Bougainvillea are an immensely showy, floriferous and hardy plant. Virtually pest-free and disease resistant, it rewards its owner with an abundance of color and vitality when it is well looked after.

When should bougainvillea be repotted, and with what?

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Repotting Bougainvillea

A bougainvillea blooms best when pot-bound. So, do not be tempted to repot unless you must. I have found that it is best to leave the bougainvillea plant in its original container until the roots have replaced all of the soil and you can't keep the plant well watered.

Soil suitable for Bougainvillea

Bougainvilleas will thrive in almost any soil as long as it is well-drained and fertile. Soils that work for other plants you grow will be fine for your bougainvillea. It is important to select a growing medium that drains well but that will also help keep plants from drying out between waterings. Keeping containers moist yet well drained is the most important key to successful bougainvillea culture in containers.

Field soils are generally unsatisfactory for growing bougainvillea in containers. This is primarily because soils do not provide the aeration, drainage and water holding capacity required. To improve this situation several "soil-less" growing media have been developed.

The best growing mixture is one that is soil-less. Soil-less media are free of any disease pathogens, insect pests, and weed seeds. They are also generally lightweight and porous, allowing for a well-drained yet moisture-retentive mix. Premixed growing media are available from garden centers. However, be careful not to use peat or peatlite mixes alone. By themselves, these media tend to become compacted, too lightweight, and hard to wet. My greatest problem with peat/peatlite mixes is when the soil dries completely, the rootball will pull away from the side of the pot, and it is almost impossible to completely wet the soil again -- the water simply runs down the side of the container and drains out the bottom. If your plant dries out and you use this type of mix, to re-wet it, let the pot sit in a pail of water until the soil ball is completely wet.

Mix Your Own Soil

You can create your own blend of soil mix by using peat moss, vermiculite or perlite, sterile potting soil or composted soil mix, and coarse builder's sand. Note: Ph of the soil is very important. If you mix your own soil, then you should consider the following: Bougainvillea plant prefer a pH in the 6.0 to 6.5 range.

Some commercially prepared growing mixtures have an added wetting agent which is a great help when it comes to planting and watering. You may also consider adding water-absorbing polymers or "gel" that absorbs and retains up to 400 times its weight in water. Polymers are nontoxic and last for a number of years before breaking down in the environment.
Here is the mix I used in my nursery for bougainvillea:
  • 70% Horticultural peat moss
  • 20% Pine Bark (old bark) - In North Florida, pine bark is a cheap and readily available ingredient.
  • 10% River Sand.
The amount of lime added was always based on soil testing and it varies.

A commonly used soil-less mixture:
  • 1 part garden soil (not clay)
  • 1 part washed builder's sand, perlite, or pumice 
  • 1 part horticultural peat moss 
  • 1 quart steamed bonemeal per bushel (8 gallons) of mixture 
  • 1 pint dolomite lime per bushel of soil mix

Mix all ingredients thoroughly by shoveling them from one pile to another at least three times. Pulverize any large lumps or clods as you mix. When thoroughly mixed add sufficient water to moisten the mixture and store in a sheltered spot until you are ready to use it. A garbage can, wastebasket, or large bucket makes a handy storage container.

This general potting mixture provides a suitable growth medium for most container plants, including vegetables, bedding plants, geraniums, begonias, fuchsias, and ivies. But, for bougainvillea I found that the 70%peat, 20%pine bark and 10%sand with the amount of dolomite lime always depending upon soil testing -- however, you should be able to use the above mixture with excellent results for your bougainvillea.

Before using your mix to repot plants, be sure it is damp. Totally dry soil mixture is difficult to handle and may damage tender roots before the plant is watered.

Table 1. Commonly used soil-less mixtures.

Volume Ratio Components
2:1 Peat, Perlite
2:1:1 Peat, Perlite, Vermiculite
3:1:1 Peat, Perlite, Vermiculite
2:1:1 Peat, Bark, Sand
2:1:1 Peat, Bark, Perlite
3:1:1 Peat, Bark, Sand