Tightly spaced perennials

dave11October 25, 2010

I tried searching for a discussion here about this but couldn't find one, though not quite sure what terms to search. If it's been hashed out recently, please say so.

I've seen pics and advice in various places about planting perennial beds with all the plants spaced tightly together, so that no soil or mulch is visible. The argument (I think) is that it keeps weeds out, and removes the need for mulch, because the soil doesn't show anyway. I've seen lots of pretty pics in magazines of these multi-color beds that look so natural, but is it that simple?

Would seem to me that it would take a lot of work to keep one plant from overunning another, and that the water requirement would go up quite a lot, if everything in the bed needed to be watered. Seems like the plants would all be competing for water otherwise, or that the more drought tolerant would win.

And do such beds really keep that many weeds out? I have a bed of ancient thick pachysandra, but tall weeds still grow in it sometimes, though not as often as in bare soil. So it still needs to be weeded.

Just curious what the collective experience has been with these tightly spaced plants. Do folks recommend them?

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woodyoak zone 5 Canada(5b)

I am a 'no bare ground' gardener - i.e. pack 'em in, in planting. Yes, it does keep the weeds down - down but not out entirely... In established beds, watering is a rare event and I've never noticed problems re water competition between the plants. In part, no doubt, because I don't plant anything with high water requirements (other than in the 'wet corner' bed where such plants are appropriate). Once established, many plants that are said to like or require moist soil will do fine with just natural rainfall.

Self-seeding plants that fill in around other plants on their own are important in my beds. One of them, feverfew, is considered a nuisance by many people. For me, it is an invaluable plant as I cut it down several times in the growing season and lay the cuttings on the ground as mulch. I let it bloom and set seed in mid-late summer to ensure I have plants for the next year (most feverfew are annuals and grow the following year from seeds dropped by the previous summer's flowers). Blue flax is a perennial self-seeder that is also a filler in the sunny garden. In the shade garden white corydalis is my main self-seeding filler plant.

Since I only remove heavy stalks and diseased or disease-prone material from the garden in the fall and leave the rest to rot down naturally over winter, the garden effectively mulches itself. The soil has improved itself a lot over the 11 years we've been gardening here. Certainly, some insect pests will overwinter in the old plant material - but so do 'good' bugs, so I find it balances out. The colder winters here probably makes that a more viable approach than it would be in areas with warmer winters.

I think whether you go for the dense planting or neatly mulched, widely spaced plants is largely a personal preference thing. Plants will grow well either way. Choose the look that you prefer and go with that.

    Bookmark   October 25, 2010 at 9:37PM
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karinl(BC Z8)

OK, so I'm a pack 'em in planter too - doesn't sound like much as a style, but there it is. I don't think I'm as methodical as Woody; I'm always doing things by the skin of my teeth, never have time to get it all done and it is never the same for long enough for me to have gotten a "system" set up.

Regarding plants sucking up the water and nutrients: yes, if they are trees or shrubs especially. Also maybe perennials, but it seems to me the woody stuff more readily outcompetes the perennials.

And yes, the perennials do grow at different rates and some smother each other out (some hostas are seriously vigorous, especially in certain beds). So I do have to go in every couple of years to each bed to sort out what's dominating what, divide things down if necessary, and I do lose the odd plant.

Weeds: they start before the plants grow in and even if I do an early weeding, I miss some or they resprout. They're always there, but definitely less - I have some containers in which the whole "ground" is not covered and if I use these as a control, then the beds are definitely less weedy.

Speaking of containers, they are part of my beds quite often. They elevate some plants so it's not just a mishmash, plus you can fit more in this way :-) and they also help the soil below to remain cooler and moist. Rocks or flagstones placed in beds will have a similar effect on the soil AND no weeds can grow under them. Besides, I love containers and they look nice in winter.

I'm actually just learning to mulch, by the way, because I think beds will benefit from it even if the plants are close.


