Combination planters and baskets, in their various forms, are a huge part of our spring, summer, and fall offerings. At Bell Nursery, we produce many types of combinations, ranging from 12-inch, 14-inch, and 18-inch combo baskets and planters, down to 6-inch, 8-inch, and 10-inch planters and window boxes. We love planning, producing, and selling combinations, as well as enjoying them ourselves as they thrive at home over the spring, summer, and fall.
When combinations are designed, a few considerations are critical that apply to any size combo. Components should be chosen and grouped from species that perform well under similar growing conditions, temperature, fertility, media pH, etc.
Plant habits should blend into a thriller-filler-spiller or intermingle into mounding and trailing habits, and finally bloom into must-have color schemes, monochromatic or contrasting, multi-textured, bold and wild, or soft and flowing pastels.
To choose from, we have the traditional favorite combos, the best sellers from year to year, and new, exciting mixes created by growers putting their own recipes together. The industry has a multitude of ready-made, named combinations offered by breeders, both single species and multi species that are tested for compatibility. Choosing the combos and successfully growing them is all that’s left to do.
Planting, Timing, and Cultural Considerations for Premium Combos
Plan on six to eight liners in a 12- to 14-inch combo basket for a good baseline. Include three to four liners in a 10-inch and two to three plants per pot in an 8-inch.
Timing the crop changes with the time of year based on daylength, average daily temperature (ADT), etc. For top quality, 12-inch combo baskets grown under short days to be ready in mid-March to early April, plan on 11 to 12 weeks crop time (under natural conditions, from a rooted 105). As days get longer and warmer, crop times can be reduced by roughly a week each month, until summer when you can finish a 12-inch combo in eight weeks for July and August.
For cultural considerations related to combination production, there are many options. The fundamentals of growing include the most basic consideration, the media pH. Breeders have done great work in selecting for plants that are less pH sensitive (e.g., calibrachoa), but be careful of mixing components that require opposite ends of the pH scale to perform well. Maintaining your pH in the optimal zone of 5.6 to 6.2, and targeting 5.8 to 6.0 will steer you clear of most issues when putting different components together.
Baskets or planters will be on the bench for four to five weeks before needing space or hung. This is the window to get critical treatments done such as plant growth regulators, preventative fungicides for roots and foliage, systemic insecticides, or beneficial sachets for baskets going in the canopy.
At transplant, feed combo pots in with 100 to 150 ppm ammonium-based feed, combining a fungicide such as Segway in with the feed. Choose your fertilizer based on your water alkalinity, but plan on using ammonium-based fertilizers such as 20-10-20 or 21-5-20 at the beginning of the crop, and transitioning to nitrate-based feeds such as 13-2-13 at the end. Run the crop a few degrees warmer for the first week than the recommended growing-on temperature to help the crop get established and off to a good start. Irrigate early and try to maintain humidity at or below 80% to help with Botrytis, especially on stems and lower leaves that may be touching the soil surface. This is also a good time to get a broad spectrum foliar fungicide on the crop.
What to Expect at Each Stage, and Tips for Maintaining Quality
7 to 14 days after transplant: The crop should be establishing and rooting out. Spray Florel at rates ranging from 300 to 350 parts per million (ppm) for combos with geraniums, and up to 500 ppm for calibrachoa, petunia, and verbena type combos. Back rates down in the early season under cooler short days, and increase rates gradually as days get warmer and longer.
14 to 21 days after transplant, or 10 days to two weeks after the Florel application: Apply a follow-up foliar plant growth regulator (if needed), typically a foliar of daminozide at 2,500 to 5,000 ppm, paclobutrazol 30 ppm, or uniconazole 10 ppm will tone them nicely prior to hanging.
21 to 28 days after transplant, before the baskets go up into the canopy: For growers using beneficials, apply the beneficials or sachets. Growers using a traditional approach, apply a systemic insecticide together with feed, such as Mainspring or Kontos. Read all labels carefully, but do not use Kontos on geraniums.
Growing on: Rotate basic type feeds, supplying calcium and magnesium as necessary, for example 13-2-13, but especially during the final third of the crop. Use feed rates of 125 to 150 ppm constant liquid feed or 175 to 200 ppm intermittent, and supplement micros especially when feeding at low rates.
Use temperature as able to tone the crop. Avoid temperature spikes and cool the crop down as it gains size and color. When combos are a couple inches over the edge of the pot, applying a 2 to 3 ppm paclobutrazol drench can be a great tool to keep the baskets toned and looking better longer at retail.