Many of our houseplants enjoy a “summer vacation,” spending the warm summer months outside in a full or part-shade location. There are several important factors to consider before bringing your indoor plants outside for the summer.
When moved outside during the warm parts of the growing season, houseplants can flourish in the warm temperatures and high humidity of an Iowa summer. The increased light levels and fresh air allow plants to put on lots of new, healthy growth. The summer rains are great for cleaning the foliage from the dust and dirt that accumulates while growing indoors. Those rains and the ability to water with a hose greatly simplifies and reduces the amount of time spent caring for your houseplants. Something that is particularly welcome during a time of the year when much of your focus tends to be outdoors in the garden rather than indoors.
Timing is Important
The warm days of spring can get us excited and inspired but wait until nighttime temperatures are consistently and reliably above 50°F before moving houseplants outdoors. In much of Iowa, this is mid to late May.
Prepare Plants for the Move
A few weeks before moving houseplants outdoors identify and evaluate those you wish to put outside for the summer. While most houseplants don't mind being slightly pot-bound, the ideal growing conditions will promote lots of new growth, and this can lead to plants quickly drying out or easily tipping over because they are top-heavy. Repot those plants that need it. Even knowing the anticipated growth, don't bump plants up more than one or two pot sizes. Houseplants do not benefit from moving from super cramped quarters to enormous pots. Consider using a broad wide-based pot or one made from a heavy material like ceramic so they will be stable and less likely to tip over in the wind.
Spring can be a nice time to also prune lanky or wayward stems. The ideal outdoor conditions will allow houseplants to quickly grow and recover. Those trimmings can also be used to propagate new plants to expand your collection or give to friends. The outdoor conditions can be great for rooting cuttings.
Find a Location in the Shade
Not all outdoor locations are suitable for houseplants. Nearly all houseplants are tropical understory plants. These plants are used to low light and warm temperatures, which is why they do so well in our homes. When you move them outside, it’s important not to move them into too much light. Even the brightest indoor locations are only a fraction of the light intensity compared to any shady spot outside. Houseplants will do best if they "vacation" in a full-shade or part-shade location outdoors.
Select locations outdoors where these tropical plants can be admired. Shady patios, porches, decks, and other frequently used outdoor spaces are great locations, and their close proximity to the house makes moving the sometimes heavy containers easier. The trays and saucers used indoors to protect floors and furniture can be put away while houseplants are outdoors.
Acclimating Houseplants is Essential
Moving houseplants outside is a big change in environmental conditions, so acclimating them is important. Never move houseplants from indoors into full sun. Leaf burn, discoloration, and drop can occur. On some species, especially succulents, the damage to the fleshy stems and leaves is permanent. Acclimate houseplants to brighter locations by moving them from an indoor location to a full-shade location outside. Then introduce more light over 10 to 14 days. Protect plants with some cloth or shade material if a full-shade location cannot be found. Many houseplants can be in full shade the entire summer, and others can be moved to a spot with part shade once acclimated.
Monitor plants closely, especially for the first several weeks. Watch for any burning or discoloration of the foliage – this could mean the light is too intense. If the plant starts to lean or stretch towards the light, find a spot with brighter light. Even with the gentlest of transitions, some indoor plants, like weeping fig and tropical hibiscus, are prone to leaf drop when moved to a new location. New leaves will emerge in a couple of weeks to replace the ones lost.
Watering and Fertilizing
Continue to water as needed, knowing that warmer temperatures and more light will change the watering frequency. Check the soil moisture frequently and water thoroughly when the soil is dry to the touch. Group houseplants together and make sure a hose and spigot are nearby to make watering easier.
With more favorable environmental conditions comes more growth. Regular fertilization will help support healthy new growth. Using an all-purpose, balanced, water-soluble fertilizer at half-strength every week (or every other week) is a good place to start. Slow-release fertilizers can be used as well. Sprinkle it on at the beginning of the season and reapply mid-summer if needed.
Timing is Important
When nighttime temperatures start to dip consistently to around 50°F in the fall, it’s time to bring houseplants back indoors. In much of Iowa, this is typically in mid to late September. Most houseplants are native to tropical areas and will not tolerate freezing temperatures. Several species of indoor plants will see damage when temperatures drop below 45°F, and nearly all will die if exposed to below-freezing temperatures. Watch the weather forecast and bring plants back indoors well before nighttime temperatures get too cold.
Watch for Insects
Before bringing houseplants inside, check for insects. Pests like scale, mealybug, aphids, and whiteflies in the foliage, as well as ants or cockroaches in the soil, can be inadvertently brought indoors without a careful look. Take the opportunity to thoroughly rinse off all the foliage while still outside. Let foliage completely dry before bringing them indoors to reduce the mess. A good rinse can not only help knock down any potential insect issues, but it can also help remove dust and dirt along with any dried leaves or flowers. If plants show signs of extensive infestations, it may be better to compost the plant rather than bring it indoors, where the problem will only get worse and control will be difficult. It is better to lose one plant than to bring it indoors and infest several others.
Once inside, keep plants isolated from other houseplants for 3 to 4 weeks. Typically, if there is going to be an issue with common indoor plant pests, it will be evident after about a month indoors. Inspect often and carefully and address any issues as soon as they are noticed to help prevent infestations from getting out of control or spreading to other plants.
Move to a Good Environment Indoors
The change in environmental conditions from outside to inside can be quite stark. Place plants brought back inside in bright indirect light. Even the brightest locations indoors are only a fraction of the light intensity of any location outside (even a shady one). Some houseplants, especially tropical hibiscus and weeping fig, will drop leaves in response to this change in light intensity. New foliage will grow to replace those leaves lost due to the big change in conditions. Provide supplemental light if conditions are too dim indoors. Even in the best of situations, plants are still likely to "pout" when brought back inside. Provide good consistent care to help them stay healthy and recover quickly from the drastic change in environmental conditions.
Resist the Urge to Prune Everything Off
Houseplants will put on a lot of new growth outdoors over the summer and may get very large. Your first inclination may be to cut stems way back before bringing them back inside. Resist this urge, as drastic pruning introduces more stress to a plant already stressed by a big change in light, temperature, and humidity levels.
If plants are too big to bring indoors, trim off only what you need to get them to fit. For some houseplant species, what is pruned off can be propagated over winter to create new plants.
If plants grow too large to come back into your home, consider donating them to a church, school, hospital, nursing home, or office building lobby. These larger indoor spaces can be great new homes for big plants, provided someone there is willing and able to care for them. Sometimes it can be difficult to find a new home for a plant that has outgrown your home, so start planning early. While it can be difficult to do, large plants can also simply be composted with the knowledge that they have provided beauty and joy for many years.
Change Watering and Fertilizing Habits
Growth rates will drop sharply when houseplants are moved from bright and ideal outdoor conditions to dimmer less-than-ideal indoor locations. Reduce or stop fertilizing plants in the fall and winter months, as abundant fertilizer will only promote growth that cannot be supported by the slower-growing houseplant leading to pale or spindly growth.
The watering frequency should change as well. When houseplants need to be watered depends on many environmental conditions including light, humidity, and temperature. Since all of these conditions will change for the plant moving back indoors, the amount of water they need will also change.