Garden

[Denial Robert]

I have a small yard surrounded by retaining walls and concrete. I have beds with mature bushes and flowering trees like lilacs rhododendrons and dogwood and perennials.

I notice that when I dig a nice hole, struggling with the roots of these bushes, to plant new perennials, they do well, growing larger for the first 2-3 years, but then decline rapidly and eventually stop returning. When I dig up to plant a new something the roots are back. Clearly my bushes are bullies, lol, choking their smaller neighbors. I'm wondering if anyone has had success delaying this process with some type of buried boundary around the perennial? I'm thinking maybe cutting the bottom out of some 10" plastic pots to make a ring around the base of the plant? Or perhaps lining the hole with multiple (15-20) layers of newspaper? I know these are only temporary and the roots will eventually return, but if it can buy me another 2-3 years I'd be willing to try it.

[ValuSkr]

I deal with the problem in spades, though I have tree roots rather than shrub roots.  The trees take so much water and nutrients from the soil and leave little for perennials.  To compensate, I do a lot of watering and fertilizing.  In addition, I regularly add leaf (or mushroom) compost since my topsoil is consumed in short order by the tree roots.

One idea I've read about but never tried:  Trees sold at nurseries have a bag around the root ball.  The bag has an interior lining that prevents roots from breaking through the bag.  Effectively the lining is a root barrier; roots just wrap around inside the bag.  It's said you can turn the bag inside out and use it for shrubs and perennials in your garden, to protect them from other plants' roots.  You're able to buy these bags individually.  It's been a few years since I looked but they're rather expensive, say $40 - $50 or so.

[Fressa]

I have had the holly take over and choke out the lillies. I decided that it's best to let the established bushes, etc. have their space. I did container gardens for the flowers and placed them in front and along the sides of the holly and hedges. So far, that's working for me and easier to maintain. 

[BirkiLady]

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@Denial Robert wrote:

I have a small yard surrounded by retaining walls and concrete. I have beds with mature bushes and flowering trees like lilacs rhododendrons and dogwood and perennials.

I notice that when I dig a nice hole, struggling with the roots of these bushes, to plant new perennials, they do well, growing larger for the first 2-3 years, but then decline rapidly and eventually stop returning. When I dig up to plant a new something the roots are back. Clearly my bushes are bullies, lol, choking their smaller neighbors. I'm wondering if anyone has had success delaying this process with some type of buried boundary around the perennial? I'm thinking maybe cutting the bottom out of some 10" plastic pots to make a ring around the base of the plant? Or perhaps lining the hole with multiple (15-20) layers of newspaper? I know these are only temporary and the roots will eventually return, but if it can buy me another 2-3 years I'd be willing to try it.

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@Denial Robert 

Your rhododendrums should be fine for many years. They have a very shallow root system which should not bother anything else if planted well in the first place (with enough room to spread above according to directions).

Lilacs and dogwoods do become territorial and require more room, fertilizer and water each year as they grow. Prune them after flowering for best results and to remove all dead wood, as well as to provide air circulation for healthiest conditions.

Many periennials may be divided every two or three years to keep the root systems smaller and the plants a reasonable size. Share the bounty with friends or take to a Weekend Market! People are always thrilled with free (or inexpensive) plants from a well-established start. 

I would not try to stiffle any plants' growth with a plastic container planted deep around it in an attempt to surround the roots. Those roots may be much stronger than you think and could break through many of those plastic pots due to winter heaving and hot summer weather or heavy rains and freezing ice. Best to divide and conquer in Mother Nature. Plus, you'll also keep the soil fresh and workable, which will be an easier job every year or two (or three). .     

[Frenchlop]

@Fressa  What u posted about the holly taking over is interesting. My lilies, that are next to a hydrangea bush, didn't come up this year. I wonder if the hydrangeas choked them? 

[Lilysmom1]

I would do what @Fressa @does and try container gardening.  When you fool with root systems you can harm the shrubs.  Using containers, you can adjust for height.  The only issue I see is with the use of containers is how to store in winter if you have four seasons.  LM

[Fressa]

Frenchlop---Our holly chokes out everything even the roadendrim (?) I pplanted lillies, iris and rosebushes and the holly has taken out most of them. This year I went with the containers since I had to replace most of them in the patio garden. Finally a compromise and the lillies and iris are blooming in them.   

[Fressa]

Lilysmom1---I only plant the bulbs that can winter in the containers.The ones that do the best are next to the foundation or the patio fence. The ones with annuals are on the front porch. Placment is mainly for convenience so I know what is planted where and for some protection from wildlife munching on them.