When perennial garden mums are cared for properly you can expect to see a long, stunning display of colorful flowers during the fall season. Basically, when growing mums as your landscape or flower gardens, you'll want to provide them with fertile soil, plenty of sun, and fertilizer. Proper pruning is important as well and I address this in another article titled How to Prune Garden Mums.
How To Fertilize Garden Mums
At Planting Time
Because the grower will have fertilized the perennial garden mums you purchased at a nursery, there is no need to fertilize plants at planting time. That being said, it is beneficial to mix in some good organic matter, such as aged compost or bagged composted manure, to get plants off to a good start rooting in.
Spring
When planting mums in spring, I usually water the plants in with a well-balanced liquid plant food or Root Stimulator to get them off to a good start. I'll also apply a slow-release, granular flower food.
Feeding Established Mums
I feed established mums with a granular, slow-release flower food in early spring, when new growth begins to emerge from the ground. If the foliage has faded some by late-summer I feed mums again with a non-burning organic plant food. Alternatively, you can feed monthly with a liquid fertilizer from early spring through mid- to late July.
Other Helpful Mum Growing Tips
Sun Needs
Mums do their best in sites that provide full to mostly sun. The more shade they get during the day the less flowers there will be in fall. Shade also causes plants to grow too tall and lanky, toppling over from the weight of the flowers. Morning sun is an absolute must as this helps to dry dew from the foliage, which protects the plants from developing foliar diseases. Be sure to plant mums at least 20 feet away from street lights or other night lights. Upsetting the normal hours of darkness will throw the mum off schedule, and it may not flower at the right time if at all.
Soil Needs
Mums, like many other perennials, prefer a well-drained, yet moist soil that is slightly acid and rich in organic matter. Constantly soggy or wet soil will likely lead to disease that effects flowering and compromises plant health. The ideal soil pH is about 5.8 to 6.8. If you are unsure about the pH of your soil your local Extension Service might provide soil testing services, or you can purchase a soil test kit or pH testing probe.
Planting
When planting mums in heavy clay soil make sure to thoroughly mix in 25 to 50 percent aged organic compost, such as mushroom compost or composted manure, with the native soil removed from the planting hole. In looser soils add maybe 10 to 20 percent compost. The planting hole should be dug two to three times as wide and no deeper than the rootball. Plant so that the top edge of the rootball is at or slightly above ground level, to allow for settling. For more details see: How To Plant Garden Mums
Mulching
A 1- to 2-inch layer of cured, shredded wood mulch or pine straw will help to conserve moisture and suppress weed growth. Over time, the mulch will decompose, providing rich organic matter your mums will love.
Watering
Soak soil well after planting mums and then provide water as necessary to keep soil moist but not wet. Established mums are tolerant of dry spells, so I usually only provide supplemental water - in the form of a deep soaking - when foliage begins to wilt during prolonged periods of dry weather.
Pruning
Mums are fall blooming plants. If allowed to bloom during the heat of the summer the flowers will quickly fade from the heat.