What's the best way to sow groundcover & perennial seeds together?

Question

I am planning to sow seed of ground-cover plants & perennials in drifts.

I have never done this before, so I am not sure if what I am planning makes sense.

For each drift, I want to use Pelted Micro Clover Seed & Creeping Phlox as the base and then add one more plant to it. For example, let's say:

• Drift-1 I would sow Pelted Micro Clover Seed/Creeping Phlox & Sweet Alyssum
• Drift-2 I would sow Pelted Micro Clover Seed/Creeping Phlox & Black Eyed Susan

Assuming I sow the seeds at a time that matches both plants:

• should I just mix the seeds and spread them together? Or
• should I first sow the base-layer (clover or Phlox) then walk over it and sow the seeds for the other plant
• Or does it make sense to sow the seed for the base layer wait a while before sowing the seed for the perennial?

Are there any pros/cons or if you have any other ideas?

Clarifications

---

• The area in question is over 2Ksqft
• My wish for this area was to create drifts of perennials on a bed of 'worry-free' ground-cover. However, I can also settle for 'worry-free' ground-cover for the first year until I figure out how to introduce drifts of perennials.
• I hope to create the drifts of perennials of different height to create interest - so I don't have any height restrictions

Answer 1

Because perennials take a year or more to get established, if you're up to a multi-year effort, then I have some possible suggestions.

First, a couple of assumptions:

• The area you want to plant is primarily a lawn right now.
• The area is in full sun (6 hrs of sun or more a day).
• You have removed all grass or other undesirable plant material from at least a part of the garden area. Given that I'm thinking "multi-year", you do not necessarily have to remove all of the lawn this year.
• You will not be turning the soil over or cultivating it before planting, as that will expose a ton of weed seeds to the light, which will then sprout like crazy. This will, of course, worsen your weed problem.
• You will not have used Preen or other pre-emergent herbicide.
• You will be using an organic mulch around the plants and to cover any non-planted area.

Here are some ways to get the garden that you want.

2022

1. Designate a space in this area to use as a "nursery bed". This is where you'll be planting the seeds for the perennials.
2. In a section of this new garden, but not in the nursery bed, sow alyssum fairly thickly, leaving some space for perennial plants. Because alyssum is a cold-weather annual, you can usually sow it a little before the last frost date, but check the seed package to be sure. This will be your groundcover for this year. It spreads quickly to prevent weeds from germinating and will reseed if not mulched.
3. If budget allows (and you really have no choice in some cases because seed just isn't available), plant some perennial plants where you want to see them as a drift. Plant them in areas where you have not planted alyssum. This is about the only way you'll get any creeping phlox, as seeds are usually not available. If you have an independent plant nursery nearby, work with them NOW on perhaps ordering you flats of 18 or 32 plants that you can pre-pay for. They'll be delivered at the nursery at the proper planting time for your area, and you won't have to fight off other customers to get them. In addition, you may be able to get a break on the price because you're both pre-ordering and pre-paying.
4. In the nursery bed, sow your choice of perennials in rows, just like a vegetable garden. Plant as many seeds as you can take care of over the summer. This includes groundcovers.
5. Use a short-term organic mulch such as cocoa bean hulls, rice hulls, pine needles, SHREDDED newspaper, or whatever is available in your area to mulch the alyssum and perennial plants.
6. Weed the nursery bed as needed; when the seedlings have been up about 4-6 weeks, mulch them as above.
7. In the fall, remove more of the lawn for next year.

2023

1. Repeat step 2 and 3 as above. In this case, the perennials you plant will come from your nursery bed and not necessarily the plant nursery.
2. Use a "permanent" organic mulch (such as arborist wood chips) to mulch the perennials from 2022. This will prevent the alyssum from reseeding; if any plants do appear, just move them into this year's new garden.
3. Repeat steps 4 through 7 as above.

Future years

Repeat the steps from 2023.

Additional advice

• I would not use clover at all in this area. When it's young it isn't a very effective groundcover, and after the first year it is TOO effective, in that it will out-compete many plants and be nearly impossible to remove. This is why I suggested Alyssum rather than clover.
• When considering plants to use, note that most perennials are not "self-cleaning" - in other words, there are going to be dead flower stalks/seedheads to remove in order to keep the garden nice looking. An exception to this is creeping phlox - I've never seen a seedhead on my phlox so I assume that they're self-cleaning.
• As noted above, you'll have to deadhead most perennials, so consider some that are sterile, such as the Calamint 'Montrose White'. This is an 18" tall plant with small glossy leaves that blooms from July until frost. Calaminth 'Marvelette White' and 'Marvelette Blue' may also be sterile.
• You will have garden maintenance over the winter or early spring, when you have to cut back all of the previous year's growth for your non-groundcovers.
• Not all groundcovers are equal! Ajuga, for example, will literally grow everywhere and WILL choke out small perennials in your garden. Personally, I hate it as an invasive plant, but posters here such as blacksmith37 really like it. Neither of us is wrong - gardens would be boring if we all planted the same thing, right? So - do your homework on groundcovers before you plant them! One thing to consider is "ease of removal" in case you change your mind. Ajuga has the benefit of being relatively easy to remove because it is shallow rooted and tends to spread along the top of the ground; Sweet Woodruff, in contrast, is difficult to remove because it has week roots that break when you try to pull them, and each root that you leave behind can become a new plant (lily of the valley is another plant that acts like this).
• To make getting around in your garden easier, you may want to plan one or more pathways using flagstones. This will keep your shoes dry when working in the garden :)
• Under no circumstances use a sheet mulch of any kind. This includes cardboard, non-shredded newspaper and landscape fabric (see next section for reasons why).

Sources for information

• Here is a free download that discusses the science behind using arborist woodchips.
• An excellent resource for home gardeners is the website Horticultural Myths.
• An excellent discussion as to why sheet mulches are terrible for the soil is in The Garden Professor's Blog Be sure to read the comments on the "cardboard" articles. Note that this link includes only the "cardboard" articles, so click on "Garden Professors Blog" at the top of the page to refresh it and view 10+ years of articles.