Defensive Shrubs For Landscaping: Tips For Using Shrubs With Thorns

Defensive Shrubs For Landscaping: Tips For Using Shrubs With Thorns

By: Bonnie L. Grant, Certified Urban Agriculturist

Who needs home security when you can plant for home protection? Wicked thorns, scratching spines, pointed leaves and serrated foliar edges can cause would-be robbers more trouble than it might be worth to break into your home. There is a unique guarding plant for almost every situation and planting zone. Let’s learn more.

What are Defensive Bushes?

Home security via plants? Sounds like a funny idea but it has both economical and aesthetically sound logic. Defensive barriers have been used for centuries. The commonly known defenses might be moats or even stone walls, but the humble plant can provide resistance and security as well. Defensive shrubs for landscaping blend in and still guard the home against invasion.

Natural barriers are a wonderful way to keep unwanted guests off the property and away from the home. Using defensive shrubs for landscaping capitalizes on their less friendly aspects while also benefiting from their beauty. So what are defensive bushes?

Placing plants with possibly harmful attributes in weak areas of the yard, intimidate, repel and prevent intruders. Planting shrubs to keep people away is a grand tradition that is reflected in huge perimeter hedges, thorny plants scaling up walls and prickly roses as foundation plantings. There is a wide variety of plant specimens from which to choose as protective home bushes.

Using Shrubs with Thorns and Other Nasty Surprises

The first step to a protected landscape is to decide where your weak points are located. You may feel that just a few windows that are near the back require protection, or you may want to fortify the entire perimeter of the property.

Using shrubs with thorns at foundation points repels possible burglars effectively unless they have a shovel or pruning shears. Even with tools, removing the sharp stems and leaves is a time consuming and potentially painful undertaking, not one the average cat burglar would be willing to attempt.

Climbing plants are another way to protect the home. Painful in their own way, the following plants can serve as a deterrent and are effective choices for fending off unfriendly visits:

  • Bougainvillea
  • Pyracantha
  • Blackberry
  • Roses
  • Barberry
  • Yucca

Additional Spiny Shrubs List

There are many choices when planting shrubs to keep people away. Medium sized to large trees that serve as excellent barriers due to their long thorns include:

  • Honey Locust
  • Cat’s Claw Acacia
  • Argentine Mesquite

In arid zones, a border of cacti and spiny tipped succulents, such as Agave, provide a spirited defense with local appeal. Old school specimens, like holly, can be trained to a wall or planted as a hedge and the serrated teeth of the leaves bite and stick as protective home bushes. Buckthorn, Osage orange and many species of rose are easy to grow and keep away uninvited visitors too.

Check with your local extension office to see what plants might be recommended for your zone.

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Read more about General Shrub Care

Mulching trees and shrubs

Mulching plants is both functional and decorative. Mulch typically is an organic material spread on the soil surface to protect roots from heat, cold, and drought, and to provide nutrients to plants as it decomposes. Once you have chosen the right plant for a given site, and followed the proper planting procedures, you should mulch the plant and create a stable environment for root growth.


What makes good mulch? Several factors should be considered when choosing mulch:

Texture. Medium-textured mulch is best. Fine particles tend to pack down and retain moisture, which then evaporates before reaching plant roots. Coarse-textured materials may be too porous to hold adequate amounts of water.

Nutrient value. Organic mulch provides nutrient- rich humus as it decomposes. This also improves soil structure.

Availability. Consider the availability of different mulch material and whether you have to haul it yourself. Bulk materials may be available free from your community.

Aesthetics. The type of mulch used is a personal preference. Choose for yourself the look you desire. The Morton Arboretum uses organic mulches because of their many plant benefits. Ideally, organic mulch should be composted or otherwise treated before use so that weed seeds, insects, and disease microorganisms are killed. Composted mulch generally has more uniform texture than mulch that is not composted. Composting is probably not needed for disease and insect control if the mulch is derived from healthy plants however, if it has been sitting outside indefinitely it is likely that weed seeds are present.


Grass Clippings. Dry or compost before using. Mix with other materials to increase porosity and reduce matting. A source for some nitrogen but also higher alkalinity, which may compromise nutrition.

Hardwood Bark. Pine bark or shredded bark, can be purchased as bags of small or large chips. Long-lasting.

Hardwood Chips. Readily available and often free from municipal sources.

Composted Leaf Litter (leaf mold). A good source of nutrients but may increase weeds if not thoroughly composted.

Animal Manure. A good source of nutrients. Compost before applying or plant damage (burn) may result due to high salt content. Ideally, should be mixed with a coarse-textured material.