    Bookmark   October 26, 2010 at 10:15PM
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Thanks Woody and Karin. That's the sort of input I was looking for. I like the look of the tightly packed beds, and with the large areas of beds I have, I like the idea of not buying/spreading 20 cubic yards of mulch every year or two. Of course it means I need to buy a lot of plants, but in the long run it seems it would be cheaper, less work, and more enjoyable.


    Bookmark   October 27, 2010 at 7:33AM
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Hmmmm......I'm not sure one can get away without using mulch, even with a tightly packed perennial border :-) First, spacing IS important but it is spacing based on the estimated mature size of the plant in question. With most perennials, this takes several seasons to accomplish and weeds can develop a serious foothold during this period. If you space closer than estimated mature size, it just increases maintenance by increasing the frequency of division or transplanting. Smaller growing plants can be easily overwhelmed. Second, the vast majority of perennials are herbaceous, dying to the ground each year, then reappearing in spring. For a significant amount of time, there is nothing there to shield the soil so unless mulched, weeds will come (many weed seeds are very cold hardy and will germinate in late fall and in very early spring, long before the perennials have had a chance to fluff out and fill in for the season).

Finally, a good organic mulch adds hugely to soil condition. It can prevent frost heaving in winter in cold climates, insulate the soil in warmer situations, reduce evaporation of soil moisture and provide necessary plant nutrients as it breaks down. Personally, I consider routine (at least annual) mulching one of the best things you can do for your garden and the health of your plants.

    Bookmark   October 27, 2010 at 11:30AM
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It is as simple as that and although not entirely without effort it is still much easier than the normal way. And like you say, I do very much enjoy the look.

The largest amount of effort comes in the spring. for as was mentioned the weeds start growing sooner than the more desirable plants. But it seems that a few minutes a day for the first month or so and you are good to go. Some plants will grow faster and overcome others. but I just pull them up and transplant them to another spot. Or you could trade them away or God forbid compost them.

Yankee Dog

    Bookmark   October 27, 2010 at 4:13PM
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woodyoak zone 5 Canada(5b)

gardengal - you can definitely get away without using traditional mulch! I have never mulched other than the mulch that the plants provide themselves. I am physically disabled and cannot possibly distribute endless cubic yards of mulch for endless years. But it hasn't stopped me from having a thriving garden! A lot of weed seeds need light to germinate. A densely planted garden that is not stripped bare to the soil during fall clean-up does a good job of limiting light available to weed seeds for germination. An attractive lay-out of paths in the garden, judicious use of garden structures and ornaments, some interesting shrubs and trees, perennials selected that will stay put for years without extensive need for division, along with spring bulbs and self-seeding filler plants and you can have a dense and attractive garden for less work than one might expect. Of course a 'no maintenance/no weeds' garden doesn't exist, however much people might want one. But you can choose what maintenance you need to do by how you plant and organize your garden. Traditional mulching is not maintenance I'd ever choose to do. And my garden does not suffer for the lack of it.

    Bookmark   October 27, 2010 at 4:41PM
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Bumblebeez SC Zone 7

I have too many fungal issues to pack tightly and much prefer working in a garden area that gives me room to walk around.
My perennial area is fairly big roughly, 30' x 40' and I have shrubs in there too.
I do mulch the whole area but having adequate air circulation around the plants is helpful. I like to be able to see the ground too...don't want any snakey surprises.

From a distance, it looks filled in.

    Bookmark   October 30, 2010 at 9:12AM
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I think we are talking about two different things here. One is disregarding traditional spacing recommendations and planting perennials closer together than the space they will ultimately need. The other is overplanting, so there is no need for mulch. The first is very common, particularly for professionals who want to give their customers a full mature looking perennial garden as immediately as possible. If i planted by the mature size spacing, I would not have a job any more. I would rather divide perennials a little sooner than 3-4 years than have a really disappointed client right after they paid me to install a garden.

Overplanting so you don't need mulch may save time in terms of mulching, but it takes a lot of time to divide plants for health and moisture requirements. It also can look overgrown and disorganized. I have disabilities too Woody- so I really understand how important it is to simplify physical jobs and I respect that you have found a solution that works for you. With my limitations I find that the investment of time and energy into mulching saves a tremendous amount of time later in the season in terms of weeding, dividing, and watering.

