Author Contributions
Conceptualization, E.P., F.L., W.G. and M.D.; methodology, E.P., F.L., M.C. and M.D.; software, E.P. and M.C.; validation, E.P. and M.C.; formal analysis, E.P. and M.C.; investigation, E.P., F.L., W.G. and M.D.; data curation, E.P.; writing—original draft preparation, E.P., F.L. and M.C.; writing—review and editing, F.L. and M.D.; visualization, E.P. and M.C.; supervision, F.L. and M.D. All authors have read and agreed to the published version of the manuscript.
Figure 1.
The rainfall and medium temperature detected during the entire experiment (elaboration from ARPA Piemonte data, Bauducchi meteorological station [
37]).
Figure 1.
The rainfall and medium temperature detected during the entire experiment (elaboration from ARPA Piemonte data, Bauducchi meteorological station [
37]).
Figure 2.
The six species selected for the research.
Figure 2.
The six species selected for the research.
Figure 3.
(a) The organization of the experimental field with 28 randomized plots of 4 m2 with the combinations of the 6 selected ornamental perennials: (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)). (b) The experimental field located in “Vivaio Purpurea di Alberto Peyron” nursery (Piobesi Torinese, Piedmont, Northwest Italy) during autumn in the first year.
Figure 3.
(a) The organization of the experimental field with 28 randomized plots of 4 m2 with the combinations of the 6 selected ornamental perennials: (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)). (b) The experimental field located in “Vivaio Purpurea di Alberto Peyron” nursery (Piobesi Torinese, Piedmont, Northwest Italy) during autumn in the first year.
Figure 4.
The input and output of the mobile device application Canopeo to obtain the percentages of ground cover by perennials after manual weeding. As an example, the figures show (a) the AB (Hemerocallis “Stella de Oro” + Phedimus spurius (M.Bieb.) “t Hart ‘John Creech”) and (b) CD (Tulbaghia violacea Harv. + Phlox subulata L. “Trot Pink”) combinations at the end of the manual weeding performed in summer in the third year.
Figure 4.
The input and output of the mobile device application Canopeo to obtain the percentages of ground cover by perennials after manual weeding. As an example, the figures show (a) the AB (Hemerocallis “Stella de Oro” + Phedimus spurius (M.Bieb.) “t Hart ‘John Creech”) and (b) CD (Tulbaghia violacea Harv. + Phlox subulata L. “Trot Pink”) combinations at the end of the manual weeding performed in summer in the third year.
Figure 5.
The mean percentages of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) during years 1, 2, and 3. Means sharing the same letter are not significantly different at p ≤ 0.05.
Figure 5.
The mean percentages of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) during years 1, 2, and 3. Means sharing the same letter are not significantly different at p ≤ 0.05.
Figure 6.
The growth performance of EF (Potentilla neumanniana Rchb. + Gaillardia “Kobold”): (a) from the final manual weeding in year 1 to the first in year 2, the Gaillardia “Kobold” plants were almost all dried up and Potentilla neumanniana Rchb. alone had not covered the ground well. (b) From the second and during the third years, Potentilla neumanniana Rchb left alone showed a good performance for ground cover.
Figure 6.
The growth performance of EF (Potentilla neumanniana Rchb. + Gaillardia “Kobold”): (a) from the final manual weeding in year 1 to the first in year 2, the Gaillardia “Kobold” plants were almost all dried up and Potentilla neumanniana Rchb. alone had not covered the ground well. (b) From the second and during the third years, Potentilla neumanniana Rchb left alone showed a good performance for ground cover.
Figure 7.
The mean percentages of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) during spring, summer, and autumn. Means sharing the same letter are not significantly different at p ≤ 0.05.
Figure 7.
The mean percentages of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) during spring, summer, and autumn. Means sharing the same letter are not significantly different at p ≤ 0.05.
Figure 8.
The best and the worst combinations, respectively, for producing perennial dry biomass during the three years at the end of the experiment (images taken after manual weeding performed on 12 November 2021). (a) Tulbaghia violacea Harv. + Phlox subulata L. “Trot Pink” (CD) with a dense and persistent vegetation. (b) Hemerocallis “Stella de Oro” + Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (AB) completely dried in autumn.
