needs.
Invest in Traps
Lastly, as a more instant solution than poison, mouse traps may be placed strategically around your greenhouse. Whether you opt for humane traps – so the mice can be released unharmed in another area – or you go “old school”, mouse traps normally represent a faster and (arguably) kinder alternative to poison.
If you do decide to use mouse traps then please be sure to check them regularly. Humane traps must be checked daily, while the old fashioned variety will need to be emptied on a regular basis if you don’t want your greenhouse smelling quite unpleasant.
While having your seeds dug up, and your precious little plants gnawed through, can be a thoroughly disappointing experience, there are are solutions. Quite which you opt for will depend on your own unique circumstances. I would certainly advise you at least try some of the more humane methods to begin with, only moving up the scale if you continue to experience losses.