    Bookmark   October 30, 2010 at 10:23AM
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Bumblebeez SC Zone 7

As the home owner doing all the work, I much prefer perennials spaced amply apart so I don't have to divide them after a year or two and the plants are much healthier.

    Bookmark   October 31, 2010 at 9:24AM
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woodyoak zone 5 Canada(5b)

There are clearly differences based on zone/climate and what works for me here in zone 5 with cold winters, is certainly less likely to work in your zone, bumblebeez. Plant selection is important - many of my perennials have not needed dividing in 8-10 years because I choose ones that can stay put in one spot for a long time, or ones that seed around as fillers. Flowering shrubs, trees, and vines are also important companions to the perennials and fulfill some of the same role without needing dividing. Only ones with easy or no pruning are included.

    Bookmark   October 31, 2010 at 9:37AM
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Glad I asked this question, because the discussion is interesting, and answers some other questions I had. For the record though, my intention when planting my own beds this way would be to space the plants based upon their full sizes, so no dividing would be needed, but weeding/mulching required till they filled in.

    Bookmark   November 1, 2010 at 8:35AM
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marquest(z5 PA)

Dave I do not know your zone. So what works for a gatdener in a cold zone may not work for you. I agree with woodyoak I pack them in and I use creeping ground cover. My experience is I have very little weeding with the packed garden and not cleaning the beds until the following Spring.

I think it is personal preference. Some people think the gardens look good if they have mulch and orderly type gardens. I use that style on the front of the property. But I still do not use mulch I use compost because we have a termite problem and moles, voles love that stuff and I hate the look especially the red dyed stuff. It is all personal taste.

The gardens in the back are full billowing flower gardens. Packed tight and I have ground cover of geranium. I do not have to dig and seperate often. It may also be the type of plants I like that do not expand.

I have never had a plant need to be divided every 2-3 years. Unless you are planting a mature plant it is going to take at least 3 years for it to really grow at its best then you need another 3 yrs for full maturity.

I have 4 acres so I have a lot of garden beds it would not be to my benefit to mulch all my gardens and I do not like the planned too neat garden look. LOL

    Bookmark   November 1, 2010 at 6:26PM
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I understand that personal considerations will always determine the amount and type of garden maintenance a homeowner is inclined to undertake and what works well for one may not work equally as well for another :-)

When designing gardens, especially mixed perennial borders, I always space plants according to their mature size. First, over-planted gardens are an unwarranted expense to the homeowner, purchasing more plants than are necessary, and can lead rapidly to plant health issues as the plants crowd each other. Ultimately, they lead to increased maintenance, with unnecessary transplanting, too frequent dividing, pruning to keep size in check, etc. A simple explanation that an initially sparse or bare appearing garden will rapidly fill in in the course of a season or two is typically sufficient to ward off concerns that the garden looks 'empty' - great gardens take time! And they can always fill in with annuals temporarily until the perennials fill out.

And I think there is some confusion about what mulch is and its purpose in the garden. Mulch is not a single product but anything applied as a covering to the surface of the soil. Could be dyed, shredded bark, could be compost, could be shredded leaves, could even be gravel or shredded tires (heaven forbid!!). Mulch is intended to accomplish numerous tasks, including but not limited to weed suppression. Preventing soil erosion and compaction, insulating or moderating soil temperatures, conserving soil moisture, disease suppression, nutrient contribution and soil improvement (in the case of an organic mulch) and aesthetic concerns are all valid reasons to mulch.

Whether or not one chooses to mulch is pretty subjective based on their own gardening style and conditions. But I would caution against mistaking the impression that mulching is only for weed control and that by tightly spacing plants, one can override the need for any additional mulching. Regardless of one's gardening situation, mulching planting beds is a good thing, whether one chooses just to leave fallen leaves in place or consciously applies any other type of organic mulch. Of all the maintenance a gardener can offer, routine mulching will provide the biggest returns.