Figure 8.
The best and the worst combinations, respectively, for producing perennial dry biomass during the three years at the end of the experiment (images taken after manual weeding performed on 12 November 2021). (a) Tulbaghia violacea Harv. + Phlox subulata L. “Trot Pink” (CD) with a dense and persistent vegetation. (b) Hemerocallis “Stella de Oro” + Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (AB) completely dried in autumn.
Table 1.
The life forms, habits, and blooming times of the six species selected for the research [
38,
39,
40].
Table 1.
The life forms, habits, and blooming times of the six species selected for the research [
38,
39,
40].
Species | Life Forms 1 | Habits | Blooming Times |
---|
Hemerocallis “Stella De Oro” | Geo | Clump forming | Summer |
Phedimus spurius (M.Bieb.) ‘t Hart ‘John Creech” | Ch | Mat forming | Summer |
Tulbaghia violacea Harv. | Geo | Tufted | Summer/autumn |
Phlox subulata L. “Trot Pink” | H | Mat forming | Spring |
Potentilla neumanniana Rchb. | H | Clump forming | Spring/autumn |
Gaillardia “Kobold” | H | Clump forming | Summer/autumn |
Table 2.
The dates of the three manual weeding schedules per year.
Table 2.
The dates of the three manual weeding schedules per year.
Year | Season | Date |
---|
1 | Spring | 21 June 2019 |
Summer | 26 August 2019 |
Autumn | 5 November 2019 |
2 | Spring | 18 May 2020 |
Summer | 30 July 2020 |
Autumn | 22 December 2020 |
3 | Spring | 13 May 2021 |
Summer | 31 August 2021 |
Autumn | 12 November 2021 |
Table 3.
Mean dry weed biomass per plot (g m−2) for years 1, 2, and 3 and total amount (g m−2) affected by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)).
Table 3.
Mean dry weed biomass per plot (g m−2) for years 1, 2, and 3 and total amount (g m−2) affected by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)).
Combinations | Year 1 | Year 2 1 | Year 3 1 | Total 1 |
---|
AB | 54.9 ± 42.2 | 4.9 ± 0.8 ab | 5.0 ± 0.4 ab | 778.5 ± 86.5 ab |
CD | 26.6 ± 15.0 | 1.4 ± 0.5 b | 0.5 ± 0.3 b | 340.6 ± 17.6 b |
EF | 9.2 ± 5.8 | 15.6 ± 6.1 ab | 14.7 ± 12.4 a | 474.1 ± 18.5 ab |
AB + CD | 41.1 ± 27.3 | 6.0 ± 4.1 ab | 1.8 ± 0.3 ab | 586.2 ± 40.8 ab |
CD + EF | 39.3 ± 33.5 | 19.9 ± 8.7 a | 15.9 ± 10.6 a | 902.0 ± 29.6 ab |
AB + EF | 47.2 ± 39.7 | 29.5 ± 13.6 a | 8.6 ± 2.0 a | 1023.3 ± 57.1 ab |
AB + CD + EF | 27.5 ± 22.9 | 52.0 ± 29.2 a | 13.4 ± 4.1 a | 1114.6 ± 127.0 a |
p | ns | *** | *** | * |
Table 4.
Two-way ANOVA was used to compare the mean percentages (%) of ground cover during years (1, 2, and 3), seasons (spring, summer, and autumn), and their interaction.
Table 4.
Two-way ANOVA was used to compare the mean percentages (%) of ground cover during years (1, 2, and 3), seasons (spring, summer, and autumn), and their interaction.
Year (A) | % 1 |
---|
1 | 66.0 ± 1.6 a |
2 | 54.0 ± 5.2 b |
3 | 52.8 ± 10.3 c |
p | ** |
Season (B) | |
Spring | 76.5 ± 7.7 a |
Summer | 54.2 ± 12.3 b |
Autumn | 42.2 ± 8.4 c |
p | *** |
Interaction | p |
A X B | *** |
Table 5.
