Potentially Invasive Garden Plants

Each spring the avid gardener thinks about what they are going to plant in their landscape and vegetable garden.  The beginners look to how they should start and what they should plant.  When I was a beginner I fell into the trap of wanting to plant EVERYTHING I laid my eyes one.

“OOOO, that’s pretty.”

“OH MAN, wouldn’t that be tasty fresh!”

A few things happened – instead of looking like a well arranged landscape with beautiful flowers and plants my gardens ended up looking like a disorganized mess AND I found out some plants aren’t meant to be kept in an open garden without some kind of restraint.

Here are a few plants that though beautiful, fragrant and having bounteous delicious crops should  be kept carefully:

• Strawberries.  Yes some have beautiful white flowers and most have delicious fruits in season, but those strawberry towers are sold for a reason.  Since strawberries spread not only from seed but also from their runners they can spread quickly becoming a tangled carpet that will invade your yard, landscape and every free piece of ground if not contained.  Each ‘daughter’ plant sends out runners of it’s own allowing the patch to sprawl even more.  A dedicated bed or strawberry tower is the best way to contain and keep tidy the strawberry patch.
• English Ivy – The dark green vining plant is one of my all time favorite things to grow. . . in a pot.  My favorites are the ones edged in white. Outside if left unkempt ivy will climb, wrap and cover anything in it’s path.  Though it may look nice growing on the side of an older brick home the fact that the aerial rootlets find any crevice that holds water and grows into it does not bode well for the structural stability of the masonry.  Also if allowed to grow on a tree it could eventually harm or kill the tree either by weighing it down or denying it of light.  If you don’t have time to trim ivy on a regular basis don’t grow it in anything other than a pot on your windowsill.
• Oregano, all varieties – I currently have 2 patches of oregano growing in my garden all from one teeny tiny pot I got on clearance at Lowe’s four years ago.  It’s Greek Oregano and it has a wonderful flavor.  I enjoy picking it fresh or cutting it back to dry and save for later or for sharing.  You have to keep control of the plant because it grow from self seeding and from rhizomes.  Thankfully since most of the seeds are lopped off when I trim back the plant I haven’t had many oregano babies invading my other garden beds BUT the spreading by rhizome has allowed the little potted plant to become a 4’x4’x4′ behemoth that choked out my beloved lemon thyme plant.  I even split the clump in two last spring and the original plant has already returned to it’s pre split size.  I’m going to have a lot of oregano.  If you don’t want that much, make sure to split and share clumps with friends and family, sell them or, dare I say it, throw it away.  The patch will only continue to grow.  Also, whether or not you plan to dry and use the oregano it’s always best to trim the plant back almost to the ground when the flowers start to bloom.  This is when the oregano flavors are at their height and trimming it back keeps the bush from getting twiggy and hard. Another option would be to grow it in a pot.  Just remember to put your pot of oregano in the garage or other protected structure to prevent it from freezing and breaking.
• Mint – all varieties.  Like oregano, mint spreads by rhizome but is much, much faster in it’s spreading habit.  Though it smells divine when you walk by and the fuzzy little flowers attract bees and butterflies you better have a plan on how to keep it from overtaking your yard.  I have a mint patch on the north side of my house in between the foundation and the sidewalk.  Still, I have to make sure that the mint doesn’t reach the yard either by getting too tall and setting down a rhizome or by growing between the sections of the sidewalk and then into the yard.  Either of those is rare, but have happened at least once since I planted it.  Be careful of using hybrids or specialized varieties of mint together with peppermint or spearmint.  They tend to be hardier, stronger and more invasive eventually choking out the heirloom varieties.  I have a lot of chocolate mint to pull up, dry and burn to allow for the peppermint to come back.  It might sound good to a chocolate lover but the smell and taste are not all they are cracked up to be.  I prefer peppermint any day.
• Lemon balm – The fragrance of this plant is like opening a new bottle of lemon pledge.  It’s delicious in summer teas and lemonades, too.  It is also one of the most aggressively self seeded herbs I’ve ever planted.  If you love this herb and can use it whatever you do, trim it down before it goes to seed.  Once those seeds hit the ground they are impossible to see because they look like little specks of dirt (kind of like basil or oregano seeds).  In the spring you will find a carpet of lemon balm seedlings anywhere the wind was able to scatter the seeds.  A few feet this year plus a few feet from each baby every year after will eventually turn into an uncontrollable lemon balm garden that you’ll have to dig up to keep from spreading more.
• Lily-Of-The-Valley – This beautiful green ground cover grows spikes of small, white, bell-shaped flowers which are commonly used in wedding arrangements.  It is invasive, but slow growing.  I keep it in the shade of my back yard between a couple trees around the patio.  It’s filled the spaces between hostas nicely but not choked anything out (yet).  A word of caution about this plant is that it is toxic.
• Kale – I have a variety of kale called Dwarf Blue Curled Vates.  It has a nice flavor and grows rather large for a plant called ‘dwarf’.  Don’t allow the plant to go to seed unless you have a plan for collecting the seed pods before they burst.  Like the other plants above, if the pods burst into your garden you’ll have tons of little kale plants to harvest from your entire garden and the walkways. Last year I had one entire 4’x8′ bed of only kale because I didn’t harvest the seeds of a mature plant in time. Gladly though they will not take seed in turfed areas.
• Cilantro – I love cilantro. It grows easily in zone 5 which makes me love it even more.  There is a catch though – it self seeds very easily.  To collect these seeds you really need to chop down the whole plant and hang it to dry before the seeds are too dry and start dropping off themselves.  Good thing about doing this is that you can clean, wash and dry the seeds for use as coriander.  This is another herb I have coming out of my ears right now.  Yet, I’ll be planting more for the greens this year :).

This is a short list and ones I’ve personally had experience with growing.  I say these are potentially invasive because with the right amount of time and care they are beautiful additions to the landscape which will bring you joy and bounty for many years.

Do you have information on a potentially invasive garden plant you’d like to share?

Here are some resources with more information about these plants –

Old Farmers Almanac: Strawberries.

About.com: English Ivy

CreationWiki: Oregano

ApartmentTherapy.com: Dos and Don’ts of Growing Mint

The Herb Gardener: How to Grow Lemon Balm (Melissa Officinalis)

About.com: Pictures of Poisonous Plants Lily-Of-The-Valley

GentleWorld.org: Kale

OrganicGardening.com: How To Grow Cilantro

Follow me on HomeTalk and check out this article on plants that should come with a warning label.