    Bookmark   November 2, 2010 at 11:41AM
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marquest(z5 PA)

I would like to add the zone you are blessed to garden will also play a big role of how fast your plants will mature, I know in my garden it takes much longer for a plant to be very large.

I do not like to buy online unless it is something I cannot find locally. Purchased online I know is going to be a 5 yr wait for a good size plant not large enough to need to be divided, Local purchased plant at 4 years the plant will be a good size but still not large, Plants that are grown in a zone 8 that is aggressive has not been aggressive in my garden zone.

I think many people do not understand weather conditions from zone to zone play a big part in gardening. Even the same zone can be vastly different.

    Bookmark   November 2, 2010 at 4:53PM
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I am not sure that the statements "spacing based on mature size" and "no dividing is needed" will always be true, together. Plants exceed their mature size, especially "happy plants." But I guess you mean, don't need dividing until they meet or exceed their mature sizes.

I have moved from mulcher, to crowder, back to somewhere in between and including more mulching ( which includes using home-made compostables) because I found I have less enthusiasm for digging and dividing and more trouble trying to place or get rid of extras because I hoard plants and then I am susceptible to just plopping them somewhere rather than putting on the compost heap. Plus, I was having some plants not able to spread gracefully if too crowded and trouble with root competition for water in dry spells.

It really depends on the plant and even then on how it likes the spot or how its growth pattern is affected and its companions. So you might end up with one happy crowded zone and another where you allow more space at certain times of the year so that the plants will achieve some peak appearance that you like enough to plan for or some disease resistance. You are on a journey, and that is the fun of it.

    Bookmark   November 3, 2010 at 6:49PM
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bahia(SF Bay Area)

I also like a very full sort of planting style with little earth showing between plants, but here in California I prefer to use mostly evergreen perennials that can go a decade or more between needing division, or that are more likely to reach a certain size and stay there. Admittedly it is easier to do this in a warmer climate, but the approach can still be used in colder climates. One example might be the use of things like Kniphofia uvaria or Anigozanthus flavidus, which only slowly clump, and are happy enough here with being left mostly alone. Agapanthus, Dianella, Libbertia, Asparagus species, etc would all be examples of large clumping flowering perennials that work in the same way.

For the slower growing perennials, until they have filled in, why not consider the use of annuals between them as filler to act as a sort of green mulch? I tend to topdress bare areas with a mulch/compost mix in lieu of pure bark mulch, as much to increase soil fertility and slow evapotranspiration as to reduce weeds.

Mixing low growing shrubs into the mix is also an excellent way to get the look of a full perennial bed without all the work of dividing perennials as well. Things like Choysia, Coleonema, Hebe species, shrubby succulents such as Aloes and Agaves and Cotyledons all work well for that purpose here, substituting hardier plants such as dwarf hollies, cotoneasters, junipers and grasses in colder climates.

Too close planting of perennials to get immediate impact, especially of things that will need rapid dividing in just a year or two sounds like more work than it is worth. Although I guess I do design local "perennial border look" plantings here in San Francisco that I do replant every 2 or 3 years. These mostly use plants such as easy to grow succulents such as Senecio mandraliscae or Cotyledon orbiculata in combination with Echeveria imbricata or E. agavoides, and instead of dividing them, I just pull them all out of the ground, separate them or take cuttings, and replant them directly back into the ground when they start looking senescent or too crowded. To do an entire bed as a revamped planting all at once is usually timed to give me new plants to use in a new client's garden, so it is a win/win situation and fairly fast.

Somehow I am not attracted to using perennials that die back in winter and fail to thrive if not regularly divided, such as Bearded Iris or fast spreading Asters. Maybe it really isn't any more work than the plants I like using, but they seem to need it more often, and don't have the year round curb appeal as compared to virtually everblooming Lantana camara cultivars or things like Calandrinia spectabilis and the like. The dwarfer growing Phormium cultivars and other grassy foliaged plants like Astelias are also great choices for foliage color in a perennial flowering scheme in zones where they will do well.

    Bookmark   November 7, 2010 at 7:11PM
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