Mushroom compost. A good source of nutrients when mixed with soil or other materials. Source of large amounts of alkalinity and sometimes salts.

Peat Moss. Compacts easily due to fine texture and dries out quickly, best mixed with soil and other materials. Not recommended as a top dressing because water will not penetrate when dry.

Pine Boughs. This is a good covering for perennials in the winter.

Pine Needles. Not widely available and should be mixed with other materials unless soil acidity is desired.

Sawdust. Compost first or mix with a nitrogen source (manure and/or fertilizer) before applying. Oak sawdust helps acidify soil and is good for azaleas, rhododendrons, and blueberries. Do not use sawdust from treated lumber.

Sewage Sludge. A good source of nutrients. Composted sludge is available commercially (i.e., Milorganite or Nutricomp) and should be incorporated with soil or mixed with other composted material.

Shredded Leaves. Leaves are variable in texture and can be collected and shredded at home. Mix into the soil in the fall and allow to break down naturally during the winter for improved soil quality.

Straw. Coarse-textured so it persists a long time, but can blow away easily unless mixed with other materials. Generally not suitable as a landscape mulch, but provides winter protection and cover for grass seed.


Spread mulch under trees, shrubs, and throughout planting beds to a recommended depth of 3-4 inches for medium to coarsetextured materials.

Pull mulch away from the bases of tree and shrub trunks creating a donut-hole (image on left.)Do not pile it up against the trunk (“volcano mulching”). Excessive mulch on the trunk causes moisture to build up, creating ideal conditions for insect pests, diseases, and decay (image on right.)

Ideally, the mulched area around a tree should extend to the drip line of the branches, or at least cover a 4-5 foot diameter area around the trunk. The larger the mulched area, the more beneficial.

Check the mulch depth annually and replenish as necessary.


Provides an insulation layer. Mulched soils are warmer in winter and cooler in summer than bare soils. Roots are protected from temperature extremes, creating less freezing and thawing of the soil in winter, which can heave and injure plants.

Conserves soil moisture. Bare soil surfaces heat-up in summer, causing water evaporation and sometimes root desiccation and death. A layer of mulch reduces moisture loss by preventing sunlight from reaching and heating the soil. Mulch also insulates the soil moisture from evaporation by wind. Less watering is required during high summer temperatures.

Improve the soil’s physical structure and fertility. As mulch breaks down it adds humus to the soil, increasing organic matter in the surface of heavy clay soils and improves the water holding capacity of light, sandy soils, and slowly releasing nitrogen and phosphorous into the soil.

Prevents erosion and water runoff. Bare soil disperses or breaks apart when impacted by rain or sprinkler droplets. Mulch protects soil from being eroded and reduces water runoff by providing a “sponge” surface that absorbs water and slows it down.

Reduces root competition. In the Midwest, most of a tree’s fine roots are in the upper 12- 18 inches of soil. Applying mulch under trees and shrubs eliminates competition from other plants for water and nutrients. Turf roots are especially aggressive and pose the largest threat of competition to trees and shrubs. Create a “living” mulch by using plants that are more compatible with tree roots: bulbs, wildflowers, ferns, ground covers, and other herbaceous perennials.

Additional benefits of mulch include

protection from lawnmower damage

recycles yard/landscape waste

provides a more natural appearance of the landscape

provides a favorable environment for earth worms and other organisms that benefit soil structure and fertility.


Problems may arise if mulch is used incorrectly. Too much mulch can be harmful. Consider the following points to make an informed choice and avoid problems:

Creates a barrier to oxygen and water. Plastic mulch or weed barriers prevent oxygen and water from penetrating the soil and should not be used unless they are porous.

Excessive moisture. Fine-textured mulch, such as peat moss, grass clippings, and sawdust, holds a lot of moisture and should be used only in mixtures with other coarser materials.

Heat injury. Dark-colored mulches absorb heat during the day and lose heat at night as surrounding air temperatures fall. This heat may sometimes injure succulent plant tissue.

Root collar rot. Excessive mulch mounded around the base of a tree can cause decay of the vital tissue at the root collar. Once decayed, serious disease organisms may more readily enter the plant.

Soil temperatures. If applying mulch as winter protection, avoid applying it too early in the fall, since mulch can delay the soil freezing process by retaining heat in the soil. Furthermore, if applied too early in the spring, mulch can inhibit soil warming and delay root growth. As a general rule: wait until after a hard frost in the fall to apply winter mulch, and after the last frost in spring to apply summer mulch..

