The gardener on your list might enjoy: a soil thermometer, a rain gauge, a "min-max" thermometer indicating minimum and maximum temperatures, a long handled watering wand with adjustable flow rates, a horticultural heating mat for providing gentle bottom heat to germinating seeds, a generous supply of sturdy plant labels, or maybe a garden journal.
Dust Your Plants
No matter how clean your house may be, houseplants eventually become dusty, reducing the amount of light they receive. Periodically clean the foliage with a soft cloth, a gentle vacuuming or the feather duster. Using tepid water, rinse smaller plants with the hand sprayer or swish them upside down in a bucket; consider setting larger plants in the shower.
Keep Amaryllis Healthy
Once the amaryllis blooms fade, trim off the bloom stalk by cutting it at the base. Set the plant in a sunny location and care for it as you would any foliage plant. This will rebuild the bulb's strength so it can rebloom next year. Keep the soil slightly moist and fertilize per label instructions with a water-soluble fertilizer for houseplants.
Live Christmas Tree Care
Living trees should be kept indoors for only a few days because the "unseasonable" warmth inside interferes with the tree's natural growth cycle. Acclimate the tree by moving it gradually from the cold outside to a cool porch or garage and then indoors. Reverse the steps when you take it outside to plant. Remember to keep the soil ball moist at all times.
Measure Your Yard
If you are planning to do landscaping next year, take time now during a spell of mild weather to record important measurements so that you can easily estimate square footage amounts, the number of plants you will need and so on when it is time to order or purchase your plants and materials.