How do they make a deer repellent that doesn’t wash off every time it rains, or you water the garden? Well, that depends on if it’s natural or chemical deer repellent, but even this can vary. There are three ways that a repellent manufacturer can make it long lasting, and rain resistant. One is to make it systemic, which means the plant takes it in through it’s roots which distributes it through all parts of the plant, and the other is to use a ‘sticker’ when the repellent is topically applied to the leaves.
To date, only one substance has been found to be effective at controlling deer damage in a systemic application, and it’s hazardous to the environment and the health of all animals – including humans. The EPA has removed all spray-on repellents that contained Bitrex from the market, and currently there is only one product that offers a systemic application, but it’s sold as a fertilizer. Why anyone would want something this toxic in their yard or garden is beyond me, but for the time being it is still available.
Most people are more interested in natural deer repellents than those with chemicals in them, but they do still have a market. Most of these products have a latex sticker in them much like Wilt-Pruf, an anti-desiccant that stops plants from drying too rapidly due to transplant shock, and winter conditions in some climates. Wilt-Pruf was never intended to be constantly applied though. It interrupts natural mechanisms in a plant’s leaves that they need to be at their best. It’s not damaging temporarily, but many horticultural pros would not recommend it’s use except in extreme conditions.
All natural or organic deer repellents that offer weeks of protection and good rain resistance use essential oils as a sticker agent, and some may call them botanical oils. They are natural plant extractions that haven’t been processed further. There are homemade deer repellent recipes that call for cooking oil are attempting to arrive at the same outcome, though it is nowhere near as long-lasting, and may be even worse than a latex sticker. There is the possibility of the sun frying leaves on the plant, because the sheen on foliage can magnify the sun’s rays and burn the foliage. It can also suffocate them if too much is applied. Essential oils are just different, as are cooking oil and motor oil. They’re all oils, but not all the same, which is why you don’t ever see a deer repellent made with canola, corn, peanut, or other oils one has in their kitchen. If it worked properly, they would use it, because even at wholesale, cooking oils are much cheaper ingredients.
Most non-chemical deer repellents rely on rotten eggs, garlic, or hot peppers to deter deer, and sometimes a combination of these. When you see one that proclaims it doesn’t stink, you know it has essential oils in it. The oils are more than just a sticker, they mask the stench of rotten eggs and garlic very nicely, thanks to their powerful aromas. And the ones used by deer repellent makers have the added benefit of sensory experiences that deer will usually avoid. Its rare that hot pepper is included with essential oils, because oils from the plants they’re extracted from have this element already: oil of cloves, cinnamon, mint, thyme, and rosemary are all very pungent, and hot on the tongue.
It’s not just the presence of these oils that makes them stand up to rain fall. The amount of oil has something to do with that, as does whether your application was totally cured before the heavens let loose. Light oil in the concentrate might not hold up to weather as well as those with a higher amount. If it works well and has less than 1% oils in the mix, there might be something in the ‘other’ ingredients that helps its rain resistance. Sometimes that ‘other’ stuff can cause burning on plants if you spray it too heavily, or it freezes before it dries. Naturally, you learn that after the damage is done! Be sure to read the entire label, and follow the directions (including cautions) that someone had the forethought to share with you for best results.
How much botanical or essential oil should be in a deer repellent to know you’ll have good rain resistance? For starters, look for brands that have more than one kind of oil, and have between 1% and 3.5% total. This information will be on the label, and if you’re shopping online, locating the product MSDS sheet in search will provide this information when you can’t see all the labeling. If you can’t find a Material Safety Data Sheet (MSDS), you might want to use a different one. Most manufacturers are happy to share this important info with prospective customers, it proves that their product is above board, and has all bases covered.
Here’s a few of deer repellent products with good levels of essential oils:
- Deer Stopper: 3.4%
- Deer Solution: 3.14%
- I Must Garden All Season (Spice Scent): 1.5%
- Everguard: .9781%