What Makes Plants Deer Resistant?

Some plants have toxicity which causes deer to avoid them. Also, deer don’t like flowers with strong odors. They turn up their noses to many herbs and flowers which we think smell delightful.

That said, sometimes there isn’t a rhyme or reason to what deer will nibble on. I do wildlife rescue and have fawns wandering about every spring with the goats. Hostas are normally a deer smorgasbord, but they never eat mine (I’m knocking on wood as I say that). However, my pine trees are a culinary delight.

What a deer will and won’t eat changes by season, region and plant variety, so you may need to do some experimentation.


Many families are well acquainted with the insect-repelling powers of citronella, thanks to its use in outdoor candles and oils. But this amazing grass is just as effective in its natural form. Planting citronella or keeping bits of it potted around your garden will protect you from mosquitoes on summer nights. Even better, keeping a small amount planted near your windows will deter bugs from trying to fly into your home. Adding citronella to your garden offers a great alternative to candles and bug spray.

The Best Home Security Plants

Here are some of the most effective plants for home security:

1. Blackberry

If you want a thorny plant that’s going to grow as quickly as possible, the Blackberry should be one of your top choices.

No, this is not one of the most attractive plants, but it can grow to be over five fight high in a short amount of time, and it’s packed with thorns and prickles that will tear up any attacking party.

The biggest downside to the Blackberry bush is that because it grows so quickly, you need to dedicate time to pruning and trimming it. As long as you’re willing to do that, it’s a good choice.

2. Century Plant

The Century Plant is, without question, one of the most beautiful yet unforgiving home security plants in existence.

With its light green leaves, the Century Plant is incredibly easy to grow, doing well even in hot and dry conditions. Maintenance is also relatively hassle free and it’s rare for it to suffer from any kind of disease.

It grows massive spikes next to its four foot long leaves, and those spikes can easily stab through skin with only a little bit of force.

The one downside to the Century Plant is its short lifespan of around one to two decades, but other than that, it’s definitely one of the best home defense plants available.

NOTE: The Century Plant is also known as the Sentry Plant.

3. Crown of Thorns (Euphorbia)

Here’s a plant where even its name is intimidating. This thorny plant is so named because it is believed to be the plant that was forcefully wrapped over the head of Jesus before his crucifixion two thousand years ago.

The plant is a five foot bush that produces beautiful red colored flowers in the summer, so it really adds to the look of your property. The thorns are only part of its defense mechanism. The sap that it produces is also highly irritating to the skin and can even cause serious sickness if orally ingested.

4. Porcupine Tomato (Solanum)

Also known as the Devil’s Thorn, the Porcupine Tomato (or Solanum) can also grow to be nearly five feet tall with massive spikes that are tough enough to rip through skin.

Like the Euphorbia, it also comes with a deadly sap that is heavily irritating to the skin and can cause severe sickness when ingested. This is another plant that’s really going to make burglars turn around and go elsewhere.

5. Firethorn (Pyracantha)

Armed with sharp barbed leaves and poisonous berries, the Pyracantha is one of the largest plants on this list. It can grow to an astonishing 20 feet in height.

Like the Blackberry bush, the Pyracantha grows and spreads easily, which is great if you need a home defense option quickly, but it also means you’ll have a lot of trimming to do.

6. Rose

The rose bush is well known for its thorny branches that also cause infection when they pierce the skin.

The rose plant is also very beautiful and can add value to your home and property. The gorgeous flowers it produces are among the most recognizable in the world.

If you happen to have a wife who loves roses, you’ll have no trouble talking her into this option.

7. Spanish Dagger (Yucca Gloriosa)

Last but not least, the Spanish Dagger is native to the southeastern United States, but it grows well in virtually any kind of warm environment.

They can grow to be over fifteen feet high and have long pointy leaves that act as an excellent deterrent against intruders. The Spanish Dagger is popular with homeowners who live in more tropical regions, not only because it grows naturally there, but also because it can add to the value of the property as well.

If you don’t have the resources or space for larger hedge plants, you may want to consider placing smaller ones for your property. Depending on your preferences, you can decide on ones that remain green or blossom each year.

One plant you should consider for a small hedge is Bog Rosemary. This plant, also known as Andromeda polifolia or Marsh Rosemary, is a plant that grows between eight inches to three feet in height.

These plants are sensitive to humid and dry weather conditions, so it would be best to keep them in well-drained soil with reasonable amounts of moisture and shade.

Although Bog Rosemary shrubs can release toxins when boiled in water, their pink and white flowers can add color to your greenery.

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