Firstly, I must confess that if deer are your issue I don’t think that anything works but a fence (actually, two fences), but that is a subject for a different article.
I got to know them better when I planted 60 tulips one winter and found five in the spring, along with some very fat rabbits.
I found a permanent solution – daffodils. Since they are poisonous to rabbits, who have keen sense of smell, I found that growing daffodils in a triangle around beds of tulips allowed me to grow tulips that had been eaten every year. Of course, the down side of daffodils is that they have huge, strapping foliage. So I needed a very small daffodil, preferably a miniature one, but they are normally very expensive. Enter W. P. Milner, a division 1 from 1869 that only grows to about 5 inches and has very small foliage that melts away weeks before the foliage of standard daffodils. I also use them around roses to keep rabbits from chewing them to the ground in winter.
It was often stated that cayenne pepper would deter squirrels. I will ever forget losing lilies in pots, and heavily sprinkling them with red pepper, until one memorable morning. I heard a very strange sound outside, stuck my head out the window, and saw a squirrel sitting in my lily pot, sneezing because its little face was cover in bright orange cayenne powder, but continuing to nibble away.
What does work, I subsequently found, was black pepper. But it must be fresh. So I found an inexpensive pepper grinder, and after planting bulbs, give it a few turns over the site. Repeat this for two more days, I found, and all my bulbs would survive intact.
These little guys, like squirrels, will tend to dig wherever earth is disturbed, in order to find "what the other guy” left in the soil. They are particularly fond of plants on pots. Over the years I have found that a sprinkling of Milorganite, an EPA approved all purpose, slow release nitrogen fertilizer that also contributes iron to the soil. As a fertilizer it is awesome, because it doesn’t burn and you don’t have to water it in. It’s 85% organic matter. It lasts ten weeks. It also smells terrible because it’s based on sewage. We humans can only detect the awful odor if we stick our heads in the bag and inhale. But chipmunks are very sensitive to its scent. After you plant in the ground or in a pot, just sprinkle some on top.
My first experience with voles was when I moved to a community of new homes. People who had been there longer complained of vole tunneling. I didn’t have any damage, at first. Then they found me one winter. They also found about 50 lily bulbs, some quite rare. Those of you who do business with B&D Lilies may recall that they lost thousands of lilies to voles that discovered their fields.
My first solution was to use Permatil, also known as Volblok. This product is an expandable slate which, if placed in the soil around plants in a trench is, in my experience, 100% effective for voles because they have tender little feet. It is also permanent, because it is left in the ground. I was able to grow lilies again. But see the rabbit section, because what works for rabbits works for voles, and it’s a lot less work.
Birds in hanging baskets:
I remember correspondence on Daves Garden from a gentleman who was having problems with geese in I his large hanging baskets. He noted that scaring them away didn’t work, because they just came back. I had the same problem with nesting mourning doves (love those things) in my four hanging baskets on the west side of my house. Scaring them away definitely didn't work; they would return every morning and give me the hairy eyeball. So at the beginning of nesting season I took some sheets of aluminum foil and bunched them up until they were about the size of a baseball. Not only are they uncomfortable to sit on, but they're shiny. Would you lay your eggs on something like that? My plants did not have any trouble growing around them, and they were light enough so that tidal wave petunias just grew around them, and it didn’t crush the plants. The doves went elsewhere (the hardscape in my back yard, which was charming). Once nesting season is over, I just tossed the aluminum balls. It worked like a charm, but didn’t harm the birds.
Organic products that must be used with caution:
There are also products that are approved for organic use but must be used with caution. One of them is spinosad. Spinosad is a bacterium that was discovered in 1982 in a still. It works on susceptible insects by ramping up their nervous systems, cause them to stop eating, and die within two days. It works best on pests that consume a lot of leaf tissue, like the viburnum beetle, and there also are several fire ant baits based on spinosad. It breaks down in sunlight, so it should be applied at the end of the day, which is said to spare our beloved bees.
Those with substantial slug damage are probably aware of the chemical metaldehyde. It is effective on slugs but can be toxic. Birds eating the bait died, along with pets in the garden. If slugs are a significant problem, iron phosphate is a better solution, but it should be used with caution. It is actually used to fortify bread. It has low toxicity and must be consumed to be effective. It is the the Food and Drug Association category of "Generally Recognized as Safe", but it can be irritating to some people. Application with goves, rather than sprinkling it with your hands, is a good idea.
Then there is the anecdotal. I grow large number of four o’clocks (mirabilis jalapa) and have noticed dead Japanese beetles near them. Since mirabilis jalapa is a gorgeous plant that can be easily grown from seed, it’s worth a try.