The percentages (%) of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) at each time point during the three-year-long experiment.
Table 5.
The percentages (%) of ground cover by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M.Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)) at each time point during the three-year-long experiment.
| Year 1 | Year 2 | Year 3 |
---|
Combinations | Spring 1 | Summer | Autumn 1 | Spring 1 | Summer 1 | Autumn 1 | Spring 1 | Summer 1 | Autumn 1 |
---|
AB | 60.1 ± 3.9 bc | 55.4 ± 2.8 | 76.4 ± 2.5 ab | 96.0 ± 0.4 a | 37.4 ± 3.0 b | 2.1 ± 0.4 c | 92.0 ± 0.4 a | 8.4 ± 3.6 d | 0.5 ± 0.1 d |
CD | 42.7 ± 3.3 d | 63.0 ± 2.8 | 84.5 ± 2.9 a | 94.3 ± 0.8 a | 70.5 ± 0.8 a | 24.5 ± 4.4 b | 84.6 ± 0.7 a | 65.0 ± 3.1 a | 43.4 ± 2.5 a |
EF | 73.5 ± 1.1 a | 63.4 ± 4.7 | 66.3 ± 1.5 b | 51.5 ± 8.3 c | 65.5 ± 5.1 a | 42.8 ± 4.8 a | 69.7 ± 4.1 b | 72.2 ± 6.2 a | 39.4 ± 3.9 a |
AB + CD | 52.6 ± 1.3 c | 66.0 ± 2.5 | 82.5 ± 2.6 a | 96.7 ± 0.3 a | 48.0 ± 1.4 b | 14.8 ± 1.5 bc | 94.6 ± 0.4 a | 26.7 ± 5.1 cd | 23.0 ± 3.4 bc |
CD + EF | 66.1 ± 1.8 ab | 60.3 ± 5.2 | 73.5 ± 3.8 ab | 71.5 ± 7.5 b | 62.2 ± 2.7 a | 28.8 ± 4.7 ab | 65.7 ± 7.5 b | 69.8 ± 9.8 a | 37.8 ± 4.6 ab |
AB + EF | 71.2 ± 1.1 a | 59.3 ± 5.7 | 69.8 ± 2.9 b | 87.8 ± 1.7 ab | 46.8 ± 2.4 b | 29.8 ± 4.2 ab | 93.6 ± 0.7 a | 37.0 ± 6.0 bc | 14.8 ± 3.5 c |
AB + CD + EF | 65.8 ± 2.7 ab | 60.7 ± 3.7 | 72.9 ± 1.8 ab | 85.3 ± 6.9 ab | 49.0 ± 2.1 b | 28.5 ± 5.5 ab | 91.0 ± 1.5 a | 50.8 ± 2.4 ab | 29.1 ± 5.6 abc |
p | *** | ns | *** | *** | *** | *** | *** | *** | *** |
Table 6.
Dry plant perennial biomass (g m−2) differences between the end and beginning of the experiment as affected by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)).
Table 6.
Dry plant perennial biomass (g m−2) differences between the end and beginning of the experiment as affected by seven perennial plant combinations: AB, CD, EF, AB + CD, CD + EF, AB + EF, and AB + CD + EF (Hemerocallis “Stella de Oro” (A), Phedimus spurius (M. Bieb.) “t Hart ‘John Creech” (B), Tulbaghia violacea Harv. (C), Phlox subulata L. “Trot Pink” (D), Potentilla neumanniana Rchb. (E), and Gaillardia “Kobold” (F)).
Combinations | Dry Perennial Biomass Variation 1 |
---|
AB | 1484.2 ± 0063.8 c |
CD | 4316.8 ± 0526.9 a |
EF | 2651.6 ± 0145.8 b |
AB + CD | 2297.5 ± 0114.6 bc |
CD + EF | 2899.7 ± 0111.2 b |
AB + EF | 2257.9 ± 0128.6 bc |
AB + CD + EF | 2150.3 ± 0087.4 bc |
p | *** |